Question

Two blocks A and B each of $20$ kg lying on a frictionless table are connected by a light string. The system is pulled horizontally with an acceleration of $2m{s}^{-2}$ by a force $F$ on B. The tension in the string will be:

• A. $10N$
• B. $40N$
• C. $100N$
• D. $120N$

Answer 1

The correct option is B $40N$

The forces in the vertical direction will cancel.
For block A, external force is only that of tension force and acceleration is $2m/s^2$

$T=m_{A}a=20\times 2=40N$