Year 5 Science: Levers
Part of the Year 5 Science levers, pulleys and gears chapter. Chapter overview · whole chapter on one page
Levers
A lever is a rigid bar that turns about a fixed point, called the pivot or fulcrum. The force you push with is the effort. The force that is lifted or moved is the load.
A lever allows a smaller force to have a greater effect, when the effort is further from the pivot than the load. The distance from the pivot to the effort is the effort arm. The longer the effort arm, the easier the load is to lift.
In a fair test, the load arm stayed at 10 cm, and the load was 6 identical weights. The effort was changed by moving the effort arm. The table shows how many identical weights were needed at the effort end to lift the load.
| Effort arm (cm) | Weights needed to lift the load |
|---|---|
| 10 | 6 |
| 20 | 3 |
| 30 | 2 |
Key ideas
- A lever is a rigid bar that turns about a pivot.
- The effort is the force you apply; the load is the force you want to lift or move.
- A longer effort arm means a smaller effort is needed to lift the same load.
- A lever allows a smaller force to have a greater effect.
Method. Find the row for 20 cm.
- Find the row. The row for an effort arm of 20 cm needs 3 weights.3 weights
- Read the number. So 3 weights are needed.3
- Write the answer. 3
Check. With the effort arm twice as long, half the weights are needed. ✓
Method. Find the smallest number of weights.
- Read the table. The fewest weights is 2, at an effort arm of 30 cm.2 weights
- Name the arm. So the effort arm is 30 cm.30
- Write the answer. 30
Check. The longest arm needs the smallest effort. ✓
Method. Read the first row of the table.
- Read the row. The first row, with an effort arm of 10 cm, needs 6 weights.6 weights
- Write the number. So the answer is 6.6
- Write the answer. 6
Check. Six weights is the same as the load itself. ✓
Watch out
Watch out: a longer effort arm does not change the load. It makes the effort easier, but the effort moves further to lift the load.
Try it (with your teacher or a grown-up). Put a ruler across a pencil, so that it balances. Put one coin at the short end, and a coin at the far end. Slide the ruler, or the coins, until it balances. Which end needs to be further from the pivot to lift the heavier object?
Exam tip
Grown-up tip. Ask: “Which end is further from the pivot? Which one needs the smaller push?” Let your child use the words effort and load.
Exercise 10A Levers
Method. Read the definition in section 10.1.
- Read the definition. A lever is a rigid bar that turns about a fixed point, the pivot.fixed point
- Name it. The word is pivot.pivot
- Write the answer. pivot
Check. The pivot is also called the fulcrum. ✓
Method. Read section 10.1.
- Read the definition. The force you push with is the effort.the effort
- Name it. The word is effort.effort
- Write the answer. effort
Check. The load is the force that is lifted or moved. ✓
Method. Read section 10.1.
- Read the definition. The force that is lifted or moved is the load.the load
- Name it. The word is load.load
- Write the answer. load
Check. The effort is the force you apply. ✓
| Effort arm (cm) | Weights needed to lift the load |
|---|---|
| 10 | 6 |
| 20 | 3 |
| 30 | 2 |
Method. Read the first row.
- Read the row. The effort arm of 10 cm needs 6 weights.6 weights
- Write the number. So the answer is 6.6
- Write the answer. 6
Check. The load arm and the first effort arm are both 10 cm. ✓
| Effort arm (cm) | Weights needed to lift the load |
|---|---|
| 10 | 6 |
| 20 | 3 |
| 30 | 2 |
Method. Read the row for 30 cm.
- Read the row. The effort arm of 30 cm needs 2 weights.2 weights
- Write the number. So the answer is 2.2
- Write the answer. 2
Check. A longer effort arm needs fewer weights. ✓
| Effort arm (cm) | Weights needed to lift the load |
|---|---|
| 10 | 6 |
| 20 | 3 |
| 30 | 2 |
Method. Subtract the 30 cm number from the 10 cm number.
- Read the numbers. At 10 cm, 6 weights are needed. At 30 cm, 2 weights are needed.6 and 2
- Subtract. The difference is 6 minus 2, which is 4 weights.6 - 2 = 4
- Write the answer. 4
Check. Check: 2 + 4 = 6. ✓
| Effort arm (cm) | Weights needed to lift the load |
|---|---|
| 10 | 6 |
| 20 | 3 |
| 30 | 2 |
Method. Find the arm that is twice 10 cm.
- Find the arm. Twice 10 cm is 20 cm.20 cm
- Check the weights. The 20 cm row needs 3 weights, which is half of 6.3 weights
- Write the answer. 20
Check. Doubling the arm halves the weights needed. ✓
Method. Think about where the push is.
- Think about the push. The child pushes down on the far end, which is the long arm.far end
- Name the part. So the effort is on the long arm.long arm
- Write the answer. long arm
Check. The effort is on the long arm, far from the pivot. ✓
Method. Read the labels in the picture.
- Read the labels. The long arm is on the effort side, labelled long arm.long arm
- Name the arm. So the effort arm is the longer one.effort
- Write the answer. effort
Check. The effort arm is the longer one in the picture. ✓
Method. Read the key ideas in section 10.1.
- Read the key idea. A lever allows a smaller force to have a greater effect.smaller force
- Fill the gap. So the missing word is smaller.smaller
- Write the answer. smaller
Check. The longer effort arm makes the effort easier. ✓
Method. Think about the pattern in the table.
- Think about the pattern. The longer the effort arm, the fewer weights are needed.fewer weights
- Make the prediction. So a 20 cm arm needs fewer weights than a 10 cm arm.fewer
- Write the answer. fewer
Check. Check with your teacher on a simple lever. ✓
Method. Think about the turning.
- Think about the arm. The effort is further from the pivot.further from the pivot
- Write the reason. So a smaller effort gives the same turning effect, lifting the load.turning effect
- Write the answer. Accept any sentence that says the longer arm gives the effort a greater turning effect, so a smaller effort lifts the same load.
Check. A longer arm gives the effort more turning effect. ✓
Method. Think about the fair test.
- Think about the test. Only the effort arm was changed, and the load was kept the same.only the effort arm
- Write the reason. So any difference in the weights is caused by the arm length.caused by the arm length
- Write the answer. Accept any sentence that says only the effort arm changed, and the load stayed the same, so the difference in weights is due to the arm length.
Check. A fair test changes one thing, here the arm length. ✓