When an object is thrown upward, its height (S), in meters, is given (approximately) by the quadratic equation S= -512 + vt + h, where v is the upward initial velocity in meters/second, t is the time of flight in seconds, and h is the height above level ground from which the object is thrown. Johnny is standing on a platform 6 meters high and throws a ball straight up as high as he can at a velocity of 13 meters/second. At what time t will the ball hit the ground? The ball will strike the ground seconds after it is thrown.​