Moments

• The turning effect of a force is called its moment
• Moment of a force (Nm) = Force (N) x Distance (m)- perpendicular distance from the pivot to line of action of the force
• The force on the spanner causes a turning effect or moment on the nut (which acts as a pivot). A larger force or a larger distance would mean a larger moment
• To get the maximum moment you need to push at right angles to the spanner. Pushing at any other angle means a smaller distance and so a smaller moment
• If the total anticlockwise moment equals the total clockwise moment about a pivot, the object is balanced and won’t turn
• Levers increase the distance from the pivot at which the force is applied. Since M=Fd this means less force is needed to get the same moment.

  This means levers make it easier to do work
• Gears are circular discs with ‘teeth’ around their edges.

  Their teeth interlock so that turning one causes another to turn in the opposite direction
• Gears are used to transmit the rotational effect of a force from one place to another
• Different sized gears can be used to change the moment of the force. A force transmitted to a larger gear will cause a bigger moment as the distance to the pivot is greater
• The larger gear will turn slower than the smaller gear