Form 3 Science Chapter 7: Energy and Power

Which of the following will increase the work done?

• Decreased power

• Decreased gravity

• Increased distance

• Decreased friction

A wood with the mass of 2 kg is dropped from a height of 6 m. What is the kinetic energy of the wood when it reaches the ground?

• 120 J

• 130 J

• 140 J

• 150 J

A rock with a mass of 2kg fell from a building of 20 metre height. What is the speed of the rock before the rock hits the ground?

The S.I. unit of power is ( ).

The S.I. unit of work is ( ).

The Principle of Conservation of Energy states that

• energy can be created

• energy can be destroyed

• energy can be converted from one form to another

• energy can be lost

Work = Force x ( )

A wooden block is put on the floor. Zi Jing pulls the wooden block horizontally using 2 N along 0.5 m. Calculate the amount of work done.

• 2 J

• 1 J

• 3 J

• 4 J

William uses a pulley to pull a box weighing 15 kg vertically from the floor. The vertical displacement is 4m. Calculate the amount of work done. (Consider 1 kg = 10 N)

• 60 J

• 600 J

• 30 J

• 300 J

A pulley is used to lift a table weighing 1000 N. The table is carried to a height of 2.5m in 50 seconds. Calculate the power of the pulley.

• 50 W

• 100 W

• 25 W

• 200 W