Reference frames
40-40 and 80-0 collisions are the exact same event viewed from different reference frames, if you ignore friction etc. They will therefore do precisely the same damage. If you cannot ignore friction (e.g. one car has brakes on, as PeteSF mentioned) then the 80-0 might do...
Hi.
The key in both problems is to consider differenct reference frames, i.e. change what point of view you look at the problem from. For example in the first one, one is running east at 6mi/h, and the other west at 5mi/h. If you look at it from the first person's point of view though, he...
Newton's second law
Hi
The figures didn't seem to work for your second question, but here's my attempt at an answer for the first.
First, choose downwards to be positive. Call the upwards force due to the hot air F_{up} , and the original mass of the balloon m_i . Therefore
m_1 g -...