http://www.smartphysics.com/images/content/mechanics/ch11/cartruckcollisionnew.png

A blue car with mass m@car = 444 kg is moving east with a speed of vc = 23 m/s and collides with a purple truck with mass m@truck = 1273 kg that is moving south with a speed of vt = 12 m/s . The two collide and lock together after the collision.

What is the speed of the car-truck combination immediately after the collision? I think 10.702m/s

Compare the initial and final kinetic energy of the total system before and after the collision: I think KEi > KEf




http://www.smartphysics.com/images/content/mechanics/ch11/twotrains2.png
Now the same two cars are involved in a second collision. The first car is again moving to the right with a speed of v1 = 8.8 m/s and collides with the second train car that is now moving to the left with a velocity v2 = -6.2 m/s before the collision. The two cars latch together at impact. m1 = 679 kg, and m2=426.86kg

What is the final velocity of the two-car system? (A positive velocity means the two train cars move to the right – a negative velocity means the two train cars move to the left.) I think 3.01m/s, right?

Compare the magnitude of the momentum of train car 1 before and after the collision: I think it should be p1 initial > p1 final because of the change in velocity.

1. a. Right.
b. You think? Either you do the calculation, or you use the fact that it's a completely inelastic collision and hence, energy is lost.

2. a. Right.
b. Right.

You have to get more confident on your work. You do well, so... keep it up! :)