If a small ping-pong ball is placed in a vertical jet of water or air, it will rise to a certain height above the nozzle and stay at that level. Explain

Due to the high velocity of the jet of water, the pressure between the ball and jet decreases. The . greater (atmospheric) pressure on the other side of the ball pushes it against the jet and the ball remains suspended. The high velocity of water takes the ball upwards along with it and makes it to spin.