Question

A plank is moving with a velocity of $4\text{m/s}$. A disc of radius $1\text{m}$ rolls without slipping on it with an angular velocity of $3\text{rad/s}$ as shown in figure. Find out the velocity of the centre of the disc.

• A. $3\text{m/s}$
• B. $4\text{m/s}$
• C. $7\text{m/s}$
• D. $11\text{m/s}$

Answer 1

The correct option is C $7\text{m/s}$

Since it is pure rolling, the velocity of the point at the bottom of the disc will be equal to the velocity of plank.
i.e $V_{cm}-R\omega =4$
$V_{cm}-3=4$
$\Rightarrow V_{cm}=7\text{m/s}$