function blowElement(element,x,y,z,speed) 
    local ex,ey,ez = getElementPosition(element) 
    x,y,z = x-ex,y-ey,z-ez 
    local dist = math.sqrt(x*x+y*y+z*z) 
    x = x*speed/dist 
    y = y*speed/dist 
    z = z*speed/dist 
    setElementVelocity(element,x,y,z) 
end 
 
Didn't test, but it should work.