The Physics of Bumping a Volleyball
What is a bump?
A bump is an underhand pass where the ball bounces off your forearms while your arms are straight and your hands are held together.
The Physics of Bumping
When bumping a volleyball, you are trying to strategically place the ball high in the air for the setter to set. When bumping a volleyball, you want to avoid following through. If you follow through your arms will be in contact with the ball for a longer amount of time, and therefore the ball will bounce off of your arms with a great velocity, be out of control, and potentially hit the ceiling. The following equation demonstrates this scenario:
FΔt=mΔv (Impulse = momentum)
Since impulse = momentum, the greater the impulse applied to the ball, the greater the momentum. Therefore, the more time your arms are in contact with the ball, the greater the momentum.
Bumps are an extremely controlled maneuver.You want to have the smallest possible momentum when your arms approach the ball for a bump. Therefore you must decrease the velocity your arms have when approaching the ball to decrease your momentum. The less momentum your arms have the less of an impulse you will apply to the ball. If you have a huge momentum when approaching the bump the impulse on the ball would be too large to control and the ball fly off your arms chaotically and result badly.