Question

Class : 9 CH : Thrust and Pressure.

Question : A piece of metal weighs 50 N in air, 36 N in water and 41N in an unknown liquid. Find the densities of

(i) The metal and
(ii) The unknown liquid.

Answer 1

Explanation:

find volume of metal first

Buoyant force in water = 14 N = weight of water displaced i!@#$%^&ravitational field

mass of water displaced = 14 N/9.8 m/s^2 = 1.43 kg of water displaced

the density of water = 1,000 kg/m^3

so

volume of metal = 1.43*10^-3 m^3

Buoyant force in unknown = 50 - 41 = 9 N

so mass of unknown displace = 9/9.8 = .918 kg

so the density of unknown = .918kg/1.43*10^-3 = 642 kg/m^3

or 64.2% of the water density.....

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