Which one of the following is not the unit of energy?

A. Joule B. Newton-metre

C. Kilowatt D. Kilowatt-hour

A boy weighing 40 kg carriers a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s²)

When an object falls freely towards the earth, then its total energy:

A. Increases B. Decreases

C. Remains constant

D. First increases and then decreases

Which of the following energy change involves frictional force?

A. Chemical energy to heat energy

B. Kinetic energy to heat energy

C. Potential energy to sound energy

D. Chemical energy to kinetic energy

Which one of the following statements about power stations is not true?

A. Hydroelectric power stations use water to drive turbines

B. In a power station, turbines drive generators

C. Electricity from thermal power stations differs from that produced in hydroelectric power stations

D. In hydroelectric power stations and thermal power stations, alternators produce electricity.