Why don't the cars slide down the hill?

WHAT IS FRICTION?

Friction is a force that resists the

motion of two surfaces that are
touching.

When a moving object comes in contact with another object, friction is the opposing force that slows or
stops the moving object.

WHAT IS FRICTION?

*Sliding...resists objects while they are moving

*Fluid…air or water
*Rolling …wheel, roller, or ball

*Static. Prevents objects sliding

Friction

• Friction is a force that appears when two objects are in contact (touching)

• When the boy pushes the box, friction pushes back in the opposite direction

• The box will only move if the pushing force is greater than the friction force

The direction of friction

• Friction acts to oppose motion

• To draw the force arrow to represent friction, we need to first think: "which way is the object trying to move?"

• In this picture, the heavy box will try to move down the hill. Therefore, friction acts up the slope.