Johnny ties a rope around his waist and throws one end of the rope over a pulley so that he can lift himself into the air. Johnny has a mass of 75 kg. a) Draw a free-body diagram b) how hard must he pull downward to raise himself slowly at a constant speed? c) If he increases this force by 15% what will his acceleration be?

Consider two less-than-desirable options. in the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. in the second option you are driving 30 mph and crash head-on into a stationary brick wall. in neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. which of these two situations would result in the greatest impact force?