A cube of wood 20cm on each side floats in water so that 7cm is above the surfac
ID: 1392625 • Letter: A
Question
A cube of wood 20cm on each side floats in water so that 7cm is above the surface of the water and 13cm is below.
a)What is the density of the wood? ( You must justify your answer)
b) How much force would have to be exerted on the wood to submerge it?
c) what volume of lead mass has to be placed on top of the block of wood so that it will just be totally submerged?
d)Suppose a 5kg mass of lead is now placed on top of the block of wood, how much of the wood would now be above the water?
Densities.in g/cm^3 Water=1 g/cm^3 Iron=7.8g/cm^3 Lead=11.3g/cm^3
Explanation / Answer
a) the wood's density is 650 kg /m^3 and water's density is 1000 kg/m^3, 65% of the wood is under water. 35% is out of water.
b)
35% of 20 cm = 7 cm of wood out of water
it would be just level the density of the object must equal the density of water.
Wood Volume = 0.2m * 0.2m * 0.2m = 0.008 m^3
Wood mass = 650 kg/m^3 * 0.008 = 5.2 Kg
Density needs to = 1000 kg/m^3
We need 1000 kg/m^3 * 0.008 m^3 = 8 kg is the total mass
8 kg