Question

Two blocks A and $B$ of masses $2m$ and $m$, respectively, are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in the figure. The magnitudes of acceleration of A and $B$, immediately after the string is cut, are respectively

• A. $g,g/2$
• B. $g/2,g$
• C. $g,g$
• D. $g/2,g/2$

Answer 1

The correct option is B $g/2,g$

The extension in spring in equilibrium $kx=3mg$
Hence tension in the string will be $3mg-2mg=mg$

When string is cut the force on B is $mg$ hence acceleration is $a_B=g$.

Force on A is $kx-Mg=3mg-2mg=mg$ upwards

$a_A=\frac{mg}{2mg}=\frac{g}{2}$

Hence correct answer is option B.