# Homework Help: Kenetic energy

1. Apr 21, 2010

Kenetic energy!!!!

[PLAIN]http://img190.yfrog.com/img190/2899/42256198.jpg [Broken]
alright for the basketball question, I don't understand why the KE doesn't drop to 0.The correct answer is B..and I picked A! because when the PE is max KE is 0.

Last edited by a moderator: May 4, 2017
2. Apr 21, 2010

### joriarty

Re: Kenetic energy!!!!

If the ball goes cleanly through the hoop without hitting the backboard or anything (which would cause it to stop momentarily when elastic potential energy is at a maximum), then it is in constant motion. Remember that it has a horizontal velocity component as well as vertical.

When the ball reaches its peak height, yes it does have maximum gravitational potential energy. But it still has that horizontal velocity component, so it is not completely stationary, therefore kinetic energy does not drop to zero.

If the ball was thrown straight up in the air, then at an instantaneous point in time it would have zero kinetic energy. But in this example, the ball is always moving in one direction or another.