Railway Science (Physics-Force and Pressure) (Part-IV)

Total Questions: 50

1. A bullet of mass 12 g is fired from a rifle. The bullet takes 0.006 sec to move through its barrel and leaves it with a velocity of 600 m/s. What is the force exerted on the bullet by the rifle ? [RRB Group D 24/09/2018 (Evening)]

Correct Answer: (d) 1200 N
Solution:

Given that, mass of the bullet (m) = 12 gm or 0. 012 kg, Time (t)= 0.006 sec, Velocity (v)= 600 m/s.
Force = Mass × Acceleration = 𝑀𝑎𝑠𝑠 × 𝑣𝑒𝑙𝑜𝑐𝑖𝑡y/𝑡𝑖𝑚e.
⇒ Force = 0.012 × 600/ 0.006 = 1200 N.

2. A bullet of mass 12g is fired from the gun. The bullet takes 0.006 seconds to exit the barrel and its velocity is 300 m/s. What will be the force applied by the gun on the bullet? [RRB Group D 25/09/2018 (Morning)]

Correct Answer: (d) 600 N
Solution:

3. The apparent mass of an object on Earth is 10 kg. What is its weight on earth? [RRB Group D 25/09/2018 (Morning)]

Correct Answer: (d) 98 N
Solution:

The weight of an object is the force exerted on it due to gravity. On Earth, the weight of an object is given by : Weight = mass (m) × Acceleration due to gravity (g). Given : m = 10 kg, g = 9.8 m/s² . Calculations : Weight = 10 × 9.8 = 98 N.

4. An object with a mass of 100 kg is accelerated uniformly from a velocity of 5 m𝑠⁻¹ to 17 m𝑠⁻¹ m in 6 s. The magnitude of the force exerted on the object is ______ . [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (c) 200 N
Solution:

Given that, Mass of the object (m) = 100
kg, The initial velocity of the object(u)= 5
m/s, The final velocity of the object (v)=
17 m/s, Time taken by the object to
accelerate (t)= 6 sec.
We know that,
Force= mass × acceleration = 𝑚(𝑣−𝑢)/t.
⇒ Force = 100(17-5)/6 = 200 N.

5. The mass of an object is 20 kg. What will be the weight of that object in the earth [g= 9.8ms⁻²] [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (a) 196 N
Solution:

Given that, Mass of an object = 20 kg, Acceleration of Gravity (g)= 9.8 ms⁻²
Weight= Mass × Acceleration of Gravity = = 20 × 9.8= 196 N.

6. The momentum of an object of mass 200 g with 10 J of kinetic energy will be : [RRB Group D 26/09/2018 (Afternoon)]

Correct Answer: (c) 2 kg m/s
Solution:

7. An object of mass 10 kg is moving with velocity 2 ms⁻². The momentum inherent in the object is _______. [RRB Group D 26/09/2018 (Afternoon)]

Correct Answer: (b) 20 kgms⁻¹
Solution:

Momentum, p = mv = 10 × 2 = 20 ms⁻¹.

8. A car accelerates uniformly from 18 kmh⁻¹ to 72 kmh⁻¹ in 5 s. The acceleration of the car is : [RRB Group D 27/09/2018 (Morning)]

Correct Answer: (d) 3 ms⁻²
Solution:

9. When a constant force acts on an object with a mass of 8 kg for a duration of 3 s, it increases the object’s velocity from 4 ms⁻¹ to 6 ms⁻¹ . What is the magnitude of the applied force? [RRB Group D 27/09/2018 (Morning)]

Correct Answer: (a) 5.33 N
Solution:

10. When a constant force acts on an object of mass 7 kg for 3 s, it increases the velocity from 3 ms⁻¹ to 8 ms⁻¹ . What is the magnitude of the applied force? [RRB Group D 27/09/2018 (Afternoon)]

Correct Answer: (c) 11.66 N
Solution: