How Do You Calculate the Diameter of a Parachute Needed for Safe Landing?

[diracy]

Homework Statement

An ideal parachute accelerates all the air it sweeps as it travels, and the air is accelerated from
0 to the parachute's velocity. Using F = dp/dt calculate the force on an ideal parachute of area A as a function of its velocity and the density of air. Assuming you wouldn't break any limbs if you jumped from 5 feet high without a parachute, this tells you what steady-state velocity you would like your parachute to reach. What diameter a circular parachute you would need? Suppose you weigh 100 kg (including the parachute, a spare, and a video camera to document your jump) and the air density is 1.2 kg/m^3

Homework Equations

The Attempt at a Solution

I'm just a little confused about where to start with this one. Any help?

 

[rude man]

What is the change in momentum of the air molecules in 1 sec?

 

[diracy]

I'm not sure. I've been working on this one for a while, but I haven't gotten very far at all. Any help?

 

[diazona]

The question is "What diameter a circular parachute you would need?" So focus on the diameter of the parachute. What does that affect?

If you prefer, you could think about it a different way: The question says "Using F = dp/dt calculate the force on an ideal parachute..." So what do you need to know in order to calculate that force?