Year 5 Science: Friction between surfaces that rub
Part of the Year 5 Science gravity, friction and resistance chapter. Chapter overview · whole chapter on one page
Friction between surfaces that rub
Friction is a force that acts between two surfaces that rub against each other. It acts against the motion, so it slows moving things down.
Friction can be helpful, for example when shoes grip the floor, or when brakes slow a bicycle. Friction can also cause heat, and wear, when moving parts rub together.
Friction is reduced by making surfaces smoother, or by adding oil or grease, so that the surfaces slide more easily.
| Example | What happens |
|---|---|
| rubbing your hands together makes them warm | friction makes heat |
| a bicycle brake pad pressing on the wheel | friction slows the wheel |
| oil put on a moving part | less friction, so less wear |
| shoes gripping a wet floor | more friction helps you not to slip |
Key ideas
- Friction acts between two surfaces that rub.
- Friction acts against the motion of a moving object.
- Friction can make heat, and it can wear moving parts.
- Oil or grease reduces friction, so that the surfaces slide more easily.
Method. Read the table.
- Read the row. The row says rubbing your hands together makes them warm.makes them warm
- Write the answer. So the friction makes heat.friction makes heat
- Write the answer. friction makes heat
Check. Friction between the hands makes heat. ✓
Method. Read the key idea.
- Read the key idea. Friction acts against the motion of a moving object.against the motion
- Choose the word. So the word is against.against
- Write the answer. against
Check. Friction slows moving things down. ✓
Method. Read the table.
- Read the row. The oil row says less friction, so less wear.less friction
- Choose the word. So oil decreases friction.decrease
- Write the answer. decrease
Check. Oil lets the surfaces slide more easily. ✓
Watch out
Watch out: friction does not always slow things down in a useful way. Without friction, shoes would slip on the floor and we could not walk safely.
Try it (with your teacher or a grown-up). Rub your hands together for 20 seconds, and feel the warmth. Then rub a smooth plastic lid and a rough piece of paper in the same way, with your teacher. Which one felt warmer? Write your answer, and say which surface was rougher.
Exam tip
Grown-up tip. Ask: “What made your hands warm? Which surface made more friction?” Let your child compare the two surfaces.
Exercise 9D Friction between surfaces that rub
Method. Read the definition in section 9.4.
- Read the definition. Friction is a force that acts between two surfaces that rub.rub
- Name it. The word is friction.friction
- Write the answer. friction
Check. Friction slows moving things down. ✓
Method. Read the key ideas in section 9.4.
- Read the key idea. Friction acts against the motion.against the motion
- Choose the word. So friction acts against the motion.against
- Write the answer. against
Check. Friction always opposes the way things move. ✓
| Example | What happens |
|---|---|
| rubbing your hands together makes them warm | friction makes heat |
| a bicycle brake pad pressing on the wheel | friction slows the wheel |
| oil put on a moving part | less friction, so less wear |
| shoes gripping a wet floor | more friction helps you not to slip |
Method. Read the first row.
- Read the row. The row says rubbing your hands together makes them warm.makes them warm
- Write the answer. So your hands become warm.warm
- Write the answer. they become warm
Check. The friction makes heat. ✓
| Example | What happens |
|---|---|
| rubbing your hands together makes them warm | friction makes heat |
| a bicycle brake pad pressing on the wheel | friction slows the wheel |
| oil put on a moving part | less friction, so less wear |
| shoes gripping a wet floor | more friction helps you not to slip |
Method. Read the rows.
- Read the rows. The oil row says oil put on a moving part makes less friction.less friction
- Name the example. So the example is oil on a moving part.oil put on a moving part
- Write the answer. oil put on a moving part
Check. Oil reduces friction and wear. ✓
| Example | What happens |
|---|---|
| rubbing your hands together makes them warm | friction makes heat |
| a bicycle brake pad pressing on the wheel | friction slows the wheel |
| oil put on a moving part | less friction, so less wear |
| shoes gripping a wet floor | more friction helps you not to slip |
Method. Read the rows.
- Read the rows. The row says shoes gripping a wet floor help you not to slip.not to slip
- Name the example. So the example is shoes gripping a wet floor.shoes gripping a wet floor
- Write the answer. shoes gripping a wet floor
Check. Friction helps shoes to grip the floor. ✓
Method. Read the key ideas in section 9.4.
- Read the key idea. Friction acts between two surfaces that rub.rub
- Fill the gap. So the missing word is rub.rub
- Write the answer. rub
Check. Friction needs surfaces that touch and rub. ✓
Method. Read section 9.4.
- Read the description. Friction can cause heat, and wear, when moving parts rub together.cause heat
- Name it. So friction makes heat.heat
- Write the answer. heat
Check. Rubbing hands warm up because of friction. ✓
Method. Read the key ideas in section 9.4.
- Read the key idea. Oil or grease reduces friction, so the surfaces slide more easily.reduces friction
- Choose the word. So oil decreases friction.decrease
- Write the answer. decrease
Check. Less friction means less wear. ✓
Method. Read the table in section 9.4.
- Read the row. The brake row says friction slows the wheel.slows the wheel
- Decide. Slowing the bicycle is helpful, so the answer is yes.yes
- Write the answer. yes
Check. Brakes use friction to slow down the wheel. ✓
Method. Think about what makes a test fair.
- Think about the test. Only the surface should change in the test.only the surface
- Write one thing. The block, the push and the place must stay the same.stay the same
- Write the answer. Accept any one of: the same block, the same push, the same starting place.
Check. Changing only the surface makes the test fair. ✓
Method. Think about the rubbing.
- Think about the rubbing. Rubbing the hands together makes friction between them.friction between them
- Write the reason. The friction changes some of the movement into heat.into heat
- Write the answer. Accept any sentence that says rubbing makes friction between the hands, and the friction makes heat.
Check. Friction makes heat when surfaces rub. ✓
Method. Think about the tyres.
- Think about the tyres. The tyres grip the road, which makes friction.grip the road
- Write the reason. The friction slows the car, so it can stop.slows the car
- Write the answer. Accept any sentence that says friction between the tyres and the road slows the car, and helps it to stop.
Check. Friction helps the car to stop safely. ✓