Moments and centre of gravityEdexcel A-Level Physics: Mind map

Exam questions on Moments and centre of gravity

1. A mechanic is loosening a stiff wheel nut using a spanner whose handle is 0.35 m long, measured from the centre of the nut to the point where she pushes. She applies a constant force of 120 N at the end of the handle.
   Explain why a mechanic can loosen a stiff nut more easily using a longer spanner.2 marks
2. A student wants to find the centre of gravity of an irregular piece of thick card. He makes a small hole near one edge, hangs the card freely from a pin through the hole, and hangs a plumb line from the same pin.
   Explain why the card comes to rest with its centre of gravity vertically below the pin.2 marks
3. A uniform wooden beam of length 6.0 m and weight 400 N rests horizontally on two supports. Support A is at the left-hand end of the beam and support B is 5.0 m from A, so the right-hand end overhangs B by 1.0 m. A person of weight 900 N stands on the beam 1.5 m from A.
   Use the principle of moments to calculate the upward force exerted on the beam by support B.3 marks