Chapter 10(Part 2)

Forces and Pressure

Quiz TimeO When you throw a ball in the air,

what will happen to the motion of the ball?

O Ball will fall towards earth after reaching a maximum height.

Why?

GravityO Gravity or gravitational force is

the force that attracts objects to the earth.

O Thus gravity causes objects to falls towards the earth.

Quiz TimeO You gave a push to a toy car across

your bedroom.O Describe the motion of the toy car.O The toy car moves but will start to

slow down and stop after a while.

WHY?

FrictionO Friction between the ground and the

wheel of the toy car slows down the toy car making it coming to a stop.

O Friction is a force acting in the opposite direction to the direction of motion of the object.

FrictionUseful Nuisance

Enables us to walk forward.

Causes wear and tear in machine or object.

Prevents us from slipping and falling.

Reduces efficiency of a machine or object.

Enables us to hold on to object.

Produces heat instead of useful work.