Question

A ball is thrown into the air. At the highest point, the ball has zero velocity and zero acceleration. True or false and why?

Answer 1

True. The reason is that while the ball is going up, it's kinetic energy is being converted to potential energy. So long as its kinetic energy isn't zero it keeps ascending. Once its kinetic energy reaches zero, it's velocity is zero and its potential energy is maximized. Gravity however, is still acting on that ball, so it is only at zero velocity for a very small amount of time before the ball starts accelerating downward, increasing it's kinetic energy as its potential energy goes down.

In equation form, the energy of the ball is always described by this equation:\[E _{ball}=KE+PE\]where KE is kinetic energy and PE is potential energy. That can be expanded to:\[E _{ball}=\frac{ 1 }{ 2 }mv ^{2}+mgh\]where m is the ball's mass; v is its velocity; g is the acceleration of gravity; and h is the ball's height above its starting point.

Answer 2

thank you so much!

Answer 3

It has zero velocity at the peak.

Although it is temporarily motionless, it has the acceleration of gravity, g, which is why it comes back down.

Answer 4

You're welcome.