# Projectile motion air resistance calculator - tutorial?

1. Jan 10, 2012

### Pega

Projectile motion air resistance calculator - tutorial??

I am not familiar with the terms/words of physics in English, but I hope you can excuse me.

I need a tutorial for how to calculate the air resistance in a projectile motion. I want to do it with my calculator and that's why I came here. I wonder if any of you might know about such a tutorial, or if you want to guide me right here.

I use a Texas Instruments TI-84 Plus.

If you want to guide me right here it would be for my advantage to use these values:

Formula --> F = (1/2)CρAv2

C = 0.45
Air density ρ = 1.22 kg/m3
Mass m = 2.58 g
A = π*r2, r = 1.91 cm
V0 = 25 m/s
anlge = 40°

Please try to be clear when explain.

2. Jan 14, 2012

### Pega

Re: Projectile motion air resistance calculator - tutorial??

*bump*

3. Jan 14, 2012

### Gordianus

Re: Projectile motion air resistance calculator - tutorial??

I see you assume a constant drag coefficient; a nice fact because it simplifies the analysis.
I also assume you know how to integrate a system of differential equations.
Mr Newton says:

dVx/dt=(-1/2 C rho A V^2 cos(theta))/m
dVy/dt=(-g-1/2 C rho A V^2 sin(theta))/m
dx/dt=Vx
dy/dt=Vy

This is the set of four differential equations I mentioned above.

V^2=Vx^2+Vy^2
cos(theta)=Vx/V
sin(theta)=Vy/V

4. Feb 4, 2012

### Pega

Re: Projectile motion air resistance calculator - tutorial??

I read the manual for my calculator and now I have gotten further.
Down below I show you print screens of how far I've gotten. Then hopefully you understand what I've done and will help me the last bit.

As you see I've managed to put in the projectile motion without air resistance. So how do I put in the air resistance in this?
I'm not sure if I have understood all of what you wrote, but I think that if you/someone show me what to do here, I will get it.
So if I were to use this practically, you mean that the drag coefficient would differ over time?? (I'm not that well-grounded in this subject) Because of the projectile changing shape? Or of some other more advanced physical explenation?

5. Feb 4, 2012

### parhim

Re: Projectile motion air resistance calculator - tutorial??

*bump*

6. Feb 6, 2012

### Pega

Re: Projectile motion air resistance calculator - tutorial??

*bump*