Buoyancy & Buoyant Force Video Lessons

Concept

# Problem: A 10 cm × 10 cm × 10 cm wood block with a density of 700 kg/m3 floats in water. What is the distance from the top of the block to the water in cm...(a) if the water is fresh?(b) What if it is sea water?

###### FREE Expert Solution

Buoyant force on block in water given by:

$\overline{){{\mathbit{F}}}_{{\mathbit{b}}}{\mathbf{=}}{{\mathbit{\rho }}}_{{\mathbit{w}}}{\mathbit{g}}{{\mathbit{V}}}_{\mathbit{u}\mathbit{n}\mathbit{d}\mathbit{e}\mathbit{r}}}$

Gravitational force on block:

$\overline{){{\mathbit{F}}}_{{\mathbit{g}}}{\mathbf{=}}{{\mathbit{m}}}_{\mathbit{b}\mathbit{l}\mathbit{o}\mathbit{c}\mathbit{k}}{\mathbit{g}}}$

Height of block above water:

$\overline{){{\mathbit{h}}}_{{\mathbit{a}}{\mathbit{b}}{\mathbit{o}}{\mathbit{v}}{\mathbit{e}}}{\mathbf{=}}{{\mathbit{h}}}_{\mathbit{b}\mathbit{l}\mathbit{o}\mathbit{c}\mathbit{k}}{\mathbf{-}}{{\mathbit{h}}}_{{\mathbit{u}}{\mathbit{n}}{\mathbit{d}}{\mathbit{e}}{\mathbit{r}}}}$

Assume block is at rest—in equilibrium.

###### Problem Details

A 10 cm × 10 cm × 10 cm wood block with a density of 700 kg/m3 floats in water. What is the distance from the top of the block to the water in cm...

(a) if the water is fresh?

(b) What if it is sea water?