The magnitude of the drag force of air resistance on a certain 20kg object is proportional to its speed. If the object has a terminal speed 80m/s, what is the magnitude of the drag force of an object when it is falling with a speed 30m/s?

Given:

object = 20kg

terminal speed of object = 80 m/s

According to the problem, drag force is proportional to speed, so Fd = kv; k is some constant

At terminal velocity Vt: Fg = Fdmg = kVtk = mg / Vt = (20.0) (9.8) / (80.0) = 2.45 kg/s

Fd = kv = 2.45v

Fd = 2.45 (30.0) = 73.5 N