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3-2.Motion in Plane
medium
A particle moves $21\, m$ along the vector $6\hat i + 2\hat j + 3\hat k$ , then $14\, m$ along the vector $3\hat i - 2\hat j + 6\hat k$ . Its total displacement (in meters) is
A
$15\hat i + 2\hat j + 12\hat k$
B
$9\hat i + 12\hat k$
C
$9\hat i + 6\hat j$
D
$24\hat i + 2\hat j + 21\hat k$
Solution
Total displacement
$=21\left(\frac{6 \hat{\mathrm{i}}+2 \hat{\mathrm{j}}+3 \hat{\mathrm{k}}}{7}\right)+14\left(\frac{3 \hat{\mathrm{i}}-2 \hat{\mathrm{j}}+6 \hat{\mathrm{k}}}{7}\right)$
$=18 \hat{\mathrm{i}}+6 \hat{\mathrm{j}}+9 \hat{\mathrm{k}}+6 \hat{\mathrm{i}}-4 \hat{\mathrm{j}}+12 \hat{\mathrm{k}}$
$=(24 \hat{i}+2 \hat{j}+21 \hat{k}) m$
Standard 11
Physics