Question

Block $A$ of weight $100\, N$ rests on a frictionless inclined plane of slope angle $30^°$ as shown in the figure. A flexible cord attached to $A$ passes over a frictionless pulley and is connected to block $B$ of weight $W$. Find the weight $W$ for which the system is in equilibrium.

• A. $25\, N$
• B. $50\,N$
• C. $75\,N$
• D. $100\,N$

Answer 1

Answer: (B)

As the system is in equilibrium,
$\therefore $ $T=W$ $\quad\ldots\left(i\right)$
and $T=mg$ $sin 30^{\circ}$ $\ldots\left(ii\right)$
From (i) and (ii), we get

$W=mg \,sin$ $30^{\circ}=\left(100\, N\right)$ $\times\frac{1}{2}=50 \,N$