Mary jumps from a plane at 3500 m She free falls with air fr

Mary jumps from a plane at 3500 m. She free falls with air friction coefficient of b = 10I. Her total mass (including parachute) 75kg. When she reaches 1500m she opens her parachute. Now her air friction coefficient is 98|. How many seconds did she wait before opening her parachute? you can use the idea that fort large enough e^-bt/m| can be treated as close enough to 0. What is her velocity 10 seconds after opening her parachute?

Solution

28.41 seconds note: here if you ignore e^-bt/m and take g=10m/s2answer would be 20 seconds.

7.5 m/s

Explanation:

Net force= mg-bv

dv/dt=g-(b/m)v

Solving this linear first order differential equation will yield: v=mg/b(1-e^-bt/m) =dx/dt

=> x=mg/b(t+me^-bt/m/b)

using these equations answer is obtained.