Suppose a teenager puts her bicycle on its back and starts the rear wheel spinning from rest to a final angular velocity of 250 rpm in 5.00 s. 

(a) Calculate the angular acceleration in rad/s².

(b) If she now slams on the brakes, causing an angular acceleration of -87.3 rad/s², how long does it take the wheel to stop?

Strategy for (a)

The angular acceleration can be found directly from its definition in  because the final angular velocity and time are given. We see that Δω is 250 rpm and Δt is 5.00 s.

Strategy for (b)
In this part, we know the angular acceleration and the initial angular velocity. We can find the stoppage time by
using the definition of angular acceleration and solving for Δt, yielding

Transcribed Image Text:

α= Δω 2 ΔΙ