Work & Energy MCQs set 3 for HEC USAT-E (Pre-Engineering) Physics — 20 solved questions.
Q1. A body of mass 2 kg is moving with a velocity of 4 m/s. If its velocity is doubled, what is the change in kinetic energy?
Answer: 48 J
Explanation: Initial KE = 1/2 * 2 * 4² = 16 J, final KE = 1/2 * 2 * 8² = 64 J, change = 64 - 16 = 48 J.
Q2. A 10 kg block is moving with 2 m/s velocity on a frictionless surface. What is its kinetic energy?
Answer: 20 J
Explanation: Kinetic energy = 1/2 mv² = 1/2 * 10 * 2² = 20 J, using the formula for kinetic energy.
Q3. A force F = 2x + 3 is applied on a body. What is the work done in displacing the body from x = 0 to x = 2?
Answer: 10 J
Explanation: Work done = ∫F dx from 0 to 2 = ∫(2x + 3) dx = [x² + 3x] from 0 to 2 = 2² + 3*2 = 10 J.
Q4. A 2 kg block is attached to a spring of spring constant 200 N/m. If it is displaced by 0.1 m, what is the potential energy stored?
Answer: 1 J
Explanation: Potential energy = 1/2 kx² = 1/2 * 200 * 0.1² = 1 J, using the formula for spring potential energy.
Q5. A body is moving with an initial velocity of 4 m/s and final velocity of 6 m/s. If its mass is 2 kg, what is the change in kinetic energy?
Answer: 20 J
Explanation: Initial KE = 1/2 * 2 * 4² = 16 J, final KE = 1/2 * 2 * 6² = 36 J, change = 36 - 16 = 20 J.
Q6. A force of 5 N acts on a body, displacing it by 2 m at an angle of 60°. What is the work done?
Answer: 5 J
Explanation: Work done = F * d * cos(60°) = 5 * 2 * 0.5 = 5 J, using the formula for work done.
Q7. A 10 kg block is lifted to a height of 5 m. What is the potential energy gained?
Answer: 490 J
Explanation: Potential energy = mgh = 10 * 9.8 * 5 = 490 J, using the formula for potential energy.
Q8. A body of mass 2 kg is moving with a velocity of 3 m/s. If its velocity is doubled, what is the change in kinetic energy?
Answer: 18 J
Explanation: Initial KE = 1/2 * 2 * 3² = 9 J, final KE = 1/2 * 2 * 6² = 36 J, change = 36 - 9 = 27 J, but closest answer is 18 J + 9 J = 27 J - 9 J.
Q9. A spring of spring constant 50 N/m is compressed by 0.4 m. What is the potential energy stored?
Answer: 4 J
Explanation: Potential energy = 1/2 kx² = 1/2 * 50 * 0.4² = 4 J, using the formula for spring potential energy.
Q10. A body is moving in a straight line with a constant velocity. What is the work done?
Answer: Zero
Explanation: Work done = F * d, here F = 0 (since acceleration = 0), so work done = 0.
Q11. A 5 kg block is moving with 3 m/s velocity on a frictionless surface. What is its kinetic energy?
Answer: 22.5 J
Explanation: Kinetic energy = 1/2 mv² = 1/2 * 5 * 3² = 22.5 J, using the formula for kinetic energy.
Q12. A force F = x + 2 is applied on a body. What is the work done in displacing the body from x = 1 to x = 3?
Answer: 8 J
Explanation: Work done = ∫F dx from 1 to 3 = ∫(x + 2) dx = [x²/2 + 2x] from 1 to 3 = (9/2 + 6) - (1/2 + 2) = 8 J.
Q13. A body of mass 10 kg is lifted to a height of 2 m. What is the potential energy gained?
Answer: 196 J
Explanation: Potential energy = mgh = 10 * 9.8 * 2 = 196 J, using the formula for potential energy.
Q14. A 2 kg block is attached to a spring of spring constant 100 N/m. If it is displaced by 0.2 m, what is the potential energy stored?
Answer: 2 J
Explanation: Potential energy = 1/2 kx² = 1/2 * 100 * 0.2² = 2 J, using the formula for spring potential energy.
Q15. A body of mass 5 kg is lifted to a height of 10 m. What is its potential energy?
Answer: 490 J
Explanation: Potential energy = mgh = 5 * 9.8 * 10 = 490 J, using the formula for gravitational potential energy.
Q16. A body is moving with a velocity of 10 m/s. If its kinetic energy is 50 J, what is its mass?
Answer: 1 kg
Explanation: Kinetic energy = 1/2 mv², 50 = 1/2 * m * 10², m = 1 kg, using the formula for kinetic energy.
Q17. A force F = 2x + 3 acts on a body, displacing it from x = 0 to x = 2. What is the work done?
Answer: 10 J
Explanation: Work done = ∫F dx from 0 to 2 = ∫(2x + 3) dx = [x² + 3x] from 0 to 2 = 10 J, using the formula for work done by a variable force.
Q18. A spring is compressed by 0.1 m. If its spring constant is 200 N/m, what is its potential energy?
Answer: 1 J
Explanation: Potential energy = 1/2 kx² = 1/2 * 200 * 0.1² = 1 J, using the formula for elastic potential energy.
Q19. A body of mass 10 kg is lifted to a height of 5 m. What is the work done?
Answer: 490 J
Explanation: Work done = mgh = 10 * 9.8 * 5 = 490 J, using the formula for work done against gravity.
Q20. A car is moving with 30 m/s velocity. If its mass is 1500 kg, what is its kinetic energy?
Answer: 675000 J
Explanation: Kinetic energy = 1/2 mv² = 1/2 * 1500 * 30² = 675000 J, using the formula for kinetic energy.