question_answer

Two blocks A and B of masses 3 m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively [NEET – 2017]

A) \[\frac{g}{3},\frac{g}{3}\]

B) \[g,\frac{g}{3}\]

C) \[\frac{g}{3},g\]

D) \[g,\,g\]

Correct Answer: C

Solution :

[c]

Before the string is cut

\[kx=T+3mg\]                           (i)

\[T=mx\]                                               (ii)

\[\Rightarrow \]   \[kx=4mg\]

After the string is cut, \[T=0\]

\[a=\frac{kx-3mg}{3m}\]

\[a=\frac{4mg-3mg}{3m}\]

\[a=\frac{g}{3}\uparrow \]