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

Total Questions: 50

31. The kinetic energy of the particles are maximum in ___________ . [RRB Group D 05/12/2018 (Afternoon)]

Correct Answer: (a) Gases
Solution:

The particles are free to move with maximum speed as there is negligible force of attraction between the particles. The kinetic energy of the particles are minimum in the solid state as the atoms are closely packed together.

32. Work is done on a body only when__________. [RRB Group D 11/12/2018 (Afternoon)]

Correct Answer: (a) It provides an increase in energy through a mechanical effect.
Solution:

When a force is applied to an object and it moves in the direction of the force, energy is transferred from the agent applying the force to the object upon which the force is applied. This transfer of energy is what we define as work.

33. On which of the following quantities the work done by a body is NOT dependent? [RRB Group D 12/12/2018 (Morning)]

Correct Answer: (a) initial velocity of the body
Solution:

Work done is defined as a product of force time displacement. Formula: W = F × d (cos θ). Hence, work done depends on displacement, the force applied and on the angle between force and displacement.

34. A moving car accelerates to four times its initial velocity. What changes in its potential energy during this process ? [RRB Group D 14/12/2018 (Morning)]

Correct Answer: (c) It remains stable.
Solution:

Potential energy is the energy possessed by a body by the virtue of its height from the ground and in the given case, the car only increases its velocity 4 times but its height from the ground remains constant. Thus, the potential energy does not change.

35. When a compressed slinky is released it converts potential energy into: [RRB ALP Tier - I (10/08/2018) Morning]

Correct Answer: (d) Kinetic energy
Solution:

When slinky is compressed work is done against the spring force, and this work done is stored as potential energy.

36. Which is the form of energy that does NOT occur while riding a bicycle? [RRB ALP Tier - I (10/08/2018) Morning]

Correct Answer: (d) Chemical energy
Solution:

Heat energy is produced while riding the bicycle due to the friction between the tires and the surface of the road. Since the bicycle is in motion hence, Kinetic energy is present and also Mechanical energy. in this case, kinetic energy is equal to the mechanical energy, since potential energy is zero.

37. The work done in one complete revolution of the moon around the earth is equal to: [RRB ALP Tier - I (10/08/2018) Evening]

Correct Answer: (c) Zero
Solution:

Work done (W) = Fd cos θ, Where F = Force applied, d = displacement of the object. In the case of the revolution of the moon around the earth, θ is 90°, Cos 90°= 0. Thus, W = F × d × cos90° = F × d × 0 = 0. So, the work done by the moon when it revolves around the earth is zero.

38. What does the kinetic energy of an object increase with? [RRB ALP Tier - I (13/08/2018) Morning]

Correct Answer: (a) Speed
Solution:

The kinetic energy of an object is the energy it has because of its motion. Kinetic Energy = 1/2 mv² (where m - Mass of the object, v - Velocity of the object). The kinetic energy of an object is directly proportional to the square of its speed. Apart from speed it also depends upon the mass of the object. SI unit for kinetic energy is Joules (kg m² s⁻²).

39. What happens to the Potential and Kinetic energies of a body as it falls down from a height? [RRB ALP Tier - I (13/08/2018) Afternoon]

Correct Answer: (d) Its Potential energy decreases while its Kinetic energy increases.
Solution:

Its Potential energy decreases while its Kinetic energy increases. The decrease in potential energy is exactly equal to the increase in kinetic energy. Kinetic energy: The energy an object has because of its motion is called its kinetic energy. K.E. = 1/2 mv².

40. Which of the following devices converts Chemical energy into Electrical energy? [RRB ALP Tier - I (14/08/2018) Afternoon]

Correct Answer: (a) Electric cell
Solution:

Electric heater is an electrical device that converts electrical energy into heat energy. Hair dryer converts electrical energy into thermal energy. Electric fan converts electrical energy into mechanical energy. Electric motor converts electrical energy into rotational kinetic energy (mechanical energy). Photovoltaic cells (Solar panels) convert sunlight into electricity. A Generator (dynamo) converts the mechanical (kinetic) energy of the rotor to electrical energy.