Vectors Question 129
Question: The torque of the force $ \overrightarrow{F}=(2\hat{i}-3\hat{j}+4\hat{k},)N $ acting at the point $ \overrightarrow{r,}=(3\hat{i}+2\hat{j}+3\hat{k}) $ m about the origin be
[CBSE PMT 1995]
Options:
A) $ 6\hat{i}-6\hat{j}+12\hat{k} $
B) $ 17\hat{i}-6\hat{j}-13\hat{k} $
C) $ -6\hat{i}+6\hat{j}-12\hat{k} $
D) $ -17\hat{i}+6\hat{j}+13\hat{k} $
Correct Answer: B $ \overrightarrow{\tau }=\overrightarrow{r,}\times \overrightarrow{F} $ $ =| \begin{matrix} \hat{i} & \hat{j} & {\hat{k}} \\ ,3, & 2, & 3 \\ ,2, & -3 & 4 \\ \end{matrix} |, $ $ =[ (2\times 4)-(3\times -3) ]\hat{i}+[ (2\times 3)-(3\times 4) ],\hat{j} $ $ +[ (3\times -3)-(2\times 2) ],\hat{k} $ $ =17,\hat{i}-6,\hat{j}-13,\hat{k} $
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Answer:
Solution:
BETA
