If the angular acceleration$\text{'}\alpha \text{'}$is zero, then it implies that

$\text{ As }\alpha =0,\omega =\text{ constant }$

$\therefore v=\text{ constant }$

(or)

In the case of uniform circular motion angular velocity remains

constant hence change in angular velocity is zero hence $\alpha =\frac{\mathrm{\Delta }\omega }{\mathrm{\Delta t}}$

$\alpha =0$

Hence speed also remains constant.