Question:

The resultant of two forces $3\,P$ and $2\,P$ is $R$. If the first force is doubled, then the resultant is also doubled. The angle between the two forces is

Updated On: Apr 13, 2024
  • 180$^\circ$
  • 90$^\circ$
  • 120$^\circ$
  • 60$^\circ$
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The Correct Option is C

Solution and Explanation

Here R =$\sqrt{9P^2 + 4P^2 + 12P^2 cos \, \theta} = \sqrt{13P^2 + 12P^2 \, cos \, \theta}$ and 2 R = $\sqrt{40P^2 + 24P^2\, cos \, \theta}$
Solving cos $\theta = - \frac{1}{2}$ i.e. $\theta$ = 120$^\circ$
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