THE SUCTION AND EJECTION PROCESSES OF A TABLE TENNIS BALL INSIDE A CUP FILLED WITH WATER

A table tennis ball is floating in a cup of water. After the cup is dropped and collides with the ground, the table tennis ball will get launched to a great height. During the free falling of the cup, the gravity and the buoyance applied on the ball vanish in the reference frame of the cup, and the ball is sucked into the water due to the interfacial tension. When the cup collides with the ground, the intense deceleration process leads to an enormous buoyance acting on the ball. Under the influence of this buoyant force, the table tennis ball is ejected from the cup, and the ejection velocity of the ball is directly proportional to the impact velocity of the cup.