Lifting water bottles
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Mrs Harvey's science class carried out three experiments with pulleys. In all of them a rope was tied to the handle of a two-litre bottle filled with water.
A spring scale was used to measure the force needed to pull the bottle one metre off the floor.
The three experiments were:
Each experiment was tried three times. Here is the table showing the students' results. The force is measured in Newtons.
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| a) |
In which experiment was the most force needed to lift the bottle? _______________
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| b) |
Explain why using one pulley decreased the force needed to lift the bottle.
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