Question

Two blocks of masses $7 \,kg$ and $5 \,kg$ are connected by a rope of mass $4\, kg$. The system is pulled up with a force of $240 \,N$ as shown in figure. The tension in the rope at its midpoint $A$ is

• A. $105\,N$
• B. $270\,N$
• C. $240\,N$
• D. $50\,N$

Answer 1

Answer: (A)

The common acceleration of the system is
$a=\frac{240}{\left(7+4+5\right)}=15\,m\,s^{-2}$
The tension in the rope at its midpoint $A$ is
$T_{A}=\left(2+5\right)a=7a=7\times15$
$=105\, N$