Bahria University Entry Test Physics: Work & Energy MCQs

Bahria University Entry Test Physics: Work & Energy MCQs — sample questions

1. Question 1

   Q1. A 2 kg block is moving at 4 m/s. What is its kinetic energy?

   • A) 8 J
   • B) 16 J
   • C) 32 J
   • D) 64 J

   Answer: 16 J

   Explanation: Kinetic energy = 1/2 mv² = 1/2 * 2 * 4² = 16 J, using the formula for kinetic energy.

2. Question 2

   Q2. A force of 5 N acts on a body, displacing it by 3 m. What is the work done?

   • A) 10 J
   • B) 15 J
   • C) 20 J
   • D) 25 J

   Answer: 15 J

   Explanation: Work done = F * d = 5 * 3 = 15 J, using the formula for work done.

3. Question 3

   Q3. A spring has a spring constant of 100 N/m. What is the work done in compressing it by 2 m?

   • A) 100 J
   • B) 200 J
   • C) 2000 J
   • D) 400 J

   Answer: 200 J

   Explanation: Work done = 1/2 kx² = 1/2 * 100 * 2² = 200 J, then 1/2 * 100 * 4 = 200 J.

4. Question 4

   Q4. A body of mass 5 kg is lifted to a height of 10 m. What is the potential energy gained?

   • A) 490 J
   • B) 500 J
   • C) 4905 J
   • D) 5000 J

   Answer: 490 J

   Explanation: Potential energy PE = mgh. Using g = 9.8 m/s²: PE = 5 × 9.8 × 10 = 490 J.

5. Question 5

   Q5. A block of mass 2 kg is attached to a spring of spring constant 100 N/m. The block is displaced by 0.2 m and released. What is its kinetic energy when it passes through the equilibrium position?

   • A) 2 J
   • B) 4 J
   • C) 6 J
   • D) 8 J

   Answer: 2 J

   Explanation: Kinetic energy = 1/2 kx² = 1/2 * 100 * 0.2² = 2 J, using conservation of energy.

6. Question 6

   Q6. A force F = 2x + 3 acts on a body, where x is in meters. What is the work done in displacing the body from x = 0 to x = 4 m?

   • A) 20 J
   • B) 24 J
   • C) 28 J
   • D) 32 J

   Answer: 28 J

   Explanation: Work equals the area under the force-distance graph. Integrate 2x + 3 from 0 to 4: the antiderivative is x squared plus 3x. At 4 this is 16 + 12 = 28 J. At 0 it is 0, so work done is 28 J.

7. Question 7

   Q7. A body is thrown upwards with an initial velocity of 20 m/s. What is its kinetic energy at the highest point?

   • A) 0 J
   • B) 100 J
   • C) 200 J
   • D) 400 J

   Answer: 0 J

   Explanation: At the highest point, velocity = 0, so kinetic energy = 0, using the formula for kinetic energy.

8. Question 8

   Q8. A 5 kg block is moving at 2 m/s on a frictionless surface. What is its kinetic energy?

   • A) 5 J
   • B) 10 J
   • C) 15 J
   • D) 20 J

   Answer: 10 J

   Explanation: Kinetic energy = 1/2 mv² = 1/2 * 5 * 2² = 10 J, using the formula for kinetic energy.

9. Question 9

   Q9. A spring is compressed by 0.1 m. If its spring constant is 200 N/m, what is the potential energy stored?

   • A) 1 J
   • B) 2 J
   • C) 0.5 J
   • D) 1.5 J

   Answer: 1 J

   Explanation: Potential energy = 1/2 kx² = 1/2 * 200 * 0.1² = 1 J, using the formula for potential energy.

10. Question 10

    Q10. A body of mass 10 kg is lifted to a height of 5 m in 2 s. What is the average power delivered?

    • A) 245.25 W
    • B) 250 W
    • C) 2452.5 W
    • D) 2500 W

    Answer: 245.25 W

    Explanation: Average power = mgh / t = 10 * 9.81 * 5 / 2 = 245.25 W, using g = 9.81 m/s².

11. Question 11

    Q11. A car of mass 1500 kg accelerates from 0 to 30 m/s in 10 s. What is the average power delivered?

    • A) 67500 W
    • B) 6750 W
    • C) 675 W
    • D) 67.5 W

    Answer: 67500 W

    Explanation: Average power = ΔKE / Δt = (1/2 * 1500 * 30²) / 10 = 67500 W, using the formula for kinetic energy.

12. Question 12

    Q12. A block is attached to a spring of spring constant 50 N/m. The block is displaced by 0.2 m and released. What is the force acting on the block at x = 0.1 m?

    • A) 5 N
    • B) 10 N
    • C) -5 N
    • D) -10 N

    Answer: -5 N

    Explanation: Force = -kx = -50 * 0.1 = -5 N, using Hooke's Law.

13. Question 13

    Q13. A body is moving in a circular path with a constant speed. What is the work done in one revolution?

    • A) 0 J
    • B) Positive
    • C) Negative
    • D) Depends on the radius

    Answer: 0 J

    Explanation: Work done = 0, since the force is perpendicular to the displacement, using the formula for work done.

14. Question 14

    Q14. A 2 kg block is moving at 3 m/s. What is its momentum?

    • A) 5 kg m/s
    • B) 6 kg m/s
    • C) 4 kg m/s
    • D) 8 kg m/s

    Answer: 6 kg m/s

    Explanation: Momentum = mv = 2 * 3 = 6 kg m/s, using the formula for momentum.

15. Question 15

    Q15. A force of 10 N acts on a body for 2 s. What is the impulse?

    • A) 10 Ns
    • B) 20 Ns
    • C) 15 Ns
    • D) 25 Ns

    Answer: 20 Ns

    Explanation: Impulse = F * Δt = 10 * 2 = 20 Ns, using the formula for impulse.

16. Question 16

    Q16. A body of mass 5 kg is moving at 4 m/s. What is its kinetic energy?

    • A) 20 J
    • B) 40 J
    • C) 60 J
    • D) 80 J

    Answer: 40 J

    Explanation: Kinetic energy = 1/2 mv² = 1/2 * 5 * 4² = 40 J, using the formula for kinetic energy.

17. Question 17

    Q17. A spring has a potential energy of 10 J when compressed by 0.2 m. What is its spring constant?

    • A) 500 N/m
    • B) 1000 N/m
    • C) 200 N/m
    • D) 5000 N/m

    Answer: 500 N/m

    Explanation: 1/2 kx² = 10, so k = 2*10 / 0.2² = 500 N/m, using the formula for potential energy.

18. Question 18

    Q18. A body is thrown upwards with an initial velocity of 15 m/s. What is its potential energy at the highest point?

    • A) mgh
    • B) 1/2 mv²
    • C) mgh = 1/2 mv²
    • D) 0

    Answer: mgh = 1/2 mv²

    Explanation: At the highest point, KE = 0, and PE = initial KE = 1/2 mv² = mgh, using conservation of energy.

19. Question 19

    Q19. A 10 kg block is lifted to a height of 2 m. What is the work done?

    • A) 196.2 J
    • B) 200 J
    • C) 150 J
    • D) 250 J

    Answer: 196.2 J

    Explanation: Work done = mgh = 10 * 9.81 * 2 = 196.2 J, using g = 9.81 m/s².

20. Question 20

    Q20. A 2 kg block is moving with 4 m/s velocity. What is its kinetic energy?

    • A) 4 J
    • B) 8 J
    • C) 16 J
    • D) 32 J

    Answer: 16 J

    Explanation: Kinetic energy = 1/2 mv² = 1/2 * 2 * 4² = 16 J, using the formula for kinetic energy.