Q142 / 180 · AIIMS 2008 · Physics

\(P, Q\) and \(R\) are three coplanar forces acting at a point and are in equilibium. Given : \(P=1.9318 \mathrm{~kg}\) wt \(\left[\sin \theta_1=0.9659\right]\), the value of \(R\) (in \(\mathrm{kg}\) wt) is Figure

  • A
    0.9659
  • B
    2
  • Correct answer
    C
    1
  • D
    \(1 / 2\).

Solution

Using Lami's theorem, we have $\begin{aligned} & \frac{P}{\sin \theta_1}=\frac{R}{\sin 150^{\circ}} \Rightarrow \frac{P}{\sin \theta_1}=\frac{R}{\sin \left(180^{\circ}-30^{\circ}\right)} \\ & \Rightarrow \frac{1.9318 \mathrm{kgwt}}{0.9659}=\frac{R}{1 / 2} \\ & \Rightarrow R=\frac{1.9318}{0.9659} \times \frac{1}{2} \mathrm{kgwt}=1 \mathrm{kgwt} .\end{aligned}$

Hence, the correct answer is option: 'C'.

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