Buoyancy

[benzimm86]

A solid object floats on ethyl alcohol, with 68.2% of the object’s volume submerged. Using Table 11.1, identify the substance from which the object is made.

ethyl alcohol has mass density of 806 kg/m
what is the other substances mass density

[benzimm86]

the problem i amhaving is that all the examples in my book do not deal with anything of his type. they all have depth amounts, sizes and none of them deal with percents there for i am totally lost please help

[ponjavic]

Figure the volume of the object is V, p=density and g=force of gravity then the upward thrust on the object would be p(alcohol)*0.68V*g whereas the weight of the object is p(object)*V*g, it is in equilibrium since it floats
p(alcohol)*0.682V*g=p(object)*V*g
thus p(object)=p(alcohol)*0.682

I'm not completely sure about this as it is late in Sweden and my brain is all achy on me but I hope it helps :P