Homework
1. A cyclist travels at a speed of 21.6 km/h. What is this speed in m/s?
2. The turning effect of a force is called a moment. What is the correct unit for a moment?
3. A crane is used to lift some bricks. The bricks have a weight of 1500 N. A counterweight is used to
balance the weight of the bricks.
The diagram shows the position of the bricks and the counterweight. What weight does the
counterweight need to be to balance the weight of the bricks?
4. The spanner is being used to tighten a nut. A moment of 25 Nm is needed to tighten the nut.
Calculate the size of the force that needs to be applied to the spanner to tighten the nut.
5. The diagram below shows the forces involved when a hand is holding up a brick. The elbow acts
as a pivot and the arm is not moving. The force, F, produced by the bicep muscle is balancing the
force of the brick. The downward force of the brick is 15 N.
(a) Calculate the clockwise moment of the force of the brick.
(b) State the size of the anticlockwise moment provided by the force of the bicep muscle.
6. What are the units for work done?
7. A climber has a weight of 690 N. They climb a cliff that is 10 m high. Calculate the work done by
the climber. Include the unit in your answer.
8. A tractor pulls a plough across a field. The field is 75 m wide.
The tractor pulls the plough with a force of 4200 N. Calculate the work done by the tractor each
time it crosses the field. You should include the unit in your answer.
9. Which energy store gains energy when a book is lifted up onto a high shelf?
10. Bungee jumping is an activity that involves jumping from a tall structure or platform while
connected to a bungee cord.
The diagram below shows a person performing a bungee jump off a platform.
(a) Name the force that pulls the bungee jumper towards the ground.
(b) The box contains the names of six different types of energy.
11. Use words from the given (with in brackets) to complete the following sentences.
[Chemical; elastic; electrical; gravitational potential; kinetic; sound]
When the bungee jumper falls from the platform his ______________ energy is transferred as
______________ energy.
As the jumper falls the bungee cord will stretch. When the bungee cord is stretched the energy is
stored as ___________ energy.
12. The diagram represents a hydroelectric power station. The upper reservoir is connected to the
turbine generator through a pipe. The turbine generator uses the energy stored in the water and
transfers it electrically.
Which two statements about the energy transfers that occur are true? Tick (✓) two boxes.
13. Some examples of energy stores and the way energy can be transferred are follows, chemical
energy; elastic potential energy; electricity; forces; gravitational potential energy; heating;
kinetic energy; light waves; sound waves
The diagram shows a simple electric circuit.
Use terms from the box to complete these sentences.
(a) The cell in the circuit stores energy as _______
(b) When the switch is closed energy is transferred to the bulb by ______
(c) The bulb transfers energy to the surroundings by _____ and by ______.
14. The diagram shows a mechanical toy moving across the floor.
A teacher draws a Sankey diagram to show the energy transfers taking place as the mechanical
toy moves.
(a) (i) State the reason why the total output energy of the mechanical toy is 200 J.
(ii) The Sankey diagram has been drawn to scale. Calculate the amount of useful energy output
when the energy input is 200 J.