Question

A thin disc is rotating with a constant angular velocity about its own axis. $A$ is a point on the rim of the disc and $B$ is a point half-way between the rim and the center. The ratio of the velocity at $A$ to that at $B$ is

• A. $1:4$
• B. $1:2$
• C. $1:1$
• D. $2:1$

Answer 1

Answer: (D)

$2:1$

We know that,

$v=\omega r$

So, $v_A=\omega r$

and $v_B=\omega \frac{r}{2}$

So, $v_A:v_B=\frac{\omega r}{\omega \frac{r}{2}}=2:1$