# Confuse about SetForce(0, force)

Hi, I'm getting confused with function **joints[i]->SetForce(0, force )** for a wheel joint. I build a PID controller for the throtte of my car running on a steep road. Using PID tuning tool in Matlab, it worked well but when i applied to Gazebo simulation, car did not run as expectation (car always could not run up). Therefore, i guess that i misunderstood the SetForce function's parameters.

Could you tell me if i put an energy's force **F** to my car, then what is the value of force put into SetForce(0, force) and the acceleration of my car ( my car is two-wheel drive and wheel's radius is **r**, its mass is m and suppose there is only additional gravity force **m gsin(alpha)**).

Here is how i computed **force** in SetForce(0, force) and apply to each wheel:
**force = F*r**

**acceleration = (F - m gsin(alpha) ) /m**

**for(i=1; i<3; i++)
{ joints[i]->SetForce(0, force ) }**

I get stuck in this issue for a lot of time. Hope a intuitive guide. Thanks