# Sands of Time

**Calculus**Level pending

This curve is then rotated along x-axis to form the surface like that of a hourglass lying sideways.

Assume that an extremely thin closed hourglass with curved portion resembling this surface is filled with sand equal to half of it's volume.

The hourglass is initially kept upright with all sand in upper half portion. Given that sand particles pass through the area of cross-section separating the upper-half and lower-half of hourglass in a uniform manner with velocity equal to \(\frac{149}{14}\) cm per second, After how may seconds will all the sand fall to lower-half.

(Use pi=\(\frac{22}{7}\))