Topic 7 - Energy, Work and Power

A ball of mass 0.3 kg is thrown at a speed of 20 m/s. What is its kinetic energy?

• 3 J

• 9 J

• 36 J

• 60 J

A rock of mass 20 kg is travelling in space at a

speed of 6 m/s. What is its kinetic energy?

• 60 J

• 120 J

• 360 J

• 720 J

A man weighs 600 N, He runs up stairs of total

height metres in 3 seconds.

How much power is exerted by the man?

Power = work done/time = (600 x 4)/3 W

• 450 W

• 800 W

• 2400 W

• 7200 W

Which quantity is calculated by multiplying the

magnitude of a force by the distance moved in

the direction of the force?

• acceleration

• power

• pressure

• work

Which of the following represents some of the main energy changes which take place in a coal-fired power station?

• heat > chemical > electrical

• heat > kinetic > electrical

• heat > light > electrical

• kinetic > electrical > potential

From which source would the release of energy be affected by a change in the Earth's gravitational field?

• chemical

• geothermal

• nuclear

• hydroelectric

An electric kettle is rated at 2.5 k W. How much energy is transferred in 3.0 minutes?

• 7.5 J

• 450 J

• 7500 J

• 450000 J

A boy pushes a toy cart along a level road and then lets it go. As the cart is slowing down, the biggest energy change is from

• heat to kinetic

• kinetic to heat

• kinetic to potential

• potential to heat

A car moves from rest with uniform acceleration along a horizontal road. After travelling a distance of 100 metres, it has kinetic energy equal to 200 000 J, What resultant force is acting on the car?

• 100 N

• 1000 N

• 2000 N

• 20000 N

Some students climb a set of stairs at school, and each student is timed, Their weights and times are recorded in the table. Which student develops the most power?

• A

• B

• C

• D