Question

In the given figure $V_B$ is (All surfaces are smooth and string is massless and inextensible)

• A. $2m/s$
• B. $6m/s$
• C. $8m/s$
• D. $10m/s$

Answer 1

The correct option is D $10m/s$

For an inextensible string velocity component of the end points along the string should be same otherwise it will break.
So, taking the component of $V_B$ along the string, we have

$V_B\cos {37}^{\circ }$
And, this velocity should be equal to $V_A$
$\Rightarrow V_A=V_B\cos {37}^{\circ }\Rightarrow V_B=\frac{V_A}{\cos {37}^{\circ }}=\frac{8}{\frac{4}{5}}=10m/s$ $\therefore \cos {37}^{\circ }=\frac{4}{5}$