How do you calculate the average angular acceleration of a spinning wheel?

[tnutty]

Homework Statement

A wheel is spinning at 43rpm with its spin axis vertical. After 15s , it's spinning at 62rpm with its axis horizontal. Find (a) the magnitude of its average angular acceleration.

ans:______rad/s/s

Homework Equations

$$\alpha$$ = $$\varpi$$ /t

attempt :

change in omega is 2pi/60 (62-43)
t = 15
so divide them to get rad/s/s
=
1.3 * 10^-1

 

[rl.bhat]

First of all find the angular momentum L.
Then find the rate of change of angular momentum.
Note that L is a vector.So when you find change in L, you have to use vector subtraction. Finally equate it to I*alpha.