Work and Energy

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CBSE Learning Objectives – Key Concepts & Skills You Must Know

Understand the concept of work and energy.
Calculate work done on an object to bring it to rest.
Analyze energy transformations in various scenarios.
Apply the law of conservation of energy in practical examples.
Differentiate between kinetic and potential energy.
Evaluate the work done by gravitational force on objects.
Discuss the implications of energy transfer in mechanical systems.
Solve problems involving energy consumption in electrical devices.

CBSE Revision Notes & Quick Summary for Last-Minute Study

Notes on Work and Energy

Concepts of Work and Energy

Work is defined as the product of force and displacement.
- Formula: Work done (W) = Force (F) × Displacement (s)

Energy Transformations

Energy can transform from one form to another, such as:
- Kinetic energy to potential energy and vice versa.
- Example: A pendulum bob oscillating demonstrates energy conversion between kinetic and potential energy.

Calculations

Work Required to Stop an Object:
- An object of mass, m, moving with a constant velocity, V, requires work to bring it to rest.
- Example: Calculate the work required to stop a car of 1500 kg moving at 60 km/h.
Energy Consumption:
- Calculate energy consumed by devices over time.
- Example: Four devices of power 500 W each consume energy in 10 hours.
Potential Energy Calculation:
- Potential energy (Eₚ) = mgh, where m is mass, g is acceleration due to gravity, and h is height.
- Example: A 40 kg object raised to a height of 5 m has a potential energy calculated as follows:
  - Eₚ = 40 kg × 9.81 m/s² × 5 m

Work Done by Forces

The work done by a force can be positive, negative, or zero depending on the direction of the force relative to displacement.
- Example: Analyze diagrams showing forces acting on objects to determine the nature of work done.

Common Scenarios

Free Fall: A freely falling object stops upon reaching the ground; its kinetic energy is transformed into other forms.
Energy Transfer: Discuss energy transfer when pushing an immovable object; energy expended does not result in displacement.

Important Diagrams

Work Done Diagram: Shows a block on a table with force applied and displacement indicated.
- Equation: W = F × s
Potential Energy Diagram: Illustrates a cube at height h with gravitational force acting on it.
Path Diagrams: Two paths from point A to B demonstrating different work done based on the path taken.

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Misunderstanding Work Done: Students often confuse the concept of work done with energy. Remember, work is only done when there is displacement in the direction of the force.
Ignoring Direction of Forces: When calculating work, the direction of the force relative to the displacement is crucial. If the force and displacement are in opposite directions, the work done is negative.
Confusing Potential and Kinetic Energy: Students may mix up potential energy (energy due to position) and kinetic energy (energy due to motion). Ensure you understand the conditions under which each type of energy is calculated.
Forgetting Units: Always include units in calculations. For example, energy should be expressed in joules (J).
Neglecting the Law of Conservation of Energy: Some students may mistakenly believe that energy can be created or destroyed. Always remember that energy can only be transformed from one form to another.

Exam Tips

Read Questions Carefully: Ensure you understand what is being asked before attempting to answer. Look for keywords that indicate whether you need to calculate work, energy, or forces.
Draw Diagrams: Visual aids can help clarify problems involving forces and motion. Sketching the scenario can provide insights into the relationships between different elements.
Practice Calculations: Familiarize yourself with common formulas, such as work done (W = F × s) and energy equations (Eₚ = mgh, Eₖ = mv²/2). Practice applying these in various contexts.
Discuss Concepts: Engage in discussions with peers or teachers about concepts like energy transformations and forces acting on objects. This can solidify your understanding and reveal any misconceptions.

CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions

Multiple Choice Questions

3 m/s

4 m/s

5 m/s

6 m/s

Correct Answer: B

Solution:

The work done on the block is converted into kinetic energy. The work done (W) is given by:

W = F \times d = 20 \text{ N} \times 3 \text{ m} = 60 \text{ J}

This work done is equal to the kinetic energy (KE) of the block:

KE = \frac{1}{2}mv^2

Set the work done equal to the kinetic energy:

60 = \frac{1}{2} \times 5 \times v^2

Solve for

v

v^2 = \frac{60 \times 2}{5} = 24

v = \sqrt{24} \approx 4.9 \text{ m/s}

The closest option is 4 m/s, which is option b.

Energy can be created and destroyed.

Energy can only be transformed from one form to another.

The total energy of a system can increase over time.

Energy transformations always result in energy loss.

Correct Answer: B

Solution:

According to the law of conservation of energy, energy can only be transformed from one form to another; it can neither be created nor destroyed.

Zero

Equal to the force applied

Equal to the force times the distance

Infinite

Correct Answer: A

Solution:

Work done is zero if there is no displacement of the object, even if a force is applied.

Positive

Negative

Zero

Undefined

Correct Answer: A

Solution:

Work done is positive when the force applied on an object causes it to move in the direction of the force.

It remains the same.

It doubles.

It quadruples.

It increases eightfold.

Correct Answer: C

Solution:

The kinetic energy

E_k

of the wind is given by

E_k = \frac{1}{2} m v^2

, where

m

is the mass of the air and

v

is the wind speed. If the wind speed doubles, the kinetic energy becomes

E_k = \frac{1}{2} m (2v)^2 = 4 \times \frac{1}{2} m v^2

, meaning it quadruples. Thus, the correct answer is that it quadruples.

\frac{1}{2} m V^2

m V^2

\frac{1}{2} m V

m V

Correct Answer: A

Solution:

The work done to bring an object to rest is equal to the kinetic energy of the object, which is given by

\frac{1}{2} m V^2

2 m

3 m

4 m

5 m

Correct Answer: C

Solution:

Given the potential energy

E_p = mgh

, we have

480 = 12 \times 10 \times h

. Solving for

h

gives

h = 4 \text{ m}

Work is done when a force is applied, regardless of displacement.

Work is done only when there is displacement in the direction of the force.

Work is done when an object is held stationary against gravity.

Work is done when energy is expended, regardless of movement.

Correct Answer: B

Solution:

According to the scientific definition, work is done when a force causes displacement in the direction of the force.

A ball thrown upwards slows down, stops, and then falls back down, gaining speed.

A car accelerates on a flat road, gaining kinetic energy without any energy input.

A light bulb glows without consuming any electrical energy.

A pendulum swings indefinitely without any external force or energy input.

Correct Answer: A

Solution:

The law of conservation of energy states that energy cannot be created or destroyed, only transformed. In option (a), the ball's kinetic energy is converted to potential energy as it rises and then back to kinetic energy as it falls, illustrating energy transformation. Options (b), (c), and (d) imply energy creation or perpetual motion, which violate the law.

50 J

25 J

75 J

100 J

Correct Answer: A

Solution:

Work done is calculated by the formula

W = F \times s

, where

F

is the force and

s

is the displacement. Here,

W = 10 \text{ N} \times 5 \text{ m} = 50 \text{ J}

300 W

30 W

3000 W

3 W

Correct Answer: A

Solution:

Power is defined as the rate of doing work. It is given by

P = \frac{W}{t}

, where

W

is work and

t

is time. Substituting the given values,

P = \frac{3000}{10} = 300

50 J

10 J

5 J

0 J

Correct Answer: A

Solution:

Work done is calculated using the formula:

W = F \times s

. Here,

F = 10 \text{ N}

and

s = 5 \text{ m}

. Therefore,

W = 10 \times 5 = 50 \text{ J}

150,000 J

300,000 J

30,000 J

15,000 J

Correct Answer: B

Solution:

The kinetic energy is given by

KE = \frac{1}{2}mv^2 = \frac{1}{2} \times 1500 \times 20^2 = 300,000 \text{ J}

125,000 J

150,000 J

250,000 J

300,000 J

Correct Answer: C

Solution:

First, convert the velocity from km/h to m/s:

60 \text{ km/h} = 16.67 \text{ m/s}

. The work done to stop the car is equal to its kinetic energy:

\frac{1}{2} \times 1500 \times (16.67)^2 = 208,335.75 \approx 250,000 \text{ J}

30 J

10 J

3 J

0 J

Correct Answer: A

Solution:

Work done is calculated as

W = F \times s = 10 \times 3 = 30 \text{ J}

9.8 m/s²

10 m/s²

9 m/s²

8 m/s²

Correct Answer: B

Solution:

The gravitational potential energy

E_p

is given by

E_p = mgh

. Substituting the given values,

500 = 10 \times g \times 5

. Solving for

g

, we get

g = 10

m/s².

Work is done only when there is displacement in the direction of the force.

Work is done whenever a force is applied, regardless of displacement.

Work is done only if the object moves in the opposite direction of the force.

Work is done only when the object is stationary.

Correct Answer: A

Solution:

In physics, work is defined as the product of the force applied and the displacement in the direction of the force. If there is no displacement, no work is done.

56 J

15 J

64 J

0 J

Correct Answer: A

Solution:

Work done is calculated as the product of force and displacement:

W = F \times s = 7 \times 8 = 56 \text{ J}

588 J

600 J

500 J

480 J

Correct Answer: A

Solution:

Potential energy

E_p

is calculated using the formula:

E_p = mgh

where

m

is the mass,

g

is the acceleration due to gravity, and

h

is the height. Here,

E_p = 12 \text{ kg} \times 9.8 \text{ m/s}^2 \times 5 \text{ m} = 588 \text{ J}

Yes, because the forces can be balanced.

No, any force will cause acceleration.

Yes, because acceleration is independent of force.

No, zero acceleration means no forces are acting.

Correct Answer: A

Solution:

Soni is correct because if the forces are balanced, the net force is zero, resulting in zero acceleration.

125,000 J

150,000 J

200,000 J

250,000 J

Correct Answer: A

Solution:

The work required to stop the car is equal to its kinetic energy. Convert the velocity to m/s: 60 km/h = 16.67 m/s. Kinetic energy,

E_k = \frac{1}{2}mv^2 = \frac{1}{2} \times 1500 \times (16.67)^2 = 125,000 \text{ J}

200 J

400 J

800 J

1600 J

Correct Answer: C

Solution:

The kinetic energy,

KE

, of an object is given by:

KE = \frac{1}{2}mv^2

where

m = 8 \text{ kg}

and

v = 10 \text{ m/s}

. Thus,

KE = \frac{1}{2} \times 8 \times (10)^2 = 400 \text{ J}.

It is destroyed.

It is converted into potential energy.

It is converted into other forms of energy, such as heat and sound.

It remains as kinetic energy.

Correct Answer: C

Solution:

When a freely falling object reaches the ground, its kinetic energy is converted into other forms of energy, such as heat and sound.

5 J

10 J

15 J

20 J

Correct Answer: B

Solution:

Work done is calculated as the product of force and displacement:

W = F \times s = 5 \times 2 = 10 \text{ J}

450,000 J

900,000 J

300,000 J

600,000 J

Correct Answer: A

Solution:

The kinetic energy

K

of an object is given by the formula:

K = \frac{1}{2} m v^2

where

m

is the mass and

v

is the velocity. Here,

m = 1000 \text{ kg}

and

v = 30 \text{ m/s}

. Therefore,

K = \frac{1}{2} \times 1000 \times 30^2 = 450,000 \text{ J}

Lifting a book vertically upwards.

Holding a book stationary at a height.

Pushing against a wall without moving it.

Carrying a book horizontally at constant speed.

Correct Answer: A

Solution:

Positive work is done when a force causes displacement in the direction of the force. Lifting a book vertically upwards involves displacement in the direction of the applied force (upwards), hence positive work is done.

250 J

500 J

50 J

100 J

Correct Answer: A

Solution:

The work done on an object is calculated using the formula:

W = F \times s

where

F

is the force applied and

s

is the displacement. Here,

W = 50 \text{ N} \times 5 \text{ m} = 250 \text{ J}

Potential energy to kinetic energy

Kinetic energy to potential energy

Chemical energy to thermal energy

Thermal energy to chemical energy

Correct Answer: A

Solution:

When the toy car is wound, potential energy is stored in the spring. Upon release, this potential energy is converted into kinetic energy.

150,000 J

300,000 J

600,000 J

30,000 J

Correct Answer: B

Solution:

The kinetic energy

E_k

of an object is given by the formula:

E_k = \frac{1}{2} m v^2

where

m

is the mass and

v

is the velocity. Here,

E_k = \frac{1}{2} \times 1500 \text{ kg} \times (20 \text{ m/s})^2 = 300,000 \text{ J}

A car moving at a constant velocity on a straight road.

A ball thrown vertically upwards.

A satellite orbiting Earth in a circular path.

A book sliding down an inclined plane.

Correct Answer: A

Solution:

An object can have zero acceleration if it is moving with constant velocity, which means the net force acting on it is zero. In option (a), the car is moving at a constant velocity, indicating balanced forces and zero acceleration.

It is destroyed.

It is converted into potential energy.

It is converted into other forms of energy, like heat and sound.

It remains as kinetic energy.

Correct Answer: C

Solution:

When a freely falling object hits the ground, its kinetic energy is transformed into other forms of energy, such as heat and sound.

240 J

360 J

480 J

600 J

Correct Answer: C

Solution:

Potential energy is given by the formula

E_p = mgh = 12 \times 10 \times 4 = 480 \text{ J}

500 J

50 J

100 J

1000 J

Correct Answer: A

Solution:

The potential energy is given by

E_p = mgh = 10 \times 10 \times 5 = 500 \text{ J}

Yes, because the person exerted a force.

No, because there was no displacement of the wall.

Yes, because the person got tired.

No, because the force was not enough.

Correct Answer: B

Solution:

In science, work is done only when there is displacement in the direction of the force. Since the wall did not move, no work was done.

56 J

15 J

7 J

0 J

Correct Answer: A

Solution:

Work done is calculated using the formula:

W = F \times s

. Here,

F = 7 \text{ N}

and

s = 8 \text{ m}

. Therefore,

W = 7 \times 8 = 56 \text{ J}

1000 J

2000 J

500 J

1500 J

Correct Answer: A

Solution:

The kinetic energy

E_k

is given by

E_k = \frac{1}{2} mv^2

. Substituting the given values,

E_k = \frac{1}{2} \times 20 \times (10)^2 = 1000

125,000 J

150,000 J

200,000 J

250,000 J

Correct Answer: A

Solution:

To stop the car, the work done is equal to the initial kinetic energy of the car. The kinetic energy,

KE

, is given by the formula:

KE = \frac{1}{2}mv^2

where

m = 1500 \text{ kg}

and

v = 60 \text{ km/h} = \frac{60 \times 1000}{3600} \text{ m/s} = 16.67 \text{ m/s}

. Thus,

KE = \frac{1}{2} \times 1500 \times (16.67)^2 = 125,000 \text{ J}.

Yes, because the forces can balance each other out.

No, because forces always cause acceleration.

Yes, because acceleration is independent of forces.

No, because zero acceleration means no forces are acting.

Correct Answer: A

Solution:

Acceleration can be zero if the net force acting on an object is zero, meaning all the forces balance each other out.

50 J

100 J

10 J

200 J

Correct Answer: B

Solution:

Potential energy is given by the formula

E_p = mgh

. Substituting the values,

E_p = 5 \times 10 \times 2 = 100

Kinetic energy

Potential energy

Thermal energy

Chemical energy

Correct Answer: B

Solution:

The energy stored in the toy car when it is wound up is potential energy, which is converted to kinetic energy when the car is released.

60 J

100 J

80 J

120 J

Correct Answer: A

Solution:

The work done on an object is calculated using the formula:

W = F \times s

where

F

is the force applied and

s

is the displacement. Here,

F = 20 \text{ N}

and

s = 3 \text{ m}

. Therefore,

W = 20 \times 3 = 60 \text{ J}

A person pushing a wall with no displacement.

A car moving on a highway.

A book falling off a table.

A windmill lifting water from a well.

Correct Answer: A

Solution:

According to the scientific definition of work, work is done when a force causes displacement. In option (a), there is no displacement, so the work done is zero.

25 J

50 J

75 J

100 J

Correct Answer: B

Solution:

The potential energy

U

stored in a compressed or stretched spring is given by:

U = \frac{1}{2} k x^2

where

k

is the spring constant and

x

is the displacement. Here,

k = 200 \text{ N/m}

and

x = 0.5 \text{ m}

. Therefore,

U = \frac{1}{2} \times 200 \times (0.5)^2 = 50 \text{ J}

Energy can be created and destroyed.

Energy can only be transformed from one form to another.

The total energy of a system can increase over time.

Energy is always lost during transformations.

Correct Answer: B

Solution:

According to the law of conservation of energy, energy can only be transformed from one form to another; it can neither be created nor destroyed. Therefore, option B is correct.

\frac{1}{2} m V^2

mgh

mg

\frac{1}{2} V^2

Correct Answer: A

Solution:

The kinetic energy of an object is given by the formula

\frac{1}{2} m V^2

490 J

50 J

98 J

980 J

Correct Answer: A

Solution:

The potential energy gained by an object is given by the formula:

E_p = mgh

, where

m

is the mass,

g

is the acceleration due to gravity, and

h

is the height. Here,

E_p = 10 \text{ kg} \times 9.8 \text{ m/s}^2 \times 5 \text{ m} = 490 \text{ J}

72,000 J

180,000 J

7,200,000 J

18,000,000 J

Correct Answer: D

Solution:

Total power = 4 devices \times 500 W = 2000 W. Energy consumed = Power \times Time = 2000 W \times 10 \times 3600 s = 72,000,000 J.

980 J

1960 J

490 J

1470 J

Correct Answer: B

Solution:

The gravitational potential energy

E_p

is given by the formula:

E_p = mgh

where

m

is the mass,

g

is the acceleration due to gravity, and

h

is the height. Here,

m = 10 \text{ kg}

g = 9.8 \text{ m/s}^2

, and

h = 10 \text{ m}

. Therefore,

E_p = 10 \times 9.8 \times 10 = 980 \times 2 = 1960 \text{ J}

490 J

980 J

196 J

245 J

Correct Answer: B

Solution:

The work done against gravity is given by the formula:

W = mgh

where

m = 10 \text{ kg}

g = 9.8 \text{ m/s}^2

, and

h = 5 \text{ m}

. Thus,

W = 10 \times 9.8 \times 5 = 490 \text{ J}.

Energy can be created or destroyed.

Energy can only be converted from one form to another.

Energy conversion always results in energy loss.

Energy conversion is not possible.

Correct Answer: B

Solution:

According to the law of conservation of energy, energy can only be converted from one form to another; it can neither be created nor destroyed.

45 J

30 J

60 J

15 J

Correct Answer: A

Solution:

Work done is calculated as

W = F \times s

, where

F

is the force and

s

is the displacement. Here,

W = 15 \text{ N} \times 3 \text{ m} = 45 \text{ J}

When a force acts on an object and it moves in the direction of the force.

When a force acts on an object regardless of its movement.

Only when the object moves at a constant speed.

Only when the object is lifted vertically.

Correct Answer: A

Solution:

According to the scientific definition, work is done when a force acts on an object and the object is displaced in the direction of the force.

10 J

5 J

15 J

20 J

Correct Answer: A

Solution:

Work done is calculated as the product of force and displacement. Therefore, work done = 5 N \times 2 m = 10 J.

Holding a heavy box without moving

Pushing a wall that does not move

Lifting a book from the floor to a table

Standing still with a bag on your back

Correct Answer: C

Solution:

Work is done when a force causes displacement. Lifting a book involves both force and displacement.

Holding a heavy box without moving

Pushing a car that doesn't move

Lifting a book from the floor to a table

Standing still with a backpack

Correct Answer: C

Solution:

According to the scientific definition, work is done when a force causes displacement. Lifting a book involves applying a force that causes the book to move, thus doing work.

4 J

8 J

10 J

12 J

Correct Answer: B

Solution:

The potential energy stored in a spring is given by the formula:

PE = \frac{1}{2}kx^2

where

k

is the spring constant and

x

is the compression distance. Substituting the given values:

PE = \frac{1}{2} \times 200 \times (0.2)^2 = \frac{1}{2} \times 200 \times 0.04 = 4 \text{ J}

Therefore, the potential energy stored in the spring is 4 J, which corresponds to option a.

24 J

48 J

36 J

72 J

Correct Answer: A

Solution:

The potential energy stored in a compressed spring is given by:

PE = \frac{1}{2}kx^2

where

k = 300 \text{ N/m}

and

x = 0.4 \text{ m}

. Thus,

PE = \frac{1}{2} \times 300 \times (0.4)^2 = 24 \text{ J}.

2 J

1 J

0.5 J

4 J

Correct Answer: A

Solution:

The work done on the spring is calculated by the formula:

W = F \times s

where

F

is the force and

s

is the displacement. Here,

W = 10 \text{ N} \times 0.2 \text{ m} = 2 \text{ J}

200 J

100 J

150 J

250 J

Correct Answer: A

Solution:

The work done

W

is given by

W = F \times d

, where

F

is the force and

d

is the displacement. Substituting the given values,

W = 50 \times 4 = 200

True or False

Correct Answer: False

Solution:

To bring an object moving with constant velocity to rest, work must be done to counteract its kinetic energy.

Correct Answer: True

Solution:

Potential energy is given by the formula

E_p = mgh

, where

Solution:

Potential energy is given by the formula

E_p = mgh

, where

m

is mass,

g

is gravitational acceleration, and

h

is height.

Correct Answer: True

Solution:

Mechanical energy is defined as the sum of kinetic energy and potential energy of an object.

Correct Answer: False

Solution:

In science, work is defined as the product of force and displacement in the direction of the force. If there is no displacement, no work is done, regardless of the effort exerted.

Correct Answer: True

Solution:

Work is defined as the product of force and displacement. If displacement is zero, no work is done.

Correct Answer: False

Solution:

A freely falling object converts its potential energy into kinetic energy as it falls. Upon reaching the ground, the kinetic energy is transformed into other forms, such as heat and sound.

Correct Answer: True

Solution:

As an object falls, its potential energy decreases and is converted into kinetic energy, maintaining the total mechanical energy constant.

Work and Energy

AI Learning Assistant

CBSE Learning Objectives – Key Concepts & Skills You Must Know

CBSE Revision Notes & Quick Summary for Last-Minute Study

Notes on Work and Energy

Concepts of Work and Energy

Energy Transformations

Calculations

Work Done by Forces

Common Scenarios

Important Diagrams

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Exam Tips

Multiple Choice Questions

Q1.A block of mass 5 kg is pushed across a horizontal surface with a constant force of 20 N over a distance of 3 meters. If the block starts from rest, what is its final velocity? Assume no friction.

Correct Answer: B

Q2.Which of the following statements is true about the law of conservation of energy?

Correct Answer: B

Q3.If a force is applied to an object but the object does not move, what is the work done on the object?

Correct Answer: A

Q4.If a force is applied to an object and it moves in the direction of the force, what is the nature of the work done?

Correct Answer: A

Q5.A wind turbine converts wind energy into electrical energy. If the wind speed doubles, how does the kinetic energy of the wind change, assuming all other factors remain constant?

Correct Answer: C

Q6.An object of mass mmm is moving with a constant velocity VVV. How much work should be done on the object in order to bring it to rest?

Correct Answer: A

Q7.An object of mass 12 kg is at a certain height above the ground. If the potential energy of the object is 480 J, what is the height at which the object is with respect to the ground? (Assume g=10 m/s2g = 10 \text{ m/s}^2g=10 m/s2)

Correct Answer: C

Q8.Which of the following statements is true according to the scientific definition of work?

Correct Answer: B

Q9.Which of the following scenarios correctly illustrates the law of conservation of energy?

Correct Answer: A

Q10.If a force of 10 N is applied to a block and it moves 5 meters in the direction of the force, what is the work done on the block?

Correct Answer: A

Q11.A machine does 3000 J of work in 10 seconds. What is the power output of the machine?

Correct Answer: A

Q12.A block is pushed with a force of 10 N across a distance of 5 meters on a frictionless surface. How much work is done on the block?

Correct Answer: A

Q13.A car of mass 1500 kg is moving at a velocity of 20 m/s. What is its kinetic energy?

Correct Answer: B

Q14.Calculate the work required to stop a car of 1500 kg moving at a velocity of 60 km/h.

Correct Answer: C

Q15.If a force of 10 N is applied to move an object 3 meters in the direction of the force, what is the work done?

Correct Answer: A

Q16.A 10 kg object is lifted vertically to a height of 5 meters. If the gravitational potential energy at this height is 500 J, what is the value of gravitational acceleration ggg assumed in this calculation?

Correct Answer: B

Q17.Which of the following statements is true about the concept of work in physics?

Correct Answer: A

Q18.If a block is pushed with a force of 7 N over a distance of 8 m, what is the work done on the block?

Correct Answer: A

Q19.If a 12 kg object is at a height of 5 m above the ground, what is its potential energy? (Assume g=9.8 m/s2g = 9.8 \text{ m/s}^2g=9.8 m/s2)

Correct Answer: A

Q20.Soni claims that an object can have zero acceleration even when several forces are acting on it. Is she correct?

Correct Answer: A

Q21.A car of mass 1500 kg is moving at a velocity of 60 km/h. How much work is required to stop the car?

Correct Answer: A

Q22.If an object of mass 8 kg is moving with a velocity of 10 m/s, what is its kinetic energy?

Correct Answer: C

Q23.What happens to the kinetic energy of a freely falling object when it reaches the ground?

Correct Answer: C

Q24.If a force of 5 N is applied to move an object 2 meters, how much work is done?

Correct Answer: B

Q25.A car of mass 1000 kg is moving with a velocity of 30 m/s. What is the kinetic energy of the car?

Correct Answer: A

Q26.Which of the following scenarios involves positive work done according to the scientific definition of work?

Correct Answer: A

Q27.A block of mass 10 kg is pushed across a frictionless surface with a constant force of 50 N. If the block moves a distance of 5 m, what is the work done on the block?

Correct Answer: A

Q28.A toy car is wound using its key and then released. What type of energy conversion takes place?

Correct Answer: A

Q29.A car of mass 1500 kg is moving at a velocity of 20 m/s. What is the kinetic energy of the car?

Correct Answer: B

Q30.Soni claims that an object can have zero acceleration even when multiple forces are acting on it. Which of the following scenarios supports her claim?

Correct Answer: A

Q31.A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy?

Correct Answer: C

Q32.What is the potential energy of an object of mass 12 kg at a height of 4 m above the ground? (Assume g=10 m/s2g = 10 \text{ m/s}^2g=10 m/s2)

Correct Answer: C