A small particle moves to position 5 i-2 j+k from its initial pos… - Vidyadip

MCQ

A small particle moves to position $5 \hat{i}-2 \hat{j}+\hat{k}$ from its initial position $2 \hat{i}+3 \hat{j}-4 \hat{k}$ under the action of force $5 \hat{i}+2 \hat{j}+7 \hat{k} N$. The value of work done will be $............J$.

A
$38$
✓
$40$
C
$39$
D
$41$

✓

Answer

Correct option: B.

$40$

b
$W=\vec{F} \cdot\left(\vec{r}_f-\vec{r}_{ i }\right)$

$=(5 \hat{i}+2 \hat{j}+7 \hat{k}) \cdot((5 \hat{i}-2 \hat{j}+\hat{k})-(2 \hat{i}+3 \hat{j}-4 \hat{k}))$

$W=40\,J$

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