When two forces acting on an object are not equal in size, we say that they are unbalanced forces.
If the forces on an object are unbalanced this is what happens:
an object that is not moving starts to move
an object that is moving changes speed or direction
The size of the overall force acting on an object is called the resultant force. If the forces are balanced, this is zero. In the example above, the resultant force is the difference between the two forces, which is 100 - 60 = 40 N.
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