The resultant of two forces $3P$ and $2P$ is $R$. If the first force is doubled then the resultant is also doubled. The angle between the two forces is ........... $^o$
The resultant of two forces $3P$ and $2P$ is $R$. If the first force is doubled then the resultant is also doubled. The angle between the two forces is ........... $^o$
${60}$
$120$
${70}$
${180}$
The resultant of two forces $3P$ and $2P$ is $R$. If the first force is doubled then the resultant is also doubled. The angle between the two forces is ........... $^o$
${R^2} = {(3P)^2} + {(2P)^2} + 2 \times 3P \times 2P \times \cos \theta $…(i)
${(2R)^2} = {(6P)^2} + {(2P)^2} + 2 \times 6P \times 2P \times \cos \theta $…(ii)
by solving (i) and (ii), $\cos \theta = - 1/2$
$⇒$ $\theta = 120^\circ $
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