Question

In the figure shown, find the tension in the string connecting the two bodies.

• A. $20\text{N}$
• B. $30\text{N}$
• C. $10\text{N}$
• D. Zero

Answer 1

The correct option is D Zero

Using $F=ma$ for both blocks without considering the tension in the spring, and thus finding $a$,

For block A,
$2g\sin {30}^{\circ }-2{\mu }_{1}g\cos {30}^{\circ }=2a_A$
$a_A=g(\sin {30}^{\circ }-0.4\cos {30}^{\circ })$

For block B,
$2g\sin {30}^{\circ }-2{\mu }_{1}g\cos {30}^{\circ }=2a_B$
$a_B=g(\sin {30}^{\circ }-0.2\cos {30}^{\circ })$
$\Rightarrow a_B>a_A$
Hence the string will be loose $\Rightarrow T=0$