MCQ
A heavy solid sphere is thrown on a horizontal rough surface with initial velocity $u$ without rolling. What will be its speed, when it starts pure rolling motion?
- A$\frac{3 u}{5}$
- B$\frac{2 u}{5}$
- ✓$\frac{5 u}{7}$
- D$\frac{2 u}{7}$
✓
Answer
Correct option: C.
$\frac{5 u}{7}$
c
(c)
(c)
Using angular momentum conservation
$m u r=m v r+\frac{2}{5} m r^2\left(\frac{v}{r}\right)$
$u=7 \frac{v}{5}$
$v=\frac{5 u}{7}$
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