A truck traveling at a constant speed of 24 m/s passes a more slowly moving car. The instant the truck passes the car, the car begins to accelerate at a constant rate of 1.4 m/s^2 and passes the truck 578 m farther down the road. What was the speed of the car (in meters/second) when it was first passed by the truck?

Answers

Answer 1

Answer:

7.15 m/s

Explanation:

We use a frame of reference in which the origin is at the point where the trucck passed the car and that moment is t=0. The X axis of the frame of reference is in the direction the vehicles move.

The truck moves at constant speed, we can use the equation for position under constant speed:

Xt = X0 + v*t

The car is accelerating with constant acceleration, we can use this equation

Xc = X0 + V0*t + 1/2*a*t^2

We know that both vehicles will meet again at x = 578

Replacing this in the equation of the truck:

578 = 24 * t

We get the time when the car passes the truck

t = 578 / 24 = 24.08 s

Before replacing the values on the car equation, we rearrange it:

Xc = X0 + V0*t + 1/2*a*t^2

V0*t = Xc - 1/2*a*t^2

V0 = (Xc - 1/2*a*t^2)/t

Now we replace

V0 = (578 - 1/2*1.4*24.08^2) / 24.08 = 7.15 m/s


Related Questions

A hot air ballo0n is ascending straight up at a constant
speedof 7.0 m/s. When the balloon is 12.0 m above the ground, agun
fires a pellet straight up from ground level with an initialspped
of 30.0 m/s. Along the paths of the ballon and thepellet, there are
two places where each of them has the altitude atthe same time. How
far above ground level are theseplaces?

Answers

Answer: The two places altitudes are: 16.17 m and 40.67 m

Explanation:

Hi!

Lets call z to the vertical direction (z= is ground) . Then the positions of the balloon and the pellet, using the values of the velocities we are given, are:

[tex]z_b =\text{balloon position}\\z_p=\text{pellet position}\\z_b=(7\frac{m}{s})t\\z_p=30\frac{m}{s}(t-t_0)-\frac{g}{2}(t-t_0)^2\\g=9.8\frac{m}{s^2}[/tex]

How do we know the value of t₀? This is the time when the pellet is fired. At this time the pellet position is zero: its initial position. To calculate it we know that the pellet is fired when the ballon is in z = 12m. Then:

[tex]t_0=\frac{12}{7}s[/tex]

We need to know the when the z values of balloon and pellet is the same:

[tex]z_b=z_p\\(7\frac{m}{s})t =30\frac{m}{s}(t-\frac{12}{7}s)-\frac{g}{2}(t-\frac{12}{7}s)^2[/tex]

We need to find the roots of the quadratic equation. They are:

[tex]t_1=2.31s\\t_2=5.81[/tex]

To know the altitude where the to objects meet, we replace the time values:

[tex]z_1=16,17m\\z_2=40,67m[/tex]

What is the magnitude of the sum of the two vectors A = 36 units at 53 degrees, and B =47 units at 157 degrees.

Answers

Answer:

51.82

Explanation:

First of all, let's convert both vectors to cartesian coordinates:

Va = 36 < 53° = (36*cos(53), 36*sin(53))

Va = (21.67, 28.75)

Vb = 47 < 157° = (47*cos(157), 47*sin(157))

Vb = (-43.26, 18.36)

The sum of both vectors will be:

Va+Vb = (-21.59, 47.11)   Now we will calculate the module of this vector:

[tex]|Va+Vb| = \sqrt{(-21.59)^2+(47.11)^2}=51.82[/tex]

A dolphin in an aquatic show jumps straight up out of the water at a velocity of 15.0 m/s. (a) List the knowns in this problem. (b) How high does his body rise above the water? To solve this part, first note that the final velocity is now a known, and identify its value. Then, identify the unknown and discuss how you chose the appropriate equation to solve for it. After choosing the equation, show your steps in solving for the unknown, checking units, and discuss whether the answer is reasonable. (c) How long a time is the dolphin in the air? Neglect any effects resulting from his size or orientation.

Answers

(a) Initial velocity (v₀) = 0 m/s,  Final velocity (v) = 15.0 m/s.

(b) The dolphin rises approximately 11.5 meters above the water.

(c) The dolphin is in the air for approximately 1.5 seconds.

(a)

Initial velocity (v₀) = 0 m/s (since the dolphin jumps straight up from the water, its initial velocity is zero)

Final velocity (v) = 15.0 m/s (given)

(b)

To solve for the height, we can use the kinematic equation that relates the final velocity (v), initial velocity (v₀), acceleration (a), and displacement (Δy):

v² = v₀² + 2aΔy

v² = v₀² + 2gh

v² = 2gh

Solving for h:

h = (v²) / (2g)

h = (15.0)² / (2 × 9.8)

h ≈ 11.5 m

Therefore, the dolphin rises approximately 11.5 meters above the water.

(c) To determine the time the dolphin is in the air, we can use the equation for time (t) derived from the kinematic equation:

Δy = v₀t + (1/2)at²

Δy = (1/2)at²

t = √((2Δy) / a)

t = √((2 × 11.5) / -9.8)

t ≈ 1.5 s

Therefore, the dolphin is in the air for approximately 1.5 seconds.

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Final answer:

The dolphin rises 8.64 meters above the water and is in the air for 1.33 seconds.

Explanation:

(a) The knowns in this problem are:

Initial velocity of the dolphin: 13.0 m/sAcceleration due to gravity: -9.8 m/s²

(b) To find the height above the water, we need to find the time taken by the dolphin to reach that height and use the equation:

Final velocity = Initial velocity + Acceleration × Time

Solving for time, we have:

Time = (Final velocity - Initial velocity) / Acceleration

Substituting the known values into the equation, we get:

Time = (0 m/s - 13.0 m/s) / -9.8 m/s² = 1.33 s

Next, we can use the formula for height:

Height = Initial velocity × Time + 0.5 × Acceleration × Time²

Substituting the known values, we have:

Height = 13.0 m/s × 1.33 s + 0.5 × -9.8 m/s² × (1.33 s)² = 8.64 m

(c) The time the dolphin is in the air is equal to the time calculated above, which is 1.33 seconds.

The output of an ac generator connected to an RLC series combination has a frequency of 12 kHz and an amplitude of 28 V. If R = 4.0 Ohms, L = 30 μH, and C = 8 μF, find a. The impedance
b. The amplitude for current
c. The phase difference between the current and the emf of the generator
Please show all steps and units. Thank you.

Answers

Answer:

(a) 4.04 ohm

(b) 6.93 A

(c) 8.53°

Explanation:

f = 12 kHz = 12000 Hz

Vo = 28 V

R = 4 ohm

L = 30 micro Henry = 30 x 10^-6 H

C = 8 micro Farad = 8 x 10^-6 F

(a) Let Z be the impedance

[tex]X_{L} = 2\pi fL=2\times3.14\times12000\times30\times10^{-6}= 2.26 ohm[/tex]

[tex]X_{c} = \frac{1}{2\pi fC}=\frac{1}{2\times3.14\times12000\times8\times10^{-6}}= 1.66 ohm[/tex]

[tex]Z = \sqrt{R^{2}+(X_{L}-X_{C})^{2}}=\sqrt{4^{2}+\left ( 2.26-1.66 \right )^{2}}[/tex]

Z = 4.04 Ohm

(b) Let Io be the amplitude of current

[tex]I_{o}=\frac{V_{o}}{Z}[/tex]

[tex]I_{o}=\frac{28}{4.04}[/tex]

Io = 6.93 A

(c) Let the phase difference is Ф

[tex]tan\phi = \frac{X_{L}-X_{C}}{R}[/tex]

[tex]tan\phi = \frac{2.26-1.66}{4}[/tex]

tan Ф =0.15

Ф = 8.53°

You are designing a ski jump ramp for the next Winter Olympics. You need to calculate the vertical height (h) from the starting gate to the bottom of the ramp. The skiers push off hard with their ski poles at the start, just above the starting gate, so they typically have a speed of 2.0 m/s as they reach the gate. For safety, the skiers should have a speed of no more than 30.0 m/s when they reach the bottom of the ramp. You determine that for a 85.0 kg skier with good form, friction and air resistance will do total work of magnitude 4000 J on him during his run down the slope.What is the maximum height (h) for which the maximum safe speed will not be exceeded?

Answers

Answer:

h = 50.49 m

Explanation:

Data provided:

Speed of skier, u = 2.0 m/s

Maximum safe speed of the skier, v = 30.0 m/s

Mass of the skier, m = 85.0

Total work = 4000 J

Height from the starting gate = h

Now, from the law of conservation of energy

Total energy at the gate = total energy at the time maximum speed is reached

[tex]\frac{1}{2}mu^2+mgh=4000J+\frac{1}{2}mv^2[/tex]

where, g is the acceleration due to the gravity

on substituting the values, we get

[tex]\frac{1}{2}\times85\times2.0^2+85\times9.81\times h=4000J+\frac{1}{2}\times85\times30^2[/tex]

or

170 + 833.85 × h = 4000 + 38250

or

h = 50.49 m

An aircraft is at a standstill. It accelerates to 140kts in 28 seconds. The aircraft weighs 28,000 lbs. How many feet of runway was used?

Answers

Answer:

runway use is 3307.8 feet

Explanation:

given data

velocity = 140 kts = 140 × 0.5144 m/s = 72.016 m/s

time = 28 seconds

weight = 28000 lbs

to find out

How many feet of runway was used

solution

we will use here first equation of motion for find acceleration

v = u + at     ..............1

here v is velocity given and u is initial velocity that is 0 and a is acceleration and t is time

put here value in equation 1

72.016 = 0 + a(28)

a = 2.572 m/s²

and

now apply third equation of motion

s = ut + 0.5×a×t²    .......................2

here s is distance and u is initial speed and t is time and a is acceleration

put here all value in equation 2

s = 0 + 0.5×2.572×28²  

s = 1008.24 m = 3307.8 ft

so  runway use is 3307.8 feet

Final answer:

To find the runway distance used by an aircraft accelerating to 140 knots in 28 seconds, we convert knots to feet per second, find the acceleration, and then apply the kinematic formula for distance to obtain approximately 3308 feet.

Explanation:

To calculate how many feet of runway an aircraft used to accelerate to 140 knots in 28 seconds, we need to convert the speed to consistent units and use the kinematic equations for uniformly accelerated motion. Knots need to be converted to feet per second (since the answer is required in feet). Since 1 knot = 1.68781 feet per second, 140 knots is equivalent to 236.293 feet per second. Now, we can use the formula for distance d when given initial velocity vi, final velocity vf, and acceleration a:

d = (vi + vf) / 2 * t

Here, as the plane is starting from a standstill, vi is 0, vf is 236.293 feet/second, and t is 28 seconds. We first need to find the acceleration:

a = (vf - vi) / t = 236.293 / 28 = 8.439 feet/second2

Now we can calculate the distance:

d = (0 + 236.293) / 2 * 28 = 3308.1 feet

The aircraft used approximately 3308 feet of runway.

A box moving on a horizontal surface with an initial velocity of 20 m/s slows to a stop over a time period of 5.0 seconds due solely to the effects of friction. What is the coefficient of kinetic friction between the box and the ground?

Answers

Answer:

μ= 0.408 : coefficient of kinetic friction

Explanation:

Kinematic equation for the box:

[tex]a=\frac{v_{f} -v_{i} }{t}[/tex] Formula( 1)

a= acceleration

v_i= initial speed =0

v_f= final speed= 20 m/s

t= time= 5 s

We replace data in the formula (1):

[tex]a=\frac{0-20}{5}[/tex]

[tex]a= -\frac{20}{5}[/tex]

a= - 4m/s²

Box kinetics: We apply Newton's laws in x-y:

∑Fx=ma : second law of Newton

-Ff= ma Equation (1)

Ff is the friction force

Ff=μ*N Equation (2)

μ is the coefficient of kinetic friction

N is the normal force

Normal force calculation

∑Fy=0  : Newton's first law

N-W=0   W is the weight of the box

N=W= m*g  : m is the mass of the box and g is the acceleration due to gravity

N=9.8*m

We replace N=9.8m in the equation (2)

Ff=μ*9.8*m

Coefficient of kinetic friction ( μ) calculation

We replace Ff=μ*9.8*m and a= -4m/s² in the equation (1):

-μ*9.8*m: -m*4 : We divide by -m on both sides of the equation

9.8*μ=4

μ=4 ÷ 9.8

μ= 0.408

A Horizontal rifel is fired at a bull's-eye. The muzzle
speedof the bullet is 670 m/s. The barrel is pointed directly at
thecenter of the bull's-eye, but the bullet strikes the
target0.025m below the center. What is the horizontal distance
betweenthe end of the rifel and the bull's eye?

Answers

Answer:

The horizontal distance is 478.38 m

Solution:

As per the question:

Initial Speed of the bullet in horizontal direction, [tex]v_{x} = 670 m/s[/tex]

Initial vertical velocity of the bullet, [tex]v_{y} = 0 m/s[/tex]

Vertical distance, y = 0.025 m

Now, for the horizontal distance, 'x':

We first calculate time, t:

[tex]y = v_{y}t - \frac{1}{2}gt^{2}[/tex]

(since, motion is vertically downwards under the action of 'g')

[tex]0.025 = 0 - \frac{1}{2}\times 9.8t^{2}[/tex]

[tex]t = \sqrt{0.05}{9.8} = 0.0714 s[/tex]

Now, the horizontal distance, x:

[tex]x = v_{x}t + \frac{1}{2}a_{x}t^{2}[/tex]

[tex]x = v_{x}t + \frac{1}{2}0.t^{2}[/tex]

(since, the horizontal acceleration will always be 0)

[tex]x = 670\times 0.714 = 478.38 m[/tex]

I have a device that can generate sounds with frequencies between 800 Hz and 1600 Hz. I also have an unlabeled tuning fork that I need to work out the fundamental frequency of. I find that it resonates at 920 Hz and 1380 Hz, but no other frequencies in that range. What's the lowest frequency that it will resonate at?

Answers

Answer:

460 Hz

Explanation:

the given resonating frequency of the device

f₁ =  920 Hz and f₂ =  1380 Hz

fundamental frequency of the device is

f₀ = n₂ - n₁

   = 1380 - 920

   = 460 Hz

expression of frequency of organic pipe open at both ends

[tex]f_0=n\dfrac{\nu}{2l}[/tex]

at n = 1

[tex]f_0=\dfrac{\nu}{2l} = 460 Hz[/tex]

the frequency ratios of the closed pipe

[tex]f_0:f_1:f_2: ...... =[1:2:3:.........]f_0[/tex]

                         =[1:2:3:.........]460 Hz

                         = 460 Hz : 920 Hz : 1380 Hz

so, the lowest frequency for the pipe open at both end is 460 Hz

You are on a train traveling east at speed of 28 m/s with respect to the ground. 1) If you walk east toward the front of the train, with a speed of 1.5 m/s with respect to the train, what is your velocity with respect to the ground? (m/s east)
2) If you walk west toward the back of the train, with a speed of 2.1 m/s with respect to the train, what is your velocity with respect to the ground? (m/s, east)
3) Your friend is sitting on another train traveling west at 22 m/s. As you walk toward the back of your train at 2.1 m/s, what is your velocity with respect to your friend? (m/s, east)

Answers

Answer:

A) 29.5m/s

B) 25.9m/s

C) 47.9 m/s

Explanation:

This is a relative velocity problem, which means that the velocity perception will vary from each observer at a different reference point.

We can say that the velocity of the train respect the ground is 28m/s on east direction If I walk 1.5m/s respect the train, the velocity of the person respect to the ground is the sum of both velocities:

Vgp=Vgt+Vtp

where:

Vgp=velocity of the person respect the ground

Vgt=Velocity of the train respect the ground

Vtp=Velocity of the person respect the train

1) Vgp=28m/s+1.5m/s=29.5m/s

2) here the velocity of the person respect the train is negative because it is going backward

Vgp=28m/s-2.1m/s=25.9m/s

3) the velocity of the train respect with your friend will be the sum of both velocities(Vft).

Vfp=Vft+Vtp

Vfp=velocity of the person respect the friend

Vft=Velocity of the train respect the friend

Vtp=Velocity of the person respect the friend

Vfp=(22m/s+28m/s)+(-2.1m/s)=47.9 m/s

Newton's second law: Rudolph the red nosed reindeer is pulling a 25 kg sled across the snow in a field. The coefficient of kinetic friction is .12 The rope that is pulling the sled is coming off at a 29 degree angle above the horizontal. Find the force in the rope when the acceleration is .12 m/s^2.

Answers

Answer:

[tex]F=39,68N[/tex]

Explanation:

Data:

Mass [tex]m=25 Kg[/tex]

Coefficient of kinetic friction [tex]\mu=0.12[/tex]

Angle = [tex]29^{0}[/tex]

Acceleration = [tex]0.12 \frac{m}{s^{2} }[/tex]

Solution:

By Newton's first law we know that for the x-axis:

[tex]F_{rope_x}-F_f=F_R[/tex] Where [tex]F_R[/tex] is the resulting force, and [tex]F_f[/tex] is the friction force.

And for the y-axis:

[tex]F_{rope_y}+N=W[/tex], where N is the normal force, and W is the weight of the sled.  

We know that the resulting force's acceleration is [tex]0.12 \frac{m}{s^{2} }[/tex], and by using Newton's second law, we obtain:

[tex]F=m.a[/tex]

[tex]F_R=25Kg. 0.12\frac{m}{s^2} \\ F_R=3N[/tex] .

Now, the horizontal component of the force in the rope will be given by

[tex]F_{rope_x}=F_{rope}.cos(29^0)=F_R+F_f[/tex], since the resulting force is completely on the x-axis, and the friction opposes to the speed of the sled.

To obtain the friction force, we must know the normal force:

[tex]F_f=\mu. N[/tex]

Clearing N in the y-axis equation:

[tex]N=W-F_{rope_y}=W-F_{rope}.sin(29^0)[/tex]

So we can express the x-axis equation as follows:

[tex]F.cos(29^0)=F_R+\mu.(W-F_{rope}.sin(29^0))[/tex]

Finally, solving for F we get

[tex]F = (F_R + \mu. m.g) / (cos (29^0) + \mu.sin (29^0))[/tex]

[tex]F=39,68N[/tex]

A 0.5 μF and a 11 μF capacitors are connected in series. Then the pair are connected in parallel with a 1.5 μF capacitor. What is the equivalent capacitance? Give answer in terms of mF.

Answers

Answer:

[tex]C_{eq}=1.97\ \mu F[/tex]

Explanation:

Given that,

Capacitance 1, [tex]C_1=0.5\ \mu F[/tex]

Capacitance 2, [tex]C_2=11\ \mu F[/tex]

Capacitance 3, [tex]C_3=1.5\ \mu F[/tex]

C₁ and C₂ are connected in series. Their equivalent is given by :

[tex]\dfrac{1}{C'}=\dfrac{1}{C_1}+\dfrac{1}{C_2}[/tex]

[tex]\dfrac{1}{C'}=\dfrac{1}{0.5}+\dfrac{1}{11}[/tex]

[tex]C'=0.47\ \mu F[/tex]

Now C' and C₃ are connected in parallel. So, the final equivalent capacitance is given by :

[tex]C_{eq}=C'+C_3[/tex]

[tex]C_{eq}=0.47+1.5[/tex]

[tex]C_{eq}=1.97\ \mu F[/tex]

So, the equivalent capacitance of the combination is 1.97 micro farad. Hence, this is the required solution.

the driver of a car slams on her brakes to avoid collidingwith
a deer crossing the highway. what happens to the car's
kineticenergy as it comes to rest?

Answers

Answer:

Its dissipated by the brake.

Explanation:

Traditional brakes use friction to stop the wheels (or axis). This friction its dissipated in the form of heat. There are others mechanism to brake that don't dissipated the energy, they stored it. In electric cars (or hybrids), there are regenerative brakes, that store the kinetic energy as electrical energy.

Final answer:

As the driver slams the brakes, the kinetic energy of the car gets converted into other forms of energy until the car comes to a stop, at which point it becomes zero.

Explanation:

When the driver of a car slams on her brakes to avoid a collision with a deer crossing the highway, the kinetic energy of the car decreases until the car comes to rest. This is due to the principle of energy conservation. Initially, when the car is moving, it has kinetic energy. However, when the brakes are applied, the kinetic energy gets converted into other forms of energy such as heat energy (due to friction between the brakes and the wheels) and potential energy (if the car is moving uphill). The kinetic energy keeps decreasing until the car comes to a complete stop. At that point, the kinetic energy of the car is zero because kinetic energy is associated with motion and the car is no longer moving.

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A barge is carrying a load of gravel along a river.
Itapproaches a low bridge, and the captain realizes that the top
ofthe pile of gravel is not going to make it under the bridge.
Thecaptain orders the crew to quickly shovel gravel from the pile
intothe water. Is this a good decision? Explain.

Answers

Answer:

Explanation:

Shoveling gravel into the water will increase the buoyancy of the barge, which will make it float higher. Without data it is hard to tell if it will raise the barge enough to be counterproductive, but in any case throwing away the payload is not a good idea. Adding some weights would make the barge float lower, and then maybe the plie can make it under the bridge.

A charge of 7.0 μC is to be split into two parts that are then separated by 9.0 mm. What is the maximum possible magnitude of the electrostatic force between those two parts?

Answers

Answer:

[tex]F = 1361.1 N[/tex]

Explanation:

As we know that a charge is split into two parts

so we have

[tex]q_1 + q_2 = 7\mu C[/tex]

now we have

[tex]F = \frac{kq_1q_2}{r^2}[/tex]

here we know

[tex]F = \frac{kq_1(7\mu C - q_1)}{r^2}[/tex]

here we have

r = 9 mm

now to obtain the maximum value of the force between two charges

[tex]\frac{dF}{dq_1} = 0[/tex]

so we have

[tex]7 \mu C - q_1 - q_1 = 0[/tex]

so we have

[tex]q_1 = q_2 = 3.5 \mu C[/tex]

so the maximum force is given as

[tex]F = \frac{(9\times 10^9)(3.5 \mu C)(3.5 \mu C)}{0.009^2}[/tex]

[tex]F = 1361.1 N[/tex]

Calculate the The wavelength of the first Balmer series of hydrogen is 6562 following: a) The ionization potential, and b) The first excitation potential of the hydrogen atom.

Answers

Answer:

(a) 13.6 eV

(b) 10.2 V

Explanation:

a) Ionization potential energy is defined as the minimum energy required to excite a neutral atom to its ionized state i.e basically  the minimum energy required to excite an electron from n=1 to infinity.

Energy of a level, n, in Hydrogen atom is, [tex]E_{n}=-\frac{13.6}{n^{2} }[/tex]

Now ionization potential can be calculated as

[tex]E_{\infty}- E_{0}[/tex]

Substitute all the value of energy and n in above equation.

[tex]=-\frac{13.6}{\infty^{2}}-(-\frac{13.6}{1^{2}})\\=13.6eV[/tex]

Therefore, the ionization potential is 13.6 eV.

b) This is the energy required to excite a atom from ground state to its excited state. When electrons jumps from ground state level(n=1) to 1st excited state(n=2) the corresponding energy is called 1st excitation potential energy and corresponding potential is called 1st excitation potential.

So, 1st excitation energy = E(n 2)- E(n = 1)

[tex]=-\frac{13.6}{2^{2}}-(-\frac{13.6}{1^{2}})\\=-3.4eV - (-13.6eV) \\=10.2eV[/tex]

Now we can find that 1st excitation energy is 10.2 eV which gives,

[tex]eV'=10.2eV\\V'=10.2V[/tex]

Therefore, the 1st excitation potential is 10.2V.

A rocket sled accelerates at 21.5 m/s^2 for 8.75 s. (a) What's its velocity at the end of that time? (b) How far has it traveled?

Answers

Answer:

(a ) vf= 188.12m/s  : Final speed at 8.75 s

(b) d= 823.04 m   : Distance the rocket sled traveled

Explanation:

Rocket sled kinematics :The rocket sled moves with a uniformly accelerated movement, then we apply the following formulas:

d =vi*t+1/2a*t² Formula (1)

vf= vi+at            Formula(2)

Where:

vi: initial speed =0

a: acceleration=21.5 m/s²

t: time=8.75 s

vf: final speed in m/s

d:displacement in meters(m)

Calculation of displacement (d) and final speed (vf)

We replace data in formulas (1) and (2):

d= 0+1/2*21.5*8.75²

d= 823.04 m

vf= 0+21.5*8.75

vf= 188.12m/s

A hot-air balloon is descending at a rate of 2.3 m/s when a pas- senger drops a camera. If the camera is 41 m above the ground when it is dropped, (a) how much time does it take for the cam- era to reach the ground, and (b) what is its velocity just before it lands? Let upward be the positive direction for this problem.

Answers

Answer:

a) time taken = 2.66 s

b) v = 28.34

Explanation:

given,

rate of descending = 2.3 m/s

height of camera above ground = 41 m              

using equation of motion                      

[tex]h = u t + \dfrac{1}{2}gt^2[/tex]              

[tex]41 =2.3t + \dfrac{1}{2}\times 9.8\times t^2[/tex]

4.9 t² + 2.3 t - 41 =0                      

t = 2.66 ,-3.13                    

time taken = 2.66 s

b) v² = u² + 2 g h

v² = 0 + 2× 9.8 × 41

v = 28.34                            

A Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds needs an initial speed of O 100 m/s. 60 m/s. 50 m/s 80 m/s. 110 m/s.

Answers

Answer:

The initial velocity of the ball should be 50 m/s.

Explanation:

Since the trip of the ball shall consist of upward ascend and the downward descend and since the ascend and the descend of the ball is symmetrical we infer that the upward ascend of the ball shall last for a time of 5 seconds.

Now since the motion of ball is uniformly accelerated we can find the initial speed of the ball using first equation of kinematics as

[tex]v=u+gt[/tex]

where,

'v' is final velocity of the ball

'u' is initial velocity of the ball

'g' is acceleration due to gravity

't' is the time of motion

Now we know that the ball will continue to ascend until it's velocity becomes zero hence to using the above equation we can write

[tex]0=u-9.81\times 5\\\\\therefore u=9.81\times 5=49.05m/s\approx 50m/s[/tex]

Tarzan, in one tree, sights Jane in another tree. He grabs
theend of a vine with length 20 m that makes an angle of 45
degreeswith the vertical, steps off his tree limb, and swings down
andthen up to Jane's open arms. When he arrives, his vine makesan
angle of 30 degrees with the vertical. determine whetherhe gives
her a tender embrace or knocks her off her limb bycalculating
Tarzan's speed just before he reaches Jane. Youcan ignore air
resistace and the mass of the vine.

Answers

Answer:

He knocks her. V = 7.97m/s

Explanation:

Let A be Tarzan's starting position and B Jane's position (Tarzan's final position).

Since there is no air resistance, energy at position A must be equal to energy at B.

At position A, Tarzan's speed is zero and since the 45° of the vine is greater than the final 30°, Tarzan will have potential energy at point A.

[tex]E_{A}=m_{T}*g*L*(cos(30)-cos(45))[/tex]

At point B, it is the lowest point (between A and B), so it has no potential energy. It will only have kinetic energy (ideally zero, for Jane's sake, but we don't know).

[tex]E_{B}=\frac{m_{T}*V^{2}}{2}[/tex]

Because of energy conservation, we know that Ea=Eb, so:

[tex]m_{T}*g*L*(cos(30)-cos(45))=\frac{m_{T}*V^{2}}{2}[/tex]  Solving for V:

[tex]V=\sqrt{2*g*L*(cos(30)-cos(45))}=7.97m/s[/tex]

Vesna Vulovic survived the longest fall on record without a parachute when her plane exploded and she fell 5 miles, 733 yards. What is this distance in meters?

Answers

Answer:

8717 meters.

Explanation:

We need to know the conversion factors. We know that:

1 mile = 1609.34 meters

1 yard = 0.9144 meters

This means that:

[tex]\frac{1609.34 meters}{1 mile}=1[/tex]

[tex]\frac{0.9144 meters}{1 yard}=1[/tex]

It is convenient to leave the units we want at the end in the numerator so the ones in the denominator cancel out with the ones we want to remove, as will be seen in the next step.

We will convert first the miles, then the yards, and add them up.

[tex]5miles=5miles\frac{1609.34 meters}{1 mile}=8046.7meters[/tex]

[tex]733yards=733yards\frac{0.9144 meters}{1 yard}=670.2552meters[/tex]

So total distance is the sum of these,  8717 meters.

Dry air will break down if the electric field exceeds 3.0*10^6 V/m. What amount of charge can be placed on a parallel-plate capacitor if the area of each plate is 73 cm^2?

Answers

Answer:

The charge on each plate of the capacitor is [tex]19.38 \mu C[/tex]

with one plate positive and one negative, i.e., [tex]\pm 19.38 \mu C[/tex]

Solution:

According to the question:

Critical value of Electric field, [tex]E_{c} = 3.0\times 10^{6} V/m[/tex]

Area of each plate of capacitor, [tex]A_{p} =73 cm^{2} = 73\times 10^{- 4} m^{2}[/tex]

Now, the amount of charge on the capacitor's plates can be calculated as:

Capacitance, C  = [tex]\frac{epsilon_{o}\times Area}{Distance, D}[/tex]        (1)

Also, Capacitance, C = [tex]\frac{charge, q}{Voltage, V}[/tex]

And

Electric field, E = [tex]\frac{Voltage, V}{D}[/tex]

So, from the above relations, we can write the eqn for charge, q as:

q = [tex]\epsilon_{o}\times E_{c}\times A_{p}[/tex]

q = [tex]8.85\times 10^{- 12}\times 3.0\times 10^{6}\times 73\times 10^{- 4}[/tex]

[tex]q = 19.38 \mu C[/tex]

a. How many atoms of helium gas fill a spherical balloon of diameter 29.6 cm at 19.0°C and 1.00 atm? b. What is the average kinetic energy of the helium atoms?
c. What is the rms speed of the helium atoms?

Answers

Answer:

a) 3.39 × 10²³ atoms

b) 6.04 × 10⁻²¹ J

c) 1349.35 m/s

Explanation:

Given:

Diameter of the balloon, d = 29.6 cm = 0.296 m

Temperature, T = 19.0° C = 19 + 273 = 292 K

Pressure, P = 1.00 atm = 1.013 × 10⁵ Pa

Volume of the balloon = [tex]\frac{4}{3}\pi(\frac{d}{2})^3[/tex]

or

Volume of the balloon = [tex]\frac{4}{3}\pi(\frac{0.296}{2})^3[/tex]

or

Volume of the balloon, V = 0.0135 m³

Now,

From the relation,

PV = nRT

where,

n is the number of moles

R is the ideal gas constant = 8.314  kg⋅m²/s²⋅K⋅mol

on substituting the respective values, we get

1.013 × 10⁵ × 0.0135 = n × 8.314 × 292

or

n = 0.563

1 mol = 6.022 × 10²³ atoms

Thus,

0.563 moles will have = 0.563 × 6.022 × 10²³ atoms = 3.39 × 10²³ atoms

b) Average kinetic energy = [tex]\frac{3}{2}\times K_BT[/tex]

where,

Boltzmann constant, [tex]K_B=1.3807\times10^{-23}J/K[/tex]

Average kinetic energy = [tex]\frac{3}{2}\times1.3807\times10^{-23}\times292[/tex]

or

Average kinetic energy = 6.04 × 10⁻²¹ J

c) rms speed = [tex]\frac{3RT}{m}[/tex]

where, m is the molar mass of the Helium = 0.004 Kg

or

rms speed = [tex]\frac{3\times8.314\times292}{0.004}[/tex]

or

rms speed = 1349.35 m/s

If a beam passes from a material with a refractive index of 1.3 into a material with a refractive index of 1.7 at an angle of 25 degrees (from normal), what is the angle of refraction of the beam? Is the beam bent towards normal or away from it? Sketch a diagram of this problem with rays, angles, and the interface labeled.

Answers

Answer:

18.86° , it will bend towards normal.

Explanation:

For refraction,

Using Snell's law as:

[tex]n_i\times {sin\theta_i}={n_r}\times{sin\theta_r}[/tex]

Where,  

[tex]{\theta_i}[/tex]  is the angle of incidence  ( 25.0° )

[tex]{\theta_r}[/tex] is the angle of refraction  ( ? )

[tex]{n_r}[/tex] is the refractive index of the refraction medium  (n=1.7)

[tex]{n_i}[/tex] is the refractive index of the incidence medium ( n=1.3)

Hence,  

[tex]1.3\times {sin\ 25.0^0}={1.7}\times{sin\theta_r}[/tex]

Angle of refraction = [tex]sin^{-1}0.3232[/tex] = 18.86°

Since, the light ray is travelling from a material with a refractive index of 1.3 into a material with a refractive index of 1.7 or lighter to denser medium, it will bend towards normal.

The diagram is shown below:

Draw, as best you can, what a velocity graph would look like as a function of time if the acceleration of the object is negative.

Answers

Answer:

Depends on the specific relation of acceleration as function of time, but it would always look like decresing or increasing negatively.

Explanation:

Acceleration is the derivative of velocity with respect to time. That means that it is the change. The fact that is negative means that it is decreasing, or increasing in the negative direction (i.e. going backwards faster).

Attached is the graph with constant negative acceleration, using kinematics relations, it would be a linear equation with negative slope.

Answer:a straight line with negative slope

Explanation:

A rocket fired two engines simultaneously. One produces a thrust 725 N directly forward while the other gives a 513N thrust at 32.4degrees above the forward direction. Find the magnitude and direction ( relative to the forward direction) of the resultant force that these engines exert on the rocket

Answers

Answer:

Magnitude of resultant force is  1190.314 N

Direction of force is 13.352°

Explanation:

given data:

thrust force = 725 N

Angle = 32.4 degree

Let x is consider as positive direction

Resultant force in x direction is  

Rx = 725 + 513cos32.4 = 1158.14 N

and Resultant force perpendicular to x direction is:

Ry = 513sin32.4 = 274.88 N

Magnitude of resultant force is

[tex]R=\sqrt{R_x^2+R_y^2} = 1190.314N[/tex]

and resultant force direction is  

[tex]\theta=tan^{-1}\frac{R_y}{R_x} = 13.352\degree[/tex]

Jack and Jill ran up the hill at 2.8 m/s . The horizontal component of Jill's velocity vector was 2.1 m/s . What was the angle of the hill?What was the vertical component of Jill's velocity?

Answers

Answer:[tex]\theta =41.409 ^{\circ}[/tex]

Explanation:

Given

Jack and Jill ran up the hill at 2.8 m/s

Horizontal component of Jill's velocity vector was 2.1 m/s

Let [tex]\theta [/tex]is the angle made by Jill's velocity with it's horizontal component

Therefore

[tex]2.8cos\theta =2.1[/tex]

[tex]cos\theta =\frac{2.1}{2.8}[/tex]

[tex]cos\theta =0.75[/tex]

[tex]\theta =41.409 ^{\circ}[/tex]

Vertical velocity is given by

[tex]V_y=2.8sin41.11=1.85 m/s[/tex]

Final answer:

The question can be solved using the Pythagorean theorem to calculate the vertical velocity component and apply trigonometry to find the angle of the hill. Remember the conversion from radians to degrees.

Explanation:

The question asks about the angle of the hill that Jack and Jill climbed, as well as the vertical component of Jill’s velocity. We know that Jill ran up the hill at a velocity of 2.8 m/s and the horizontal component of her velocity was 2.1 m/s. These two components form a right angle triangle where the hypotenuse is the total velocity (2.8 m/s), one side is the horizontal velocity (2.1 m/s), and the other side, which we're finding, is the vertical component of the velocity.

We can find the angle of the hill, θ, using the tangent function of trigonometry. Tan θ = opposite side / adjacent side. In this case, the 'opposite side' is the vertical velocity component we're after, and the 'adjacent side' is the horizontal component (2.1 m/s). To find the vertical velocity component, you can use the Pythagorean theorem, which states that: (Hypotenuse)² = (Adjacent Side)² + (Opposite Side)² or (2.8 m/s)² = (2.1 m/s)² + (vertical velocity)².

Once you solve for the vertical velocity through the Pythagorean theorem, you then insert it into the tangent equation to solve for the angle θ. Remember that when you use the arctangent function on a calculator to find the angle, the answer will likely be in radians, so you might need to convert them into degrees.

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Which of the following statements about electric field lines are true? (choose all that are true) a) They are only defined for positive charges.
b) They are always tangent to electric field vectors.
c) They are always perpendicular to charged surfaces.
d) They are a simple way to visualize the electric field vectors. e) None of the above.

Answers

Answer:  b) TRUE and d) TRUE

Explanation:  a) FALSE the electric field lines are used to represent the charges postives and negatives.

b) TRUE it is the definition of  electric field lines , they are tangent to the electric field vector.

c) FALSE  the electric field lines only for conductor are perpendicular to the surface in other any situation there is a tangencial electric field components.

d) TRUE since it is a way to describe and imagine the effect of vectorial fields.

e) FALSE

A boat’s speed in still water is 1.60 m/s . The boat is to travel directly across a river whose current has speed 1.05 m/s. Determine the speed of the boat with respect to the shore.
Express your answer using three significant figures and include the appropriate units

Answers

The speed of the boat with respect to the shore is 1.91 m/s.

From the information given, we have that;

A boat's speed in still water is 1.60 m/s

The boat is to travel directly across a river whose current has speed 1.05 m/s

We can see that the movement is in both horizontal and vertical directions.

Using the Pythagorean theorem, let use determine the resultant speed of the boat with respect to the shore, we have that;

Resultant speed² = √((boat's speed)² + (current's speed)²)

Substitute the value as given in the information, we have;

= (1.60)² + (1.05 )²)

Find the value of the squares, we get;

= (2.56 + 1.1025 )

Find the square root of both sides, we have;

=  √3.6625

Find the square root of the value, we have;

= 1.91 m/s.

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Which of the following would describe a length that is 2.0×10^-3 of a meter? a: 2.0 kilometers
b: 2.0 megameters
c: 2.0 millimeters
d: 2.0 micrometers

Answers

Answer:

Option (c) [tex]2\times 10^{-3}\ m=2\ millimeters[/tex]

Explanation:

Here, it is required to describe the given length in a particular unit. Firstly, we need to see the following conversions as :

1 meter = 0.001 kilometers

1 meter = 10⁻⁶ megameters

1 meter = 1000 millimeters

1 meter = 1000000 micrometers

From the given option, the correct one is (c) because, 1 meter = 1000 millimeters

So, [tex]2\times 10^{-3}\ m=2\ millimeters[/tex]

Hence, the correct option is (c). Hence, this is the required solution.

Final answer:

2.0×10^-3 of a meter is equivalent to 2.0 millimeters, hence option c is the correct answer.

Explanation:

The given length, 2.0×10^-3 of a meter, corresponds to a unit of length commonly used in the metric system. In this system, 1 meter is equal to 10^3 millimeters. Therefore, 2.0×10^-3 of a meter equates to 2.0 millimeters. This means the best answer from the provided options would be option c: 2.0 millimeters.

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