Finding Terminal Velocity given Mass and magnitude

[Matt_h]

I'm in physics 1 in college and reviewing for an up comming exam, ran into this problem and can't seem to figure out how to solve it.

A 70 kg skydiver experiences a drag force as a function of velocity (in m/s), opposite the direction of motion, whose magnitude is given

Fd(v)=0.19v^2

What is the skydiver's terminal velocity?

Any help would be appreciated!

 

[TSny]

Hi, Matt h. Welcome to PF!

The rules here require you to show some attempt at a solution before receiving help. So, how do you think you could get started on this problem? What physics principles or laws are relevant?

 

[Matt_h]

Oh, ok

Using F=ma i found out that the force due to gravity is
70kg*9.81m/s^2=686.7N

Would i then just plug this force into the magnitude equation above to find the velocity?

After plugging it in i got 60.1 m/s

Does that sound about right?

 

[TSny]

Yes, that looks very good. Do you see why you should set the magnitudes of the two forces equal to each other?

 

[Matt_h]

Yes, that looks very good. Do you see why you should set the magnitudes of the two forces equal to each other?

I'm not sure that i do, do you mind explaining it?

 

[TSny]

Newton's 2nd law: F_net = ma

For an object moving at terminal velocity, what is the value of the acceleration a?

 

[Matt_h]

Acceleration would be 0, right?

or no acceleration?

 

[TSny]

Yes. So,...