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I'm making a game on Corona that launches a ball.

The force is based on the magnitude of the drag: the larger is the drag -> the higher is the force.

I'm having some trouble to do this, because I can't calculate the magnitude of the drag.

I tried a simple (finalX - initialX) but that's not a good idea.

local function onTouch(event)

    if "began" == event.phase then

    end
    if "ended" == event.phase then
        local finalX = event.x
        local finalY = event.y

        forceX = event.x - event.xStart
        forceY = event.y - event.yStart


        print(forceX, forceY)

    end
end


local function gameComponents()
    local crate = display.newImageRect( "images/sonic.png", 90, 90 )
    crate.x, crate.y = 60, 360
    crate.rotation = 0
    --physics.addBody( crate, "static", { friction=0.3} )

    Runtime:addEventListener( "touch", onTouch )
    return crate

end

local Game = {}
Game.new = gameComponents
return Game
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Use the hypotenuse lenght of the triangle described by the differences on th x and y axis. This traduces to:

dx = event.x - event.xStart
dy = event.y - event.yStart
force = math.sqrt(dx ^ 2 + dy ^ 2)

And that's it. Good luck with your game!

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