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

Total Questions: 50

41. If a body is projected vertically upward, what will be the velocity of the body at the highest point of motion? (g = acceleration due to gravity, h = height, t = time) [RRB Group D 15/10/2018 (Morning)]

Correct Answer: (a) Zero
Solution:

At the highest point of its motion, just before it starts to descend, its velocity becomes zero momentarily. This is because at the highest point, the body comes to a momentary stop before gravity starts pulling it downward.

42. A bus accelerates uniformly from 36 kmh⁻¹ to 72 kmh⁻¹ in 5 s. Calculate the acceleration of the bus. [RRB Group D 15/10/2018 (Morning)]

Correct Answer: (d) 2 ms⁻²
Solution:

43. A bus starts from rest and travels down a hill with constant acceleration. It travels a distance of 200 m in 10 s. Its acceleration is: [RRB Group D 15/10/2018 (Afternoon)]

Correct Answer: (c) 4 m/s²
Solution:

44. The distance traveled by a particle starting from rest and moving with an acceleration (4/3) m/s² in the 4 3 third second will be _______ [RRB Group D 22/10/2018 (Morning)]

Correct Answer: (c) 10/3 m
Solution:

45. A car starting from rest moves with uniform acceleration of 1ms⁻² for 2 minutes. Find the speed acquired by the car. [RRB Group D 22/10/2018 (Afternoon)]

Correct Answer: (c) 120 ms⁻¹
Solution:

Given that : Acceleration = 1 ms⁻² , Time (t) = 2 minutes or 120 sec.
We know that,
Velocity = Acceleration × Time
= (1 ms⁻²) × (120 sec) = 120 ms⁻¹.

46. If the weight of an object is 200 N, find its mass (g = 10 ms⁻²) [RRB Group D 22/10/2018 (Evening)]

Correct Answer: (d) 20 kg
Solution:

Given that : Weight of the object (W) = 200 N, Acceleration due to gravity (g) = 10 m/s²
mass of object, m = 𝑊/g = 200 N/10 ms⁻² = 20 kg.

47. The weight of an object when measured on the surface of the earth is 60 N. What will be its weight when measured on the surface of the Moon? [RRB Group D 22/10/2018 (Evening)]

Correct Answer: (a) 10 N
Solution:

Given that : Weight of the object on the earth surface (Wₑ) = 60 N
∵ Weight of the object on the moon surface (Wₘ) = ⅙ × Weight of the object on the Earth’s surface
Wₘ = 1/6 × 60 = 10 N.

48. The mass of an object on the earth's surface is 60 kg. So what will be its mass on the Moon? [RRB Group D 23/10/2018 (Morning)]

Correct Answer: (b) 60 kg
Solution:

The mass of an object remains constant regardless of its location in the universe. Therefore, the mass of an object on the Moon would be the same as its mass on Earth. The weight of an object on the moon is about 1/6 of its weight on the earth.

49. Starting from rest a boat moves in a straight line at a constant rate with an acceleration of 3 ms⁻² for 8 seconds. Find the total distance covered by the boat during this time. [RRB Group D 23/10/2018 (Afternoon)]

Correct Answer: (c) 96 m
Solution:

50. A cricket ball of mass 100 g moving with a velocity of 30 m/s is stopped by a player in 0.05 sec. The average force exerted by the player is: [RRB Group D 23/10/2018 (Afternoon)]

Correct Answer: (c) -60 N
Solution: