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5.Work, Energy, Power and Collision
normal
A body constrained to move along $y-$ axis is subjected to a constant force $\vec F = - \hat i + 2\hat j + 3\hat k\,N$ The work done by this force in moving the body a distance of $4\, m$ along $y-$ axis is ............... $\mathrm{J}$
A
$4$
B
$8$
C
$12$
D
$24$
Solution
Here, $\overrightarrow{\mathrm{F}}=(-\hat{\mathrm{i}}+2 \hat{\mathrm{j}}+3 \hat{\mathrm{k}}) \mathrm{N}$
As the body moves a distance of $4 \mathrm{m}$ along
$\mathrm{y}$$ -axis,$
$\therefore \overrightarrow{\mathrm{d}}=4 \hat{j} \mathrm{m}$
Work doen by the given force is
$\mathrm{W}=\overrightarrow{\mathrm{F}} \cdot \overrightarrow{\mathrm{d}}=(-\hat{\mathrm{i}}+2 \hat{\mathrm{j}}+3 \hat{\mathrm{k}} \mathrm{N}) \cdot(4 \hat{\mathrm{j}} \mathrm{m})=8 \mathrm{J}$
Standard 11
Physics
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