need to make a ball travel in the angle it was hit from

Question

self.hitBall = function (ball, x, y){

        var angle = Math.atan2((x - ball.centerX), (y - ball.centerY));
        ball.velocityY = (Math.sin(angle) * 10);
        ball.velocityX = (Math.cos(angle) * 10);


    }

So the function takes in the ball, which has a centerX variable and a centerY variabe. The x and y passed into the function is the x and y is the point the ball was hit. I want to make the ball travel in the direction it was hit from.

Not really sure why my code isn't working.. it's behaving very strangely and I'm not that good with trig so I'm not really quite sure why it isnt working.

Answer 1

Assuming that you mean the x,y passed in is the point on the ball that you hit. A bit like the cue position when you hit a ball with a snooker cue. You can do it with a bit of vector maths.

    // create direction vector for ball to go. 
    var dirX = ball.centerX - x;
    var dirY = ball.centerY - y;

    // convert dir to unit vector. this'll make it easier to create a set magnitude later
    var magnitude = Sqrt( (dirX * dirX) + (dirY * dirY) );
    dirX /= magnitude;
    dirY /= magnitude;

    ball.velocityX = dirX * 10;
    ball.velocityY = dirY * 10; 

Answer 2

Physical 4 State Linear Translation----------

FORCE- The amount of force the ball was hit.(kg)

ACCELERATION- That same force divided by the mass of the ball

(Force/Mass)

VELOCITY- Acceleration over time is Velocity

(Force/Mass)*T

POSITION-

Velocity over time changes the position

(Force/Mass)*T^2

DIRECTION Position is determined by direction on both axis

X=(Force/Mass)*T^2 *sin(Direction)
Y=(Force/Mass)*T^2 *cos(Direction)