Balanced Forces
A force is a push or a pull on an object. Forces are at work all around you all the time. More than one force can-and
usually does- act on an object at the same time. Sometimes two forces act in the same direction. An example is when
two people work together to push a heavy object. Sometimes the forces act in different directions.
Imagine a tug-of-war between you and one friend. If
you are stronger, you apply more force to the rope.
You pull your friend across the line, and you are the
winner! If your friend is stronger, he might pull you
across the line. Sometimes the forces are equal.
Neither you nor your friend moves across the line. The
two forces are balanced.
We say that the net force on an object is the combination of all the forces
acting on it. To find the net force of forces that are acting in the same
direction, add them together. For example, if you pull on a box with a force of
25 newtons (N) while your friend pushes the box (in the same direction you are
pulling) with a force of 30 N, the net force applied to the box in that direction is
55 newtons. To find the net force of forces that are acting in opposite
directions, subtract the smaller force from the larger one. If you are pulling on
a tug-of-war rope with a force of 40 N, and your friend is pulling with a force of
35 N in the opposite direction, the net force on the rope is 5 newtons in your
direction. You win! When the net force on an object is zero, the two forces are balanced. Balanced forces don't
cause any change in the motion of an object.
Balanced forces are equal and in opposite directions. If the object is not moving and two forces are applied to it that
equal zero when combined, then the object will not move. If the object is already moving and two balanced forces
are applied to it, the object will continue moving at the same speed and in the same direction that it was before the
forces were applied. That doesn't mean that balanced forces have no effect on an object, however.
Think about what would happen to an empty soda can if you pushed against it in one direction, and a friend pushed
against it in the opposite direction with an equal amount of force. If the amount of force was equal, the can wouldn't
move. But the two opposing forces would probably crush the can.
