A boy is standing on a metal bar of length 8 m. The bar is supported at point A and is balanced horizontally. The boy (400 N) is standing 2 metres from point A, at one end of the bar. The weight of the metal bar, W, acts at the centre of the bar.

1. aState the principle of moments. [2]
2. bWhich term describes the turning effect of a force at point A? [1]
3. cCalculate the turning effect of a force about point A due to the boy. [2]
4. dCalculate the weight of the metal bar. [2]

You'll mark your own answer against the marking guide when you hand it in.