Answer:
The resistance must be 6.67[tex]\Omega[/tex]
Solution:
Resistance, [tex]R_{1} = 20\Omega[/tex]
Resistance, [tex]R_{2} = 10\Omega[/tex]
For the current to be the same when the switch is open or closed, the resistances must be connected in parallel as current is distributed in parallel with the same voltage across the circuit:
Thus in parallel:
[tex]\frac{1}{R_{eq}} = \frac{1}{R_{1}} + \frac{1}{R_{2}}[/tex]
[tex]\frac{1}{R_{eq}} = \frac{1}{20} + \frac{1}{10}[/tex]
[tex]R_{eq} = 6.67\ \Omega[/tex]
An ideal parallel-plate capacitor consists of a set of two parallel plates of area Separated by a very small distance 푑. This capacitor is connected to a battery that charges the capacitor such that the energy stored in the capacitor is 푈'. Now the battery is disconnected and the separation between the plates is doubled, how much energy is stored in the capacitor?
Answer:
doubled the initial value
Explanation:
Let the area of plates be A and the separation between them is d.
Let V be the potential difference of the battery.
The energy stored in the capacitor is given by
U = Q^2/2C ...(1)
Now the battery is disconnected, it means the charge is constant.
the separation between the plates is doubled.
The capacitance of the parallel plate capacitor is inversely proportional to the distance between the plates.
C' = C/2
the new energy stored
U' = Q^2 / 2C'
U' = Q^2/C = 2 U
The energy stored in the capacitor is doubled the initial amount.
which of the following tends to increase in a system?
A. temperature
B. Heat
C. Entropy
D. Energy
Answer: entropy
Explanation: entropy is the degree of disorderliness or randomness in a system
A diffraction grating that has 4500 lines/cm is illuminated by light that has a single wavelength. If a second order maximum is observed at an angle of 42° with respect to the central maximum, what is the wavelength of this light?
Answer:
The wavelength is 742.7 nm.
Explanation:
Given that,
Grating = 4500 lines/cm
Angle = 42°
Order number =2
We need to calculate the distance
[tex]d=\dfrac{1\times10^{-2}}{4500}[/tex]
[tex]d=2.22\times10^{-6}\ m[/tex]
We need to calculate the wavelength
Using diffraction formula
[tex]d\sin\theta=m\times\lambda[/tex]
[tex]\lambda=\dfrac{d\sin\theta}{m}[/tex]
[tex]\lambda=\dfrac{2.22\times10^{-6}\times\sin42}{2}[/tex]
[tex]\lambda=7.427\times10^{-7}[/tex]
[tex]\lambda=742.7\ nm[/tex]
Hence, The wavelength is 742.7 nm.
The wavelength of this light was found to be 7.08 × 10⁻⁴ m.
To find the wavelength of light that results in a second-order maximum at a 42° angle when striking a diffraction grating with 4500 lines per centimeter, we use the formula for diffraction grating: d sin θ = mλ, where d is the distance between adjacent grating lines, θ is the angle of the maximum, m is the order of the maximum, and λ is the wavelength of the light. First, calculate the distance between grating lines (d) as the reciprocal of the grating's line density (4500 lines/cm or 4.5×105 lines/m), yielding d = 1/4.5×105 m. Then, substituting the given values into the formula with m = 2 and θ = 42°, solve for the wavelength λ.
λ = (1/4.5×105) * sin(42°) / 2
= 7.08 × 10⁻⁴ m
Motor oil , with a viscosity of 0 . 250 Ns / m2 , is flowing through a tube that has a radius of 5 . 00 mm and is 25 . 0 cm long . The drop in pressure is 300 kPa . What is the volume of oil flowing through the tube per unit time ?
Answer:
1.1775 x 10^-3 m^3 /s
Explanation:
viscosity, η = 0.250 Ns/m^2
radius, r = 5 mm = 5 x 10^-3 m
length, l = 25 cm = 0.25 m
Pressure, P = 300 kPa = 300000 Pa
According to the Poisuellie's formula
Volume flow per unit time is
[tex]V=\frac{\pi \times Pr^{4}}{8\eta l}[/tex]
[tex]V=\frac{3.14 \times 300000\times \left ( 5\times 10^{-3} \right )^{4}}{8\times 0.250\times 0.25}[/tex]
V = 1.1775 x 10^-3 m^3 /s
Thus, the volume of oil flowing per second is 1.1775 x 10^-3 m^3 /s.
Future space stations will create an artificial gravity by rotating. Consider a cylindrical space station of 380 m diameter rotating about its axis. Astronauts walk on the inside surface of the space station. What rotation period will provide "normal" gravity? On a space walk on the outside of the space station how much gravity would they experience?
Answer:
27.66 s
Explanation:
Space station creates artificial gravity by rotational movement about its axis .
The object inside also move in circular motion creating centrifugal force which creates acceleration in them .
centrifugal acceleration = ω² R where ω is angular velocity and R is radius of the cylindrical space station .
R = 380 /2 = 190 m
Given
ω² R = g = 9.8
ω² = 9.8 / R
= 9.8 / 190
= 5.15x 10⁻²
ω = 2.27 x 10⁻¹
= .227 rad / s
2π / T = .227 ( T is time period of rotation )
T = 2π / .227
= 27.66 s .
outside of the space station they will experience zero acceleration , because they are rotating around the earth.
Write the ground-state electron configurations of the following ions. (a) Li+ (b) N3− (c) In3+ (Use the noble gas core electron configuration in your answer.) (d) Tl+ (Use the noble gas core electron configuration in your answer.)
Li+ [He]
N³- [Ne]
In³+ [Kr] 4d10
Tl+ [Xe] 4f14 5d10 6S2
The ground-state electron configuration of the ions Li+, N3−, In3+, and Tl+ are [He], [Ne], [Kr]4d10, and [Xe]4f145d106s26p1 respectively. This notation suggests these ions have similar electronic structures to the noble gases and additional electrons in certain cases.
Explanation:The ground-state electron configurations of the ions Li+, N3−, In3+, and Tl+ can be described using the noble gas core electron configuration. The noble gas core is essentially the electron configuration of the closest noble gas with less atomic number than the atom we are considering.
(a) Li+ has lost an electron compared to neutral Lithium. Its electron configuration becomes [He] - it resembles helium, a noble gas.
(b) N3− has gained three electrons compared to neutral Nitrogen and its electron configuration becomes [Ne] - it resembles neon, a noble gas.
(c) In3+ has lost three electrons compared to neutral Indium. Its electron configuration becomes [Kr]4d10 - core is like Kr (krypton), a noble gas, plus 10 electrons added in the d orbital.
(d) Tl+ has lost one electron compared to neutral Thallium and its electron configuration is [Xe]4f145d106s26p1 - core is like Xe (xenon), a noble gas, plus additional electrons.
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(a) Triply charged uranium-235 and uranium-238 ions are being separated in a mass spectrometer. (The much rarer uranium-235 is used as reactor fuel.) The masses of the ions are 3.90x10—25 kg and 3.95x10—25 kg , respectively, and they travel at 3.00x105 m/s in a 0.250-T field. What is the separation between their paths when they hit a target after traversing a semicircle? (b) Discuss whether this distance between their paths seems to be big enough to be practical in the separation of uranium-235 from uranium-238.
Answer:
(a) 2.5 cm
(b) Yes
Solution:
As per the question:
Mass of Uranium-235 ion, m = [tex]3.95\times 10^{- 25}\ kg[/tex]
Mass of Uranium- 238, m' = [tex]3.90\times 10^{- 25}\ kg[/tex]
Velocity, v = [tex]3.00\times 10^{5}\ m/s[/tex]
Magnetic field, B = 0.250 T
q = 3e
Now,
To calculate the path separation while traversing a semi-circle:
[tex]\Delta x = 2(R_{U_{35}} - 2R_{U_{38}})[/tex]
The radius of the ion in a magnetic field is given by:
R = [tex]\frac{mv}{qB}[/tex]
[tex]\Delta x = 2(R_{U_{35}} - 2R_{U_{38}})[/tex]
[tex]\Delta x = 2(\frac{mv}{qB} - \frac{m'v}{qB})[/tex]
[tex]\Delta x = 2(\frac{m - m'}{qB}v)[/tex]
Now,
By putting suitable values in the above eqn:
[tex]\Delta x = 2(\frac{3.95\times 10^{- 25} - 3.90\times 10^{- 25}}{3\times 1.6\times 10^{- 19}\times 0.250}\times 3.00\times 10^{5}) = 2.5\ cm[/tex]
[tex]\Delta x = 1.25\ cm[/tex]
(b) Since the order of the distance is in cm, thus clearly this distance is sufficiently large enough in practical for the separation of the two uranium isotopes.
In a mass spectrometer, uranium-235 and uranium-238 ions can be separated based on their masses and velocities. The separation distance between their paths can be determined using the equation: d = mv/(qB). The distance between their paths is practical for the separation of uranium-235 from uranium-238.
Explanation:In a mass spectrometer, triply charged uranium-235 and uranium-238 ions are separated based on their masses and velocities.
The separation of their paths when they hit a target after traversing a semicircle can be calculated using the equation:
d = mv/(qB)
where d is the separation, m is the mass of the ion, v is the velocity, q is the charge, and B is the magnetic field.
The distance between their paths seems to be big enough to be practical in the separation of uranium-235 from uranium-238, as even a small separation can result in significant enrichment over multiple passes through the mass spectrometer.
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Be sure to answer all parts. In a future hydrogen-fuel economy, the cheapest source of H2 will certainly be water. It takes 467 kJ to produce 1 mol of H atoms from water. What is the frequency, wavelength, and minimum energy of a photon that can free an H atom from water? Enter your answers in scientific notation. Frequency = 7.05 × 10 -32 s−1 Wavelength = 4.26 × 10 -25 m Minimum energy = × 10 kJ/photon
Answer:
[tex]7.7549\times 10{19}\ J[/tex]
[tex]1.17037\times 10^{15}\ Hz[/tex]
[tex]2.56329\times 10^{-7}\ m[/tex]
Explanation:
c = Speed of light = [tex]3\times 10^8\ m/s[/tex]
[tex]N_A[/tex] = Avogadro's number = [tex]6.022\times 10^{23}[/tex]
[tex]\nu[/tex] = Frequency
[tex]\lambda[/tex] = Wavelength
The minimum energy is given by
[tex]E=\frac{1\ mol}{N_A}\\\Rightarrow E=467\times 10^{3}\times \frac{1}{6.022\times 10^{23}}\\\Rightarrow E=7.7549\times 10{19}\ J[/tex]
The minimum energy is [tex]7.7549\times 10{19}\ J[/tex]
The energy of a photon is given by
[tex]E=h\nu\\\Rightarrow \nu=\frac{E}{h}\\\Rightarrow \nu=\frac{467\times 10^{3}\frac{1}{6.022\times 10^{23}}}{6.626\times 10^{-34}}\\\Rightarrow \nu=1.17037\times 10^{15}\ Hz[/tex]
The frequency of the photon is [tex]1.17037\times 10^{15}\ Hz[/tex]
Wavelength is given by
[tex]\lambda=\frac{c}{\nu}\\\Rightarrow \lambda=\frac{3\times 10^8}{1.17037\times 10^{15}}\\\Rightarrow \lambda=2.56329\times 10^{-7}\ m[/tex]
The wavelength is [tex]2.56329\times 10^{-7}\ m[/tex]
17. (a) Will the electric field strength between two parallel conducting plates exceed the breakdown strength for air ( 3.0×106 V/m ) if the plates are separated by 2.00 mm and 5.0×103 V a potential difference of is applied? (b) How close together can the plates be with this applied voltage?
Answer:
Explanation:
Distance between plates d = 2 x 10⁻³m
Potential diff applied = 5 x 10³ V
Electric field = Potential diff applied / d
= 5 x 10³ / 2 x 10⁻³
= 2.5 x 10⁶ V/m
This is less than breakdown strength for air 3.0×10⁶ V/m
b ) Let the plates be at a separation of d .so
5 x 10³ / d = 3.0×10⁶ ( break down voltage )
d = 5 x 10³ / 3.0×10⁶
= 1.67 x 10⁻³ m
= 1.67 mm.
A child is sitting on the seat of a swing with ropes 5 m long. Her father pulls the swing back until the ropes make a 30o angle with the vertical and then releases the swing. If air resistance is neglected, what is the speed of the child at the bottom of the arc of the swing when the ropes are vertical?
Answer:
v = 3.7 m/s
Explanation:
As the swing starts from rest, if we choose the lowest point of the trajectory to be the zero reference level for gravitational potential energy, and if we neglect air resistance, we can apply energy conservation as follows:
m. g. h = 1/2 m v²
The only unknown (let alone the speed) in the equation , is the height from which the swing is released.
At this point, the ropes make a 30⁰ angle with the vertical, so we can obtain the vertical length at this point as L cos 30⁰, appying simply cos definition.
As the height we are looking for is the difference respect from the vertical length L, we can simply write as follows:
h = L - Lcos 30⁰ = 5m -5m. 0.866 = 4.3 m
Replacing in the energy conservation equation, and solving for v, we get:
v = √2.g.(L-Lcos30⁰) = √2.9.8 m/s². 4.3 m =3.7 m/s
A CD player rotates at a variable speed so that a laser can scan pits and lands on the disk’s bottom surface at a constant tangential speed of 1.2 m/s. The disk has a moment of inertia of 1.2 x 10-4 kg m2and the music is first detected when the laser is located 15 mm from the disk’s center. Assuming the disk started from rest, find the work done by the motor during this start-up.
Answer:
W = 0.384 J
Explanation:
Work and energy in the rotational movement are related
W = ΔK = [tex]K_{f}[/tex] - K₀
W = ½ I [tex]w_{f}[/tex]² - 1 /2 I w₀²
where W isthe work, I is the moment of inertia and w angular velocity
With the system part of the rest the initial angular speed is zero (w₀ = 0)
The angular and linear quantities are related
v = w r
w = v / r
Let's replace
W = ½ I (v / r)²
Let's calculate
W = ½ 1.2 10⁻⁴ 1.2² / (1.5 10⁻²)²
W = 0.384 J
W = 38.4 J
In some applications of ultrasound, such as its use on cranial tissues, large reflections from the surrounding bones can produce standing waves. This is of concern because the large pressure amplitude in an antinode can damage tissues. For a frequency of 1.0 MHz, what is the distance between antinodes in tissue?
a. 0.38 mm
b. 0.75 mm
c. 1.5 mm
d. 3.0 mm
Answer:
b. 0.75 mm
Explanation:
The distance between antinodes d is half the wavelength [tex]\lambda[/tex]. We can obtain the wavelength with the formula [tex]v=\lambda f[/tex], where f is the frequency given ([tex]f=1MHz=1\times10^6Hz[/tex]) and v is the speed of sound in body tissues (v=1540m/s), so putting all together we have:
[tex]d=\frac{\lambda}{2}=\frac{v}{2f}=\frac{1540m/s}{2(1\times10^6Hz)}=0.00077m=0.77mm[/tex]
which is very close to the 0.75mm option.
An alien spaceship traveling at 0.600c toward the Earth launches a landing craft with an advance guard of purchasing agents and physics teachers. The lander travels in the same direction with a speed of 0.800c relative to the mother ship. As observed on the Earth, the spaceship is 0.200 ly from the Earth when the lander is launched.(a) What speed do the Earth observers measure for the approaching lander?(b) What is the distance to the Earth at the time of lander launch, as observed by the aliens?
Answer:
Explanation:
Let the velocity of lander with respect to earth be v .
In relativistic mechanism the expression for relative velocity is
v_r = [tex]\frac{v -u}{1-\frac{uv}{c^2}}[/tex]
Given u = .6c , v_r = .8 c
Substituting the values
.8c = [tex]\frac{v -0.6c}{1-\frac{.6c\times v}{c^2} }[/tex]
.8c-.48v = v - .6c
v = .946c
b )
Distance in terms of time = .2 ly
In relativistic mechanism , expression for relativistic time is given by the following relation
t = [tex]\frac{t_0}{\sqrt{1-\frac{v^2}{c^2} }}[/tex]
Substituting v = .946c
t₀ = .2
t = [tex]\frac{.2}{\sqrt{1-\frac{0.946\times .946c^2}{c^2}}}[/tex]
.2 / √.1050
= .62 ly
distance to the Earth at the time of lander launch, as observed by the aliens will be .62 ly.
Final answer:
The speed of the lander as observed on Earth is 0.865c. The distance to the Earth at the time of lander launch, as observed by the aliens, is 0 ly, which is an unreasonable result.
Explanation:
(a) To find the speed of the lander as observed on Earth, we need to use the relativistic velocity addition formula. The formula is given by:
v' = (v1 + v2)/(1 + (v1*v2)/c^2)
Substituting in the values, where v1 = 0.800c and v2 = 0.600c, we get:
v' = (0.800c + 0.600c)/(1 + (0.800c*0.600c)/c^2) = 1.280c/1.480 = 0.865c
So, the speed of the lander as observed on Earth is 0.865c.
(b) To find the distance to the Earth at the time of lander launch, as observed by the aliens, we can use the time dilation formula. The formula is given by:
t' = t/sqrt(1 - (v^2/c^2))
Where t' is the time measured by the aliens, t is the time measured on Earth, v is the velocity of the spaceship relative to Earth, and c is the speed of light.
In this case, t' = 0 (since the lander is launched at the same time as observed on Earth), t = 0.200 ly (given in the question), v = 0.600c (velocity of the spaceship relative to Earth), and c is the speed of light. Substituting the values, we get:
0 = 0.200/sqrt(1 - (0.600c)^2/c^2)
0 = 0.200/sqrt(1 - 0.360)
0 = 0.200/sqrt(0.640)
0 = 0.200/0.8
0 = 0.25
Since 0 = 0.25 is not possible, this result is unreasonable. It suggests that there is a discrepancy in the calculations or assumptions made.
A spaceship in distress sends out two escape pods in opposite directions. One travels at a speed v1 = + 0.70 c in one direction, and the other travels at a speed v2 = − 0.76 c in the other direction, as observed from the spaceship. Part A What speed does the first escape pod measure for the second escape pod? Express your answer using two significant figures.
To develop this problem it is necessary to apply the related concepts at relative speed.
When an observer perceives the relative speed of a second observer, the function is described,
[tex]v' = \frac{v_1-v_2}{1-\frac{v_1v_2}{c^2}}[/tex]
Where,
[tex]v_1[/tex] = The velocity of the first escape pod
[tex]v_2[/tex] = The velocity of the second escape pod
c = Speed of light
v' = Speed of the first escape pod relative to the second escape pod.
Our values are given as,
[tex]v_1[/tex]= 0.7c
[tex]v_2[/tex]= -0.76c
Replacing we have,
[tex]v' = \frac{v_1-v_2}{1-\frac{v_1v_2}{c^2}}[/tex]
[tex]v' = \frac{0.7c-(-0.76c)}{1-\frac{(0.7c)(-0.76c)}{(3*10^8)^2}}[/tex]
[tex]v' = \frac{0.7c-(-0.76c)}{1-\frac{(0.7c)(-0.76c)}{(3*10^8)^2}}[/tex]
[tex]v' = 2.85*10^8m/s[/tex]
Therefore the speed of the first escape pod measure for the second escape pod is [tex]v' = 2.85*10^8m/s[/tex]
The relative speed of the second escape pod as measured by the first escape pod, using relativistic velocity addition, is approximately -0.04c (or just 0.04c considering the magnitude), where c is the speed of light.
Explanation:The question involves calculating the relative speed of one escape pod as observed by the other escape pod in a scenario where they are moving in opposite directions. To do this, we must use the formula for relativistic velocity addition. The formula is as follows:
V = (v1 + v2) / (1 + v1*v2/c²),
where V is the relative velocity as measured by one escape pod, v1 and v2 are the velocities of the escape pods, and c is the speed of light. For this particular problem:
v1 = +0.70c (the velocity of the first escape pod as observed from the spaceship)v2 = -0.76c (the velocity of the second escape pod as observed from the spaceship, note the negative sign because it is in the opposite direction)We substitute the values into the relativistic velocity addition formula to find the relative speed:
V = (0.70c - 0.76c) / (1 - 0.70*(-0.76)c²/c²)
Doing the calculations:
V = -0.06c / (1 + 0.532)c²/c²)
V = -0.06c / 1.532
V = -0.039c ≈ -0.04c
The negative sign indicates that the second escape pod is moving in the direction opposite to the first pod as measured by the first pod. It's important to keep in mind that this result is only an approximation, rounded to two significant figures as per the question's request.
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You and your friends find a rope that hangs down 16m from a high tree branch right at the edge of a river. You find that you can run, grab the rope, swing out over the river, and drop into the water. You run at 2.0 m/s and grab the rope, launching yourself out over the water. How long must you hang on if you want to drop into the water at the greatest possible distance from the edge?
Answer:
[tex]t = 2\ s[/tex]
Explanation:
given,
length of the rope = 16 m
speed of the man = 2 m/s
using the formula of time period
[tex]T =2 \pi \sqrt{\dfrac{L}{g}}[/tex]
[tex]T =2 \pi \sqrt{\dfrac{16}{9.8}}[/tex]
[tex]T = 8.028\ s[/tex]
To cover the maximum distance you need to leave the when the rope is shows maximum displacement.
To reach the displacement time to leave the rope is one fourth of the time period.
[tex]t = \dfrac{T}{4}[/tex]
[tex]t = \dfrac{8.03}{4}[/tex]
[tex]t = 2\ s[/tex]
The time period of pendulum is time taken by it to complete one cycle of swing left to right and right to left.
The total time taken to hang on if you want to drop into the water at the greatest possible distance from the edge is 2 seconds.
What is time period of pendulum?The time period of pendulum is time taken by it to complete one cycle of swing left to right and right to left.
It can be given as,
[tex]T=2\pi\sqrt{\dfrac{T}{g}}[/tex]
Here, [tex]g[/tex] is the gravitational force of Earth.
Given information-
Total length of the rope is 16 m.
The speed of the man is 2.0 m/s.
Let the time of to swing by rope both side is [tex]T[/tex]. Thus put the values in the above formula as,
[tex]T=2\pi\sqrt{\dfrac{16}{9.8}}[/tex]
[tex]T=8.028 \rm s[/tex]
Now the greatest possible distance from the edge will be at the greatest displacement.
Thus the time to cove the greatest possible distance will be one forth (1/4) of the total time. Thus,
[tex]t=\dfrac{8.028 }{4}\\t=2\rm s[/tex]
Hence, the total time taken to hang on if you want to drop into the water at the greatest possible distance from the edge is 2 seconds.
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A 15.5 kg mass vibrates in simple harmonic motion with a frequency of 9.73 Hz. It has a maximum displacement from equilibrium of +14.6 cm at time, t = 0.00 s. The displacement from equilibrium of the mass at time, t = 1.25 s is_______?
The displacement of a 15.5 kg mass undergoing simple harmonic motion with a frequency of 9.73 Hz, at a point in time 1.25 s after it was at its maximum displacement of 14.6 cm, is found to be -14.1 cm.
Explanation:The displacement of a mass undergoing simple harmonic motion at any given point of time can be found using the formula x(t) = A cos(wt + φ), where 'A' is the amplitude (maximum displacement), 'w' is the angular frequency, and 'φ' is the phase constant. Given that the maximum displacement or amplitude 'A' is 14.6 cm (or 0.146 m), the frequency 'f' is 9.73 Hz, and the phase constant φ = 0 (as the displacement is maximum at t = 0), the angular frequency 'w' can be calculated as 2πf, which equals approximately 61.1 rad/s. Substituting all these values into the formula, we find that the displacement at time t = 1.25 s is x(t) = 0.146 cos(61.1*1.25 + 0) = -0.141 m, or -14.1 cm. Note that the negative sign indicates that the displacement is in the opposite direction of the initial maximum displacement.
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The displacement from equilibrium at time t = 1.25s is -0.042m.
Explanation:The displacement from equilibrium of the mass at time t = 1.25 s can be calculated using the formula for simple harmonic motion. The displacement at any given time t is given by the equation x = A * cos(2πft), where A is the amplitude and f is the frequency. In this case, the amplitude is 0.146 m and the frequency is 9.73 Hz. Plugging in the values, we get x = 0.146 * cos(2π * 9.73 * 1.25), which gives us x = -0.042 m.
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A white dwarf has a greater mass than either a red dwarf or a brown dwarf. Yet a white dwarf has a smaller radius than either a red dwarf or a brown dwarf. Explain why, in terms of the types of pressure that keep the different kinds of dwarfs from collapsing under their own gravity.
Explanation:
Red dwarf and brown dwarf masses are less than a typical white dwarf mass measuring around 1.2 solar masses. But it's only a few kilometers of the radius. This is precisely because there is no force to overcome the contraction due to gravity. There is a constant battle between the external force of fusion (who wants to expand the star) and inward pressure because of gravity (who wants to compact the star) of regular stars on the main sequence. There remains a balance between these two forces as long as the star remains on the celestial equator.
Red dwarfs are helped by the nuclear fusion force, but brown dwarfs were not large enough to cause the fusion of hydrogen, they are massive enough to generate sufficient energy in the core by fusing deuterium to sustain their volume. However as soon as the star runs out of hydrogen to burn it weakens the force of the external fusion and gravity starts to compact the center of the star. The contraction heats up the core into more massive stars and helium fusion begins, rendering the star once again stable. However this helium fusion does not occur in stars with masses below 1.44Mo. Tightness persists for such stars until the star's gasses degenerate.
The speed of sound in air is around 345 m/s. A tuning fork vibrates at 850 Hz above the open end of the sound resonance tube. What is the wavelength (in cm) of the sound waves in the tube? Never include units with a numerical answer.
For the development of this problem it is necessary to apply the concepts related to the wavelength depending on the frequency and speed of light.
By definition we know that frequency can be expressed as
[tex]f = \frac{v}{\lambda}[/tex]
Where,
v = Velocity
[tex]\lambda =[/tex] Wavelength
Our values are
[tex]v=345m/sec[/tex]
[tex]f=850Hz[/tex]
Re-arrange to find Wavelength
[tex]f = \frac{v}{\lambda}[/tex]
[tex]\lambda = \frac{v}{f}[/tex]
[tex]\lambda = \frac{345}{850}[/tex]
[tex]\lambda = 0.4058m[/tex]
Converting to centimeters,
[tex]\lambda = 0.4058m(\frac{100cm}{1m})[/tex]
[tex]\lambda = 40.58cm[/tex]
Therefore the wavelength of the sound waves in the tube is 40.58cm
Force F = − + ( 8.00 N i 6.00 N j ) ( ) acts on a particle with position vector r = + (3.00 m i 4.00 m j ) ( ) .
What are
(a) the torque on the particle about the origin, in unit-vector notation
(b) the angle between the directions of r and F ?
Explanation:
Given that,
Force, [tex]F=((-8i)+6j)\ N[/tex]
Position of the particle, [tex]r=(3i+4j)\ m[/tex]
(a) The toque on a particle about the origin is given by :
[tex]\tau=F\times r[/tex]
[tex]\tau=((-8i)+6j) \times (3i+4j)[/tex]
Taking the cross product of above two vectors, we get the value of torque as :
[tex]\tau=(0+0-50k)\ N-m[/tex]
(b) Let [tex]\theta[/tex] is the angle between r and F. The angle between two vectors is given by :
[tex]cos\theta=\dfrac{r.F}{|r|.|F|}[/tex]
[tex]cos\theta=\dfrac{(3i+4j).((-8i)+6j)}{(\sqrt{3^2+4^2} ).(\sqrt{8^2+6^2}) }[/tex]
[tex]cos\theta=\dfrac{0}{50}[/tex]
[tex]\theta=90^{\circ}[/tex]
An ice skater is spinning at 5.2 rev/s and has a moment of inertia of 0.32 kg * m2.
Calculate the angular momentum, in kilogram meters squared per second, of the ice skater spinning at 5.2 rev/s.
Suppose instead he keeps his arms in and allows friction of the ice to slow him to 2.75 rev/s. What is the magnitude of the average torque that was exerted, in N * m, if this takes 12 s?
Explanation:
The angular momentum is given by the moment of inertia, multiplied by the angular speed of the rotating body:
[tex]L=I\omega[/tex]
The angular speed is given by:
[tex]\omega=2\pi f\\\omega=2\pi 5.2\frac{rev}{s}\\\omega=32.67\frac{rad}{s}[/tex]
Now, we calculate the angular momentum:
[tex]L=0.32kg\cdot m^2(32.67\frac{rad}{s})\\L=10.45\frac{kg\cdot m^2}{s}[/tex]
The average torque is defined as:
[tex]\tau=I\alpha[/tex]
[tex]\alpha[/tex] is the angular acceleration, which is defined as:
[tex]\alpha=\frac{\omega_f-\omega_0}{t}[/tex]
We have to calculate [tex]\omega_f[/tex]:
[tex]\omega_f=2\pi (2.75\frac{rad}{s})\\\omega_f=17.28\frac{rad}{s}[/tex]
Now, we calculate the angular acceleration:
[tex]\alpha=\frac{17.28\frac{rad}{s}-32.67\frac{rad}{s}}{12s}\\\alpha=-1.28\frac{rad}{s^2}[/tex]
Finally, we can know the average torque:
[tex]\tau=0.32kg\cdot m^2(-1.28\frac{rad}{s^2})\\\tau=-0.41N\cdot m[/tex]
(a) The angular momentum of the skater is 10.45 kgm²/s
(b) The magnitude of the average torque that was exerted, is 0.41 Nm.
Angular momentum of the ice skaterThe angular momentum of the skater is calculated as follows;
L = Iω
where;
ω is angular speed (rad/s)ω = 5.2 rev/s x 2π rad = 32.67 rad/s
L = 0.32 x 32.67
L = 10.45 kgm²/s
Angular acceleration of the skaterThe angular acceleration is calculated as follows;
[tex]\alpha= \frac{\omega _f - \omega _i}{t}[/tex]
ωf is the final angular speed = 2.75 rev/s x 2π rad = 17.28 rad/s[tex]\alpha = \frac{17.28 -32.67 }{12} \\\\\alpha = -1.28 \ rad/s^2[/tex]
Average torqueThe magnitude of the average torque that was exerted, is calculated as;
τ = Iα
τ = 0.32 x (1.28)
τ = 0.41 Nm.
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The hollow tube is pivoted about a horizontal axis through point O and is made to rotate in the vertical plane with a constant counterclockwise angular velocity = 2.9 rad/sec. If a 0.15-lb particle is sliding in the tube toward O with a velocity of 4.8 ft/sec relative to the tube when the position θ = 36° is passed, calculate the magnitude N of the normal force exerted by the wall of the tube on the particle at this instant.
To solve the problem it is necessary to apply the concepts related to Newton's second law, as well as to the sum of forces in this type of bodies.
According to the description I make a diagram that allows a better understanding of the problem.
Performing sum of forces in the angular direction in which it is inclined we have to
[tex]\sum F = ma_{\theta}[/tex]
[tex]N - W cos\theta = ma_{\theta}[/tex]
[tex]N = ma_{\theta}+Wcos\theta[/tex]
Tangential acceleration can be expressed as
[tex]a_{\theta} = (r\ddot{\theta}+2\dot{r}\dot{\theta})[/tex]
Our values are given by,
[tex]\dot{\theta} = 2.9rad/s[/tex]
[tex]m = 0.15 lb[/tex]
[tex]\theta = 36\°[/tex]
[tex]v = 4.8ft/s[/tex]
Substituting [tex]\ddot{\theta}=0rad/s^2 , \dot{r}=-4.8ft/s, \dot{\theta}=2.9 rad/s[/tex]
[tex]a_{\theta} = r*0+2*(4.8*2.9)\\a_{\theta}=27.84ft/s^2[/tex]
At the same time we acan calculate the mass of the particle, then
W = mg
Where,
W = Weight of the particle
m = mass
g = acceleration due to gravity
[tex]0.15lb = m(32.2ft/s^2)[/tex]
[tex]m = 4.66*10^{-3}Lb[/tex]
Now using our first equation we have that
[tex]N = ma_{\theta}+Wcos\theta[/tex]
[tex]N = (4.66*10^{-3})(27.84)+0.2cos36[/tex]
[tex]N = 0.2914Lb[/tex]
Therefore the normal force exerted by the wall of the tube on the particle at this instant is 0.2914Lb
The magnitude of the normal force [tex]\( N \)[/tex] exerted by the wall of the tube on the particle at the instant when the angle [tex]\( \theta = 36^\circ \)[/tex] is approximately 0.249 lb
To determine the normal force [tex]\( N \)[/tex]exerted by the wall of the tube on the particle, we analyze the forces acting on the particle in a rotating reference frame. Here’s the step-by-step process:
1. Identify the given data:
- Angular velocity [tex]\( \omega = 2.9 \)[/tex] rad/sec
- Particle weight [tex]\( W = 0.15 \)[/tex] lb
- Relative velocity towards O [tex]\( v_r = 4.8 \)[/tex] ft/sec
- Angle [tex]\( \theta = 36^\circ \)[/tex]
2. **Convert the weight to mass:**
-[tex]\( W = mg \)[/tex]
-[tex]\( m = \frac{W}{g} \)[/tex]
- Using[tex]\( g = 32.2 \text{ ft/sec}^2 \)[/tex]:
- [tex]\( m = \frac{0.15 \text{ lb}}{32.2 \text{ ft/sec}^2} = 0.00466 \text{ slugs} \)[/tex]
3. Calculate the distance ( r ):
- Since [tex]\( v_r = 4.8 \)[/tex] ft/sec is towards O and the tube is rotating with [tex]\( \omega \),[/tex] the distance [tex]\( r \)[/tex] can be found using [tex]\( r = \frac{v_r}{\omega} \)[/tex]:
- [tex]\( r = \frac{4.8 \text{ ft/sec}}{2.9 \text{ rad/sec}} = 1.655 \text{ ft} \)[/tex]
4. **Determine the forces:**
- Centrifugal force [tex]\( F_c = m \omega^2 r \)[/tex]:
[tex]\[ F_c = 0.00466 \text{ slugs} \times (2.9 \text{ rad/sec})^2 \times 1.655 \text{ ft} = 0.0638 \text{ lb} \][/tex]
- Component of gravitational force in the radial direction [tex]\( F_{g, r} = W \cos \theta \)[/tex]:
[tex]\[ F_{g, r} = 0.15 \text{ lb} \times \cos 36^\circ = 0.1214 \text{ lb} \][/tex]
5. Calculate the normal force [tex]\( N \)[/tex]:
- Normal force [tex]\( N \)[/tex] must balance the radial forces:
[tex]\[ N = F_c + F_{g, r} + m \cdot (\omega^2 r) \][/tex]
[tex]\[ N = 0.0638 \text{ lb} + 0.1214 \text{ lb} + 0.0638 \text{ lb} \][/tex]
[tex]\[ N = 0.249 \text{ lb} \][/tex]
A uniform disk with a mass of 5.0 kg and diameter 30 cm rotates on a frictionless fixed axis through its center and perpendicular to the disk faces. A uniform force of 4.0 N is applied tangentially to the rim of the disk. What is the angular acceleration of the disk?
Answer:[tex]\alpha =10.66 rad/s^2[/tex]
Explanation:
Given
mass of disk [tex]m=5 kg[/tex]
diameter of disc [tex]d=30 cm[/tex]
Force applied [tex]F=4 N[/tex]
Now this force will Produce a torque of magnitude
[tex]T=F\cdot r[/tex]
[tex]T=4\dot 0.15[/tex]
[tex]T=0.6 N-m[/tex]
And Torque is given Product of moment of inertia and angular acceleration [tex](\alpha )[/tex]
[tex]T=I\cdot \alpha [/tex]
Moment of inertia for Disc [tex]I= \frac{Mr^2}{2}[/tex]
[tex]I=0.05625 kg-m^2[/tex]
[tex]0.6=0.05625\cdot \alpha [/tex]
[tex]\alpha =10.66 rad/s^2[/tex]
Consider a motor that exerts a constant torque of 25.0N \cdot m to a horizontal platform whose moment of inertia is 50.0kg \cdot m^2 . Assume that the platform is initially at rest and the torque is applied for 12.0rotations . Neglect friction.
Part A ) How much work W does the motor do on the platform during this process?
Enter your answer in joules to four significant figures.
W =
1885
\rm J
Part B ) What is the rotational kinetic energy of the platform K_rot,f at the end of the process described above?
Enter your answer in joules to four significant figures.
K_rot,f =
1885
\rm J
Part C ) What is the angular velocity omega_f of the platform at the end of this process?
Enter your answer in radians per second to three significant figures.
omega_f =
8.68
{\rm rad / s}
Part D ) How long \Delta t does it take for the motor to do the work done on the platform calculated in Part A?
Enter your answer in seconds to three significant figures.
\Delta t =
17.4
\rm s
Part E ) What is the average power P_avg delivered by the motor in the situation above?
Enter your answer in watts to three significant figures.
P_avg = 109 \rm W
Part F ) Note that the instantaneous power P delivered by the motor is directly proportional to omega, so P increases as the platform spins faster and faster. How does the instantaneous power P_f being delivered by the motor at the time t_{\rm f} compare to the average power P_avg calculated in Part E?
Note that the instantaneous power delivered by the motor is directly proportional to , so increases as the platform spins faster and faster. How does the instantaneous power being delivered by the motor at the time compare to the average power calculated in Part E?
P = P_{\rm avg}
P = 2 * P_{\rm avg}
P = P_{\rm avg} / 2
none of the above
Answer:
A) W = 1885 J , B) [tex]K_{f}[/tex] = 1885 J , C) w = 8.68 rad / s , D) t = 8,687 s , E) P = 109 W F) P = 2 [tex]P_{rms}[/tex]
Explanation:
Part A The work in the rotational movement is
W = τ θ
Let's look at the rotated angle
θ = 12.0 rot (2pi rad / 1rot) = 75.398 rad
W = 25.0 75.40
W = 1885 J
Part B Let's use the relationship between work and kinetic energy
W = ΔK = Kf - Ko
As the body leaves the rest w₀ = 0 ⇒ K₀ = 0
W = [tex]K_{f}[/tex] -0
[tex]K_{f}[/tex] = 1885 J
Part C The formula for kinetic energy is
K = ½ I w²
w² = 2k / I
w = √ (2 1885/50)
w = 8.68 rad / s
Part D The power in the rotational movement
P = τ w
P = 25 8.68
P = 217 W
P = W / t
t = W / P
t = 1885/217
t = 8,687 s
Part E At average power is
P = τ ([tex]w_{f}[/tex] -w₀)/ 2
We look for angular velocity with kinematics
[tex]w_{f}[/tex = w₀ + α t
τ = I α
α = τ / I
α = 25/50
α = 0.5 rad / s²
calculate
P = 25 (0.5 8.687)
P = 108.6 W
P = 109 W
Part F
The average power is
[tex]P_{rms}[/tex] = τ ([tex]w_{f}[/tex] -w₀) /
The instant power is
P = τ w
The difference is that in one case the angular velocity is instantaneous and between averages
P / [tex]P_{rms}[/tex] = τ w / (τ ([tex]w_{f}[/tex]-w₀) / 2)
P / [tex]P_{rms}[/tex]= 2 w / Δw
For this case w₀ = o
p / [tex]P_{rms}[/tex] = 2
The motor exerts rotational motion to do 1885 Joules of work on the platform. The final angular velocity of the platform is 8.68 rad/s. The time it takes to do this work is 17.4 seconds. The average power delivered by the motor is 109 Watts and the instantaneous power is twice the average power.
Explanation:A motor exerts a constant torque on a horizontal platform and we need to determine the work done, the rotational kinetic energy, the angular velocity, the time it takes, the average power, and compare the instantaneous power to the average power.
Firstly, the work done by the motor is calculated using the formula W = Torque x angular displacement. The angular displacement for 12.0 rotations will equals to 12.0 x 2π radians. So, W = 25.0 N.m x 12 x 2π rad = 1885 J. Hence, the motor does 1885 Joules of work on the platform.
For the rotational kinetic energy, since there is no friction, all of the work done on the platform is converted into kinetic energy, so, K_rot,f = 1885 J.
The final angular velocity ωf can be found from the rotational kinetic energy and the moment of inertia by the relation K_rot,f = 1/2 I ωf^2. From this, we can find ωf = √(2K_rot,f / I)= 8.68 rad/s.
The time it takes Δt to do the work can be calculated using Δt = angular displacement / average angular velocity. Hence, Δt= (12 x 2π) / ((0 + ωf) / 2)= 17.4 s.
The average power P_avg is given by the total work done divided by the total time, which gives P_avg= W / Δt = 109 Watts.
On the final part, the instantaneous power Pf is proportional to the final angular velocity. As Pf = Torque x ωf, we get Pf = 2 x P_avg. So, the instantaneous power being delivered by the motor at the end is twice the average power calculated before.
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Time to be a crash investigator! Two cars are in an accident: Car A was driving due east when Car B, driving due North, ran a stop sign and collided with his car, causing an inelastic collision (the cars stuck together). The skid marks from the accident go off at a 66 degree angle above the horizontal (East). A traffic camera witnessed Car A going 30 mph prior to the crash, and both cars traveling 29.5 mph after the crash. Unfortunately, the camera was angled so it did not see Car B prior to the crash.
Car A has a mass of 1000 kg, and Car B has a mass of 1500 kg.
The driver of Car B claims that he was driving the 30 mph speed limit, and didn’t see the stop sign because of foggy weather. Driver A claims Driver B was speeding and that is why he missed the stop sign.
How fast was Car B traveling prior to the crash?
Answer:
The carriage speed B was 67.4 mph
Explanation:
This is an exercise for the moment, that as a vector we must look for the solution of each axis (x, y). We define a system formed by the two cars, for this system the forces during the crash are internal, so the moment is preserved.
The data they give is the car more A m = 1000kg and its speed is v1₁₀ = 30 mph i^ and the mass of the car B M = 1500 kg
Let's write the moment for each axis
X axis
p₀ₓ = [tex]p_{fx}[/tex]
m v₁ₓ + 0 = (m + M) vₓ
Y axis
poy = [tex]p_{fy}[/tex]
0 + M [tex]v_{2y}[/tex] = (m + M) [tex]v_{y}[/tex]
Let's look for the components of the final velocity with trigonometry
sin 66 = [tex]v_{y}[/tex] / v
cos 66 = vₓ / v
[tex]v_{y}[/tex] = v sin 66
vₓ = v cos 66
We substitute and write the system of equations
m v₁ₓ = (m + M) v cos 66
M [tex]v_{2y}[/tex] = (m + M) v sin66
From the first equation
v = m / (m + M) v₁ₓ / cos 66
v = 1000 / (1000 + 1500) 30 / cos 66
v = 29.5 mph
From the second equation
[tex]v_{2y}[/tex] = (m + M)/m v sin 66
[tex]v_{2y}[/tex] = (1000 + 1500) /1000 29.5 sin 66
[tex]v_{2y}[/tex] = 67.4 mph
The carriage speed B was 67.4 mph
A box with a weight of 50 N rests on a horizontal surface. A person pulls horizontally on it with a force of 10 N and it does not move. To start it moving, a second person pulls vertically upward on the box. If the coefficient of static friction is 0.4, what is the smallest vertical force for which the box moves?
Answer:
25 N
Explanation:
Given that
Weight ,mg = 50 N
m=Mass of the box
g=acceleration due to gravity
Horizontal force F= 10 N
Coefficient of friction ,μ = 0.4
Lets take vertical force = R N
In vertical direction
R + N = mg
N= mg - R
The friction force Fr
Fr= μ N
Fr= μ ( mg - R)
To start the motion
F > Fr
10 > 0.4 ( 50 - R )
25 > 50 - R
R > 50 - 25
R > 25 N
Therefore minimum force R= 25 N
In the given problem, the minimum vertical force required to set the box into motion is greater than 15N. This force reduces the normal force and consequently the frictional force such that it becomes less than the horizontally applied force.
Explanation:In this physical situation, you need to understand the role of static friction and normal force in setting the box into motion. The frictional force is calculated by multiplying the coefficient of static friction (0.4 in this case) and normal force. The normal force on the box is the weight of the box minus the upward force applied. Initially, the upward force is zero, so the frictional force is 0.4 * 50N = 20N. This is greater than the 10N horizontal force applied, so the box does not move.
To make the box move, the vertical force has to reduce the normal force such that the frictional force (which is now less due to the decreased normal force) becomes less than the applied horizontal force (10N). Let's consider the vertical upward force needed as F. Hence, the new frictional force will be 0.4 * (50N - F) and should be less than 10N for the box to move. Solving this inequality, the minimum F needed is >15N, anything above this will make the box move.
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A 1.40 mH inductor and a 1.00 µF capacitor are connected in series. The current in the circuit is described by I = 14.0 t, where t is in seconds and I is in amperes. The capacitor initially has no charge.
(a) Determine the voltage across the inductor as a function of time. mV
(b) Determine the voltage across the capacitor as a function of time. (V/s2) t2
(c) Determine the time when the energy stored in the capacitor first exceeds that in the inductor.
Answer:
Explanation:
Inductance L = 1.4 x 10⁻³ H
Capacitance C = 1 x 10⁻⁶ F
a )
current I = 14 .0 t
dI / dt = 14
voltage across inductor
= L dI / dt
= 1.4 x 10⁻³ x 14
= 19.6 x 10⁻³ V
= 19.6 mV
It does not depend upon time because it is constant at 19.6 mV.
b )
Voltage across capacitor
V = ∫ dq / C
= 1 / C ∫ I dt
= 1 / C ∫ 14 t dt
1 / C x 14 t² / 2
= 7 t² / C
= 7 t² / 1 x 10⁻⁶
c ) Let after time t energy stored in capacitor becomes equal the energy stored in capacitance
energy stored in inductor
= 1/2 L I²
energy stored in capacitor
= 1/2 CV²
After time t
1/2 L I² = 1/2 CV²
L I² = CV²
L x ( 14 t )² = C x ( 7 t² / C )²
L x 196 t² = 49 t⁴ / C
t² = CL x 196 / 49
t = 74.8 μ s
After 74.8 μ s energy stored in capacitor exceeds that of inductor.
Two electrons 1 and 2 move along antiparallel paths separated by a distance of 10 nm, traveling at speeds 4.5 x 10^7 m/s and 8.0 x 10^6 m/s.
Part A) What is the magnitude of the magnetic force exerted by electron 2 on electron 1? Express your answer with the appropriate units.
Answer:
The magnetic force on electron 1 by electron 2=[tex]9.22\times 10^{-15} N[/tex]
Explanation:
We are given that
Distance between two electrons=10 nm
Speed of electron 1=[tex]4.5\times 10^7[/tex] m/s
Speed of electron 2=[tex]8.0\times 10^6[/tex] m/s
We have to find the magnitude of the magnetic force exerted by electron 2 on electron 1.
Magnetic force on electron 1 by electron 2
[tex]F=\frac{\mu_0e^2v_1v_2}{4\pi r^2}[/tex]
[tex]\frac{\mu_0}{4\pi}=10^{-7}[/tex]
[tex]e=1.6\times 10^{-19} C[/tex]
[tex]v_1=4.5\times 10^7 m/s[/tex]
[tex]v_2=8.0\times 10^6 m/s[/tex]
[tex]r=10nm=10\times 10^{-9}m[/tex] [tex](1nm=10^{-9} m[/tex])
Substitute the values in the given formula
The magnetic force on electron 1 by electron 2=[tex]\frac{10^{-7}\times (1.6\times 10^{-19})^2\times 4.5\times 10^7\times 8\times 10^6}{(10\times 10^{-9})^2}[/tex]
The magnetic force on electron 1 by electron 2=[tex]9.22\times 10^{-15} N[/tex]
Hence, the magnetic force on electron 1 by electron 2=[tex]9.22\times 10^{-15} N[/tex]
The magnitude of the magnetic force exerted by electron 2 on electron 1 is [tex]9.22\times10^{-15}[/tex] N.
What is magnetic force?Magnetic force is the force of attraction of repulsion between two poles of the two magnets. The magnetic force is also appears between two electrically charged bodies.
The magnetic force can be given as,
[tex]F=\dfrac{\mu_oq_1q_2(v_1v_2)}{4\pi r^2}[/tex]
Here, ([tex]\mu_o[/tex]) is the magnetic constant, (q) is the charge on the body, (v) is the speed of the body and (r) is the distance between them.
The distance between the electrons 1 and 2 is 10 nm. As the speed of the electron 1 is [tex]4.5 \times10^7[/tex] m/s and the speed of the electron 2 is [tex]8.0 \times10^6[/tex] m/s.
Thus, put the values in the above formula as,
[tex]F=\dfrac{4\pi \times10^{-7}\times1.6\times10^{-19}\times1.6\times10^{-19}\times4.5\times10^{7}(8.0\times10^6)}{4\pi (10^{-9})^2}[/tex]
[tex]F=9.22\times10^{-15}\rm N[/tex]
Thus the magnitude of the magnetic force exerted by electron 2 on electron 1 is [tex]9.22\times10^{-15}[/tex] N.
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Suppose that the resistance between the walls of a biological cell is 4.2 × 109 Ω. (a) What is the current when the potential difference between the walls is 75 mV? (b) If the current is composed of Na+ ions (q = +e), how many such ions flow in 0.74 s?
Answer:
(a) Current will be [tex]17.857\times 10^{-12}A[/tex]
(b) Number of ions will be [tex]8.258\times 10^6[/tex]
Explanation:
We have given that resistance of the biological cell [tex]R=4.2\times 10^9ohm[/tex]
(a) We have given potential difference of 75 mV
So [tex]V=75\times 10^{-3}volt[/tex]
From ohm's law we know that current is given by
[tex]i=\frac{V}{R}=\frac{75\times 10^{-3}}{4.2\times 10^9}=17.857\times 10^{-12}A[/tex]
(b) We have given time t = 0.74 sec
We have to find the charge
We know that charge is given by Q = it, here i is current and t is time
So charge will be [tex]Q=17.857\times 10^{-12}\times 0.74=13.214\times 10^{-12}C[/tex]
So number of ions will be [tex]n=\frac{13.214\times 10^{-12}}{1.6\times 10^{-19}}=8.258\times 10^6[/tex]
You wish to boil 1.9 kg of water, which has a specific heat capacity of 4186 J/kg-K. The water is initially at room temperature (293 K). Water boils at 373 K.
1) How much energy must be added to the water by heating it in order for it to start boiling?
Answer:
6.36 105 J
Explanation:
In calorimetry all the energy given to a system is converted to heat and the equation for heat is
Q = m [tex]c_{e}[/tex] ΔT
The temperature can be in degrees Celsius or Kelvin since the interval between them is the same, substitute and calculate
Q = 1.9 4186 (373-293)
Q = 6.36 105 J
This heat equals the energy supplied
calculate the density of a neutron star with a radius 1.05 x10^4 m, assuming the mass is distributed uniformly. Treat the neutron star as a giant ucleaus and consider the mass of a nucleon 1.675 x 10^-27 kg. Your answer should be in the form of N x 10^17 kg/m^3. Enter onlt the number N with teo decimal places, do not enter unit.
To develop this problem it is necessary to apply the concepts related to the proportion of a neutron star referring to the sun and density as a function of mass and volume.
Mathematically it can be expressed as
[tex]\rho = \frac{m}{V}[/tex]
Where
m = Mass (Neutron at this case)
V = Volume
The mass of the neutron star is 1.4times to that of the mass of the sun
The volume of a sphere is determined by the equation
[tex]V = \frac{4}{3}\pi R^3[/tex]
Replacing at the equation we have that
[tex]\rho = \frac{1.4m_{sun}}{\frac{4}{3}\pi R^3}[/tex]
[tex]\rho = \frac{1.4(1.989*10^{30})}{\frac{4}{3}\pi (1.05*10^4)^3}[/tex]
[tex]\rho = 5.75*10^{17}kg/m^3[/tex]
Therefore the density of a neutron star is [tex] 5.75*10^{17}kg/m^3[/tex]