Question

If force, $F=120N$ is acting parallel to the inclined plane, find tension $T$ in the string as shown in the figure. All surfaces are smooth.
(Take $g=10{\text{m/s}}^2$).

• A. $15N$
• B. $30N$
• C. $48N$
• D. $60N$

Answer 1

The correct option is C $48N$


Considering ($4kg+6kg$) as a system and the FBD of the $10kg$ body is given as

As $120N>10g\sin {37}^o(=60N)$, the system will accelerate up the plane.
Hence, $a=\frac{F_{net}}{m_{total}}=\frac{120-60}{10}=6m/s^2$

For calculating $T$, consider the FBD of $4kg$,

Using Newton's second law,
$T-4g\sin {37}^o=ma=4\times 6\Rightarrow T=24+(4\times 10\times \frac{3}{5})=48N$