Work And Energy - Practice Test, Class 9 Science - Class 9 MCQ

Examples of Kinetic Energy:
There are several examples of kinetic energy that can help illustrate this concept. Some common examples include:
1. Moving Car:
- A moving car is a classic example of kinetic energy.
- As the car moves, it possesses energy due to its motion.
- This energy is known as kinetic energy.
- The faster the car moves, the more kinetic energy it has.
2. Charged Particle in an Electric Field:
- A charged particle moving in an electric field also possesses kinetic energy.
- The particle's motion and interaction with the electric field result in energy.
- This energy is again referred to as kinetic energy.
- The magnitude of the kinetic energy depends on the speed and charge of the particle.
3. Stretched Rubber Band just Released:
- When a rubber band is stretched and then released, it returns to its original shape.
- As it returns, it possesses kinetic energy due to its motion.
- The energy stored in the stretched rubber band is converted into kinetic energy as it moves.
4. All of the Above:
- All the examples mentioned above, i.e., a moving car, a charged particle in an electric field, and a stretched rubber band just released, exhibit kinetic energy.
- Kinetic energy is present in all cases where there is an object or particle in motion.
In conclusion, kinetic energy can be observed in various scenarios, including a moving car, a charged particle in an electric field, and a stretched rubber band just released. The energy associated with the motion of these objects or particles is referred to as kinetic energy.

Newton-meter is the SI unit of work.
Explanation:
- The SI unit of work is the newton-meter (N·m).
- Work is defined as the product of force and displacement in the direction of the force.
- The newton (N) is the SI unit of force, and the meter (m) is the SI unit of displacement.
- Therefore, when force is applied over a distance, the product of the force and the distance gives the amount of work done.
- The unit newton-meter represents the amount of work done when a force of one newton is applied over a distance of one meter in the direction of the force.
- The work done can also be expressed in joules (J), where 1 joule is equal to 1 newton-meter.
- In summary, the newton-meter is the SI unit of work, representing the amount of work done when a force of one newton is applied over a distance of one meter.

Potential Energy
Definition:
Potential energy is the energy possessed by an object due to its position or state.
Examples of Potential Energy:
D. Both B and C (A battery and a book resting on the table) are examples of potential energy.
Explanation:
The given options are:
A. A moving car: This is an example of kinetic energy, not potential energy. Kinetic energy is the energy possessed by a moving object.
B. A battery: A battery stores potential chemical energy. This energy is converted into electrical energy when the battery is used.
C. A book resting on the table: The book has potential energy due to its position above the ground. If the book were to fall, the potential energy would be converted into kinetic energy.
Therefore, options B and C (a battery and a book resting on the table) are examples of potential energy.
In conclusion:
Potential energy refers to the energy that an object possesses due to its position or state. In the given options, a battery and a book resting on the table are examples of potential energy.

The other name of Nm is joule.
Joule is the standard unit of energy in the International System of Units (SI). It is named after the English physicist James Prescott Joule, who contributed significantly to the study of energy and thermodynamics.
Explanation:
- The SI unit for energy is the joule (J), which is equivalent to one newton-meter (Nm).
- The newton-meter (Nm) is a derived unit that represents the amount of work done when a force of one newton is applied over a distance of one meter.
- The joule is used to measure various forms of energy, including mechanical, electrical, and thermal energy.
- In the context of electricity, the joule is used to measure the energy transferred by an electrical current. For example, when a battery delivers one joule of energy to a circuit, it means that one watt of power has been supplied for one second.
- The joule is also used to measure the energy content of food and fuels, as well as the energy released during chemical reactions.
- In summary, the other name for Nm is joule, which is the SI unit of energy and represents the work done when a force of one newton is applied over a distance of one meter.

Unit of kWh:
- The unit kWh stands for kilowatt-hour.
- It is a unit used to measure energy consumption or production.
- It is a derived unit of energy in the International System of Units (SI).
- The kilowatt-hour is defined as the amount of energy consumed or produced by a device with a power rating of one kilowatt over a period of one hour.
- It is commonly used to measure the electricity consumption of households, businesses, and industries.
- The unit is widely used by electric utilities to determine the energy usage for billing purposes.
Explanation of options:
A: Acceleration
- The unit of acceleration is meters per second squared (m/s^2).
B: Work
- The unit of work is the joule (J) or the foot-pound (ft-lb).
C: Power
- The unit of power is the watt (W), which is equal to one joule per second.
D: Energy
- The unit of energy is the kilowatt-hour (kWh).
- It represents the amount of work done or the amount of energy consumed or produced.
- It is used to measure the total energy usage or production over a period of time.
In summary:
- The unit kWh is used to measure energy consumption or production.
- It is not related to acceleration, work, or power.
- Therefore, the correct answer is D: energy.

Energy and Work
- Energy is defined as the ability to do work.
- Work is the transfer of energy that occurs when a force is applied to an object and it is displaced.
- The relationship between work, force, and displacement is given by the equation: Work = Force x Displacement.
Unit of Power
- Power is the rate at which work is done or energy is transferred.
- The unit of power is the watt (W), not the joule (J).
- The watt is defined as 1 joule of work done per second.
Explanation of Incorrect Option
- Option C states that the unit of power is the joule, which is incorrect.
- The joule is the unit of energy, not power.
- Power is measured in watts, which is the unit of work done per unit of time.
- Therefore, option C is not correct.
Correct Options
- Option A: Energy is the ability to do work, which is correct.
- Option B: Work can be expressed as Force x Displacement, which is correct.
- Option D: Power is the amount of work done per unit of time, which is correct.
Conclusion
- The correct answer is option C: unit of power is Joule.

Problem:
A body of mass 3 kg is dropped from a height of 1m. Find the kinetic energy of the body when it touches the ground.

To find the kinetic energy of the body when it touches the ground, we can use the principle of conservation of mechanical energy. The total mechanical energy of the body is the sum of its potential energy and kinetic energy.
Given:
Mass of the body, m = 3 kg
Height, h = 1 m
Step 1: Calculate Potential Energy:
Potential energy (PE) is given by the formula: PE = mgh
where m is the mass, g is the acceleration due to gravity (9.8 m/s²), and h is the height.
PE = 3 kg × 9.8 m/s² × 1 m
PE = 29.4 J
Step 2: Calculate Kinetic Energy:
The total mechanical energy (E) is the sum of potential energy (PE) and kinetic energy (KE).
E = PE + KE
Since the body is dropped from a height and there is no initial velocity, the initial kinetic energy is zero.
E = PE + 0
E = PE
Therefore, the kinetic energy of the body when it touches the ground is equal to its potential energy.
Answer:
The kinetic energy of the body when it touches the ground is 29.4 joules (J).
So, the correct answer is option B.

Problem:
Two objects of masses 1Kg and 3Kg have equal momentum. What is the ratio of their kinetic energies?

The formula for momentum is given by p = mv, where p is momentum, m is mass, and v is velocity.
Given that the momentum of both objects is equal, we can write:
p1 = p2
The kinetic energy of an object is given by the formula KE = 1/2mv^2.
Let's calculate the kinetic energies of the two objects individually:
For the first object (mass = 1 Kg):
KE1 = 1/2 * 1 * v1^2
For the second object (mass = 3 Kg):
KE2 = 1/2 * 3 * v2^2
Since the momentum is the same for both objects, we can write:
m1v1 = m2v2
Simplifying this equation, we get:
v1/v2 = m2/m1
v1/v2 = 3/1
v1/v2 = 3
Now, let's substitute this value in the kinetic energy equations:
For the first object (mass = 1 Kg):
KE1 = 1/2 * 1 * (3v2)^2
KE1 = 1/2 * 1 * 9v2^2
KE1 = 4.5v2^2
For the second object (mass = 3 Kg):
KE2 = 1/2 * 3 * v2^2
KE2 = 1.5v2^2
Now, let's calculate the ratio of their kinetic energies:
KE1/KE2 = (4.5v2^2)/(1.5v2^2)
KE1/KE2 = 3
Therefore, the ratio of their kinetic energies is 3:1. Hence, the correct answer is option A.

Potential Energy:
- When an object is in freefall, it experiences a gravitational force.
- As the object falls, its distance from the ground decreases, and hence its potential energy also decreases.
- The potential energy of the object is converted into kinetic energy as it falls.
Kinetic Energy:
- Kinetic energy is the energy possessed by an object due to its motion.
- As the object falls, its velocity increases, and hence its kinetic energy also increases.
- The kinetic energy of the object is directly proportional to the square of its velocity.
Sum of Potential and Kinetic Energies:
- The sum of potential and kinetic energies of the free-falling body remains constant.
- As the potential energy decreases, the kinetic energy increases by the same amount.
- This conservation of energy is known as the Law of Conservation of Energy.
- The total mechanical energy (sum of potential and kinetic energies) of the body remains fixed throughout the freefall.
Air Resistance Negligible:
- The given statement assumes that air resistance is negligible.
- In real-life scenarios, air resistance can affect the motion of the object and change the sum of potential and kinetic energies.
- However, if air resistance is negligible, the only significant force acting on the object is gravity, and the energy transformation between potential and kinetic energies remains constant.
Therefore, the correct answer is D: remains fixed.

Given:
Mass of the block, m = 1 kg
Vertical displacement, h = 1 m
The work done by the boy can be calculated using the formula:
Work (W) = Force (F) x Displacement (d) x cosθ
In this case, the force exerted by the boy is equal to the weight of the block, which can be calculated using the formula:
Weight (W) = mass (m) x acceleration due to gravity (g)
Where acceleration due to gravity, g = 9.8 m/s^2
So, the weight of the block is:
W = 1 kg x 9.8 m/s^2 = 9.8 N
Since the block is lifted vertically, the angle between the force and displacement is 0 degrees (cosθ = 1).
Therefore, the work done by the boy is:
W = 9.8 N x 1 m x cos 0° = 9.8 J
Hence, the work done by the boy is 9.8 J. Therefore, the correct answer is option C.

To determine which body has greater kinetic energy, we need to understand the relationship between momentum and kinetic energy.
1. Momentum: Momentum is the product of an object's mass and velocity. It is a vector quantity, meaning it has both magnitude and direction.
2. Kinetic Energy: Kinetic energy is the energy possessed by an object due to its motion. It depends on the mass and velocity of the object and is given by the equation KE = (1/2)mv^2, where m is the mass and v is the velocity.
Now, let's consider the given scenario where a light body and a heavy body have equal momenta.
3. Equal Momenta: If the light and heavy bodies have equal momenta, it means their product of mass and velocity is the same.
4. Comparing Kinetic Energy: Since kinetic energy depends on the mass and velocity of the object, we can compare the kinetic energy of the light and heavy bodies.
5. Light Body: The light body has a smaller mass compared to the heavy body. Therefore, to have the same momentum, the light body must have a higher velocity than the heavy body.
6. Kinetic Energy Comparison: As kinetic energy depends on the square of the velocity, the higher velocity of the light body results in a greater kinetic energy compared to the heavy body.
7. Conclusion: Thus, the light body has a greater kinetic energy than the heavy body when they have equal momenta.
Therefore, the answer is A: the light body.

The total energy of a body falling freely towards the Earth remains constant.
Explanation:
When a body falls freely towards the Earth, it experiences a constant gravitational force. The total energy of the body is the sum of its kinetic energy and potential energy.
1. Kinetic Energy: As the body falls freely, its velocity increases due to the acceleration caused by gravity. The kinetic energy of the body is directly proportional to the square of its velocity. Therefore, as the body falls, its kinetic energy increases.
2. Potential Energy: The potential energy of the body decreases as it falls towards the Earth. This is because the body moves closer to the Earth's center, reducing its distance from the Earth's surface. The potential energy is inversely proportional to the distance between the body and the Earth's center.
3. Total Energy: The total energy of the body is the sum of its kinetic energy and potential energy. While the kinetic energy increases, the potential energy decreases at the same rate. As a result, the total energy of the body remains constant throughout its free fall towards the Earth.
Therefore, the correct answer is C: remains constant.

Explanation:
When a car is accelerated on a level road, the potential energy of the car remains the same. This can be explained using the following points:
1. Potential energy is the energy possessed by an object due to its position or state. In the case of a car on a level road, the potential energy is directly related to its height from the ground.
2. The level road has a constant height from the ground, so the potential energy of the car remains constant throughout the acceleration process.
3. The change in velocity of the car does not affect its potential energy. Potential energy is only dependent on the height and the acceleration due to gravity, not the velocity.
4. The given information states that the car attains a velocity 4 times its initial velocity. This information is related to the kinetic energy of the car, not the potential energy.
5. Kinetic energy is the energy possessed by an object due to its motion, and it is directly proportional to the square of the velocity. So, if the velocity becomes 4 times the initial velocity, the kinetic energy increases by a factor of 16 (4^2).
6. In conclusion, the potential energy of the car does not change during the acceleration process on a level road. Therefore, the correct answer is option A: does not change.

Work done W = F.d cos 0
∴Work done at θ= 0°, W = F.d cos 0°                         (∴cos0° = 1)
 ⇒   W = F.d
For angle θ = 0°,
Work done Is positive, so it is not true.
(b) We know that work done, W = F .d cos 0

For angle 0 = 45°,
work done is positive, so it is not true.
(c) We know that work done, W = d cos θ
Work done at θ = 90°,      W = F.d cos 90°                                      (∴cos 90° = 0)
W = 0
So, it is not true.
(d) Work done at θ = 180°, W = F.d cosθ (∴ cos 180°= -1)
W = - F. d
For negative work, the angle between the force and displacement should be 180°. (/.e„ force and displacement are anti parallel to each other) So, it is true.

Yes, because acceleration of an object due to gravity, when under free fall, is not affected by it's mass as it's equation states and all bodies of varying mass and with same shape and size, fall with the same rate towards the Earth irrespective of their mass.

Problem:
A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a leveled road. The work done against the gravitational force will be (g =10 m s–2)

Given:
- Mass of the school bag = 3 kg
- Distance moved = 200 m
- Acceleration due to gravity (g) = 10 m/s–2
Formula:
The work done against the gravitational force is given by the formula:
Work = Force * Distance
Explanation:
The work done against the gravitational force is equal to the force required to lift the school bag to a height equal to the distance moved.
To calculate the work done against the gravitational force, we need to determine the force required to lift the school bag.
The force required to lift the school bag is given by the formula:
Force = Mass * Acceleration due to gravity
Substituting the given values:
Force = 3 kg * 10 m/s–2
Force = 30 N
Now, we can calculate the work done against the gravitational force using the formula:
Work = Force * Distance
Work = 30 N * 200 m
Work = 6000 Nm
Converting Nm to Joules (J):
1 J = 1 Nm
Work = 6000 J
Answer:
The work done against the gravitational force is 6000 J, which is equivalent to 6 × 10^3 J. Therefore, the correct answer is option A: 6 × 10^3 J.

Not the unit of energy:
A: joule
- The joule (J) is the SI unit of energy and is defined as the amount of work done when a force of one newton is applied over a displacement of one meter.
B: newton metre
- The newton metre (Nm) is also a unit of energy, often used interchangeably with the joule. It represents the work done when a force of one newton is applied over a displacement of one meter.
C: kilowatt
- Kilowatt (kW) is not a unit of energy, but a unit of power. It measures the rate at which energy is transferred or converted. One kilowatt is equal to 1000 watts.
D: kilowatt hour
- The kilowatt hour (kWh) is a unit of energy commonly used in electricity billing. It represents the amount of energy consumed or produced by a device with a power output of one kilowatt over a period of one hour.
Conclusion:
- The correct answer is C. Kilowatt is not a unit of energy, but a unit of power. The other options (A, B, and D) are all units of energy.

Explanation:
The work done on an object is defined as the product of the force applied on the object and the displacement of the object in the direction of the force. However, there are certain factors that do not affect the work done on the object.
Displacement:
- The work done on an object is directly proportional to its displacement.
- The greater the displacement, the greater the work done on the object.
- Therefore, the work done on an object does depend upon its displacement.
Force applied:
- The work done on an object is directly proportional to the force applied on it.
- The greater the force applied, the greater the work done on the object.
- Therefore, the work done on an object does depend upon the force applied.
Angle between force and displacement:
- The work done on an object is given by the equation: work = force * displacement * cos(theta), where theta is the angle between the force and displacement vectors.
- The cosine of the angle determines how much of the force is being applied in the direction of the displacement.
- Therefore, the work done on an object does depend upon the angle between force and displacement.
Initial velocity of the object:
- The initial velocity of the object does not affect the work done on it.
- Work is only dependent on the force applied and the displacement of the object.
- Therefore, the work done on an object does not depend upon its initial velocity.
Conclusion:
- The work done on an object depends on the displacement, force applied, and the angle between the force and displacement vectors.
- However, it does not depend on the initial velocity of the object.

Water stored in a dam possesses potential energy.

• Definition of potential energy: Potential energy is the energy possessed by an object due to its position or condition.


• Explanation: When water is stored in a dam, it is at a higher position compared to its natural state, such as a river or a reservoir. This elevation creates a potential energy imbalance.


• Gravitational potential energy: The potential energy in the water stored in a dam is a form of gravitational potential energy. The higher the water is stored above its natural state, the greater the potential energy it possesses.


• Conversion to other forms of energy: The potential energy stored in the water can be converted into other forms of energy, such as kinetic energy or electrical energy, depending on the design and purpose of the dam.


• Hydroelectric power generation: In the case of a hydroelectric dam, the potential energy in the stored water is converted into electrical energy through the use of turbines and generators.


• Importance of potential energy in dams: The potential energy stored in a dam allows for controlled release of water, enabling various uses such as irrigation, flood control, and power generation.

Therefore, the correct answer is D: potential energy.

When a body is falling from a height h and it has fallen a height h/2, it will possess a combination of potential and kinetic energy. Let's break down the solution:
1. Initial state:
- The body is at a height h, which means it has potential energy due to its position above the ground.
- The body does not have any kinetic energy as it is not in motion yet.
2. After falling a height h/2:
- The body has fallen halfway, so its new height is h/2.
- At this point, the body possesses both potential and kinetic energy.
3. Potential energy:
- The potential energy of an object at a certain height is given by the formula PE = mgh, where m is the mass of the body, g is the acceleration due to gravity, and h is the height.
- As the body falls from h to h/2, its potential energy decreases by half.
- So, at a height of h/2, the body will have half of its initial potential energy.
4. Kinetic energy:
- As the body falls, it gains kinetic energy due to its motion.
- The kinetic energy of an object is given by the formula KE = (1/2)mv^2, where m is the mass of the body and v is its velocity.
- When the body falls a height h/2, its velocity increases, and therefore, its kinetic energy also increases.
- So, at a height of h/2, the body will have more kinetic energy compared to its initial state.
5. Conclusion:
- After falling a height h/2, the body will possess both potential and kinetic energy.
- The potential energy will be half of its initial value, and the kinetic energy will be greater than its initial value.
- Therefore, the correct answer is option C: half potential and half kinetic energy.

Explanation:
Joule (J) and ergs (erg) are units of energy. They are related to each other through a conversion factor.
Conversion factor:
1 Joule (J) is equal to 10^7 ergs (erg).
Explanation:
To understand the relationship between Joule and erg, we need to know the conversion factor between them.
- 1 Joule (J) is equal to 10^7 ergs (erg).
- This means that 1 Joule is 10 million times larger than 1 erg.
- Similarly, 1 erg is 10^-7 Joules.
- So, the correct answer is option B: 1 erg = 10^-7 J.
Summary:
Joule (J) and ergs (erg) are related through a conversion factor. 1 Joule is equal to 10^7 ergs, and 1 erg is equal to 10^-7 Joules.

Potential and Kinetic Energies of a Freely Falling Body:
The sum total of potential and kinetic energies of a freely falling body remains the same when air resistance is negligible. Let's break down the explanation into key points:
1. Potential Energy:
- Potential energy is the energy possessed by an object due to its position or height relative to a reference point.
- In the case of a freely falling body, potential energy is directly proportional to the height from which the object falls. As the object falls, its potential energy decreases.
2. Kinetic Energy:
- Kinetic energy is the energy possessed by an object due to its motion.
- In the case of a freely falling body, kinetic energy is directly proportional to the velocity of the object. As the object falls, its velocity increases and hence its kinetic energy also increases.
3. Conservation of Mechanical Energy:
- When air resistance is negligible, the total mechanical energy of a system remains constant.
- The total mechanical energy of a system is the sum of potential energy and kinetic energy.
- According to the principle of conservation of mechanical energy, the total mechanical energy at any point will be equal to the total mechanical energy at any other point.
4. Negligible Air Resistance:
- When air resistance is negligible, it means that the effects of air resistance on the motion of the falling body can be ignored.
- In this case, the only external force acting on the body is the force due to gravity.
- Since the force due to gravity is a conservative force, the total mechanical energy of the system remains constant.
5. Conclusion:
- Due to the conservation of mechanical energy, the sum total of potential and kinetic energies of a freely falling body remains the same when air resistance is negligible.
- Therefore, the answer is option D: remains the same.

Physical Quantity: Power
Explanation:
Power is the physical quantity that is equal to the product of force and velocity. Power is a measure of how quickly work is done or how quickly energy is transferred.
- Power is defined as the rate at which work is done or energy is transferred. It represents the amount of work done per unit of time.
- Mathematically, power (P) is equal to the product of force (F) and velocity (v): P = F * v.
- Force is the push or pull applied to an object, and velocity is the rate at which an object changes its position.
- When a force is applied to an object and it moves with a certain velocity, work is done. Power measures how quickly this work is done.
- The unit of power is the watt (W), which is equal to one joule per second (1 W = 1 J/s).
- Power is an important concept in various fields, including physics, engineering, and everyday life.
- It is used to describe the performance of machines, the efficiency of energy conversion processes, and the consumption of electrical devices, among other applications.
In conclusion, the physical quantity that is equal to the product of force and velocity is power (C).

The potential energy of an object is given by the equation PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object.
Given that the mass of the object is 1 kg and the potential energy is 1 joule, we can use this equation to find the height.
1 joule = 1 kg * g * h
Solving for h:
h = 1 joule / (1 kg * g)
The acceleration due to gravity, g, is approximately 9.8 m/s^2.
So, h = 1 joule / (1 kg * 9.8 m/s^2) = 0.102 m
Therefore, the object has a potential energy of 1 joule when it is at a height of 0.102 m above the ground.
So, the correct answer is option A: 0.102 m.

K.E = 1/2 m v^2
1 = 1/2 * 1 * v^2
2 = v^2
v^2 = 2
v = √2
or
1.4m/s

To determine what properties the iron and aluminium spheres have in common when they are 10 m from the ground, we can analyze the following:
1. Acceleration:
- When an object is in free fall near the surface of the Earth, it experiences a constant acceleration due to gravity.
- The acceleration due to gravity is the same for all objects regardless of their mass or composition.
- Therefore, both the iron and aluminium spheres will have the same acceleration when they are 10 m from the ground.
- Therefore, the correct answer is A: acceleration.
2. Momentum:
- Momentum is defined as the product of an object's mass and velocity.
- Since the spheres are dropped simultaneously, they will have the same initial velocity.
- However, the iron sphere has a greater mass than the aluminium sphere.
- Therefore, they will have different momenta at any given point during their fall.
- Therefore, the correct answer is not B: momentum.
3. Potential Energy:
- Potential energy is the energy possessed by an object due to its position relative to other objects.
- The potential energy of an object in free fall depends on its mass, height, and the acceleration due to gravity.
- Since the spheres have different masses, they will have different potential energies at any given height.
- Therefore, the correct answer is not C: potential energy.
4. Kinetic Energy:
- Kinetic energy is the energy possessed by an object due to its motion.
- It is given by the equation KE = 0.5 * mass * velocity^2.
- Since the spheres are dropped simultaneously, they will have the same initial velocity.
- However, the iron sphere has a greater mass than the aluminium sphere.
- Therefore, they will have different kinetic energies at any given point during their fall.
- Therefore, the correct answer is not D: kinetic energy.
In conclusion, when the iron and aluminium spheres are 10 m from the ground, they have the same acceleration. Therefore, the correct answer is A: acceleration.

In a simple pendulum with no friction, mechanical energy is conserved. Total mechanical energy is a combination of kinetic energy and gravitational potential energy. As the pendulum swings back and forth, there is a constant exchange between kinetic energy and gravitational potential energy.

The potential energy of an object at a certain height is given by the formula PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height.
Given:
Mass of the man (m) = 50 kg
Height (h) = 1 m
Acceleration due to gravity (g) = 10 m/s^2
To calculate the potential energy at the highest point, we can use the formula:
PE = mgh
Substituting the given values:
PE = 50 kg * 10 m/s^2 * 1 m
Simplifying the equation:
PE = 500 J
Therefore, the potential energy of the man at the highest point is 500 J.
The correct answer is option C.

Conversion of 1.5 kW to watts:
To convert kilowatts (kW) to watts (W), we need to multiply the value by 1000.
Given that 1 kilowatt (kW) is equal to 1000 watts (W), we can calculate the conversion as follows:
1.5 kW * 1000 = 1500 W
Therefore, 1.5 kW is equal to 1500 watts.
Answer: A. 1500

Explanation:
When the speed of an object is doubled, its kinetic energy increases. This can be explained by the relationship between kinetic energy and speed, which is given by the equation:
Kinetic energy (KE) = (1/2) * mass * speed^2
To understand why the answer is option B (quadrupled), let's consider the following:
1. Initial kinetic energy:
- Let's assume the initial speed of the object is v.
- The initial kinetic energy (KE1) can be calculated using the equation mentioned above.
2. Doubling the speed:
- When the speed is doubled, the new speed becomes 2v.
- The new kinetic energy (KE2) can be calculated using the same equation.
3. Comparing the kinetic energies:
- Let's substitute the values in the equation for KE1 and KE2.
- KE1 = (1/2) * mass * v^2
- KE2 = (1/2) * mass * (2v)^2 = (1/2) * mass * 4v^2 = 2 * (1/2) * mass * v^2 = 2 * KE1
4. Conclusion:
- Comparing KE2 with KE1, we can see that KE2 is double the value of KE1.
- Therefore, when the speed of an object is doubled, its kinetic energy is quadrupled (option B).