These are two questions that I am having problems with. Here is the first. 1. The air in a 200km/h wind stikes a 30m by 20m face of building at the rate of 5.4 * 10^4 kg/s. Find the net force on the building, assuming the air comes to rest on impact. Now for this I found the force by mutiplying the velocity by the mass per second. But I don't know where to go from there. Wouldn't the net force just be 0? 2. Calculate the impulse suffered when a 70 kg person lands on firm on the ground after jumping from a height of 5.0m. I don't think I have enough info to answer this question.