Bouncing Impulse and The conservation of

Momentum

Bouncing Impulse

• When something bounces there is more impulse involved than if the object just falls and stops.

• This is due to the fact that when an object bounces it is essentially hitting an object and being thrust back in the opposite direction.

Conservation of Momentum

• From Newton’s Laws of Motion we know that you need a force in order to make something accelerate.

• Similarly if you wish to change the momentum of an object, exert an impulse on it.

Conservation of Momentum

• In order to exert an impulse on an object you must exert the impulse from an outside force

• In the picture to the right you can see the white ball exerts an impulse (a collision) which will give momentum to the yellow ball.

Conservation of Momentum

• Just like in our lab with the balloon rockets, we must remember that for every action there is an equal but opposite reaction

• In the case with the cannon, the ball launched forward is equal but opposite to the recoil of the cannon.

Conservation of Momentum

• In this scenario we have 0 momentum in the before image.

• In the after image we have 0 net momentum because the momentum of the ball going forward is equal but opposite to the momentum of the cannon’s recoil

• Net Momentum is the sum of all the momentum.

Conservation of Momentum

• Momentum, like velocity and force, has both direction and magnitude.

• Momentum is a vector quantity.

Conservation of Momentum

• The law of conservation of momentum states:

• In the absence of an external force, the momentum of a system remains unchanged.

Try it!

• Newton’s second law states that if no net force is exerted on a system, no acceleration occurs.

• Does it follow that no change in momentum occurs?

Try It• Newton’s third law stats that the force of a cannon exerts on a cannon ball is equal but opposite tot he force the cannonball exerts on the cannon.

• Does it follow that the impulse the cannon exerts on the cannonball is equal and opposite to the impulse the cannonball exerts on the cannon?