The figures show a block of wood on a table. When the block is pulled at point A, it begins to move towards the left and if the block is pulled at the point B it moves towards the right.
Example of Unbalanced Forces
But if the block is pulled from both sides with the same effort the block remains stationary. The forces are equal and opposite and therefore the block does not move. The resultant of the forces acting on the body is zero.
Example of Balanced Forces
In a game of tug of war when both the teams pull the rope with equal and opposite forces, then the rope remains stationary as the forces acting on it are equal and opposite and their resultant is zero.
Example of Balanced Forces
Squeeze a rubber ball between the palms of your hands. What do you observe? The shape of the rubber ball changes. The forces applied on the ball are equal and opposite and the resultant of these forces does not move the object, instead the object gets deformed as long as the force is applied. This is a temporary deformation.
Deformation of a Spherical Ball by Unbalanced Forces
Hammer a piece of nail, it gets permanently deformed.
From the above examples we can conclude that if the forces acting on an object are equal and opposite then they do not change the state of rest of the object or uniform motion along a straight line, but they can deform the object. These types of forces which do not cause any change in state of rest or of uniform motion along a straight line are called balanced forces. The resultant of balanced forces is always equal to zero (because the forces are equal and opposite).
In tug of war, usually the weaker team is pulled by the other team, which is stronger. In this case, the forces are not equal and opposite i.e., they are not balanced and hence the weaker team is pulled by the stronger team.
Unbalanced Forces
All of us know that when we stop pedaling a bicycle, the speed of the bicycle decreases due to the action of friction, which is the only force acting on the bicycle. Thus, if the forces acting on a body produce any change in state of rest or motion, then the forces are said to be unbalanced. An unbalanced force acting on an object changes its speed or direction. The resultant of unbalanced forces is always greater than zero.
