Conservation of Energy Practice Questions

A shop worker lifts a tin of paint of mass $400\,\mathrm{g}$ from the floor onto a shelf $1.5\,\mathrm{m}$ above the floor.

Calculate the change in gravitational potential energy of the tin of paint.

Use the equation

$$\Delta\mathrm{GPE} = m \times g \times \Delta h$$

gravitational field strength $(g) = 10\,\mathrm{N/kg}$

change in gravitational potential energy = ............................................... J

A runner of mass $65\,\mathrm{kg}$ is running at a steady speed of $8.0\,\mathrm{m/s}$.

Calculate the kinetic energy of the runner.

Use the equation

$$KE = \tfrac{1}{2} \times m \times v^2$$

kinetic energy = ............................................... J

State what is meant by the conservation of energy.

Describe the energy transfers that take place as the kettle brings the water to the boil.

Show that a speed of $144\,\mathrm{km/h}$ is equal to $40\,\mathrm{m/s}$.

Calculate the kinetic energy of the cricket ball.

kinetic energy = ............................................... J

A crane lifts a steel beam vertically through a height of $15\,\mathrm{m}$.

The gravitational potential energy store of the beam increases by $27\,000\,\mathrm{J}$.

gravitational field strength $(g) = 10\,\mathrm{N/kg}$

Calculate the mass of the steel beam.

mass = ............................................... kg

An arrow of mass $0.025\,\mathrm{kg}$ leaves a bow with a kinetic energy of $80\,\mathrm{J}$.

Calculate the speed of the arrow as it leaves the bow.

speed = ............................................... m/s

Calculate the change in the gravitational potential energy store of the stone as it falls.

change in gravitational potential energy = ............................................... J

Assume that all of this energy is transferred to the kinetic energy store of the stone.

Calculate the speed of the stone just before it hits the water.

speed = ............................................... m/s

Use the principle of conservation of energy to calculate the energy transferred to the thermal energy store of the torch and its surroundings.

energy transferred to thermal store = ............................................... J

The torch and its surroundings can be treated as a closed system.

Explain why there is no net change to the total energy in this closed system.

Calculate the kinetic energy of the car just before it hits the barrier.

kinetic energy = ............................................... J

Describe the changes in the way energy is stored as the car hits the barrier and comes to rest.

The train starts from rest and is accelerated along a level track by a constant driving force.

Describe the changes in the way energy is stored as the train speeds up.

Calculate the kinetic energy of the train when it is travelling at $20\,\mathrm{m/s}$.

kinetic energy = ............................................... J

The driver applies the friction brakes and the train slows to a stop at a station.

Describe the energy transfers that take place while the train is slowing down.

Use data from the table to show that the total mass of the go-kart and driver is $160\,\mathrm{kg}$.

Predict the kinetic energy of the go-kart and driver at a speed of $25\,\mathrm{m/s}$.

kinetic energy = ............................................... J

The driver brakes so that the speed of the go-kart falls from $20\,\mathrm{m/s}$ to $10\,\mathrm{m/s}$.

Calculate the energy transferred out of the kinetic energy store of the go-kart and driver, and state where this energy is transferred to.

energy transferred = ............................................... J

Assume that all of the kinetic energy of the ball is transferred to its gravitational potential energy store.

Calculate the maximum height reached by the ball above the point where it left her hand.

maximum height = ............................................... m

In practice the ball does not reach the height calculated in part (a).

Explain why, in terms of energy.

Calculate the energy transferred from the skier to the thermal energy store of the surroundings during the descent.

energy transferred to thermal store = ............................................... J

Explain, using the principle of conservation of energy, what has happened to this energy.