Answer the following about force.

A ruler is placed next to a spring to measure the changes in the length of the spring when various weights are hung on it. Weights and readings: 0 N — 30 mm; 1 N — 32 mm; 10 N — 50 mm.

1. aState the SI unit of force. [1]
2. bCalculate the weight which would correspond to a reading of 31 mm. Show your working. [2]
3. cA similar set-up was used at the Moon. How would the readings compare with those in the table? [1]
4. dExplain your answer. [1]

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