# Work, Energy, and Power Multiple Choice Questions

Q1. Calculate the power developed when the force of 10 N is exerted on a body moving with a velocity of 3.65 m/s.

1. 0.365 W
2. 36.5 W
3. 365 W
4. 3.65 W

Q2. If a body in rest breaks up into two pieces of equal masses, then, the parts will

1. Move in the same direction.
2. Move in opposite directions with equal speeds
3. Remain at rest.
4. Move in opposite directions with unequal speeds.

Q3. An electric motor creates a tension of 4500 N in a hoisting cable and reels it in at the rate of 2 m/s. What is the power of the electric motor?

1. 15 kW
2. 9 kW
3. 225 W
4. 900 W

Q4. Work done in motion of the body over a closed loop for conservative forces is

1. zero
2. non-zero
3. infintesimal
4. infinity

Q5. How should the force applied on a body be varied with velocity to keep the power of force constant?

1. Force should be directly proportional to the velocity of the body
2. Force should be inversely proportional to the square root of the velocity of the body
3. Force should not be varied. It should remain constant with the velocity
4. Force should be inversely proportional to the velocity of the body

Q6. A shell, in its flight explodes into five unequal parts. Which of the following is conserved?

1. Momentum
2. Kinetic energy
3. Potential energy
4. Both potential energy and kinetic energy.

Q7. A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

1. A
2. B
3. Both A and B have developed equal power but B has more energy
4. Both A and B have developed equal power but A has more energy

Q8. What is the CGS unit of power?

1. 1 erg / hr
2. 1 dyne / sec
3. 1 erg / sec
4. 1 dyne / hr

Q9. For a varying force work done can be expressed as a

1. definite integral of force over displacement
2. differentiation of force with displacement
3. product of force and displacement
4. force divided by the displacement

Q10. If you drop a rubber ball from rest from a height of 3 m, what is the maximum height to which it will bounce back in the presence of air?

1. = 3 m
2. > 3 m
3. 4 m
4. < 3 m

Q11. How much water a pump of 2 kW can raise in 1 minute to a height of 10 m, take g=10 m/s2.

1. 1000 litres
2. 1200 litres
3. 100 litres
4. 2000 litres

Q12. A bomb of mass 4 kg explodes in air into two pieces of masses 3 kg and 1 kg. The smaller mass goes at a speed of 90 m/s. The total energy imparted to two fragments is.

1. 2.4 kJ
2. 5.9 kJ
3. 3.8 kJ
4. 5.4 kJ

Q13. Which of the following statement is not related to conservative force?

1. Work done in closed path is zero
2. Work done is recoverable
3. Path dependent
4. Path independent

Q14. Which of the following is correct?

1. 1 H.P = 55016 ft/s
2. 1 H .P = 746 W
3. Both A and B
4. none of the above

Q15. Raindrops fall on the earth with certain kinetic energy on the earth. From where do they get this energy?

1. Gravitational Potential Energy
2. Energy between molecules of water
3. Chemical Energy
4. Heat Energy

Q16. If only the conservative forces are acting on the body, then its total

1. Potential energy is conserved
2. Kinetic energy is conserved
3. Mechanical energy is conserved
4. Either potential or kinetic energy could be conserved

Q17. A force is conservative if

1. the sum of the initial forces equals the final forces
2. a constant force acts on the system
3. work done over a closed path is zero
4. work done for every path is zero

Q18. A force which does not depend on the path taken to increase the potential energy is

1. Conservative force
2. Non-conservative force
3. Frictional force
4. Viscous force

Q19. A ball of mass 2 kg is raised to the height of 60 m and then dropped from the top. In this case, the quantity which has different magnitude from the other given quantities is

1. Work done by gravity
2. Kinetic energy before hitting the ground
3. Potential energy at the top
4. Velocity just hitting the ground

Q20. Select the odd one out

1. Viscous force
2. Air-resistance
3. Electrostatic force
4. Frictional force

Q21. Which of the following statements is false:

1. potential energy is negative
2. kinetic energy is negative
3. potential energy is positive
4. kinetic energy is positive

Q22. What is the relationship between joule and erg?

1. 1 J = 10erg
2. 1 J = 10erg
3. 1 J = 10erg
4. 1 J = 10erg

Q23. An astronomer has total weight of 80 kg. On reaching moon, he climbs up 10 m to enter his aircraft by the ladder. His gravitational potential energy is increased by 1000 J. The value of the gravitational acceleration on the moon is

1. 1.25 N/kg
2. 2 N/kg
3. 2.25 kg
4. 2.22 kg

Q24. Which of the following is not an example of zero work?

1. The work done by a coolie when he travels on a horizontal platform, with a load on his head.
2. The work done by the tension in the string, when a body tied with the string move along a circular path.
3. When a person holds some amount of load but, does not move from his position.
4. When a horse pulls a cart on a level road.

Q25. Time rate at which work is done by a force is

1. Power
2. Acceleration
3. Torque
4. Centrifugal Force

Q26. When conservative force does positive work on a body, the potential energy of the body:

1. increases
2. decreases
3. remains unaltered
4. there is no relationship between force and potential energy

Q27. You are in a lift moving from the 3rd floor to the 12th floor, having a height difference of H = 40 m. Your mass is M = 80 kg and the acceleration due to gravity is g = 10 m/s2. If the elevator moves at a constant speed without stopping, what is the total work performed by all of the forces together (the net force) acting on you?

1. MgH
2. -MgH
3. Mg
4. 0

Q28. Work done by or against a conservative force in a round trip is

1. Maximum
2. Minimum
3. Zero
4. May be maximum or zero

Q29. When a ball is allowed to fall from a height of 20 m, 40% of its energy is lost due to impact. After one impact the ball will go up to a height of

1. 10 m
2. 8 m
3. 12 m
4. 15 m

Q30. In an elastic collision in one dimension if a body A collides against the body B of equal mass at rest, then the body A will

1. move with twice its initial velocity
2. moves with the same velocity but in opposite direction.
3. moves with the same velocity in the same direction.
4. come to rest.

Q31.A plot of potential energy and kinetic energy versus displacement x for a block attached to a spring obeying Hooke’s law is

1. a parabola
2. a straight line
3. an ellipse
4. a hyperbola

Q32. If the momentum of a body is doubled, then its kinetic energy will increase by

1. 50%
2. 400%
3. 300%
4. 100%

Q33.If a ball of mass 1 kg makes a head-on collision with a ball of an unknown mass initially at rest such that the ball rebounds to one third of its original speed, what is the mass of the other ball?

1. 1 kg
2. 3 kg
3. 2 kg
4. 4 kg

Q34. A hawk of mass 10 kg dives to catch a mouse. During dive it loses 500 J of its potential energy. The height from where it begins its dive is    (take g = 10 m/s2)

1. 50 m
2. 10 m
3. 5 m
4. 1 m

Q35. The potential energy of a hammer of mass 10 kg, lifted to the height of 10 m is

1. 100 J
2. 10 J
3. 98 J
4. 980 J

Q36. If momentum of an object is doubled, how does its kinetic energy change?

1. increases 4 times
2. decreases 4 times
3. increases 2 times
4. decreases 2 times

Q37. The total mechanical energy of a system is conserved if the forces that act on it are

1. Non-conservative
2. path dependent
3. conservative
4. frictional forces

Q38. Which of the following is not correct for the condition for work not to be done:

1. force is zero
2. displacement is zero, though force is non-zero
3. force and displacement are perpendicular to each other.
4. force and displacement are at 180 degrees with each other

Q39. Frictional force is an example of

1. Non conservative force
2. Conservative force
3. Nuclear force
4. Electrostatic force

Q40.The potential energy of the spring when stretched

1. Does not change
2. Increases
3. Decreases
4. Depends on the material of the spring