Understand balanced and unbalanced forces, friction, and how forces affect the motion of objects.
When forces acting on an object are balanced, there's no change in motion. When forces are unbalanced, the object's motion changes — it speeds up, slows down, or changes direction.
A book resting on a table isn't moving. Are the forces acting on it balanced or unbalanced?
Balanced — gravity pulling down is balanced by the table pushing up
A ball rolling on grass gradually slows down. What does this tell us about the forces acting on it?
The forces are unbalanced — friction from the grass is slowing the ball down
Friction is a force that opposes motion between two surfaces in contact. It can be useful (like walking) or a hindrance (like in machines).
Why is it harder to walk on ice than on a rough pavement?
Ice has much less friction than rough pavement, making it harder to grip and push against
Why do machines need lubricants like oil?
To reduce friction between moving parts, preventing excess wear and energy loss
1. What happens to an object's motion when forces acting on it are balanced?
2. What happens to an object's motion when forces acting on it are unbalanced?
3. What is friction?
4. Why do cars have treaded tyres instead of smooth ones?
5. Name one situation where friction is helpful.