If all three collisions in the figure shown are totally inelastic, which cause(s) the most damage?

1. If all three collisions in the figure shown are totally inelastic, which cause(s) the most damage? 1. I 2. II 3. III 4. I, II 5. I, III 6. II, III 7. all three

2. Suppose you are on a cart, initially at rest on a track with very little friction. You throw balls at a partition that is rigidly mounted on the cart. If the balls bounce straight back as shown in the figure, is the cart put in motion? 1. Yes, it moves to the right. 2. Yes, it moves to the left. 3. No, it remains in place.

3. The device in the photograph above is called a "fan cart" because of the electrical fan mounted on it. The fan blows air toward the right in the photograph, so with the sail removed and the fan ON the cart will move to the left (click here for video). On the other hand, with the fan OFF and the sail mounted on the cart, you can blow into the sail from the left with your breath or a larger stationary fan and make the cart move to the right (click here for video). Notice that the propeller is not rotating and the wind from the fan at the left causes the sail to bend to the right. When the fan is turned ON with the sail mounted on the cart, if you hold the cart you can again notice the sail bending due to the air from the cart fan blowing into the sail (click here for video). Suppose that the sail is mounted in place as shown in the photograph, the fan turned ON, and the cart released to move if it wants to. What will the cart do? (1) It will move to the left. (2) It will move to the right. (3) It will remain motionless.

4. A compact car and a large truck collide head on and stick together. Which undergoes the larger momentum change? 1. car 2. truck 3. The momentum change is the same for both vehicles. 4. Can’t tell without knowing the final velocity of combined mass.

5. A compact car and a large truck collide head on and stick together. Which vehicle undergoes the larger acceleration during the collision? 1. car 2. truck 3. Both experience the same acceleration. 4. Can’t tell without knowing the final velocity of combined mass.

6. Example: A wooden block is covering a hole in a table. A gun is fired at the block through the hole in the table, and the bullet becomes embedded in the wooden block. If the block has a mass of 1.5 kg, the bullet has a mass of 10 g and the muzzle velocity of the gun is 200 m/s, how high does the block go?

7. Two - Dimensional Collisions Most collisions do not occur from two objects traveling along the same line. Momentum is conserved along each direction separately. Assuming there in no external force acting on the system along either direction. and If the collision is perfectly elastic the kinetic energy will also be conserved. Steps for working in two - dimensions Draw a picture of the interaction. (before and after pictures are useful). Define the coordinate system to be used. Break vectors into appropriate components. Define your system. Write out momentum conservation expressions (if there are no external forces). Determine the type of collision and act accordingly (Is kinetic energy conserved?). Solve. Check answer (does it make sense?). When working in two dimensions you automatically have two equations to work with. You may need to look in both directions before you can solve.

8. Example: Two cars, A and B, are driving along a straight stretch of road, when car B suddenly drifts into the other lane and collides with car A. Just before the collision car A was traveling in a straight line at 100 kph and car B was traveling at 110 kph at an angle of 10o relative to the horizontal. The two cars, both with the same mass, stick together after the collision. What is the velocity of the fused cars after the collision? A +B B A 0