A ball is thrown vertically upwards from the top of a tower with a velocity $u$. This ball reaches the ground level with a velocity $4\,u$. The height of the tower is
A ball is thrown vertically upwards from the top of a tower with a velocity $u$. This ball reaches the ground level with a velocity $4\,u$. The height of the tower is
- A
$\frac{3u^2}{g}$
- B
$\frac{4u^2}{g}$
- C
$\frac{6u^2}{g}$
- D
$\frac{15u^2}{2g}$
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