Railway Science (Physics-Gravitation)

Total Questions: 59

31. Which of the phenomenon mentioned in the options is NOT explained by the universal law of gravitation? [RRB Group D 15/10/2018 (Afternoon)]

Correct Answer: (d) The motion of sun around the planets
Solution:

The planets rotate and revolve in circular orbits around the sun and the motion repeats after a fixed time period so the motion of planets is rotatory, circular and periodic. The Universal law of gravitation - Every object in the universe attracts every other object with a force which is proportional to the product of their masses and inversely proportional to the square of the distance between them.

32. Which of the following statements is true? [RRB Group D 16/10/2018 (Evening)]

Correct Answer: (b) The Mass of a body remains same while the Weight changes from place to place.
Solution:

Mass represents the amount of matter in an object and is a fundamental property independent of location. It remains constant regardless of gravity's influence.Weight is the force exerted on an object due to gravity. It depends on the mass of the object and the strength of the gravitational field, which varies depending on location.

33. The work done by gravity depends on: [RRB Group D 22/10/2018 (Morning)]

Correct Answer: (b) The difference in the vertical heights of the initial and final position of the object.
Solution:

Work done - The product of the displacement and the component of the applied force of the object in the direction of displacement. It depends on the angle between force and displacement so it is positive as well as negative. Formula : W = Fd.cosθ. Unit - Joule (J). Gravity - The force that attracts a body towards the earth or towards any other physical body having mass.

34. When a body is taken from the equator to the North and South poles then its weight [RRB Group D 22/10/2018 (Afternoon)]

Correct Answer: (d) increases
Solution:

The Earth isn't a perfect sphere but slightly bulges at the equator and flattens at the poles. When the Earth spins, objects feel an outward force called centrifugal force, countering gravity, especially strong at the equator. Gravity pulls objects toward the Earth's center, stronger at the poles due to more concentrated mass there compared to the equator.

35. The gravitational potential energy of an object at a point above the ground is defined as the work done in________. [RRB Group D 22/10/2018 (Afternoon)]

Correct Answer: (c) raising it from the ground to that point against gravity
Solution:

Gravitational potential energy (GPE) represents the stored energy an object possesses due to its position in a gravitational field. Equation: GPE = m⋅g⋅h. Where, ‘m’ is the mass in kilograms. ‘g’ is the acceleration due to gravity (9.8 m/sec² on earth). ‘h’ is the height above the ground in metres.

36. The work done by gravity does not depend on which of the following? [RRB Group D 22/10/2018 (Evening)]

Correct Answer: (a) On the path on which the object is moving.
Solution:

The work done by a conservative force such as gravity depends on the initial and final positions only. The work done by the force is defined to be the product of the component of the force in the direction of the displacement and the magnitude of the displacement.

37. The formula for gravitational potential energy is: [RRB Group D 23/10/2018 (Evening)]

Correct Answer: (c) U = mgh
Solution:

Gravitational Potential Energy - The energy stored in an object as the result of its vertical position or height. Energy - Capacity to do work. SI Unit - Joule. Kinetic Energy - The energy that is possessed due to its motion. Formula : 1/2mv².

38. The motion of the Moon around the Earth is due to_____. [RRB Group D 24/10/2018 (Morning)]

Correct Answer: (a) gravitational force
Solution:

The gravitational attraction provides the centripetal force needed to keep planets in orbit around the Sun and all types of satellites in orbit around the Earth. The average gravitational pull of the Earth is 9.8 m/s². Centrifugal force is the apparent outward force on a mass when it is rotated. Centripetal force - It can be defined as the force that causes a body to move in circular motion.

39. Which of the following is not an example of gravity? [RRB Group D 24/10/2018 (Afternoon)]

Correct Answer: (b) It is helpful in the rotation of the black hole
Solution:

Gravity: It is the force by which an earth draws objects toward its center. The acceleration due to gravity is the rate of increase of velocity of a body falling freely towards the earth. The value of g at the surface of earth is 9.8 m/s² .

40. Which of the following is a weak force? [RRB Group D 26/10/2018 (Afternoon)]

Correct Answer: (b) gravitational force
Solution:

Universal Law of Gravitation: Everybody in the universe attracts every other body with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Neutrons and protons are bound in a nucleus by the short-range strong nuclear force.