Railway Science (Physics-Work, Energy and Power)

Total Questions: 50

41. An object is thrown vertically upwards and it reaches a maximum height 'h' above the ground. During its movement up, the object will have ________ at 3/4 of the height 'h'. [RRB Group D 01/10/2018 (Afternoon)]

Correct Answer: (c) Potential energy is more and kinetic energy is less.
Solution:

When an object is thrown vertically upward, its velocity decreases continuously, leading to a decrease in kinetic energy (KE). As kinetic energy decreases, potential energy (PE) increases to compensate. At the maximum height (h), velocity is zero, resulting in zero kinetic energy and maximum potential energy. At ₃/₄th of the height, potential energy (PE) surpasses kinetic energy because PE increases with height.

42. A car, while moving, is facing a wind from the opposite direction. The work done by the wind on the car will be ______. [RRB Group D 01/10/2018 (Evening)]

Correct Answer: (d) Negative
Solution:

Three types of Work - Positive work, Negative work and Zero work. The nature of work depends on the angle between force and displacement. Positive work - If the applied force displaces the object in its direction, then the work done is known as positive work. Negative work - If the force and displacement work in the opposite direction. Zero work - If the force and displacement act in perpendicular to each other.

43. 1 KW = ? [RRB Group D 03/10/2018 (Morning)]

Correct Answer: (a) 1000 W
Solution:

One Kilowatt hour is the energy used in one hour at the rate of 1000 J s⁻¹ (or 1 kW). The energy used in households, industries and commercial establishments are expressed in Kilowatt hour. SI unit of power is Watt (W).

44. Which of the following is not dependent on the work done on an object ? [RRB Group D 03/10/2018 (Evening)]

Correct Answer: (b) mass of the object
Solution:

Work done does not depend upon the initial velocity of the object. Work is a scalar quantity. Its SI unit is joule (J).

45. Which of the following does not have kinetic energy ? [RRB Group D 05/10/2018 (Afternoon)]

Correct Answer: (b) raised hammer
Solution:

The gravitational potential energy of an object depends on its height or position relative to a reference point. Because the hammer is above the ground, it possesses non-zero potential energy. Kinetic energy is associated with the motion of an object or particle and is influenced by both its velocity and mass.

46. Work is the product of ________. [RRB Group D 08/10/2018 (Morning)]

Correct Answer: (d) force and displacement of the object in the direction of the force
Solution:

Work is the result of multiplying the component of force acting in the direction of displacement by the magnitude of that displacement. Work = F. d, Unit- Joule (J), Dimension- [ML²T ⁻²].

47. Work done on an object does not depend on which of the following? [RRB Group D 09/10/2018 (Afternoon)]

Correct Answer: (b) mass of the object
Solution:

Work done is the product of force and displacement. Hence, work done depends on displacement, the force applied and on the angle between force and displacement. Mass is defined as the amount of matter contained in the object or body.

48. The kinetic energy of an object increases with ___________. [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (b) velocity
Solution:

Formula K.E = 1/2 mv² . When the velocity of an object doubles, its kinetic energy quadruples. It must always be either zero or a positive value. It is a scalar quantity because it has magnitude but no direction.

49. 1 joule = ? [RRB Group D 09/10/2018 (Evening)]

Correct Answer: (b) 1 newton × 1 meter
Solution:

One Joule is equal to the energy transferred to an object when a force of one Newton acts on that object in the direction of the force's motion through a distance of one meter.

50. When you stretch a rubber band, the energy transferred is stored as ______. [RRB Group D 10/10/2018 (Morning)]

Correct Answer: (a) Potential energy
Solution:

When elastic is stretched, it's loaded with potential energy, when released there is a shift to kinetic energy. The potential energy is the ‘stored energy’ by virtue of the position or configuration of a body. The dimensions of potential energy are [ML²T⁻²] and the unit is Joule (J).