JSMU Karachi Entry Test Physics Force & Motion — Set 3

JSMU Karachi Entry Test Physics Force & Motion — Set 3

1. Question 1

   Q1. A block of mass 5 kg is attached to a horizontal spring with a spring constant of 200 N/m. How much will the spring stretch when a force of 20 N is applied to the block?

   • A) 0.05 m
   • B) 0.1 m
   • C) 0.2 m
   • D) 0.5 m

   Answer: 0.1 m

   Explanation: The displacement of the spring can be calculated using Hooke's law, F = kx, where F is the applied force, k is the spring constant, and x is the displacement, giving a displacement of 0.1 m.

2. Question 2

   Q2. A ball is thrown upwards with an initial velocity of 20 m/s. How long will it take for the ball to reach its maximum height?

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

   Answer: 4 s

   Explanation: The time it takes for the ball to reach its maximum height can be calculated using the equation v = u - gt, where v is the final velocity, u is the initial velocity, g is the acceleration due to gravity, and t is the time, giving a time of 4 s.

3. Question 3

   Q3. A force of 10 N is applied to an object for 5 seconds. What is the impulse of the force?

   • A) 20 Ns
   • B) 50 Ns
   • C) 100 Ns
   • D) 200 Ns

   Answer: 100 Ns

   Explanation: The impulse of a force can be calculated using the formula J = F x Δt, where F is the force and Δt is the time over which it is applied, giving an impulse of 100 Ns.

4. Question 4

   Q4. A car travels 100 km in 2 hours. What is its average speed?

   • A) 40 km/h
   • B) 50 km/h
   • C) 60 km/h
   • D) 80 km/h

   Answer: 60 km/h

   Explanation: The average speed of the car can be calculated using the formula v = d / t, where v is the average speed, d is the distance traveled, and t is the time taken, giving an average speed of 60 km/h.

5. Question 5

   Q5. A force of 20 N is applied to an object for 10 seconds. What is the work done by the force?

   • A) 100 J
   • B) 200 J
   • C) 300 J
   • D) 400 J

   Answer: 300 J

   Explanation: The work done by a force can be calculated using the formula W = F x d, where F is the force and d is the distance over which it is applied, giving a work done of 300 J.

6. Question 6

   Q6. A ball is thrown horizontally with an initial velocity of 15 m/s. What is its acceleration?

   • A) 0 m/s^2
   • B) 5 m/s^2
   • C) 10 m/s^2
   • D) 15 m/s^2

   Answer: 0 m/s^2

   Explanation: The acceleration of a horizontally thrown ball is zero, as there is no net force acting on it, making it an example of uniform motion.

7. Question 7

   Q7. A 2 kg block is attached to a horizontal spring with a spring constant of 300 N/m. What is the frequency of oscillation?

   • A) 1 Hz
   • B) 2 Hz
   • C) 3 Hz
   • D) 4 Hz

   Answer: 3 Hz

   Explanation: The frequency of oscillation of a spring can be calculated using the formula f = (1 / 2π) √(k / m), where f is the frequency, k is the spring constant, and m is the mass, giving a frequency of 3 Hz.

8. Question 8

   Q8. A car accelerates from rest to 25 m/s in 15 seconds. What is its acceleration?

   • A) 5 m/s^2
   • B) 7.5 m/s^2
   • C) 10 m/s^2
   • D) 12.5 m/s^2

   Answer: 7.5 m/s^2

   Explanation: The acceleration of the car can be calculated using the formula a = Δv / Δt, where a is the acceleration, Δv is the change in velocity, and Δt is the time taken, giving an acceleration of 7.5 m/s^2.

9. Question 9

   Q9. A force of 15 N is applied to an object for 20 seconds. What is the impulse of the force?

   • A) 150 Ns
   • B) 300 Ns
   • C) 400 Ns
   • D) 500 Ns

   Answer: 400 Ns

   Explanation: The impulse of a force can be calculated using the formula J = F x Δt, where F is the force and Δt is the time over which it is applied, giving an impulse of 400 Ns.

10. Question 10

    Q10. A ball is thrown upwards with an initial velocity of 25 m/s. How long will it take for the ball to reach its maximum height?

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

    Answer: 6 s

    Explanation: The time it takes for the ball to reach its maximum height can be calculated using the equation v = u - gt, where v is the final velocity, u is the initial velocity, g is the acceleration due to gravity, and t is the time, giving a time of 6 s.

11. Question 11

    Q11. A force of 25 N is applied to an object for 30 seconds. What is the work done by the force?

    • A) 500 J
    • B) 750 J
    • C) 1000 J
    • D) 1250 J

    Answer: 1000 J

    Explanation: The work done by a force can be calculated using the formula W = F x d, where F is the force and d is the distance over which it is applied, giving a work done of 1000 J.

12. Question 12

    Q12. A car travels 150 km in 3 hours. What is its average speed?

    • A) 40 km/h
    • B) 50 km/h
    • C) 60 km/h
    • D) 80 km/h

    Answer: 60 km/h

    Explanation: The average speed of the car can be calculated using the formula v = d / t, where v is the average speed, d is the distance traveled, and t is the time taken, giving an average speed of 60 km/h.

13. Question 13

    Q13. A 3 kg block is attached to a horizontal spring with a spring constant of 400 N/m. What is the frequency of oscillation?

    • A) 2 Hz
    • B) 3 Hz
    • C) 4 Hz
    • D) 5 Hz

    Answer: 3 Hz

    Explanation: The frequency of oscillation of a spring can be calculated using the formula f = (1 / 2π) √(k / m), where f is the frequency, k is the spring constant, and m is the mass, giving a frequency of 3 Hz.

14. Question 14

    Q14. A force of 30 N is applied to an object for 40 seconds. What is the impulse of the force?

    • A) 800 Ns
    • B) 1200 Ns
    • C) 1600 Ns
    • D) 2000 Ns

    Answer: 1600 Ns

    Explanation: The impulse of a force can be calculated using the formula J = F x Δt, where F is the force and Δt is the time over which it is applied, giving an impulse of 1600 Ns.

15. Question 15

    Q15. A car is moving at 50 km/h. What is the work done by the car's engine in 10 seconds?

    • A) W = F x d
    • B) W = F x v
    • C) W = F x t
    • D) W = F x a

    Answer: W = F x v

    Explanation: The correct formula is W = F x v, as work is done when a force is applied over a distance, and here, distance and velocity are related.

16. Question 16

    Q16. A 2 kg mass is attached to a spring. If the spring constant is 100 N/m, what is the force exerted on the mass when it is displaced by 0.2 m?

    • A) F = k x x
    • B) F = k / x
    • C) F = m x g
    • D) F = m x v

    Answer: F = k x x

    Explanation: The correct formula is F = k x x, as Hooke's law states that force is directly proportional to displacement.

17. Question 17

    Q17. A particle is moving in a circular path with a radius of 3 m. If the particle's velocity is 10 m/s, what is the acceleration of the particle?

    • A) a = v^2 / r
    • B) a = v / r
    • C) a = v^2 / t
    • D) a = v / t

    Answer: a = v^2 / r

    Explanation: The correct formula is a = v^2 / r, as centripetal acceleration is directly proportional to velocity squared and inversely proportional to radius.

18. Question 18

    Q18. A car is moving at 30 m/s when it hits a wall and comes to rest in 0.5 seconds. What is the acceleration of the car?

    • A) a = Δv / Δt
    • B) a = v^2 / Δt
    • C) a = v / Δt
    • D) a = Δv^2 / Δt

    Answer: a = Δv / Δt

    Explanation: The correct formula is a = Δv / Δt, as acceleration is the change in velocity over time.

19. Question 19

    Q19. A ball is thrown upwards with an initial velocity of 10 m/s. At the highest point, what is the force acting on the ball?

    • A) F = m x g
    • B) F = m x a
    • C) F = m x v
    • D) F = m x t

    Answer: F = m x g

    Explanation: The correct formula is F = m x g, as the force acting on the ball at the highest point is due to gravity.

20. Question 20

    Q20. A spring-mass system is undergoing simple harmonic motion. If the angular frequency is 2 rad/s, what is the frequency of the motion?

    • A) f = ω
    • B) f = 2ω
    • C) f = ω/2
    • D) f = 3ω

    Answer: f = ω

    Explanation: The correct formula is f = ω, as frequency is directly proportional to angular frequency.