Section+7+chap+3

=__//**Section 7- Impulse and Changes in Momentum: Crumple Zone**//__= toc

What Do You See?
3/15/11 page 321

dummie hitting a wall with a spring, hes going towards the wall

What Do You Think?
3/15/11 page 321

how big the hood is, where the persons feet will be. making it a farther distance to crumple, the less force

Investigate
3/16/11 page 322

Physics Talk
3/23/11 page 324

w=fd=deltaKE
 * velocity:** speed in a given direction; displacement divided by the time interval; velocity is a vector quantity, it has magnitude and direction
 * acceleration:** the change in velocity per unit time, acceleration is a vector quantity
 * Newton's second law of motion:** if a body is acted upon by a net external force, it will accelerate in the direction of the net force with an acceleration proportional to the force and inversely proportional to the mass
 * momentum:** the product of the mass and the velocity of an object; momentum is a vector quantity
 * impulse:** a change in momentum of an object

Checking Up
3/23/11 page 329

1. a crumple zone increases the time during a crash which minimizes the force 2. It is safer to collide with a soft cushion because they decrease the force and increase the distance to stop a car 3. momentum is the product of the mass and the velocity of object 4. Impulse is a change in momentum of an object

Physics To Go
3/23/11 page 332

1. Impulse and inertia both doth deal with force 2. the passengers slows down gradually instead of coming to a sudden stop 3a. it takes an unbalanced force to stop the person and padded would require less force 3b. the person will slow down more gradually because there is more time for the force 4. You bend your knees because they absorb some of the force as you hit the ground 5. They would use a lot of padding so it uses less force over more time 6a. 120 N 6b. 60 N 7. 8. 9. There is less force over more time 10. The first one has a larger force acting over a shorter time and the other one is a small force over longer time

Test
3/29/11 page 340

1. b 2. d 3. c 4. b 5. d 6. a 7. a 8. c 9. (5)(7)=35 (.4)(30)=12 (20)(2)=40 (.3)(60)=18 c 10. d 11. a 12. b 13. (2)(3)+(6)(1) =12 d 14. b 15. c 16a. determine the mass and velocity before and after b. look at the change in momentum c. measure the impulse 17a. 1 b. 1 and 2 c. 1 and 2 18. momentum and impulse can change the force which is what crumple zones and air bags do to slow the passenger down. 19a. The wider belt because there is the same force over a larger area so there is less pressure b. If it stretched the passenger can gradually slow down 20a. GPE=mgh 1: GPE=(2)(9.8)(.3) GPE= 5.8 2: GPE=(1)(9.8)(.5) GPE=4.9 20b. KE=1/2mv^2 trial 1: KW=(1/2)(2) c. W=fd trial 1 21. 1500(20)= 30000 30000/10=3000 3000/1500=20mph 22. MaVai+MbVbi=(Ma+Mb)Vf (120)(5)+(80)(10)=(120+80)Vf Vf=7m/s 23. (.160)(40)=6.4 (.160)(60)=9.6 =3.2