1. Welcome back!
Monday, November 26

2. Momentum is inertia in motion
Momentum, continued...
Open your notebooks and be prepared to take some notes.
Remember:
Momentum is inertia in motion

3. What is the equation for calculating momentum?
(Find it in your notebook.)

4. Review:
Open your notebooks and review how to calculate the momentum of an object.
Now, calculate the momentum of a kg car travelling at 12 m/s.
Show your calculations with SI units in your notebook!

5. Answer:
The momentum of a 2500-kg car travelling at 12 m/s is 30,000 kg-m/s
P = mv
P = (2500-kg)(12 m/s)
P = 30,000 kg-m/s

6. Impulse changes momentum:
The change in momentum depends on the force that acts and the length of time it acts.

7. Recap:
If an object (with mass) speeds up (change in acceleration), it is usually because there is more force on it.
Hence, there is a change in momentum as the object (mass) speeds up (velocity increases).
In this case, momentum increases.
P = mv

8. See the board for equations.
The quantity of force multiplied by the time interval is called impulse.
The greater the impulse exerted on something, the greater will be the change in momentum.
The exact relationship is
impulse = change in momentum.

9. To increase momentum of an object, apply the greatest force possible for as long as possible.
examples:
A golfer teeing off and a baseball player trying for a home run do both of these things when they swing as hard as possible and follow through with their swings.

10. For example: How long a force is exerted on an object is important.
Apply a brief force on something, and you will change the object's momentum.
But, if you apply the same amount of force over a longer period of time, you will yield a greater change in momentum.

11. more examples: The longer the barrel of a gun, the greater the range.
Pulling a slingshot or a bow back as far as you can to get maximum range.

12. In the case of decreasing momentum, a longer contact time reduces the force and decreases the resulting deceleration.
A padded dashboard in a car is safer than a rigid metal one because the padded dashboard increases the time of contact.

13. examples: Pulling your hand back when catching a ball.
Bending your knees when jumping from a high place and landing on your feet.
Driving into a haystack versus a brick wall.

14. Bouncing
The impulse required to bring an object to a stop and then to "throw it back again" is greater than the impulse required merely to bring the object to a stop.

15. examples:
It takes a greater impulse to catch a flower pot and throw it back up than merely to catch it.
The time interval of impact is twice as long, therefore twice as much impulse.
A karate expert strikes the bricks in such a way that her hand is made to bounce back, yielding as much as twice the impulse to the bricks.

16. Review past assignment:
Take out the worksheet titled
Chapter 8 Momentum - exercises #
Assigned about two weeks ago.

21. complete Review Questions # 3 - 13,
Today's Assignment:
In your notebook,
complete Review Questions # ,
Ch. 7, pages in text.
Put the questions right after
the notes you took today.
Draw sketches where applicable.
If you complete the assignment, Mr. Kipp will come around and check it before you leave.