Derive the differential equation(s) describing the given physical situation. Under some...

Derive the differential equation(s) describing the given physical situation.

Under some circumstances a falling body B of mass m, such as the skydiver shown in Figure 1.15, encounters air resistance proportional to its instantaneous velocity v. Use Newton's second law to find the differential equation for the velocity v of the body at time t. Recall that acceleration is a = dv/dt. Assume in this case that the positive direction is downward.