For an uniformly accelerated motion, the following relationship is used:
(1)
where a is the acceleration, S the distance covered, and vf and vi the final and initial speeds of the motion.
In our problem we are dealing with a rotational motion. Initially, the salad spinner has constant angular speed, which is given by
where f is the rotational frequency, which is the number of revolutions per second:
so the initial angular speed is
Then, the salad spinner starts to decelerate with constant deceleration , and during its deceleration it spins for other 6 revolutions, so covering a total angle of
until it stops, so until it reaches a final speed of .
To find the angular acceleration, we can use the equivalent of equation (1) for angular motions:
and so, since the final speed is :
where the negative sign means the salad spinner is decelerating.