Kick a ball, pull a wagon, open a door: each time you use a force.
Key idea
A force is a push or a pull. A force can start something moving, stop it, make it faster or slower, or change its direction.
Forces have a size (strong or weak) and a direction. When two equal forces push opposite ways, as in a tug-of-war that nobody is winning, they are balanced and nothing changes. When one side is stronger, the forces are unbalanced and the rope moves toward it.
Worked example: Balanced or unbalanced?
Two children push a box from opposite sides. One pushes hard, one pushes gently. What happens?
- The pushes are not equal, so the forces are unbalanced.
- The box moves the way the harder push points.
Answer: The box slides away from the child pushing hard.
Common mistake
Thinking a moving thing needs a push to keep going. A puck on smooth ice glides a long way. Things slow down because friction or air pushes against them.
Try it at home
- Roll a toy car across a smooth floor. Then give it a gentle push from the side while it rolls.
- What changed: its speed, its direction, or both?
Going further. Newton's Laws of Motion in the Science Lab, and Forces in Physical Science when you are older.