Newton’s Third Law of Motion

Newton’s Third Law of Motion

If you pushed against a wall, what would happen?

What would happen if you had roller skates on?

The harder you push? The farther you roll

Newton’s Third Law of MotionYour action caused a reaction.

Your pushing on the wall caused you to roll backward.

Newton’s Third Law of Motion states:When an object exerts a force on a

second object, the second one exerts a force on the first that is equal and opposite in direction.

AKA – For every action there is an equal and opposite reaction.

Action & Reaction

When you apply a force on something a reaction occurs.

When you jump on a trampoline, you exert a downward force on the trampoline.

The trampoline then exerts an equal upward force on you, sending you into the air.

Action & ReactionRemember that action-

reaction forces are acting on different objects.

Even though forces are equal, they are not balanced because they act on different objects.

Action & Reaction

What is the action and reaction of a swimmer pushing off the wall?

As the swimmer pushes on the wall, the wall exerts a force pushing her forward.

As the swimmer pushes the water out of the way, the water pushes the swimmer back.

Action & Reaction

What is the action and reaction of the diver?

Rocket Propulsion

In a rocket engine, burning fuel makes a hot gas.

The engine exerts a force on the gases causing the gases to escape outside the back of the rocket.

The gases exert a force on the rocket and push it forward.

Momentum

Which is easier to stop?A slow moving bike or a fast

moving bike?A slow moving bike or a slow

moving car?

MomentumIncreasing the speed or mass of an

object makes it harder to stop.Momentum is the product of an objects

mass and velocity.Momentum is abbreviated with the

symbol p.p = mvMomentum = (mass)(velocity)Momentum = kg m/s

The Law of Conservation of Momentum

The momentum of an object doesn’t change unless its mass, velocity, or both change.

Momentum can be transferred from one object to another.

The Law of Conservation of Momentum

What happens when a bowling ball hits the pins? If there is no other forces applied…

The total momentum of the bowling ball is transferred to the pins and the pins go flying.

The momentum that the pins gained is equal to the total momentum the bowling ball had before it hit the pins.

Momentum is not lost or created only transferred.