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1. Pushing, pulling, twisting and squeezing are all examples of ------. (lesson 5a)
2. Force-meters measure the size of a force in -------. (5a)
3. Forces can change three things about an object. What are these three things? (5a)
4. What is the force produced when two things rub together? (5b)
5. How can the force in question 4 be reduced? (5b)
6. Why things have weight? (5b)
7. What do we call that a low air resistance? (5b)
8. when an object floats the upthrust is equal to the weight. The two forces are --------. (5c)
9. A boat floats higher in sea water than in fresh-water. Why? (5c)
10. What do we call a lever that lifts a large load with a small effort? (5d)
11. Give an example of a lever used as a distance magnifier. (5d)
12. Besides a lever what other machine can make lifting easier? (5d)
13. You push something with a force of 5N and the force of friction is 2N. What is the resultant force. (5e)
14. If a push force is equal to the friction force what can you say about the movement of an object? (5e)
15. An athlete runs 50metres in 5 seconds. What is the athletes average speed, in metres per second? (5f)

ANSWERS

1. Forces.
2. Newtons (N).
3. Shape, speed, direction.
4. Friction.
5. Lubrication.
6. Due to the pull of gravity.
7. Streamlined.
8. Balanced.
9. Sea water is denser than fresh-water so it has a bigger upthrust.
10. A force-magnifier.
11. Arm, hands of a clock, a pedal bin.
12. A pulley.
13. 3N
14. It does not move or if it is already moving it it continues to do so at the same speed. There is no resultant force.
15. 10 metres/second.