Power and conservation of mechanical energy - One Line Questions

1. A spring is stretched by 2 cm. If the spring constant is 100 N/m, calculate the potential energy stored in the spring. — 0.02 J
2. A spring is compressed by 5 cm. If the spring constant is 200 N/m, calculate the potential energy stored. — 0.25 J
3. A force F = (3i - 2j + k) N acts on a particle, and the particle is displaced by d = (4i + 5j + 3k) m. Calculate the work done by the force. — 1 J
4. A block of mass 2 kg is moving with a velocity of 5 m/s. What is its kinetic energy? — 25 J
5. A body of mass 1 kg falls from a height of 10 m. Its kinetic energy just before hitting the ground is (g=10 m/s²): — 100 J
6. A body of mass 5 kg is projected vertically upwards with an initial velocity of 20 m/s. What is its maximum height? (g = 10 m/s²) — 40 m
7. What is the power of a person who lifts 20 kg of mass to a height of 5 m in 10 seconds? (g = 10 m/s²) — 100 W
8. A 2 kg object is moving with a velocity of 3 m/s. If a force of 6 N acts on it in the direction of motion, what is its kinetic energy after 2 seconds? — 40.5 J
9. A machine does 1200 Joules of work in 10 seconds. What is its average power? — 120 W
10. A force F = (2i + 3j) N moves an object through a displacement d = (4i + 2j) m. Calculate the work done. — 14 J
11. A 1000 kg car travels at 20 m/s. If the engine develops a power of 50 kW, how much time does it take to cover 1 km? — 40 s
12. An electric motor lifts a load of 10 kg by a height of 5 meters in 2 seconds. If g = 10 m/s², calculate the power developed by the motor. — 250 W
13. A 60 kg person climbs stairs of height 10 m in 20 seconds. The power developed by the person is (g=10 m/s²): — 300 W
14. If a force of 50 N is applied to an object moving at a constant velocity of 10 m/s in the same direction, what is the power developed? — 500 W
15. A car engine does 5000 J of work in 10 seconds. What is its power output? — 500 W
16. A spring is compressed by 0.1 m. If the potential energy stored is 5 J, what is the spring constant? — 1000 N/m
17. A person climbs a hill of height 100 m. If the person's mass is 60 kg, what is the work done against gravity? (g = 10 m/s²) — 60000 J
18. 1 horsepower (hp) is approximately equal to: — 746 Watts
19. What is the power of a pump that lifts 500 kg of water to a height of 10 m in 1 minute? (g = 10 m/s²) — 833.3 W
20. In which scenario is mechanical energy conserved? — A planet revolving around the sun
21. In the absence of non-conservative forces, the sum of kinetic and potential energy of a particle moving under a central force is: — Constant
22. When work is done against a conservative force, the potential energy of the system: — Increases
23. Which of the following is an example of potential energy? — Energy stored in a compressed spring
24. Which of the following is a scalar quantity? — Power
25. Which of the following is a conservative force? — Gravitational force
26. If the speed of a body is doubled, its kinetic energy becomes: — Four times
27. If the velocity of a body is halved, its kinetic energy becomes: — One fourth
28. Conservation of mechanical energy states that in the absence of non-conservative forces, the total mechanical energy of a system remains: — Constant
29. When a body falls freely under gravity from a certain height, its mechanical energy: — Remains constant
30. When a conservative force does positive work on a system, the potential energy of the system: — Decreases
31. If the total mechanical energy of a system is conserved, then the sum of kinetic and potential energy: — Remains constant
32. A body is projected upwards. Its mechanical energy: — Remains constant (ignoring air resistance)
33. What is the SI unit of power? — Watt
34. Which of the following is a unit of power? — Watt
35. If a system is subjected to only conservative forces, then the work done by these forces is equal to the change in: — Potential energy
36. When a spring is stretched or compressed from its equilibrium position, work is done against the spring force, which is stored as: — Elastic potential energy
37. Total mechanical energy (E) of a system is the sum of: — Kinetic energy and potential energy
38. A spring with spring constant k is stretched by a distance x. The work done to stretch it further by x is: — 3kx²/2
39. A body of mass m is at rest. If it is acted upon by a constant force F for time t, its kinetic energy is proportional to: — F²t²
40. Consider a pendulum swinging. At the extreme positions, the velocity is zero. What is the nature of mechanical energy at these points? — Zero kinetic energy, maximum potential energy
41. The potential energy of a system can change due to the work done by: — Only conservative forces
42. If a force F acts on a particle such that the position vector is r, the instantaneous power is given by: — P = F · (dr/dt)
43. If a force F acts on an object moving with velocity v, the instantaneous power developed by the force is given by: — P = F * v
44. Power is defined as the rate of doing work. If work (W) is done in time (t), what is the formula for average power? — P = W / t
45. The work done by friction on a moving object is always: — Negative
46. Which of the following statements about power is correct? — Power is a scalar quantity.
47. When a non-conservative force does work on a system, the total mechanical energy: — Decreases
48. A body of mass m is at rest. If a constant force F acts on it, its kinetic energy after time t will be proportional to: — t²
49. A constant power P is supplied to a particle. The velocity of the particle is proportional to: — t^(1/2)
50. Which of the following is NOT a non-conservative force? — Gravitational force
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