# Rotating Object - zero KE

1. Sep 6, 2013

### esmeralda4

Hi,

Since velocity is a vector quantity I assume it follows that KE must also by a vector since KE=1/2mv squared.

Is it true to say a rotating object has zero total velocity since + = - and therefore the total KE is zero?

Thanks

2. Sep 6, 2013

### Staff: Mentor

No, because kinetic energy is not a vector quantity. It is a scalar. Think of the $v^2$ as coming from the vector dot product of the velocity with itself: $v^2 = \vec v \cdot \vec v = v_x^2 + v_y^2 + v_z^2$.

There is such a thing as rotational kinetic energy.

http://hyperphysics.phy-astr.gsu.edu/hbase/rke.html

Last edited: Sep 6, 2013