Unit Test Energy

A coal-fired power station generates electricity. Coal is burned and the energy released is used to boil water. The steam from the water makes the generator move and this produces electricity. 

Which row gives the name of the energy store in the coal and the energy store of the moving generator?

coal​ (a)   generator​ ​ (b)  

• chemical
• kinetic
• thermal
• electrical
• mechanical

A cyclist stops his bicycle using the brakes. Which row about energy stores is correct?

decrease ​ (a)   increase ​ ​ (b)  

• kinetic energy
• thermal energy
• potential energy
• chemical energy

A stone is dropped from a tall tower and falls a distance of 50 m to the ground. The stone has a mass of 3.0 kg. At which speed does the stone hit the ground?

• 25 m/s

• 15 m/s

• 31 m/s

• 40 m/s

An object of mass m falls from a higher shelf to a lower shelf. How much gravitational potential energy does the object lose?

• m * g * (h₁ - h₂)

• m * g * h₂

• m * g * (h₁ + h₂)

• m * g * h₁

A box of mass 2.0 kg and weight 20 N is carried to the top of some stairs. How is the work done against gravity on the box calculated?

• 20 x 1.2

• 2.0 x 1.2

• 2.0 x 1.2 x 1.8

• 2.0 x 1.8

A man applies a force of 40 N to push a box along the floor. How much power is required to push the box 4.0 m in 3.0 seconds?

• 100 W
• 20 W
• 53 W

• 80 W

A pump does 460 000 J of work to raise water to fill a tank. It takes 7 minutes to fill the tank. What is the power of the pump?

• 0.8 kW

• 1.5 kW

• 1.2 kW

• 1.1 kW

A box is initially at rest at the top of a rough slope. The box slides down the slope. The weight of the box is 50 N. The slope is 4.0 m long and 2.0 m high. The box does 36 J of work against friction as it slides down the slope. What is the speed of the box as it reaches the bottom of the slope?

• 6.0 m/s

• 6.5 m/s

• 5.2 m/s

• 5.1 m/s

The statements describe what happens when the power of a machine is increased.

1 The work done in a given time decreases.

2 The work done in a given time increases.

3 The time taken to do a given quantity of work decreases.

4 The time taken to do a given quantity of work increases.

Which statements are correct?

• 2 and 3

• 3 and 4
• 1 and 2
• 1 and 4

A girl holds a rubber ball out of a window of a tall building. The mass of the ball is 0.20 kg. The ball is at rest 10 m above a concrete path. Calculate the gravitational potential energy of the ball relative to the concrete path. gravitational potential energy = ............ J