A force is a push or a pull. Forces can make things start moving, stop, speed up, slow down, change direction or change shape. Kicking a ball is a push; opening a drawer is a pull. A bigger force has a bigger effect.
Forces have a size and a direction, and we draw them as arrows. When two forces on an object are the same size but push in opposite directions, they are balanced and the object's motion does not change. In a tug of war where nobody moves, the forces are balanced. If one team pulls harder, the forces are unbalanced and the rope moves towards the stronger team.
Worked example
A box is pushed right with 10 N and left with 10 N. What happens?
- The forces are the same size.
- They act in opposite directions, so they are balanced.
Answer:The box does not start to move.
Key words
- force
- a push or a pull
- balanced
- equal forces in opposite directions; no change in motion
- unbalanced
- one force is bigger, so motion changes
- newton (N)
- the unit we measure force in
Practise this
New questions every time.
NGSS-referenced: 3-PS2-1