Volleyball has so much physics involved its crazy. With every basic component of volleyball comes physics. One of the more exciting parts of volleyball is hitting, and without physics there would be no hitting! With hitting, the player jumps into the air and at her highest point she contacts the ball. When the hitter is about to jump, her initial velocity would be 0. Then, she must do work in order to reach the ball to hit. Work=Force(distance) therefore, the hitter must at least exert a force of whatever her weight is on to the floor in order to jump. If the player wants to be in the air for longer and higher, she must do more work.
As the hitter is at their highest point, their gravitational potential energy is the highest and then that energy changes into kinetic energy. Energy is never lost or created it is simply changed. When the hitter makes contact with the ball, she applies a force to it that gives it velocity both horizontally and vertically. If the hitter exerts a greater force on the ball it will have a greater acceleration causing it to go faster and hopefully result in a point!