When two forces acting on an object are equal in size but act in opposite directions, we say that they are balanced forces.
If the forces on an object are balanced (or if there are no forces acting on it), this is what happens:
Remember that an object can be moving, even if there are no forces acting on it.
We can show the forces acting on an object using a force diagram. In a force diagram, an arrow represents each force. The arrow shows:
The arrow should be labelled with the name of the force and its size in newtons. Textbooks often show a force with a thick coloured arrow so that it looks nice, but it is more accurate if you just use a ruler and pen or pencil to draw an arrow with a single line.
Here are some examples of situations involving balanced forces.
Objects float in water when their weight is balanced by the upthrust from the water. The object will sink until the weight of the water it pushes out of the way is the same as the weight of the object.
When an object rests on a surface such as the ground, the reaction force from the ground balances its weight. The ground pushes up against the object. The reaction force is what you feel in your feet as you stand still. Without this balancing force you would sink into the ground.