Question

You place a block of wood into a beaker of water and it floats. What can you say about the buoyant force on the block?

Answer 1

The buoyant force is stronger than the gravity force (the block's weight). Consequently, the block's density is smaller than water's density.

Explanation:

Archimedes principle affirms that a body submerged in a fluid (for example a liquid, or more precisely, water) experiences an upward force equal to the weight of fluid (liquid, water) displaced.

Mathematically,

buoyant force `= F_b = V_b *d_w*g`
`V_b =` body volume
`d_w =` water density
`g =` gravity acceleration

while the weight `W= V_b*d_b*g`

`d_b= body density`

As the body floats `=> F_b > W => d_w>d_b`