PhysicsJS - moving an object - physicsjs

Question

I'm trying to figure out how to use PhysicsJS. I first off just want to simply figure out how to change lets say a position or a speed of an object on click... but I just cant figure it out!
( function()
{
var viewWidth = 500,
viewHeight = 300,
renderer = Physics.renderer( 'canvas',
{
el: 'viewport',
width: viewWidth,
height: viewHeight,
meta: false,
styles:
{
'circle' :
{
strokeStyle: 'hsla(60, 37%, 17%, 1)',
lineWidth: 1,
fillStyle: 'hsla(60, 37%, 57%, 0.8)',
angleIndicator: 'hsla(60, 37%, 17%, 0.4)'
}
}
}),
viewportBounds = Physics.aabb(0, 0, viewWidth, viewHeight),
constraint = {
aabb: viewportBounds,
restitution: 0.99,
cof: 0.99
},
ballOptions = {
x: 100, // x-coordinate
y: 100, // y-coordinate
vx: 0.0, // velocity in x-direction
vy: 0.0, // velocity in y-direction
radius: 20
},
gravity = Physics.behavior('constant-acceleration',
{
acc: { x : 0, y: 0.0004 }
}),
ball = Physics.body('circle', ballOptions );
Physics( function( world )
{
// add the renderer
world.add( renderer );
// add circle
world.add( ball );
// subscribe to ticker to advance the simulation
Physics.util.ticker.subscribe(function( time, dt )
{
world.step( time );
});
// on every step...
world.subscribe( 'step', function()
{
world.render();
});
world.subscribe( 'collisions:detected', function( $collision )
{
});
var onElementClick = function()
{
// do something
};
document.getElementById( 'viewport' ).addEventListener( 'click', onElementClick, false );
// Lets GO!
Physics.util.ticker.start();
});
})();
any help much appreciated

Answer 1

One option is to take the gravity that was created but never added to the world and do that onclick.
world.add(gravity);
That's cheating in the sense that you asked about changing the position or speed of an object. To do that, modify the state of the ball. See the docs on Bodies, specifically the properties. You can set state.pos to move it. To put it in motion, set the velocity:
ball.state.vel.set(.1,-.5); // move right and upward
jsfiddle that sets velocity