Question

Two blocks A and B are connected to each other by a string and a spring of force constant k, as shown in the figure. The string passes over a frictionless pulley. Block B slides over the horizontal top surface of a stationary block C and block A slides along the vertical side of C both with the same uniform speed. If the coefficient of friction between the surfaces of the blocks is $\mu$ and the mass of block A is m, what is the mass of block B?

• A. $\frac{m}{\sqrt{\mu }}$
• B. $\frac{m}{\mu }$
• C. $\sqrt{\mu m}$
• D. $\mu m$

Answer 1

The correct option is B

$\frac{m}{\mu }$

Let the mass of block B be M. Since the blocks slide at the same uniform speed, no net force acts on them.
For block B, $T=mg$
For block A, $T=f\Rightarrow mg=\mu Mg\Rightarrow M=\frac{m}{\mu }$
Hence, the correct choice is (b).