Railway Science (Physics-Work, Energy and Power)

Total Questions: 50

31. If work has a positive value, the body on which work has been done would: [RRB Group D 20/09/2018 (Morning)]

Correct Answer: (d) Gain energy
Solution:

If the work done by a force on a body is positive, then its kinetic energy increases. The work-energy theorem states that the work done on an object is equal to the change in its kinetic energy.

32. Fill in the blanks with the correct option. [RRB Group D 20/09/2018 (Afternoon)]

A body is thrown vertically upwards. During its rise the Potential Energy ______ and Kinetic energy _______ .

Correct Answer: (b) increases, decreases
Solution:

Kinetic energy (KE) - The energy possessed by a body by virtue of its motion is called kinetic energy. Potential energy (PE) - The energy possessed by a body by virtue of its position or configuration is called potential energy. Kinetic energy decreases (as velocity decreases). Potential energy increases (as height increases).

33. When a bullet is fired from a gun, the kinetic energy of the bullet is _________. [RRB Group D 22/09/2018 (Morning)]

Correct Answer: (b) more than the gun
Solution:

The kinetic energy is inversely proportional to the mass keeping momentum constant, therefore kinetic energy of the gun is lesser than the kinetic energy of the bullet.

34. A compressed spring possesses: [RRB Group D 22/09/2018 (Afternoon)]

Correct Answer: (b) Potential energy
Solution:

The energy that is stored in an object due to its position . Examples - a raised hammer and a stretched rubber band. Electric energy - Energy associated with the movement of electrons. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass.

35. During free fall of an object, which of the following energy increases at any one point in its path ? [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (a) kinetic energy
Solution:

Chemical energy: It remains constant during the object's free fall. Potential energy: Potential energy decreases during free fall. As the object falls closer to the ground, its potential energy relative to the ground decreases. Mechanical energy: It is the sum of kinetic and potential energy.

36. Water stored in a dam possesses ? [RRB Group D 26/09/2018 (Morning)]

Correct Answer: (a) potential energy
Solution:

Energy due to the object's position. Electrical energy: Hydroelectric dams convert water's potential energy into electrical energy. Kinetic energy: Energy associated with an object's motion.

37. 1 kWH = ______ J [RRB Group D 27/09/2018 (Morning)]

Correct Answer: (d) 3.6 × 10⁶
Solution:

Power - The rate of doing work. SI unit of power is Watt. 1 kW= 10³ watt. The commercial unit of electrical energy is kilowatt hour (Kwh). One kilowatt-hour is the energy consumed by an electrical appliance of power one kilowatt used for one hour.

38. When an arrow is released from its bow, its energy is transformed into___. [RRB Group D 27/09/2018 (Afternoon)]

Correct Answer: (c) From potential energy to kinetic energy
Solution:

The kinetic energy of an object is the energy that it possesses due to its motion. Formula, Kinetic energy (KE) = 1/2 mv² , where m is maas and v is velocity. Potential energy is the energy held by an object because of its position or configuration. Formula - Potential energy (PE) = mgh, where m is mass , g is acceleration due to gravity and h is height.

39. If a constant force applied on an object is given as the product of force and distance moved by the object in the direction of force, then it is termed as: [RRB Group D 27/09/2018 (Evening)]

Correct Answer: (a) Work done
Solution:

Work done : Formula : W = F.s , Where F = Force, s = Displacement in the direction of force, Unit joule (J). Impulse - The effect of force acting over time to change the momentum of an object. Unit - Newton seconds or kg m/s. Acceleration - The rate of change of velocity. Unit - Newton-seconds (Ns) or kg m/s. Retardation (a negative acceleration) - The rate of decrease of velocity with time.

40. _______energy contains two types of energy. [RRB Group D 01/10/2018 (Morning)]

Correct Answer: (a) mechanical
Solution:

The types of mechanical energy include Kinetic Energy (the energy an object has because of its motion) and Potential Energy (the stored energy in any object or system by virtue of its position).