Balanced and Unbalanced Forces

A force is a push or a pull that causes a change in an objects motion. Forces are measured in units called Newtons.

There are always two or more forces that affect an objects motion. The size of the forces determines the motion an object will have.

When two forces acting on an object are equal and in opposite directions then the forces are balanced and the object will not move. The forces "cancel" each other out.

When two forces acting on an object are in opposite directions but are not equal then the forces are unbalanced and the object will move. The forces don't "cancel" each other out so there is movement.

When forces are unbalanced they cause a change in an objects motion. Unbalanced forces can cause objects to start or stop moving, speed up or slow down, or change directions.

The motion of a baseball that gets hit by a batter changes because of forces.

When a batter hits a ball the ball rises into the air and at point A it starts to SLOW DOWN because of the force of gravity.

At point B the ball CHANGES DIRECTIONS. It was moving upward but at point B it has changed directions and is moving downward.

At point C gravity pulls the ball towards the center of the Earth and it SPEEDS UP.

At point D the ball hits the ground and once it stops moving it is experiencing balanced forces.