Hi daniel.weiss1, thanks for the question. Since the grinding wheel is rotating with a constant angular velocity (2200 rpm) this means there is no tangential acceleration of any point on the edge of the wheel. Points on the edge (or anywhere since there's nothing special about the edge) are all going at a constant speed, in other words. The direction of their velocity is changing, despite the constant speed, and it's the radial acceleration which causes this change in direction.

## Comments

For part b, how do we know were are looking for the radial acceleration and not the tangential acceleration?

Thanks

Hi daniel.weiss1, thanks for the question. Since the grinding wheel is rotating with a constant angular velocity (2200 rpm) this means there is no tangential acceleration of any point on the edge of the wheel. Points on the edge (or anywhere since there's nothing special about the edge) are all going at a constant speed, in other words. The direction of their velocity is changing, despite the constant speed, and it's the radial acceleration which causes this change in direction.

Hope that helps,

Mr. Dychko