Question

Two blocks (of masses $400kg$ and $30kg$) are attached to the two ends of a string passing over a smooth pulley as shown in the figure. The tension in the string will be :

• A. $400N$
• B. $850N$
• C. $1000N$
• D. $2000N$

Answer 1

The correct option is A $400N$

For $400kg$ block, $400a=400g\sin {37}^{\circ }-T.....\left(1\right)$

for $30kg$ block, $30a=T-30g\sin {53}^{\circ }......\left(2\right)$

Adding $\left(1\right)$ and $\left(2\right)$

$(400+30)a=(400\sin {37}^{\circ }-30\sin {53}^{\circ })g=2400-240$

As, $(\sin {37}^{\circ }\sim \frac{3}{5},\sin {53}^{\circ }\sim \frac{4}{5},g=10)$

So, $a=\frac{2160}{430}=5m/s^2$

Now using $\left(1\right)$,

The tension, $T=400g\sin {37}^{\circ }-400a=2400-2000=400N$