Question

I need to know how to use box2d for projectile motion.

initially, projectileTime=0;
then i call the following function for projectile motion. It works pretty good.
But i want to achieve the same thing using box2d. As far as i know Box2d works only with force, it does not encourage placing object directly, So how to use Box2d for projectile movement??

-(void)projectilelaunched:(ccTime)dt 
{
    projectileTime+=(5*dt);

    double vh=v*cos(theta);

    x=vh*projectileTime;

    double y = x*tan(theta)- 10*((x/vh)*(x/vh))/2;

    projectile.position=ccp(projectilePositionBeforeLaunched.x + x,projectilePositionBeforeLaunched.y+y);

} 

Answer 1

With box2D, you’d only need to set its initial position and initial velocity (via applyForce). Box2d will take care of the rest, applying gravity, stopping when hitting other objects etc.