MCQ
A $120\, g$ mass has a velocity $\vec v = 2\hat i + 5\hat j\,m{s^{ - 1}}$ at a certain instant. Its kinetic energy is .................. $\mathrm{J}$
- A$3$
- B$4$
- C$5$
- ✓$1.74$
✓
Answer
Correct option: D.
$1.74$
d
$\mathrm{K.E}=\frac{1}{2} \mathrm{mv}^{2}$
$\mathrm{K.E}=\frac{1}{2} \mathrm{mv}^{2}$
$=\frac{1}{2} m(\vec{v} . \vec{v})$
$=\frac{1}{2} m(2 \hat{i}+5 \hat{j}) \cdot(2 \hat{i}+5 \hat{j})$
$=\frac{1}{2} \times \frac{120}{1000}(4+25)$
$=1.74 \mathrm{J}$
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