How Do I Calculate Acceleration with Air Resistance in Projectile Motion?

[hallowon]

Homework Statement

I'm trying to find the acceleration due to air resistance in x direction and acceleration due to air resistance +gravity in y component.

given variables
m-0.14273(baseball)
Cd=0.4
Vi=20m/s
angle= 45 degrees

Basically, I have to program a projectile motion program accounting air resistance, but my biggest problem physics wise is my huge ax, and y acceleration, which prevent my program to loop even more:/

Homework Equations

ax= fairx/mass = -cdVix^2/mass
ay= fairy+fg

The Attempt at a Solution

fairx= (0.4)(20cos45)^2=80N
ax= 80n/0.14263kg = 560.498844m/s^2
ay = well...its in the thousands >.>


does this mean i have to assume f=Cd*V instead of being proportional to V^2?

 

[tiny-tim]

Hi hallowon!

ax= fairx/mass = -cdVix^2/mass

No, that can't be right …

a is L/T², and the RHS is L²/T² …

you need an extra factor with dimensions 1/length (or area/volume).

Maybe this will help … http://en.wikipedia.org/wiki/Drag_coefficient"