1. Momentum and Impulse

2. Inertia In Motion Which is harder to stop? Why is it harder to stop?
A car moving at 25 m/s
A bicycle moving at 25 m/s
Why is it harder to stop?

3. Momentum
Momentum can be defined as the measurement of how difficult it is to change the motion of an object.
Mathematically:
Momentum = (mass) * (velocity)

4. Which has more momentum?
A sumo wrestler running towards you?
A ballerina running towards you at the same speed?

5. Calculating momentum
What is the momentum of a 10 kg bowling ball rolling at 4 m/s?
Momentum = (mass) * (velocity)
Momentum = (10 kg) * (4 m/s)
Momentum = 40 kg*m/s

6. Units for momentum The units for momentum are (kg*m/s).
The units are not abbreviated into any other form (unlike Newtons)

7. Changing momentum
If the momentum of an object changes, then either the mass, velocity or both has changed.
Usually, the mass of an object remains the same, so it’s the velocity that is changing.
What is the quantity that measures the change in velocity?

8. Change in momentum continued
What causes an acceleration?
Therefore, the greater the force on an object, the greater the change in momentum.
Now for a little bit of math…

9. Force*Time is also known as “Impulse”
Newton’s 2nd Law
Change in momentum
Force =
mass
acceleration * *
Time
Force*Time is also known as “Impulse”

10. Impulse A force can be used to change an object’s motion.
Impulse is how quickly or slowly that change in momentum occurs.
The amount of time it takes to change the object’s motion is called impact.

11. Increasing momentum Force*Time = change in momentum
To get the greatest change in momentum, you need a greater force acting for a longer period of impact time.
Example: hitting a golf ball - Wlk
Example: Hitting a baseball
with a metal bat.

12. Decreasing momentum
This is the situation where you are trying to STOP something from moving. (change the momentum to zero)
Force * Time = change in momentum
Suppose an object has very high momentum
How can we decrease the force the object will feel when we try to stop the object?

13. Decreasing momentum examples
Bungee jumping
Air bags
Boxing glove
Baseball glove
Pole vault mats
Catching a lacrosse ball

14. Calculating Impulse
An 8kg bowling ball traveling at 4 m/s rolls into a pillow and stops in 2 seconds. Calculate the force the pillow exerts on the bowling ball.
Force*Time = change in momentum
Force*Time = mass*velocity
Force*(2 seconds) = (8kg)*(4m/s)
Force*(2 seconds) = 32 (kg*m/s)
Force = 16 Newtons