A cylinder is full of water, a ball is sinking vertically along the central height the cylinder (ie the centre of the ball is along the central axis of the cylinder) with a constant speed V ,if the radius of the ball is r and the radius of the cylinder is R (r<R), find the volume of water displaced by the ball per unit time(adsbygoogle = window.adsbygoogle || []).push({});

the answer is "Volume displaced per unit time = pi*r^2*V''(area of a circle*V)

whereas I think it should be 2*pi*r^2*V ("area of a semi-spherical*V)

How to imagine this correctly?

Thanks very much for any hints!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Fluid mechanics of a sinking ball

**Physics Forums | Science Articles, Homework Help, Discussion**