Resultant of two vectors $\vec{P}$ and $\vec{Q}$ is of magnitude $R_{1}$. If direction of $\vec{Q}$ is reversed, the resultant is of magnitude $\mathrm{R}_{2}$. The value of $\left(\mathrm{R}_{1}^{2}+\mathrm{R}_{2}^{2}\right)$ is $[\cos (\pi-\theta)=-\cos \theta]$. A $\left(\mathrm{P}^{2}+\mathrm{Q}^{2}\right)$ B $2\left(\mathrm{P}^{2}+\mathrm{Q}^{2}\right)$ C $2\left(P^{2}-Q^{2}\right)$ D $\left(\mathrm{P}^{2}-\mathrm{Q}^{2}\right)$

Resultant of two vectors $\vec{P}$ and $\vec{Q}$ is of magnitude $R_{1}$ . If direction of $\vec{Q}$ is reversed, the resultant is of magnitude $\mathrm{R}_{2}$ . The value of $\left(\mathrm{R}_{1}^{2}+\mathrm{R}_{2}^{2}\right)$ is $[\cos (\pi-\theta)=-\cos \theta]$ .
A $\left(\mathrm{P}^{2}+\mathrm{Q}^{2}\right)$
B $2\left(\mathrm{P}^{2}+\mathrm{Q}^{2}\right)$
C $2\left(P^{2}-Q^{2}\right)$
D $\left(\mathrm{P}^{2}-\mathrm{Q}^{2}\right)$

Physics

Solution:
Correct option is B
Resultant of two vectors $\vec{P}$ and $\vec{Q}$ is of magnitude $R_{1}$ . If direction of $\vec{Q}$ is reversed, the resultant is of magnitude $\mathrm{R}_{2}$ . The value of $\left(\mathrm{R}_{1}^{2}+\mathrm{R}_{2}^{2}\right)$ is $2\left(\mathrm{P}^{2}+\mathrm{Q}^{2}\right)$

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