Name: ________________________________

Momentum Transfer ModelNew Representation: IF ChartsPlease save this space—we’ll use it for a specific purpose together in class.

Physics! / Unit III / MTM

– 1 – from Modeling Workshop Project © 2006

Experiment: Cart CrashUse this space to take data in a careful, organized way.

Physics! / Unit III / MTM

from Modeling Workshop Project © 2006 ! – 2 –

Physics! / Unit III / MTM

– 3 – from Modeling Workshop Project © 2006

Activity/Notes: Collisions and Conservation

Physics! / Unit III / MTM

from Modeling Workshop Project © 2006 ! – 4 –

Practice 1: IF Charts in Action

1. An astronaut whose mass is 80 kg carries an empty oxygen tank with a mass of 10 kg. He throws the tank away from himself with a speed of 2 m/s. With what velocity does he start to move off into space?

2. A 2 kg melon is balanced on your bald uncle’s head. His son, Throckmorton, shoots a 50 g arrow at it with a speed of 30 m/s. The arrow passes through the melon and emerges with a speed of 18 m/s. Find the speed of the melon as it flies off the man’s head.

image from thingsonyourhead.com (no, seriously)

Physics! / Unit III / MTM

– 5 – from Modeling Workshop Project © 2006

3. A raft of mass 180 kg carries two swimmers with masses 50 kg and 80 kg.

The raft is initially floating at rest. The two swimmers simultaneously dive off opposite ends of the raft, each with a horizontal velocity of 3 m/s. With what velocity and in what direction does the raft start to move?

4. One way of measuring the muzzle velocity of a bullet is to fire it horizontally into a massive block of wood placed on a cart. Assuming no friction, we then measure the velocity with which the wood containing the bullet and cart begin to move. In one experiment the bullet had a mass of 50 g and the wood and its cart had a combined mass of 10 kg. After the shot, the cart, wood, and bullet moved at a constant speed, traveling 0.80 m in 0.40 s. From this data determine the original speed of the bullet. (That is, the speed of the bullet right before it hits the cart.)

Physics! / Unit III / MTM

from Modeling Workshop Project © 2006 ! – 6 –

5. A 50 kg cart is moving across a very low friction floor at 2.0 m/s. A 70 kg boy, riding in the cart, jumps off so that he hits the floor with zero velocity. That is, his speed is 0 m/s (horizontally) even before he hits the floor. What is the change in momentum of the cart?

6. A ball of mass 3 kg, moving at 2 m/s eastward, strikes head-on a ball of mass 1 kg that is moving at 2 m/s westward. The balls stick together after the impact. What is the magnitude and direction of the velocity of the combined mass after the collision?

Physics! / Unit III / MTM

– 7 – from Modeling Workshop Project © 2006

7. During alpha decay, an atom ejects two protons and two neutrons (an alpha particle, which is also a helium nucleus). When radium-226 decays, it becomes radon-222 by ejecting an alpha particle.

©Modeling Instruction 2010 2 U9 Momentum – ws 4 v3.0

3. During alpha decay, an atom ejects two protons and two neutrons (an alpha particle, which is also a helium nucleus). When radium-226 decays, it becomes radon-222 by ejecting an alpha particle.

a. Complete the momentum conservation diagram for the radioactive decay of radium-226. (Recall from chemistry that the isotopic number of an element is related to its mass.)

initial final

mass/object/velocity

- 0 +

mass/object/velocity

- 0 +

event:

Momentum conservation equation: b. Momentum conservation equation:

c. How many times larger will the final velocity of the alpha particle be compared to the final velocity of the radon-222? 4. An apple falls from a tree.

a. Complete a qualitative conservation of momentum diagram where the apple is initially attached to the tree and the final situation is just before the apple hits the ground.

initial final

mass/object/velocity

- 0 +

mass/object/velocity

- 0 +

event:

Momentum conservation equation: b. Momentum conservation equation:

226Ra 22Rn 4He

! decay occurs !

How many times larger will the final velocity of the alpha particle be compared to the final velocity of the radon-222?

8. On an icy road, a 5000 kg truck rear-ends a 1200 kg car that had been traveling at 13 m/s, causing the truck to slow from 14 m/s to 12 m/s and the car to speed up. What is the final velocity of the car?

Physics! / Unit III / MTM

from Modeling Workshop Project © 2006 ! – 8 –