A rigid winding handle can rotate about a spindle at one end. Force P is applied at the free end along the handle towards the spindle. An equal force Q is applied halfway along the handle at right angles to the handle. Force Q turns the handle, but force P does not.
Why does force Q turn the handle when force P does not?
Q turns the handle because the distance is measured from the free end to the force; this distance is zero for P.
Q turns the handle because its perpendicular distance from the spindle is not zero; P's line of action passes through the spindle.
Q turns the handle because it is applied nearer the spindle; P is too far from the spindle to produce a turning effect.
Q turns the handle because it gives a moment in one direction; P gives equal clockwise and anticlockwise moments.
124 exam-style questions on AQA GCSE Physics 5.4 Moments, levers and gears, covering 5.4 Moments, levers and gears. Each one has a worked solution and a mark scheme showing where the marks go.