Work & Energy MCQs set 3 for King Edward Medical University Entry Test Physics — 20 solved questions.
Q1. A 5 kg block is lifted 2 m vertically. What is the work done against gravity?
Answer: 98 J
Explanation: Work done = mgh = 5 kg * 9.8 m/s^2 * 2 m = 98 J. Option B is incorrect due to rounding g to 10 m/s^2.
Q2. A force of 10 N acts on a body, displacing it 5 m at an angle of 60°. What is the work done?
Answer: 25 J
Explanation: Work done = F * d * cos(θ) = 10 N * 5 m * cos(60°) = 25 J. Option B is incorrect due to miscalculation.
Q3. A spring with k = 100 N/m is compressed by 0.2 m. What is the potential energy stored?
Answer: 2 J
Explanation: Elastic potential energy = 0.5 * k * x^2 = 0.5 * 100 N/m * (0.2 m)^2 = 2 J. Option B is incorrect due to calculation error.
Q4. A 2 kg object moves at 4 m/s. What is its kinetic energy?
Answer: 16 J
Explanation: Kinetic energy = 0.5 * m * v^2 = 0.5 * 2 kg * (4 m/s)^2 = 16 J. Option B is incorrect due to miscalculation.
Q5. A body of mass 10 kg is raised to a height of 2 m. If the acceleration due to gravity is 9.8 m/s^2, what is the work done?
Answer: 196 J
Explanation: Work done = mgh = 10 kg * 9.8 m/s^2 * 2 m = 196 J. Option B is incorrect due to rounding g to 10 m/s^2.
Q6. A car accelerates from 0 to 20 m/s in 4 s. If its mass is 1500 kg, what is the average power delivered?
Answer: 75 kW
Explanation: Average power = ΔKE / Δt = (0.5 * 1500 kg * (20 m/s)^2) / 4 s = 75 kW. Option A is incorrect due to miscalculation.
Q7. A 50 N force is applied at an angle of 30° to the horizontal, displacing a body 10 m horizontally. What is the work done?
Answer: 433 J
Explanation: Work done = F * d * cos(θ) = 50 N * 10 m * cos(30°) = 433 J. Option B is incorrect due to miscalculation.
Q8. A 1000 kg elevator is lifted 20 m in 10 s. What is the average power delivered?
Answer: 19.6 kW
Explanation: Average power = mgh / t = (1000 kg * 9.8 m/s^2 * 20 m) / 10 s = 19.6 kW. Option B is incorrect due to rounding g to 10 m/s^2.
Q9. A body is projected upwards with a velocity of 20 m/s. What is its kinetic energy at the highest point?
Answer: 0 J
Explanation: At the highest point, velocity = 0, so kinetic energy = 0. Option B is incorrect as it assumes some velocity at the highest point.
Q10. A force F = (2x + 3) N acts on a body, displacing it from x = 0 to x = 2 m. What is the work done?
Answer: 10 J
Explanation: Work done = ∫F dx = ∫(2x + 3) dx from 0 to 2 = [x^2 + 3x] from 0 to 2 = 10 J. Option B is incorrect due to miscalculation.
Q11. A 2 kg block is attached to a spring with k = 50 N/m. If it is displaced by 0.1 m, what is the elastic potential energy?
Answer: 0.25 J
Explanation: Elastic potential energy = 0.5 * k * x^2 = 0.5 * 50 N/m * (0.1 m)^2 = 0.25 J. Option B is incorrect due to miscalculation.
Q12. A body of mass 5 kg is moving with a velocity of 4 m/s. What is its kinetic energy?
Answer: 40 J
Explanation: Kinetic energy = 0.5 * m * v^2 = 0.5 * 5 kg * (4 m/s)^2 = 40 J. Option B is incorrect due to miscalculation.
Q13. A 100 g bullet is fired at 400 m/s. What is its kinetic energy?
Answer: 8000 J
Explanation: Kinetic energy = 0.5 * m * v^2 = 0.5 * 0.1 kg * (400 m/s)^2 = 8000 J. Option B is incorrect due to miscalculation.
Q14. A 50 kg person climbs a staircase 4 m high in 10 s. What is the average power delivered?
Answer: 196 W
Explanation: Average power = mgh / t = (50 kg * 9.8 m/s^2 * 4 m) / 10 s = 196 W. Option B is incorrect due to rounding g to 10 m/s^2.
Q15. A spring is compressed by 0.2 m, storing 4 J of energy. What is its spring constant?
Answer: 200 N/m
Explanation: Elastic potential energy = 0.5 * k * x^2. Rearranging, k = 2 * energy / x^2 = 2 * 4 J / (0.2 m)^2 = 200 N/m. Option B is incorrect due to miscalculation.
Q16. A body is moving with a constant velocity. What is the net work done on it?
Answer: Zero
Explanation: Since the body is moving with constant velocity, the net force acting on it is zero, so the net work done is zero. Option A is incorrect as it implies acceleration.
Q17. A 5 kg block is pulled 2 m along a frictionless surface by a 10 N force. What is the work done by the force?
Answer: 20 J
Explanation: Work done = F * d = 10 N * 2 m = 20 J. Option B is incorrect due to miscalculation.
Q18. A 2 kg object has a kinetic energy of 16 J. What is its velocity?
Answer: 4 m/s
Explanation: Kinetic energy = 0.5 * m * v^2. Rearranging, v = sqrt(2 * KE / m) = sqrt(2 * 16 J / 2 kg) = 4 m/s. Option B is incorrect due to miscalculation.
Q19. A body is projected upwards. At what point is its kinetic energy minimum?
Answer: At the highest point
Explanation: At the highest point, velocity is zero, so kinetic energy is minimum. Option A is incorrect as it has maximum kinetic energy at the ground.
Q20. A 10 kg block is lifted 1 m in 2 s. What is the average power delivered?
Answer: 49 W
Explanation: Average power = mgh / t = (10 kg * 9.8 m/s^2 * 1 m) / 2 s = 49 W. Option B is incorrect due to rounding g to 10 m/s^2.