1. Chapter 10, Section 4 Action and Reaction
Wednesday, March 17, 2010
pages

2. Objectives State Newton’s third law of motion.
Define and calculate momentum and state the law of conservation of momentum.

3. Vocabulary Words
Momentum
Law of Conservation of Momentum

4. Newton’s Third Law of Motion
Newton’s 3rd Law of Motion states that for every action, there is an equal and opposite reaction.

5. Do Action-Reaction Forces Cancel?
Action-Reaction forces cancel out ONLY if the forces are equal in strength but opposite in direction.
Newton’s 3rd law refers to forces on 2 different objects.
In the volleyball example, one force is on the ball and the other is on the player.

6. Momentum
Momentum of an object is the product of its mass and its velocity.
Momentum=Mass x Velocity
Unit of measurement is for mass is kg and the unit of measurement for velocity is m/s.

7. Momentum -- cont’d
The more momentum an object has, the harder it is to stop.
A high velocity can also produce a large momentum even when the mass is small.

8. Practice Problems Read and solve the practice problems on page 335.
We will correct in 10 minutes.

9. Conservation of Momentum
The law of conservation of momentum states that the total momentum of the objects that interact does not change.
The quantity of momentum is the same before and after they interact.
The total momentum of any group of objects remains the same unless outside forces act on the objects.

10. Momentum of 2 Moving Objects
If 2 cars are traveling in the same direction and one car is going faster than the other, eventually the faster car will catch up with the slower car.
The two cars will contact.
The faster car will slow down and the momentum of the slower car will increase.
See Figure 9A on page 336.

11. Momentum of 1 Moving Object
If a car is moving and hits a car that is not moving, the moving car will stop but the car that was not moving will begin to move.
The total momentum is the same except the momentum of the moving car is now transferred to the non-moving car.
See Figure 9B on page 337.

12. Momentum of 2 Connected Objects
If a moving car hits a non-moving car but instead of bouncing off each other, the cars couple together (attach), momentum is still conserved.
After the collision, the velocity of the first car will now be halved with the remaining half shifted to the non-moving car.
See figure 9C on page 337.

13. Homework Workbook 10.4 (3/23) Vocabulary quiz (3/23)
Worksheet 10.3 and 10.4 (3/19)