Name:______________ Class:________
Momentum (p)
Momentum is mass times velocity
momentum is a ____________________________! momentum has units _____________________
Which has more momentum?
 1 kg object moving at 1000 m/s -or- a 1000 kg object moving at 1 m/s?
 a rolling marble –or-stationary truck?
 a marble moving at 0.5 m/s –or- truck moving at 0.5 m/s?
The way we use the word ‘momentum’ in everyday life actually does relate to its physics definition.
For example, in game, a sports announcer might say that one team ‘has momentum’. What do they mean?
The sports announcer means that the team ______________________________________ and is going to be
______________________________.
In this way, the everyday usage and the physics definition of momentum are the same:
________________________________________________________________________________________________
How do we change momentum?
Since mass doesn’t (usually) change, a change in momentum occurs when the _______________________ of an object changes.
What is necessary to change an object’s velocity? ____________________________________
Changes in momentum are produced by the action of _______________________________________.
Force applied over time _________________________ is an called an________________________.
Impulse & Momentum
Is it harder to stop an object with more mass or less?
Is it harder to stop a fast moving object or a slow moving object?

Two cars are moving with the same velocity. In car A, the driver applies the brakes, and the car stops due to the force of friction. The time period over which friction acts is 30 seconds. Car B hits a tree. The time period over which the tree applies a force is 0.5 seconds.
How does the change in momentum of the two objects compare?
How does the force applied in each circumstance compare?
Other examples of minimizing force applied by maximizing time of contact
We do
You do
1) A compact car with mass 725 kg is moving 115 km/hr to the East. The driver suddenly applies the brakes hard for 2.0s, applying an average force of 5.0 X 10 3 N on the car.
a) What is the change in momentum of the car?
b) What is the final velocity of the car?
2.
In a ballistics test at the police department, Officer Rios fires a 6.0 g bullet at 350 m/s into a container that stops it in 0.0018 s. What is the average force that stops the bullet?
Graphical Determination of Momentum
In the problems we’ve done so far, the we’ve dealt with average or constant force. If force changes over time, we can find the change in momentum graphically.

Change in momentum, Δp, is the _______________________________________________________________.
The graph shows the force applied to a 57 g tennis ball by a racquet over time. a) What is the change in momentum? b) If the ball starts at rest, what is
its final velocity?
You Do a) What is the change in momentum of the football as a result of being kicked? b) If the football started at rest, what is its final velocity? (mass = 400 g)