# Physics - Work Energy and Power Questions Answers

1. An electric lamp whose resistance is 10 ohm, and a conductor of 2 ohm resistance are connected in series with a 6 V battery. The total current through the circuit and the potential difference across the electric lamp are

• A. 3.6A,6V  • B. 0.5A,5V  • C. 2.0 A, 0.2 V  • D. 0.3 A, 3 V  2. When a body falls freely

• A. its PE is converted into KE  • B. its KE is converted into PE  • C. its mechanical energy is converted into heat energy  • D. None of the above  • Option : A
• Explanation : (A) When a body falls freely, the potential energy due to its height converted into kinetic energy due to its motion.

3. Heat energy of an object is

• A. the average energy of the molecules of the object  • B. The total energy of the molecules of the object  • C. the average velocity of the molecules of the object  • D. the average potential energy of the molecules of the object  • Option : B
• Explanation : (B) Heat energy or thermal energy of an object is the total thermal kinetic energy and thermal potential energy of all its atoms and molecules. So, we can say that heat energy of an object is the total energy of the molecules of the object

4. Rocket works on the principle of conservation of

• A. mass  • B. energy  • C. momentum  • D. None of these  • Option : C
• Explanation : (C) A rocket works by expelling gases from one end at a very high speed which inturn, upthrust the rocket. This illustrates law of conservation of momentum.

5. The momentum of a heavy object at rest will be

• A. zero  • B. small  • C. large  • D. None of these  • Option : A
• Explanation : (A) Momentum = Mass x velocity
At rest velocity = 0
So, momentum = 0