Question

An object weighs 20N in air and 15N when fully immersed in water.calculate;volume of an object,(ii)density of an object

Answer 1

weight of water displaced = 5 N
mass of water displaced = F/a = 5 N / 9.81 m/s^2 = 0.510 kg
density of water = 1000 kg / m^3
so volume = 0.5510 kg *1 m^3 / 1000 kg = 5.51 * 10^-4 m^3
density = mass /volume = ( 20/9.81) / 5.51*10^-4 = 0.37 *10^4 kg/m^3
= 3.7 *10^3 kg/m^3
or 3.7 times the density of water

Answer 2

I saw that the weight was reduced by 1/4, so I was confused by that density of 3.7
somehow we went from 0.510 to 0.5510 kg
picking up where that happened,
so volume = 0.510 kg *1 m^3 / 1000 kg = 5.1 * 10^-4 m^3
density = mass /volume = ( 20/9.81) / 5.1*10^-4 = 0.3997 *10^4 kg/m^3
= 4.0 *10^3 kg/m^3
or 4.0 times the density of water

Answer 3

whoops, pushed wrong button. Thank you!