Calculate Angular Displacement: 2.1rad/s to 0rad/s in 4.7s

[tica86]

A fan rotating at 2.1 radian/s slows down with a constant acceleration and comes to a stop in a time of 4.7 s. What is its angular displacement in this time?

Is this what I'm supposed to use: Δθ = Δθ2 − Δθ1?

if it is I'm not sure how to begin to solve this problem, if anyone could help me out, thanks!

 

[issacnewton]

For the case of constant acceleration, you need to use

$$\delta\theta=\omega_{i}t+\frac{1}{2}\alpha t^2$$

find alpha from

$$\omega_{f}=\omega_{i}+\alpha t$$

you have been given initial and final angular velocities

 

[issacnewton]

For the case of constant acceleration, you need to use

$$\Delta\theta=\omega_{i}t+\frac{1}{2}\alpha t^2$$

find alpha from

$$\omega_{f}=\omega_{i}+\alpha t$$

you have been given initial and final angular velocities

 

[tica86]

For the case of constant acceleration, you need to use

$$\Delta\theta=\omega_{i}t+\frac{1}{2}\alpha t^2$$

find alpha from

$$\omega_{f}=\omega_{i}+\alpha t$$

you have been given initial and final angular velocities

Ok, I tried the following and I know it's wrong but I'm really lost:

=2.1*10+1/2*.4468

.4468(2.1/4.7)

 

[issacnewton]

Initial angular velocity $\omega_i= 2.1 \, rad/sec$ and since the stuff comes to rest, final angular velocity $\omega_f=0$ and the time t is given. With this information , can you find the $\alpha$ using one of the equations I have given ?