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Explain solution RD Sharma class 12 Chapter 22 Algebra of Vectors Exercise 22.6 question 10 subquestion (i)

Answers (1)

Answer:

\frac{-\hat{\imath}+4 \hat{\jmath}+3 \hat{k}}{3}

Hint:

Use position vector formula.

Given:

P(\hat{\imath}+2 \hat{\jmath}+\hat{k}) \text { and } Q(-\hat{\imath}+\hat{\jmath}+\hat{k})   in the ratio 2 : 1.

Solution:

A vector divides an line Internally as in

Position vector of P and Q are given as:  \mathrm{m}: \mathrm{n}=\frac{m Q+n P}{m+n}

O \vec{P}=(\hat{\imath}+2 \hat{\jmath}+\hat{k}) \text { and } O \vec{Q}=(-\hat{\imath}+\hat{j}+\hat{k})

\frac{m}{n}=\frac{2}{1}

The position vector pf point R which divides the line joining two points P and Q internally in the ratio 2 : 1 is given by:

\begin{aligned} &O \vec{R}=\frac{(\hat{\imath}+2 \hat{\jmath}+\hat{k})+2(-\hat{\imath}+\hat{\jmath}+\hat{k})}{2+1}=\frac{-\hat{\imath}+4 \hat{\jmath}+3 \hat{k}}{3} \\\\ &O \vec{R}=-\frac{1}{3} \hat{\imath}+\frac{4}{3} \hat{\jmath}+\hat{k} \end{aligned}

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