A) \[\hat{i}+4\hat{j}+4\hat{k}\]
B) \[2\hat{i}+\hat{j}+2\hat{k}\]
C) \[2\hat{i}-7\hat{j}-2\hat{k}\]
D) \[2\hat{i}+4\hat{j}-\hat{k}\]
Correct Answer: C
Solution :
[c] Let point P is (1, -1, 2) and point Q is (2, -1, 3) \[\Rightarrow \] Position vector of P w.r.t Q is \[\vec{r}=(1-2)\hat{i}+(-1+1)\hat{j}+(2-3)\hat{k}\] \[\Rightarrow \overset{\to }{\mathop{r}}\,=-\hat{i}+0\hat{j}-\hat{k}\] and \[\overset{\to }{\mathop{F}}\,=3\hat{i}+2\hat{j}-4\hat{k}\] \[\Rightarrow \,Moment=\overset{\to }{\mathop{r}}\,\times \overset{\to }{\mathop{F}}\,=\left| \begin{matrix} {\hat{i}} & {\hat{j}} & {\hat{k}} \\ -1 & 0 & -1 \\ 3 & 2 & -4 \\ \end{matrix} \right|\] \[=\hat{i}(0+2)-\hat{j}(4+3)+\hat{k}(-2+0)=2\hat{i}-7\hat{j}-2\hat{k}\]
You need to login to perform this action.
You will be redirected in
3 sec
