# Balancing turning forces

When an object is balanced on a pivot the turning effect of the forces on one side of the pivot must balance the turning effect of the forces on the other side of the pivot - if they didn't it would not balance.

In the first picture two girls are sitting on a see saw. They have moved until it is balanced. They are the same weight and so to balance the see saw they must sit the same distance from the pivot.

In the second picture one of the girls gets off and a man sits on instead. They move until the see saw is balanced. The girl is much lighter than the man and so she has to sit further away from the pivot then he does so that she can balance his extra weight.

The turning effect of a force is called the moment of the force. When the see saw is balanced the anticlockwise moments (those trying to turn the object anticlockwise) equals the clockwise moments (those trying to turn the object clockwise). In our example the man's weight tries to turn the see saw clockwise and the girl's weight tries to turn it anticlockwise.