Year 5 Science: Pulleys
Part of the Year 5 Science levers, pulleys and gears chapter. Chapter overview · whole chapter on one page
Pulleys
A pulley is a wheel with a groove, which a rope runs over. There are two kinds that are useful for this chapter:
- a fixed pulley, which is fixed to a support. It changes only the direction of the pull. Pulling down lifts the load up, but the effort is the same as the weight of the load.
- a movable pulley, which moves with the load. The load is shared between the two parts of the rope, so the effort needed is about half the load.
The table shows how many identical weights were needed to lift the same load, for three set-ups.
| Set-up | Weights needed to lift the same load |
|---|---|
| no pulley, lifting the load straight up | 8 |
| a fixed pulley, fixed to a support | 8 |
| a movable pulley, which moves with the load | 4 |
Key ideas
- A fixed pulley changes the direction of the pull, but not the size of the effort.
- A movable pulley shares the load between two ropes, so the effort is about half.
- Pulleys help to lift heavy loads with less effort.
- The pulley picture shows the effort pulling down, and the load going up.
Method. Find the movable pulley row.
- Find the row. The movable pulley row shows 4 weights.4 weights
- Read the number. So the answer is 4.4
- Write the answer. 4
Check. A movable pulley needs about half the weights. ✓
Method. Find the no pulley row.
- Find the row. The no pulley row shows 8 weights.8 weights
- Read the number. So the answer is 8.8
- Write the answer. 8
Check. The fixed pulley row also shows 8. ✓
Method. Subtract the movable pulley number from the no pulley number.
- Read the two numbers. No pulley needs 8 weights, and a movable pulley needs 4.8 and 4
- Subtract. The difference is 8 minus 4, which is 4 weights fewer.8 - 4 = 4
- Write the answer. 4
Check. Check: 4 + 4 = 8. ✓
Watch out
Watch out: a fixed pulley does not make the lift easier. It only changes the direction of the pull. Only a movable pulley shares the load.
Try it (with your teacher or a grown-up). With a grown-up, tie a rope to the back of a chair, and loop it over a broom handle or a wooden dowel that is held up. Pull the rope down to lift a small bag. Then tie the bag to a second loop of rope so that it moves with the bag. Compare how hard each one is to lift.
Exam tip
Grown-up tip. Ask: “Which set-up was easier? Did the pulley change the direction, or the size of the pull?” Keep the bag light and the set-up safe.
Exercise 10B Pulleys
Method. Read section 10.2.
- Read the definition. A pulley is a wheel with a groove, which a rope runs over.a wheel
- Name it. The word is pulley.pulley
- Write the answer. pulley
Check. Pulleys are used to lift loads. ✓
Method. Read the bullet points in section 10.2.
- Read the bullet. A fixed pulley changes only the direction of the pull.changes the direction
- Choose the word. So the answer is fixed.fixed
- Write the answer. fixed
Check. A fixed pulley is fixed to a support. ✓
Method. Read the bullet points in section 10.2.
- Read the bullet. A movable pulley moves with the load, and shares it between two parts of the rope.shares the load
- Choose the word. So the answer is movable.movable
- Write the answer. movable
Check. Sharing the load halves the effort needed. ✓
| Set-up | Weights needed to lift the same load |
|---|---|
| no pulley, lifting the load straight up | 8 |
| a fixed pulley, fixed to a support | 8 |
| a movable pulley, which moves with the load | 4 |
Method. Read the fixed pulley row.
- Read the row. The fixed pulley row shows 8 weights.8
- Write the number. So the answer is 8.8
- Write the answer. 8
Check. A fixed pulley does not reduce the effort. ✓
| Set-up | Weights needed to lift the same load |
|---|---|
| no pulley, lifting the load straight up | 8 |
| a fixed pulley, fixed to a support | 8 |
| a movable pulley, which moves with the load | 4 |
Method. Read the movable pulley row.
- Read the row. The movable pulley row shows 4 weights.4
- Write the number. So the answer is 4.4
- Write the answer. 4
Check. The movable pulley halves the 8 weights. ✓
| Set-up | Weights needed to lift the same load |
|---|---|
| no pulley, lifting the load straight up | 8 |
| a fixed pulley, fixed to a support | 8 |
| a movable pulley, which moves with the load | 4 |
Method. Compare the numbers.
- Compare the numbers. The movable pulley needs 4 weights, and no pulley needs 8.4 and 8
- Decide. Fewer weights means it is easier, so the answer is yes.yes
- Write the answer. yes
Check. The movable pulley needs less effort. ✓
| Set-up | Weights needed to lift the same load |
|---|---|
| no pulley, lifting the load straight up | 8 |
| a fixed pulley, fixed to a support | 8 |
| a movable pulley, which moves with the load | 4 |
Method. Compare the numbers in the table.
- Compare the rows. The no pulley and fixed pulley rows both show 8 weights.8 and 8
- Name the two. So no pulley and a fixed pulley needed the same number.no pulley and a fixed pulley
- Write the answer. no pulley and a fixed pulley
Check. A fixed pulley only changes the direction. ✓
Method. Read section 10.2.
- Read the bullet. The effort needed is about half the load.half
- Fill the gap. So the missing word is half.half
- Write the answer. half
Check. The load is shared by two parts of the rope. ✓
Method. Read the labels.
- Read the labels. The right-hand pulley is labelled movable pulley.right-hand
- Name the pulley. So the movable pulley is the one on the right.movable
- Write the answer. movable
Check. The movable pulley moves with the load. ✓
Method. Think about the rope.
- Think about the rope. The load is shared between two parts of the rope.shared
- Make the prediction. So the load feels lighter to lift.lighter
- Write the answer. lighter
Check. Check the prediction in the Try it box. ✓
Method. Think about what a fixed pulley does.
- Think about the pulley. A fixed pulley is fixed to a support.fixed to a support
- Write the reason. So it changes only the direction, not the size of the effort.direction
- Write the answer. Accept any sentence that says a fixed pulley only changes the direction of the pull, so the effort is the same as the load.
Check. A fixed pulley is useful for pulling down to lift. ✓
Method. Think about the rope.
- Think about the rope. The rope is in two parts, holding the load.two parts
- Write the reason. So each part carries about half the load, and the effort is about half.about half
- Write the answer. Accept any sentence that says the load is shared between two parts of the rope, so the effort needed is about half.
Check. Sharing the load makes lifting easier. ✓