Bouncing ball, stroboscopic image. The strobe light was set to flash 50 times every second, and the exposure time was about 1.5 seconds, so about 75 separate images were obtained on this single exposure. The sequence of images shows that the ball's trajectory is a parabola, as predicted by theory. The sequence also shows the changing speed of the ball: the ball moves fastest near the ground and slowest at the top of an arc. The sequence also shows that the horizontal speed is approximately constant, and only the vertical speed is changing (due to gravity). The height of successive bounces is less as the ball loses energy by hitting the ground.