When you kick a ball, does it move forever or it slows down and stops?

Why does it slow down and stops?

When two surfaces touch each other or rub each other, like the ball and the ground. It

produces a force called friction

The friction causes the object to slow down.

What kind of force is there when you are walking?

Friction force

What happens when there is water on the ground? Why?

Water reduces friction

What else reduces friction ?

Oil

Which is difficult to ride a bicycle on?

Rough surface like sand, produces more friction.

Which is easier to ride a bicycle on?

Smooth surfaces, produces less friction.

Rough surfaces

Smooth surfaces

Force that happens between objects that

touch each other.

1) Magnetism

2) Gravity

3) Friction

Which of these is a contact force?

Force that happens between objects without

touching each other.

1) Magnetism

2) Gravity

3) Friction

Which of these is a non-contact force?