Question

A dentist's drill starts from rest. After 3.30 s of constant angular acceleration it turns at a rate of 2.1x10^4 rev/min.
(a) Find the drill's angular acceleration.
rad/s2

(b) Determine the angle (in radians) through which the drill rotates during this period.
rad

Answer 1

(a) Divide the final angular velocity (in rad/s, NOT rpm) by the time interval.

(b) angle = (1/2)*(angular acceleration)*t^2
OR
(1/2)*(final angular velocity)*time

Answer 2

Why do you multiply by .5?

Answer 3

it is based off the equation:

displacement = (initial velocity)*(change in time) + 1/2(acceleration)*(change in time squared)

since that equation is linear, the equation recommended for this problem is:

"angle" = 0 + 1/2(acceleration)*(change in time squared)

that is how one gets the 1/2