Answer
a) $\omega_f=+18rad/s$
b) $\omega_f=+6rad/s$
c) $\omega_f=-6rad/s$
d) $\omega_f=-18rad/s$
Work Step by Step
We have $$\overline\alpha=\frac{\Delta \omega}{\Delta t}=\frac{\omega_f-\omega_0}{\Delta t}$$
Therefore, $$\omega_f=\overline\alpha\Delta t+\omega_0$$
a) $$\omega_f=(+3\times2)+12=+18rad/s$$
b) $$\omega_f=(-3\times2)+12=+6rad/s$$
c) $$\omega_f=(+3\times2)-12=-6rad/s$$
d) $$\omega_f=(-3\times2)-12=-18rad/s$$
