# Engineering Physics Questions and Answers – Work and Energy

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This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Work and Energy”.

1. The total energy of the universe is constant.
a) True
b) False

Explanation: As the entire universe may be regarded as an isolated system, the total energy of the universe is constant. If one part of the universe loses energy, another part must gain an equal amount of energy.

2. How much mass is converted into energy per day in Tarapur nuclear power plant operated at 107 kW?
a) 10g
b) 9g
c) 9.6g
d) 2g

Explanation: Power, P = 107 kW = 1010J/s
Time, t=1day=24×60×60s
Energy produced per day, E = Pt = 864×1012J
E = mc2
m = E/c2 = 9.6g.

3. A machine gun fires 60 bullets per minute, with a velocity of 700m/s. If each bullet has a mass of 50g, find the power developed by the gun.
a) 1225W
b) 12250W
c) 122.5W
d) 122W

Explanation: Mass of the bullets = 60×50 = 3000g = 3kg
v = 700m/s t = 1min = 60s
Power = W/t = (Kinetic energy)/t = 12250W.
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4. For a collision to occur, the actual physical contact is necessary.
a) True
b) False

Explanation: A collision is said to occur between two bodies, either if they physically collide against each other or if the path of one is affected by the force exerted by the other. For a collision to take place, the actual physical contact is not necessary.

5. Which of the following is an example of inelastic collision?
a) Collision between two vehicles
b) Collision between glass balls
c) A bullet fired into a wooden block
d) Collision between two railway compartments

Explanation: If there is a loss of kinetic energy during a collision, it is called an inelastic collision. Collision between two vehicles is an example for inelastic collision.

6. Mud thrown on a wall and sticking to it is an example for ___________
a) Inelastic collision
b) Elastic collision
c) Super elastic collision
d) Perfectly inelastic collision

Explanation: If two bodies stick together after the collision and move as a single body with a common velocity, then the collision is said to be perfectly inelastic collision. A mud thrown on a wall sticks to the wall, hence it is an example for perfectly inelastic collision.

7. Collision between two carom coins is an example for ___________
a) Oblique collision
b) Perfectly inelastic collision
c) Inelastic collision
d) Elastic collision

Explanation: If two bodies do not move along the same straight line path but lie in the same plane before and after the collision, the collision is said to be oblique or two dimensional collisions.

8. When a light body collides with a massive body at rest ___________
a) The light body rebounds after the collision
b) The light body Remains at rest
c) The massive body rebounds after the collision
d) No reaction happens

Explanation: When a light body collides against a massive body at rest, the light body rebounds after the collision with an equal and opposite velocity while the massive body practically remains at rest. A light ball striking a wall rebounds almost with the same speed and the wall remains at rest.

9. When a massive body collides against a light body at rest ___________
a) The light body starts moving
b) The light body rebounds
c) The velocity of the bodies get exchanged
d) The massive body comes to rest

Explanation: When a massive body collides against a light body at rest, the velocity of the massive body remains almost unchanged while the light body starts moving with a velocity wise the velocity of the massive body.

10. If a force acts perpendicular to the direction of motion of a body, what is the amount of work done?
a) Infinity
b) Constant
c) Zero
d) Sinθ

Explanation: If a force acts perpendicular to the direction of a body, the amount of work done is zero because there is no displacement in the direction of a force.

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