Year 5 Science: Gears
Part of the Year 5 Science levers, pulleys and gears chapter. Chapter overview · whole chapter on one page
Gears
Gears are toothed wheels that fit together, so that one turns the other. The gear that is turned by the motor or by the person is the driver. The gear that is turned is the driven gear.
When a small gear turns a large gear, the large gear turns more slowly, but it can turn with a greater effect on a load. When a large gear turns a small gear, the small gear turns faster. Two meshed gears turn in opposite directions.
| Gear | Number of teeth |
|---|---|
| small gear (driver) | 10 |
| large gear (driven) | 20 |
Key ideas
- Gears are toothed wheels that mesh, so that one turns the other.
- A small gear turning a large gear makes the large gear turn more slowly.
- Meshed gears turn in opposite directions.
- A gear with more teeth turns more slowly, with more effect on the load.
Method. Read the table.
- Read the row for the large gear. The large gear has 20 teeth.20 teeth
- Write the number. So the answer is 20.20
- Write the answer. 20
Check. The large gear has twice as many teeth as the small gear. ✓
Method. Divide the large gear’s teeth by the small gear’s teeth.
- Read the teeth. The large gear has 20 teeth, and the small gear has 10.20 and 10
- Divide. The small gear turns 20 divided by 10, which is 2 times.20 divided by 10 is 2
- Write the answer. 2
Check. The small gear turns twice for each turn of the large gear. ✓
Method. Think about how many turns each makes.
- Think about the turns. The large gear makes one turn while the small gear makes two.one turn
- Choose the gear. So the large gear turns more slowly.large gear
- Write the answer. large gear
Check. The large gear has more teeth, so it turns more slowly. ✓
Watch out
Watch out: a gear with more teeth turns more slowly, but it can turn with more effect. A bigger gear does not turn faster.
Try it (with your teacher or a grown-up). Look at two gear wheels, or pictures of a bicycle’s front and back gears, with your teacher. Count the teeth on each wheel. Which one would turn more slowly if the other one turned once? Write one sentence about your answer.
Exam tip
Grown-up tip. Ask: “Which gear has more teeth? Which turns more slowly? Why is that easier when climbing a hill?” Let your child count the teeth.
Exercise 10C Gears
Method. Read section 10.3.
- Read the definition. Gears are toothed wheels that fit together.toothed wheels
- Name them. The word is gears.gears
- Write the answer. gears
Check. Gears can change the speed of turning. ✓
Method. Think about the gear that is turned first.
- Think about the first gear. In the picture, the small gear is turned first, so it is the driver.turned first
- Name the gear. So the driver is the small gear.small gear
- Write the answer. small gear
Check. The driver is the gear that turns the other gear. ✓
| Gear | Number of teeth |
|---|---|
| small gear (driver) | 10 |
| large gear (driven) | 20 |
Method. Read the row for the small gear.
- Read the row. The small gear row shows 10 teeth.10
- Write the number. So the answer is 10.10
- Write the answer. 10
Check. The large gear has 20 teeth. ✓
| Gear | Number of teeth |
|---|---|
| small gear (driver) | 10 |
| large gear (driven) | 20 |
Method. Read the row for the large gear.
- Read the row. The large gear row shows 20 teeth.20
- Write the number. So the answer is 20.20
- Write the answer. 20
Check. The large gear has twice as many teeth. ✓
| Gear | Number of teeth |
|---|---|
| small gear (driver) | 10 |
| large gear (driven) | 20 |
Method. Subtract the small gear teeth from the large gear teeth.
- Read the numbers. The large gear has 20 teeth and the small gear has 10.20 and 10
- Subtract. The difference is 20 minus 10, which is 10 teeth.20 - 10 = 10
- Write the answer. 10
Check. Check: 10 + 10 = 20. ✓
Method. Divide the large gear teeth by the small gear teeth.
- Read the teeth. The large gear has 20 teeth and the small gear has 10.20 and 10
- Divide. 20 divided by 10 is 2, so the small gear turns twice.2
- Write the answer. 2
Check. The large gear turns once while the small gear turns twice. ✓
Method. Think about the number of turns.
- Think about the turns. The large gear turns once while the small gear turns twice.turns once
- Choose the gear. So the large gear turns more slowly.large gear
- Write the answer. large gear
Check. More teeth means a slower turn. ✓
Method. Look at two gears that mesh.
- Look at the gears. When two gears mesh, each tooth pushes the next one round.mesh
- Choose the answer. So the two gears turn in opposite ways.opposite ways
- Write the answer. opposite ways
Check. Meshed gears turn in opposite directions. ✓
Method. Read the key ideas in section 10.3.
- Read the key idea. A gear with more teeth turns more slowly, with more effect on the load.more slowly
- Fill the gap. So the missing word is slowly.slowly
- Write the answer. slowly
Check. The large gear turns slowly but with more effect. ✓
Method. Think about the turns.
- Think about the turns. A large gear turning a small gear makes the small gear turn many times.many times
- Make the prediction. So the small gear is the one that turns faster.small
- Write the answer. small
Check. Check with your teacher, using two gears. ✓
Method. Think about the teeth.
- Think about the teeth. The large gear has more teeth, so each tooth moves it only a little.more teeth
- Write the reason. So it turns more slowly than the small gear.more slowly
- Write the answer. Accept any sentence that says the large gear has more teeth, so one turn of the small gear moves it only part of the way round.
Check. More teeth means each turn covers less distance per tooth. ✓
Method. Think about the effect on the pedals.
- Think about the gear. A small gear at the back makes the wheel turn more slowly.more slowly
- Write the reason. So the pedals are easier to turn, with more effect on the hill.easier to turn
- Write the answer. Accept any sentence that says the small gear makes the wheel turn more slowly, but with more effect, so the pedals are easier to turn.
Check. A slow gear with more effect helps on a hill. ✓