Question

An object weighing 300 N in air is immersed in water after being tied to a string connected to a balance. The scale now reads 255 N. Immersed in oil, the object appears to weigh 280 N.

(a) Find the density of the object.


(b) Find the density of the oil.
kg/m³

Answer 1

here,

weight of object , W = 300 N

mass of object , m = W/g

m = 30.58 kg

a)

let the volume of object be V

when it is immersed in water

buoyant force , F = W - 255

p * V * g = 300 - 255

1000 * V * 9.81 = 45

solving for V

V = 4.59 * 10^-3 m^3

the density of the object , po = mass /volume

po = 30.58 / (4.59 * 10^-3) = 6.66 * 10^3 kg/m^3

b)

the density of the oil be p'

when it is immersed in oil

buoyant force , F = W - 280

p' * V * g = 300 - 280

p' * 4.59 * 10^-3 * 9.81 = 20

solving for p'

p' = 444.2 kg/m^3