1. DAILY QUESTION January 20, 2009 1. What is Newton’s 3 rd law?

2. Agenda1/20/09 Daily Question Ch 11 Section 3 Notes Assignments: 1. 11- 2 and 3 worksheet Test on Friday!

3. Newton’s 3 rd Law For every action force, there is an equal and opposite reaction force –Force always occurs in pairs (action and reaction) Equal size Opposite direction

4. Momentum A property of all moving objects Momentum = mass x velocity p = mv

5. Momentump=mv The more mass an object has the more momentum it has The more velocity an object has the more momentum it has Momentum has direction: it is in the direction of the velocity

6. Using the Momentum Equation Find the momentum of a 6.0 kg bowling ball moving at 10.0 m/s down the alley toward the pins. p = mvp= 6 kg x 10 m/s p = 60 kg-m/s down the alley

7. Momentum and Force Extending time it takes to change the momentum of the object decrease the force –Softball glove –Gymnasts –Air bags

8. Momentum and Force Which situation would do less damage to your car? Explain in terms of momentum. –Hitting a tree and completely stopping immediately OR –Hitting plastic barrels of water that spread the stopping process over a longer time

9. Momentum is conserved in collisions Law of conservation of momentum: the total amount of momentum in an isolated system is conserved. Momentum before = Momentum after Momentum can be transferred from object to object, but it always remains the same

10. Action and Reaction Force Pairs Page 365 Figure 22 Hand hit table with a force – table puts a force on your hand Bat exerts a force on the ball – the ball exerts a force on the bat Rabbit exerts a force on the ground – ground exerts a force on the rabbit