A 0.008 [kg] bullet is fired from a 2 [kg] gun and leaves the barrel at 800 [m/s]. Both were at rest beforehand. With what velocity does the gun recoil?

Why do we choose a positive direction before adding any momenta up?

A 3 [kg] object sitting at rest breaks into two pieces. Which Cop setup is right?

In an elastic collision between two objects, the mass m1 shows up on both sides of the Cop equation. Why?

A system’s total momentum is 0 [kg m/s]. What does that tell us about the objects in it?

Why does the Cop equation work on an elastic collision without any extra terms for the bounce?

Two cars are about to collide on a straight road. What is the most useful system to draw for the problem?

Taking north as positive, a Cop problem gives a final velocity of -8 [m/s]. How is that reported?

What kind of pontic design would you plan for #10?   

In the above scenario, you also notice that #9 has existing decay under the previous ML and DL composite restorations. #11 has some minor fractures and incipient caries. What kind of restoration would you plan for Jack?