# Homework Help: Terminal velocity

1. Apr 20, 2010

### bobey

1. The problem statement, all variables and given/known data

A parachutist whose mass is 100kg drops from rest to an altitude of 3000m and falls under of gravity. Assume that the force due to to air resistance is proportional to the velocity of the parachutist , with the proportionality constant k1 = 20kg/s when the chute is closed and k2=100 kg/s when the chute is opened. The chute does not open until after 30s of free fall (9.81 m/s^2)

what is the terminal velocity after the chute opens?

2. Relevant equations

i found the definition of terminal velocity : The terminal velocity of a falling body occurs during free fall when a falling body experiences zero acceleration...

thus my understanding is this terminal velocity is when f=mg (falling depends on gravity only)

3. The attempt at a solution

==> k2v=mg
v=mg/k2
= 100(9.81)/100 = 9.81 m/s

i think this is wrong... but i dont know where to start... i think my concept on terminal velocity is wrong... can anybody help me... plz3

2. Apr 20, 2010

### Filip Larsen

Your understanding is correct. The terminal velocity is the velocity at which the sum of the drag and gravity force equals zero.

3. Apr 20, 2010

### bobey

ok! then, is my understand is reflected by the correct calculations??? help me to clarify this thing...

4. Apr 20, 2010

### Filip Larsen

Yes, your calculation is also correct.

5. Apr 20, 2010

### bobey

thanx 4 d clarification... rely appreciated it...