Question

Two blocks of masses 8 kg and 12 kg are connected at the two ends of a light inextensible string. The string passes over a frictionless pulley. The acceleration of the system is :

• A. $\frac { \mathrm { g } } { 4 }$
• B. $\frac { \mathrm { g } } { 5 }$
• C. $\infty$
• D. $\frac { \mathrm { g } } { 6 }$

Answer 1

Answer: (B)

$\frac { \mathrm { g } } { 5 }$

Answer 2

Let a be the common acceleration of the system and T be tension of the string

The equation of motion of two blocks are

$T - 8 g = 8 a$ ……(i)

And $12 g - T = 12 a$ ….. (ii)

Adding (i) and (ii) we get

$4 g = 20$ aor $a = \frac { g } { 5 }$