Free Work-Energy Theorem MCQs with Answers

1. The work-energy theorem states that the net work done on a body equals

• A. its total mechanical energy
• B. the change in its kinetic energy
• C. the change in its potential energy
• D. its momentum

Explanation: The work-energy theorem equates net work with the change in kinetic energy, which is why a braking force doing negative work brings a car to rest. It holds whether the force is constant or varying. Changes in potential energy relate to the work done by conservative forces specifically, which is a narrower statement.

2. For a body sliding down a frictionless slope, the speed at the bottom depends on

• A. the length of the slope
• B. the vertical height dropped, but not on the angle of the slope
• C. the mass of the body
• D. the angle only

Explanation: Energy conservation gives half mv squared equal to mgh, so the mass cancels and only the height matters, which means a gentle ramp and a steep one of the same height give the same final speed. The gentle slope simply takes longer. Friction would break this result, since the longer path would then waste more energy.

3. The law of conservation of energy states that energy

• A. can be created when needed
• B. can be destroyed by friction
• C. can be transformed from one form to another but the total remains constant
• D. always increases in an isolated system

Explanation: Friction does not destroy energy; it converts organised kinetic energy into disordered thermal energy, which is harder to use but is still energy. Every apparent loss in mechanics is a transfer to a form outside the system being considered. Including mass as a form of energy through E equals mc squared makes the law hold in nuclear reactions too.