Answer
a) $\overline\alpha=+0.75rad/s^2$
b) $\overline\alpha=-0.75rad/s^2$
c) $\overline\alpha=+1rad/s^2$
d) $\overline\alpha=-2rad/s^2$
Work Step by Step
We have $$\overline\alpha=\frac{\Delta \omega}{\Delta t}=\frac{\omega-\omega_0}{\Delta t}$$
a) $$\overline\alpha=\frac{(+5)-(+2)}{4}=+0.75rad/s^2$$
b) $$\overline\alpha=\frac{(+2)-(+5)}{4}=-0.75rad/s^2$$
c) $$\overline\alpha=\frac{(-3)-(-7)}{4}=+1rad/s^2$$
d) $$\overline\alpha=\frac{(-4)-(+4)}{4}=-2rad/s^2$$
