p11_009.pdf

9. We assume the sense of initial rotation is positive. Then, with ω 0 > 0and ω = 0 (since it stops at time

t ), our angular acceleration is negative-valued.

(a) The angular acceleration is constant, so we can apply Eq. 11-12 ( ω = ω 0 + αt ). To obtain the

requested units, we have t =30 / 60 = 0 . 50min. Thus,

α =

−

33 . 33rev / min

0 . 50min

−

66 . 7rev / min 2

(b) We use Eq. 11-13:

2 αt 2 =(33 . 33)(0 . 50) + 1

2 (

−

66 . 7)(0 . 50) 2 =8 . 3rev .

θ = ω 0 t + 1