question_answer

Two blocks of masses 2 kg and 4 kg are attached by an inextensible light string as shown in the figure. If a force of 120 N pulls the blocks vertically upward, the tension in the string is (Take\[g\text{ }=\text{ }10\text{ }m{{s}^{-2}}\])               

A) 20N

B) 15N

C) 35N

D) 40N

Correct Answer: D

Solution :

[d] Acceleration of the system \[a=\frac{F-4g-2g}{4+2}=\frac{120-40-20}{6}\] \[=10\text{ }m{{s}^{-2}}\] From figure \[T-2g=2a\] \[T=2\left( a+g \right)=2\left( 10+10 \right)\] \[=40\text{ N}\]