21. Is it possible for a skydiver who jumps second from a plane to put himself in an aerodynamic position and overtake a person who jumped first?
Yes. When you skydive, your velocity doesn't increase indefinitely because the upward force of air resistance eventually balances the downward force of gravity. At that point, you reach a constant velocity (called "terminal velocity"). Just how large this terminal velocity is depends on your shape. It is possible to increase your terminal velocity by rolling yourself into a very compact form. In that case, you can overtake a person below you who is in a less compact form.