A scientific theory

1)Holds the highest level of acceptance


2)Explains a number of facts


3)Uses specific hypotheses and descriptive laws that have been well-tested


4)All of the above


5)None of the above

Answer: C. both visible and invisible

Explanation:

Stars not only emit light in the visible range of the electromagnetic spectrum (what our eyes can see), they also emit light that is "invisible" to our eyes, because we do not have the receptors to perceive those frequencies.

In this sense, among this invisible range is ultraviolet light and infrared, for example.

Therefore, among the proposed options, the correct one is C:

Both visible and invisible

Answer:

2

Explanation:

The second payment method will be highly profitable.

We have a person who agreed to hire you for 30days. For the mode of payment he presented two offers to you - either $1000 a day or one penny on the first day, two pennies on the second day and continue to double your daily pay each day up to day 30.

We have to investigate which option will be the most profitable for you.

Your monthly pay will be = $500 x 30 = $15000

According to the question -

You selected first method of payment.

Therefore -  $1000 a day for 30 days will be = $30000

You selected second method of payment.

Now -

For day 1 → $1

For day 2 → $2

For day 3 → $4

For day 4 → $8

For day 5 → $16

and so on.

We will get the following series (till n = 30)

1 + 2 + 4 + 8 + 16 + ......

Now - this sequence is a Geometric progression. The sum of n terms of a GP is given by -

[tex]$S_{n} = \frac{a(1-r^{n)} }{1-r} \;\;\;(r\neq 1)[/tex]

Substituting values, we get -

[tex]$S_{30} = \frac{1(1-2^{30)} }{1-2}[/tex]

On solving, we get -

S(30) = $1,073,741,823

Hence, the second payment method will be highly profitable.

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Answer:

The time the ball it takes to have the downward speed 4 m/s is 1.22 sec.

Explanation:

Lets explain the motion of the ball

The ball is kicked straight upwards with an initial vertical speed of 8.0 m/s

Its velocity decreases util it reaches the maximum height

At the maximum height its velocity is equal to zero

Then it fall down to the ground

We can ignore air resistance

Lets find the time it takes the ball to reach the maximum height

The acceleration of gravity is -9.8 m/s²

The initial velocity is 8 m/s upward

The final velocity is zero

So lets use the rule v = u + gt, where v is the final velocity, u is the initial

velocity, g is the acceleration of gravity and t is the time

u = 8 , v = 0 , g = -9.8

Substitute these value in the equation above

0 = 8 - 9.8 t

Add 9.8 t for both sides

9.8 t = 8

Divide both sides by 9.8

t = 40/49 seconds

The ball falls withe initial velocity zero and increases to reach 4 m/s

The velocity 4 m/s is downward

The acceleration of gravity is 9.8 m/s²

By using the same rule

u = 0 , v = 4 , g = 9.8

4 = 0 + 9.8 t

4 = 9.8 t

Divide both sides by 9.8

t = 20/49

The time the ball it takes to have the downward speed 4 m/s is the sum

of the two times above

The time the ball it takes = [tex]\frac{40}{49}+\frac{20}{49}=\frac{60}{49}=1.22[/tex] seconds

The time the ball it takes to have the downward speed 4 m/s is 1.22 sec.

Answer:

Explanation:

a=v-u/t

v=final velocity

u=initial velocity

u=0(when a body starts from rest the initial velocity is 0)

v=100m/s

t=8s

a=100-0/8

=12.5m/s²

The statement that best describes gravitational force is as follows:

Thus, the correct option for this question is A.

Gravitational force may be defined as a phenomenon that involves the force of attraction that occurs between objects that have significant masses in the universe, especially the attraction of the earth's mass to bodies near its surface.

This specific type of force is always applied to objects that have mass. This force generally works by attracting the mass object towards its surface. It is a type of universal attractive force which is directly proportional to the product of the masses of two bodies.

But still it is considered as the weakest force that significantly operating in the nature.

Therefore, the correct option for this question is A.

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Explanation:

Given:

x₀ = 0 m

v₀ = 4.2 m/s

t = 11.6 s

a = 2.3 m/s²

Find: x

x = x₀ + v₀ t + ½ at²

x = 0 m + (4.2 m/s) (11.6 s) + ½ (2.3 m/s²) (11.6 s)²

x ≈ 203 m

Round as needed.

Answer:

[tex]-30m/s^{2}[/tex]

Explanation:

The first equation of motion given as,

v = u +at

Here, u is initial and v is final velocity and a is acceleration and t is time taken.

As per question car initial velocity, u = 90 m/s, final velocity, v =0 and time taken, t = 3.00 s.

Substituting these values in first equation of motion, we get

   0 = 90 m/s + a×3.00 s

or, [tex]a = \frac{-90m/s}{3.00s}[/tex]

            [tex]a=-30m/s^{2}[/tex]

Thus, the deacceleration of the car is [tex]-30m/s^{2}[/tex]

The acceleration of the car that goes from 90.0 m/s to a stop in 3.00s is -30.0 m/s².

The acceleration of the car can be calculated by using the equation:

Acceleratin = (final velocity - initial velocity) / time

= (0-90)/3

= -30.0 m/s².

Answer:

C. 125

Explanation:

Given:

y₀ = h m

v₀ = 0 m/s

a = -10 m/s²

@ t − 1, y = 9/25 h m

@ t, y = 0 m

Find: h

Use constant acceleration equation:

y = y₀ + v₀ t + ½ at²

@ t:

0 = h + (0) (t) + ½ (-10) t²

0 = h − 5 t²

h = 5 t²

@ t − 1:

9/25 h = h + (0) (t − 1) + ½ (-10) (t − 1)²

9/25 h = h − 5 (t − 1)²

9/25 h = h − 5 (t² − 2t + 1)

9/25 h = h − 5 t² + 10 t − 5

0 = 16/25 h − 5 t² + 10 t − 5

Substitute:

0 = 16/25 (5 t²) − 5 t² + 10 t − 5

0 = 16/25 t² − t² + 2 t − 1

0 = -9/25 t² + 2 t − 1

0 = 9 t² − 50 t + 25

0 = (t − 5) (9t − 5)

t = 5/9 or 5

Since t > 1, t = 5.

Solving for h:

h = 5 t²

h = 125

Answer:

Option D: 21.8 degrees

Explanation:

In a parallel RL circuit, the current in the resistor R and that in the inductor L are separated among themselves 90 degrees as illustrated in the attached image. In the image the current in the resistor is represented in orange, that of the inductor in blue, and the total current (vector addition of the previous two) is represented  in red, forming a certain angle (theta) with respect to the current in the resistor. The output voltage is the same as the input voltage as measured over the resistor R.

Therefore, the phase angle that separated output voltage and total current can be obtained using the fact that tan(phase angle) = [tex]\frac{I_l}{I_R} = \frac{x}{y} \frac{4}{10}[/tex], therefore the angle is the arctangent of 4/10:

[tex]arctang(\frac{4}{10} )= 21.801[/tex] degrees.

Answer:

The phase angle between voltage and current in a parallel [tex]RL[/tex] circuit is 21.8°

Explanation:

In this question  input voltage [tex]V_i_n[/tex]  across both the components, the resistor and inductor is same since it is  a  parallel [tex]RL[/tex] circuit.  

Current cross resistor [tex]I_R=10 mA[/tex]

Current across inductor [tex]I_L=2 mA[/tex]  

Inductive reactance [tex]X_L= \frac{ V_i_n}{I_L} = \frac{V_i_n}{(2 mA)}[/tex]

Resistance of the resistor [tex]R= \frac{V_i_n}{I_R} = \frac {V_i_n}{(10 mA)}[/tex][tex][/tex]

Phase angle between voltage and current ∅ [tex] =tan^-^1 R/X_L[/tex]

[tex]=tan^-^1 \frac{(V_i_n /10)}{(V_i_n /2)}=  tan^-^1 \ \frac{2}{10}=tan^-^1\ 0.4[/tex]

=21.8°

Answer:

Option D) Both B and C

Explanation:

A textbook is dropped from the 2nd story stairs and falls freely. When an object falls freely, the only force acting on it is the force of gravity which results in a constant acceleration of g. So, whenever an object falls freely, its acceleration will be constant and equal to g(9.8 m/s²). Therefore, the acceleration of the textbook will remain constant. Option C is a correct option.

Since, the acceleration is constant and equal to 9.8 m/s², this implies that with every second, the velocity of the textbook will increase by 9.8 m/s. Since initial velocity is 0, the velocity after 1st second would be 9.8 m/s so that the acceleration is constant and equal to 9.8 m/s². Similar, after 1 sec the velocity is 9.8 m/s, so the velocity after 2 seconds would be 19.6 m/s so that the acceleration is constant and equal to 9.8 m/s². This way, after every second the velocity of the textbook, and every free fall object, increases by 9.8 m/s in ideal cases. So, option B is also correct.

Therefore, Both B and C are correct for the given scenario.

The textbook is in free fall motion because it is falling (in motion) due to gravity alone

The changes that will be observed are;

The velocity increases and the acceleration remains constant

The correct option is; Both B & C

Reason:

The type of motion of a text book dropped from the second story stairs is known as free fall motion

The kinematic equation of the motion is v = u + g·t

Where;

v = The velocity of the textbook

u = The initial velocity of the textbook = 0 m/s

t = The time after which it is dropped

g = The constant acceleration due to gravity ≈ 9.81 m/s²

Which gives;

v = g·t

Therefore, the velocity of the textbook increases as the time of free fall increases while the acceleration, g remains constant at 9.81 m/s²

Therefore, the correct option is both B & C

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Melting tin and then cooling it into a mold is an example of reversible physical changes.

Explanation:

         When an object undergoes a change in size, state, or shape and not in their chemical compositions referred to as physical change. But chemical change occurs as a result of the change in substances composition. It also forms a new one by the combination/ breakage of one or more objects.

         In the case of making gold cube into two pieces, there is no possibility of getting the original state again even the physical change happens. Match burning and relighting and sodium plus chlorine forming table salt show chemical change. But in tin melting and cooling it to form mold is the physical change i.e changes in state(liquid to solid) and are reversible too.

Answer:

yes, melting tin and then cooling it into a mold

Explanation:

Which would show an example of how physical changes are reversible?

cutting a gold bar in two pieces and then putting the pieces next to each other

burning a match and then relighting it

melting tin and then cooling it into a mold

combining sodium and chlorine to make the new material of table salt

Answer:

Greatest ~ Corn Syrup, Seawater, Water, Oil, Gasoline ~ Least

Explanation:

Density (g/mL)

Corn Syrup: 1.4 g/mL

Seawater: 1.029 g/mL

Water: 0.997 g/mL

Oil: 0.93 g/mL

Gasoline: 0.7489 g/mL

We have that for a list from densest to least dense we have

From the question we are told

list these liquids from densest to least dense:

Generally

Density

This is simply defined as the ratio of mass to volume of a material or substance

Therefore

For a list from densest to least dense we have

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Answer:

1732.05 J

Explanation:

The man is doing 100N of force on the rope at an angle of 30° where he is pulling a box 20 meters across the floor.

Work is equal to the force exerted in the direction of motion multiplied by the distance.

Mathematically, Work=F×D×CosineФ

where F=force in newtons

D=displacement in meters

Ф=the angle between the force vector and the direction of motion

Substitute values in formula

Work=100×20×cosine 30°

Work=100×20×0.86602540378

Work=1732.05 J

Answer:

The average velocity is 50 km/h south

Explanation:

The average velocity of an object is its total displacement divided by

the total time taken.

That means it is the rate at which an object changes its position from

one place to another.

Average velocity is a vector quantity.

The SI unit is meters per second.

A bicycle that starts 100 km south and is 120 km south of town after

0.4 hour​.

The displacement = 120 - 100 = 20 km south

The time = 0.4 hour

The average velocity = [tex]\frac{D}{T}[/tex], where D is the displacement

and t is the time

The average velocity of the bicycle = [tex]\frac{20}{0.4}=50[/tex] km/h

The average velocity is 50 km/h south

If you want it in meter per second, change the kilometer to meter

and change the hour to seconds

1 km = 1000 m

1 hour = 60 × 60 = 3600 seconds

The average velocity of the bicycle = [tex]\frac{50(1000)}{3600}=13.89[/tex] m/s south

Answer:

Molecules are made up of atoms that are held together by chemical bonds. These bonds form as a result of the sharing or exchange of electrons among atoms. The atoms of certain elements readily bond with other atoms to form molecules. Examples of such elements are oxygen and chlorine.

Explanation:

A molecule forms from electrons shared between two atoms. The correct option is B.

Atoms join forces and engage in interaction to create molecules. To achieve a stable electron configuration, this frequently entails sharing electrons between atoms.

Covalent bonds, a sort of chemical bond, are made possible by this sharing of electrons.

The exchange of electrons between two atoms at their outermost energy levels, or valence shells, results in covalent bonds.

Atoms can acquire a more stable structure and fill their outermost energy levels by sharing electrons, just like the noble gases do.

The atoms can achieve a lower overall energy state thanks to this electron sharing, which makes the molecule more stable than the sum of its parts.

Thus, the correct option is B.

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Answer:

3. Mowing the lawn

Explanation:

Aerobic exercise is any type of cardiovascular conditioning.

Mowing the lawn is the only thing that is actively moving.

Answer:

3- MOWING THE LAWN

Explanation:

Mowing the lawn is an aerobic exercise because it is use on a daily basis. lawn mower is a machine that is used to cut grass surface.

Mowing the lawn help to burn calories and It is an exercise comparable to running.

Mowing the lawn by pushing it acts as a form of cardiovascular exercise which makes the heart and lungs work harder .

Mowing the lawn begin in the legs which build up strength and burn down calories from the constant movement and muscles in the lower back can also be worked by mowing the lawn.

Answer:

All of the above

Explanation:

Scientific theories are explanations of various well known facts. They are hypotheses that best explain a scientific phenomenon. More development of theories doesn’t make it acceptable.  

Instead they have to supported by the results of  several tests performed by employing proper scientific methods. It is only after several years of thorough scientific research a theory is accepted as the best explanation of a phenomenon. Unlike facts that are accepted as universal truths theories can be proven wrong over time .

Answer:

all of the above

Explanation:

Answer:

a=12

Explanation:

- add 13 to both sides

3/2a = 5+13

- multiply by 2/3

2/3 * 3/2 * a = 2/3 * 18

a = 12

Answer:

Diffusion is net movement of anything from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in concentration. The concept of diffusion is widely used in many fields, including physics, chemistry, biology, sociology, economics, and finance.

Explanation:

Diffusion is the passive transport of molecules from an area of higher concentration to an area of lower concentration until the same concentration is reached throughout a space. Only molecules that are soluble in the medium and can cross barriers will diffuse. Variations on diffusion include the processes of filtration and osmosis.

Diffusion is a process by which molecules disperse in space in response to differences in concentration. It is a passive transport process, requiring no energy, occurring naturally in various situations such as the dispersal of a sample of gas in a closed container. Molecules move from areas of higher concentration to areas of lower concentration until equilibrium is reached where concentrations are equal throughout.

A principle of diffusion is that only substances which are soluble and can cross the membrane will diffuse through it. This is seen, for example, in the process of osmosis, which is the diffusion of water through a concentration gradient in living systems.

Importantly, in living organisms, the rate of diffusion must match the rate of oxygen uptake and carbon dioxide removal for the process to work effectively.

There are variations to this process, such as filtration and facilitated transport, which also move substances in response to a concentration gradient but may be enhanced by other factors such as pressure.

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Answer:

9000 m

Explanation:

To calculate the distance traveled by cyclist, using the relation between distance, velocity and time as

d = v × t

Here, d is distance traveled, v is velocity and t is time taken.

We have, v = 30 m/s and t = 5 min = 5×60= 300 s.

Substituting these values in above formula we get

d = 30 m/s × 300 s

d = 9000 m.

Thus, the distance traveled by cyclist is 9000 m.

Answers:

a) 10 m

b) time=1.6 s, frquency=0.625 Hz

c) 6.25 m/s

Explanation:

a) If there is a crest at each dock and another three crests between the two docks, and the wavelength [tex]\lambda[/tex] is the distance between to crests; this means we have [tex]4\lambda[/tex] in [tex]40 m[/tex]:

[tex]40 m=4\lambda[/tex]

Clearing [tex]\lambda[/tex]:

[tex]\lambda=\frac{40 m}{4}[/tex]

[tex]\lambda=10 m[/tex]

b) This part can be solved by a Rule of Three:

If 10 waves ---- 16 s

1 wave ----- [tex]T[/tex]

Then:

[tex]T=\frac{(1 wave)(16 s)}{10 waves}[/tex]

[tex]T=1.6 s[/tex] This is the period of the wave

On the other hand, the frequency [tex]f[/tex] of the wave has an inverse relation with its period [tex]T[/tex]:

[tex]f=\frac{1}{T}[/tex]

[tex]f=\frac{1}{1.6 s}[/tex]

[tex]f=0.625 Hz[/tex] This is the frequency of the wave

c) The speed [tex]v[/tex] of a wave is given by the following equation:

[tex]v=\frac{\lambda}{T}[/tex]

[tex]v=\frac{10 m}{1.6 s}[/tex]

Finally:

[tex]v=6.25 m/s[/tex]

Answer:

60 km an hour. If you travel 10 miles in 10 mins there are 60 minutes in an hour so your traveling 60 miles an hour

Explanation:

The speed of the truck is 16.67 m/s

To calculate the speed of the truck, we can use the following formula:

speed = distance ÷ time

In SI notation, we denote speed in meters per second.

So, we convert 10 km to meters (1 km = 1000 m)

⇒ (10 × 1000) m = 10000 m

Now, we convert 10 minutes to seconds (1 minute = 60 seconds)

⇒ (10 × 60) s = 600 s

∴ speed = 10000 m ÷ 600 s = 16.67 m/s

Answer:

A waffle iron heated by coils

Explanation:

A waffle iron heated by coils - conduction

Food heated in a microwave oven - radiation

Pavement heated by the sun - radiation

A room heated by moving air - convection

The final speed of the boat is 24m/s. This is found by multiplying 1.5 by 10, then adding that number to the original speed, 9.

If you need more help, comment below and I'd be happy to assist.

Answer:

Weight of the suitcase, W = 220.5 N

Explanation:

It is given that,

Mass of the suitcase, m = 22.5 kg

Let W is the weight of the suitcase. The weight of an object is equal to the force acting on it due to the gravity. It is given by the product of mass and acceleration due to gravity.Mathematically, it is given by :

W = mg

[tex]W=22.5\times 9.8[/tex]

W = 220.5 N          

So, the weight of the suitcase is 220.5 N. Hence, this is the required solution.              

The weight of the suitcase is 220.5 Newton.

Given the following data:

We know that acceleration due to gravity (a) for an object is equal to 9.8 meter per seconds square.

To find how much this suitcase weigh, we would determine the weight of the suitcase by using the value of its mass.

Mathematically, the weight of an object is calculated by using the formula;

[tex]Weight = mg[/tex]

Where:

Substituting the values into the formula, we have;

[tex]Weight = 22.5[/tex] × [tex]9.8[/tex]

Weight = 220.5 Newton.

Therefore, the weight of the suitcase is 220.5 Newton.

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The focus of community psychology is to improve the quality of one’s life through prevention and second order change.  

Explanation:

             Community psychology travels beyond an individual approach and integrates “social, cultural, environmental and international influences” to promote positive change. Additionally, it makes health and personal responsibility at the individual and system levels. It uses different psychological and external perspectives to address the attitudes and behavior of communities, their relationships and the people involved.  

             Community psychologists try to promote healthy and empowering groups and communities. They use concepts and knowledge from various disciplines, such as social, ecology, and intercultural psychology. Second-order change means paying attention to the system and structures that are involved in the problem to suit the human-environment good.  

Answer:

Avoidance-Avoidance

Explanation:

You don't want either, but you have to pick one.  

Final answer:

The type of conflict that you would likely experience when having to choose between being unemployed and accepting a job you do not like is called an intrapersonal conflict.

Explanation:

The type of conflict that you would likely experience when having to choose between being unemployed and accepting a job you do not like is called an intrapersonal conflict. This type of conflict occurs within an individual when they have conflicting desires or goals. In this case, you may have the desire to be employed and financially stable, but also the desire to find a job that you enjoy and are passionate about.

Answer:

The distance covered by the rocket after fuel ran out is [tex]3442.04 m[/tex]

Explanation:

Given that the rocket moves with an acceleration [tex]a=30m/s^2[/tex]

time [tex]t=5 s[/tex]

Since the rocket starts from rest initial velocity  [tex]u=0 s[/tex]

The distance it travelled within this time is given by  [tex]s=ut+ \frac{1}{2} at^2[/tex]                                                                                                  [tex]=0 \times 5+ \frac{1}{2} (30\times25)=375 m[/tex]

Velocity at this point is given by [tex]v=u+at[/tex]

[tex]v=0+30\times5=150m/s[/tex]

Given that at this height it runs out of fuel but travels further. Here final velocity [tex]v=0[/tex](maximum height), initial velocity[tex]u=150 m/s[/tex]  and time to zero velocity [tex]t=\frac{v}{g} = \frac{150}{9.8} =15.3 s.[/tex]

Thus it travels [tex]15.3 seconds[/tex] more after fuel running out. The distance covered during this period is given

[tex]s= ut+\frac{1}{2} gt^2=150 \times 15.3+1/2 \times9.8 \times 15.3^2=3442.04 m[/tex]

Answer:

26 m/s

Explanation: