2. Critical Questions
When have you heard the word momentum used?
Which do you think has more momentum?
Two identical Honda Accords, one going 20mph, the other going
40mph.
Two vehicles going 30mph, one is a VW Bug, the other an
18-wheeler.
3. Momentum
Momentum is the study of inertia in motion.
Recall Inertia: The tendency of an object to remain in motion or
stay at rest due to its mass.
So, momentum only deals with objects that are in motion.
4. Momentum
Momentum is the mass of an object multiplied by its velocity.
p = mv
Where: p = momentum (kg m/s)
m = mass (kg)
v = velocity (m/s)
5. Momentum
Change in Momentum generally refers to a change in velocity, mass
is constant.
p = mv
Or
p = m(vf vi)
6. Momentum Examples
Find the momentum of a 1500kg car traveling at 30m/s.
A 1200kg car has a momentum of 18,000kg m/s.What is its
velocity?
A 1000kg car slows from 45m/s to 30m/s.Find its change in
momentum.
7. Critical Question
Could an 18-wheeler and a 4-wheeler ever have the same
momentum?
8. Impulse
If an object changes velocity, what is it doing?Accelerating!
What causes acceleration of an object?Force!
The greater the force on an object, the more acceleration it
obtains, the more velocity changes and, therefore, the more change
in momentum it has!
9. Impulse
Time is also a factor a force applied over a long time is different
than a force applied over a short time
A short force only causes a small change in velocity.
A long force can cause a great change in velocity.
Think about the Skateboard Lab!
10. Warm Ups (4/18/08 PROM DAY)
1. Find the momentum of a 1200kg car traveling at 37 m/s.
2. Find the momentum of a 2.6kg dove flying at 3.2 m/s.
3.Find the change in momentum if the same dove speeds up to
4.7m/s.
11. Impulse Cases
Increasing Momentum
Decreasing Momentum over a Long Time
