A gardener uses a wheelbarrow to move a heavy load of soil. The wheelbarrow acts as a lever, with the wheel acting as the pivot. Explain how the design of a wheelbarrow allows the gardener to lift the load using a smaller effort force than the weight of the soil.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A wheelbarrow is a simple machine. The handles are at the rear, the wheel (pivot) is at the front, and the load sits in the tray between them.
Model answer (4 marks)
A wheelbarrow is a lever of class 1. The wheel is the pivot, the load is the load arm and the handles are the effort arm.
1. A moment is the turning effect of a force about a pivot.
2. The effort applied at the handles acts at a greater perpendicular distance from the pivot than the load.
3. For equilibrium the clockwise moment (load) must equal the anticlockwise moment (effort).
4. Because the effort arm is longer, a smaller effort force is required to produce the same moment as the load, allowing the gardener to lift the soil with less force.
1. A moment is the turning effect of a force about a pivot.
2. The effort applied at the handles acts at a greater perpendicular distance from the pivot than the load.
3. For equilibrium the clockwise moment (load) must equal the anticlockwise moment (effort).
4. Because the effort arm is longer, a smaller effort force is required to produce the same moment as the load, allowing the gardener to lift the soil with less force.
Examiner tips
- Use the word "lever" and class 1. Show the moment equation: Effort×d_effort = Load×d_load. Explain why a longer effort arm reduces the required effort.
- common_mistakes
- :
- Not recognising the wheelbarrow as a lever. Using the wrong direction for moments. Failing to state that the effort arm is longer than the load arm.
Mark scheme (4 marks)
- A moment is the turning effect of a force (about a pivot)
- The effort (applied at the handles) acts at a greater perpendicular distance from the pivot than the load
- For the wheelbarrow to be in equilibrium, the clockwise moment must equal the anticlockwise moment
- Because the effort distance is greater, a smaller effort force is needed to produce the same (balancing) moment as the load
Key terms in this question
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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