Railway Science (Physics-Work, Energy and Power) (Part-IV)

Total Questions: 50

1. An object of mass 20 kg is moving with a uniform velocity of 10 ms⁻¹ . What is the kinetic energy possessed by the object? [RRB Group D 05/10/2018 (Evening)]

Correct Answer: (c) 1000 J
Solution:

Given, Mass = 20 kg, Velocity = 10 m/s.
Kinetic Energy = 1/2 mv² = 1/2 × 20 × 100 =  1000 J.

2. A laborer picks up a 10 kg object from the ground and places it 1.2 m above his head. Calculate the work done by him on the goods. (g = 10 ms⁻²) [RRB Group D 08/10/2018 (Morning)]

Correct Answer: (a) 120 J
Solution:

Given that, Mass = 10 kg, g = 10 ms⁻²,
Height (h) = 1.2 m.
∵ Work done = Change in potential energy = mgh.
∴ W = mgh = 10 × 10 × 1.2 ⇒ W = 120 J.

3. An object of mass 15 kg is moving with a velocity of 6 m/s. What is the kinetic energy possessed by the object? [RRB Group D 09/10/2018 (Morning)]

Correct Answer: (a) 270 J
Solution:

Given that, Mass (m) = 15 kg, Velocity (v) = 6 ms⁻¹ .
Using the equation of Kinetic energy,
Kinetic Energy = 1/2 mv²
Kinetic Energy = 1/2 × 15 × 36 = 270 J.

4. A force of 125 N is acting on an object. The object is moved 5 meters in the direction of the force. [RRB Group D 09/10/2018 (Morning)]

Correct Answer: (b) 625 J
Solution:

Given, Force, F = 125 N
Displacement, s = 5m
Work done = Force (F) × Displacement (s) = 125 × 5 = 625 J.

5. An object of mass 15 kg is moving with a uniform velocity of 8 ms⁻¹ . What is the kinetic energy of that object? [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (a) 480 J
Solution:

6. The kinetic energy of an object is 120 J and mass is 15 kg. Find the velocity of the object. [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (b) 4 ms⁻¹
Solution:

7. An object of mass 15 kg is moving with a uniform velocity of 2 m𝑠⁻¹ What is the kinetic energy possessed by the object ? [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (d) 30 J
Solution:

Given that, mass (m) = 15 kg, velocity (v) = 2 ms⁻¹
Using the equation of Kinetic energy,
Kinetic Energy = 1/2 mv²
Kinetic Energy = 1/2 × 15 × 2² = 30 J.

8. An object of mass 10 kg is moving with a uniform velocity of 5 ms⁻¹ . How much kinetic energy has that object possessed? [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (b) 125 J
Solution:

Given : Mass (m) = 10 kg, Velocity (v) = 5 m/s. Kinetic energy, KE = ?
Kinetic Energy (K.E.) = 1/2 × mv²
K.E. = 1/2 × 10 × (5)²
= 1/2 × 10 × 25 ⇒ = 125 J.

9. A car covers a distance of 100 m with a constant force of 50 N. So the work done by the car is: [RRB Group D 10/10/2018 (Evening)]

Correct Answer: (c) 5000J
Solution:

Given that : Distance traveled by car (d) = 100 m, Force (F) = 50 N
Work done by car (W) = F × d = 100 × 50 = 5000 J.

10. An object of mass 13 kg is moving with a uniform velocity of 5 ms⁻¹ . What is the kinetic energy possessed by the object? [RRB Group D 11/10/2018 (Morning)]

Correct Answer: (c) 162.5 J
Solution:

Given, Mass (m) = 13 kg, Velocity (v) = 5 m/s
Kinetic Energy = 1/2 mv²
= 1/2 × 13 ×  5 × 5 = 162.5 J.