Looking for classes? Ksquare Career Institute, Bengaluru →
Two blocks A and B of masses 3m 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
Explanation
Spring force cannot change instantly; string tension vanishes.
Detailed Solution
Before the string is cut: $kx = T + 3mg$ ...(1) and $T = mg$ ...(2), so $kx = 4mg$
After the string is cut, T = 0.
For A: $a = \frac{kx - 3mg}{3m} = \frac{4mg - 3mg}{3m} = \frac{g}{3}$
For B: only mg acts, so a = g
So the accelerations of A and B are $\frac{g}{3}$ and g.