Q130 / 180 · COMEDK 2019 · Physics

Two equal forces ( $p$ each) act at a point inclined to each other at an angle of $120^{\circ}$. The magnitude of their resultant is

  • Correct answer
    A
    $p$
  • B
    $2 p$
  • C
    $p / 2$
  • D
    $p / 4$

Solution

The magnitude of the resultant force can be given by parallelogram's law of vector addition i.e., $$ \begin{aligned} \Rightarrow \quad F_{\text {net }} &=\sqrt{2 p^{2}+2 p^{2} \times \cos \left(120^{\circ}\right)}\left(\because \theta=120^{\circ}\right) \\ &=\sqrt{2 p^{2}+2 p^{2}\left(-\frac{1}{2}\right)} \\ &=\sqrt{p^{2}} \\ &=p \end{aligned} $$

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

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