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## Homework Statement

A 20cm^3 block of lead and a 20cm^3 block of copper are completely under water. Each is suspended by a thread so that they both hand at the same height in an aquarium filled with water. Which of the following is true?

a) The buoyant force is greater on the lead than on the copper

b)*** The buoyant force is greater on the copper than on the lead

c) The buoyant force is the same on both blocks

d) More information is needed

## Homework Equations

F

_{b}=[tex]\rho[/tex]vg

## The Attempt at a Solution

This problem was on a test and I was pretty sure the correct answer was B, but I was wrong. My revised way of thinking about it is since the volume is the same then the material with the greater density should have the larger buoyant force.

[tex]\rho[/tex]

_{lead}=11300 kg/m

^{3}

and

[tex]\rho[/tex]

_{copper}=8920kg/m

^{3}

Soooo

F

_{lead}= (11300 kg/m

^{3})(.020 m

^{3})(9.8 m/s

^{2})

= 2214.8

F

_{copper}= (8920kg/m

^{3})(.020 m

^{3})(9.8 m/s

^{2})

= 1748.3

F

_{lead}> F

_{copper}

Make sense? Thanks!