1. Mostly straight-forward, I think! Use an impact speed of 20 km/s and a composition of rock for all parts of this question. Feel free to explore ice or iron projectiles on your own or ... really BIG impactors! :)
2. Numbers! For all of these problems you are asked to count up how many times the pressure is doubled (or halved). How many 2's do you need to multiply together to get 64? 128? 1,000,000,000? For each doubling (or halving) you need to move up or down in the atmosphere by 5km.
3. Come to class on Thursday, Aug. 7! If you can't (didn't) make it to class, get the notes from another student!