# Are the forces I'm using correct? (ball in air) [closed]

I have been working on a program which should simulate all the forces on a spherical object. Right now those are balls, but they can easily be changed to something else. These are the formulas I use for the forces so far. My question is, if all of them are correct for this situation and if I get the correct resultant force.

$$\matrix{ F_{zw} &=& g m \\ F_d &=& \frac12 \rho v_y^2 C_d A \\ F_b &=& \rho V g \\ Fres &=& F_{zw} + F_d - F_b \\ }$$

Would this work when the ball is falling down? Will I have to change the sign of one of these forces when the ball is going up? (It's a bouncing ball)

EDIT:

$$\matrix{ m &=& 0.0425\,\text{kg} \\ \text{radius} &=& 0.125\,\text{m} \\ }$$

To get the speed I get the acceleration ($F_{res} / m$) and then multiply that by the difference in time.

$F_{zw}$ is gravity, $F_b$ is buoyancy, and $F_d$ is drag.

-

## closed as off-topic by Emilio Pisanty, Dan, BebopButUnsteady, Nathaniel, DilatonJul 25 '13 at 21:55

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – Emilio Pisanty, Dan, BebopButUnsteady, Nathaniel, Dilaton
If this question can be reworded to fit the rules in the help center, please edit the question.