archimedes principle

hi, I've recently been learning about archimedes principle and have gotten lost in confusion so this is my question i cant figure out whats wrong with the working out or my understanding but here it is so pressure increases iwth depth and pressure of liquid = density x gravity x change in height and upthrust = density of liquid x gravity x volume and pressure = force over area so i would assume pressure = upthrust / cross sectioanl area of my object. my object is 15kg cube with volume 0.2m^3. the mass of displaced water = mass of object so the mass of displaced water is 15kg. so upthrust is 1000 x 0.2 x 9.8 which gives your a force of 1960n so pressure = 1960/0.34 which is 5765n. and that means 5765n = 1000 x 9.8 x height. so height is therefore 0.6m however this is clearly not correct
if i were to guess the problems with the pressure = upthrust / cross sectional area even if i use an object with much higher density i get results below 1 meter from surface

(edited 1 year ago)

Reply 1

mosaurlodon

so P=F/A
F=pVg
A=V/h
so P=pgh
"mass of displaced water = mass of object" is wrong - it should be volume of displaced water = volume of object

so for your problem you would do P=pgh=1000x9.81x0.58
P=F/A=1000x0.2x9.81/0.34
both give the same answer.