# Homework Help: Another Grade 11 Dynamics Problem Needing Urgent Help!

1. Nov 15, 2009

### physics_newb

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

The drag coefficient works like the coefficient of friction when an object is moving through the air, but it increases its effects as the object moves faster. A skydiver plus the parachute has a combined mass of 94.0kg. if the formula for the drag coefficient of the parachute is F_fric=C_D v^2, find the terminal velocity of the 54.0kg/m

2. Relevant equations

m=94.0kg a=9.8m/s^2
Cd=54.0kg

3. The attempt at a solution

I do not understand the question and am not even sure what terminal velocity is in the first place

2. Nov 15, 2009

### ideasrule

As an object falls under gravity, air resistance gets stronger and stronger. Eventually, at a certain speed, air resistance will equal the force of gravity and the object stops accelerating. So what's the first step?

3. Nov 15, 2009

### physics_newb

Oh ok how do you find out when that point is?

4. Nov 15, 2009

### ideasrule

At that point, the force of gravity is equal to the force of air resistance. Write that out as a formula and you're basically done.

5. Nov 15, 2009

### physics_newb

Fg=Fa?

6. Nov 15, 2009

### ideasrule

Yes.

7. Nov 15, 2009

### physics_newb

8. Nov 15, 2009

### ideasrule

Fg=?
Fa=?

Write them out using the information you know and the information you want to find (namely, Cd, v, m, and g).

9. Nov 15, 2009

### physics_newb

ok ill try and post back

10. Nov 15, 2009

### ideasrule

F_fric=C_D v^2

What's Fg?

11. Nov 15, 2009

### physics_newb

Fg is 9.8m/s/s

12. Nov 15, 2009

### ideasrule

That's g, the acceleration due to gravity. F=ma, so Fg=?

13. Nov 15, 2009

### physics_newb

921.2m/s/s?

14. Nov 16, 2009

### physics_newb

wow i need serious help with this

15. Nov 16, 2009

### ideasrule

Fg=mg. Remember this.

16. Nov 16, 2009

### physics_newb

ok i think i might have gotten it....is this all i have to do:
m=94.0kg
a=9.8m/s^2
CD=54kg/m
v=?
F_fric=?
Step 1
F_fric=ma
F_fric=94.0*9.8
F_fric=921.2m/s
Step 2:
921.2=54*v^2
921.2/54=v^2
17.1=v^2
√17.1=v
4.1=v
v=4.1m/s

17. Nov 16, 2009

is it right?