1. ## physics relation

derive a theoretical relation between g and D assuming air friction is f = -bv

Hints: mg(t) = mg - bv(t) Newton's Law
g(t) = dv(t) / dt Definition of Acceleratioin
D(t) = integral from t to 0 of v(r)d(r) based on Definition of velocity

2. Use the chain rule:
dr=(dr/dt)dt=vdt

Use newton's law to find what is v in regards with g(t), and then plug it instead of v to find the relation between D and g.