Would you rather be hit by a tennis ball or a bowling ball? Momentum Would you rather be hit by a tennis ball or a bowling ball?

To answer the question, you would want to consider mass but also velocity. That is momentum.

momentum = mass x velocity p = mv Momentum is inertia in motion. momentum = mass x velocity p = mv Ex: What is the momentum of a 10 kg bowling ball moving at 20 m/s ? p = m x v p = 10 kg x 20 m/s p = 200 kg m/s

What would you have to change to change momentum? To change momentum, you can change mass or velocity. What is the name for a change in velocity? Acceleration.

What does it take to cause an acceleration? A force is needed to cause an acceleration. The longer a force is applied, the greater the change in momentum.

Baseball Many sports involve a change in momentum. Golf Soccer

Impulse relates a force and the amount of time it is applied. Impulse = force x time J = Ft Example: What impulse is applied to a baseball if the batter uses a 50 N force for 0.2 seconds?

F = 50 N t = 0.2 s Impulse = force x time 50 N x 0.2 s = 10 Ns

It is impulse that causes a change in momentum. Impulse = change in momentum Ft = ∆ p Ft = pf - pi Ft = mvf - mvi

This equation is called the impulse – momentum theorem. Ft = mvf – mvi Since impulse and momentum are equal their units are interchangeable. So Ns or kg m/s can be used for both impulse and momentum.

What is the change in momentum if a 1000 kg car accelerates from 20 m/s to 50 m/s? ∆ p = pf – pi = mvf – mvi = 1000 (50) – 1000 (20) ∆ p = 30,000 kg m/s

A 5 kg mouse is moving at 10 m/s A 5 kg mouse is moving at 10 m/s. If he comes to a stop, what was his change in momentum? The negative indicates a loss of momentum. m = 5 kg vi = 10 m/s vf = 0 m/s final momentum = 0 kg m/s initial momentum = 50 kg m/s ∆ p = 0 kg m/s – 50 kg m/s ∆ p = - 50 kg m/s

F = 400 N Ft = mvf – mvi F(5) = 20 (100) – 20 (0) Example: A 20 kg object starts at rest. In 5 s, it has a speed of 100 m/s. How much force was used? Ft = mvf – mvi F(5) = 20 (100) – 20 (0) F = 400 N

Give examples of a moving object coming to a rest. How could you minimize the force felt by these objects? Give examples of ways in which the time for an object to stop is increased to minimize the force. Airbags Water Balloon

A 800 kg car is moving at 30 m/s. The driver slams on the brakes A 800 kg car is moving at 30 m/s. The driver slams on the brakes. It takes the car 3 s to stop. What force did the brakes supply? - 8000 N The negative indicates the force is in the opposite direction of the motion. If the driver of the car above eased on the brakes for 30 s to come to a stop, how much force did the brakes supply? - 800 N

100 m/s Example: A 40 N force is applied to a 5 kg object for 10 s. If the object was initially moving at 20 m/s, what is its new speed? 100 m/s