Homework Help: Physics help ?

1. Jan 4, 2010

Neveda

Physics help!!?

1. The problem statement, all variables and given/known data
A skydiver has mass of 75g, travelling at 80mph, drag force on skydiver is 650N. Find acceleration of skydiver at 80mph (g=10n/kg??)

2. Relevant equations

Do I use a=f/m
3. The attempt at a solution
No attempt - im really stuck!

2. Jan 4, 2010

tiny-tim

Welcome to PF!

Hi Neveda! Welcome to PF!

(do you mean 75kg?)

Yes, use Ftotal = ma.

What is the total force on the skydiver?

3. Jan 4, 2010

Stonebridge

Re: Physics help!!?

Yes, use a=F/m
You need to find the resultant force on the diver.
There are two forces acting on him in this question.

4. Jan 4, 2010

Neveda

Re: Physics help!!?

EEk.. I think maybe it is 75kg and the total force is 650N But I have no idea how to even begin to work something like this out :(

5. Jan 4, 2010

jegues

Re: Physics help!!?

The total force is not 650N, that's simply the drag force.

What other forces act on the sky diver?

6. Jan 4, 2010

Neveda

Re: Physics help!!?

Thats the only force mentioned in the question - sorry..I need to work out acceleration yes? Do I need to find other forces..? Thanks!

7. Jan 4, 2010

Neveda

Re: Physics help!!?

Or could anyone just advise me on how I would work out/answer a question thats similar to above..? Then I can apply the knowledge to those kind of questions..... :)

8. Jan 4, 2010

Centurion1

Re: Physics help!!?

excuse me if you have already found it but you need to find the force of gravity pulling him downwards.

9. Jan 4, 2010

Re: Physics help!!?

do you guys in America need to convert your speed of 80mph to SI units of m/s ?

10. Jan 4, 2010

jegues

Re: Physics help!!?

I guess it depends on the units in which they want the answer in. Generally,(in my experience atleast) answers tend to be in SI units.

11. Jan 4, 2010

Centurion1

Re: Physics help!!?

we always use si in my class. its easier that way. (especially for conversion

12. Jan 5, 2010

Neveda

Re: Physics help!!?

Ok..but how do I work out the answer for a question similar to above?!!!! PLease can someone advise??