In a lecture demonstration, an object is suspended from a spring scale which rea

Question

In a lecture demonstration, an object is suspended from a spring scale which reads 8N when the object is in air. The object is then lowered into a beaker of water, and when the object is fully submerged in the water, the scale reads 6N.

a) Find the density of the object.

b) During the entire demonstration, the beaker is standing on a kitchen scale which reads 20N before the object is lowered into the water. What does this scale read when the object is fully submerged?

c) Compare the sum of the two scale readings before and after the object is submerged.

Explanation / Answer

a)
mass of the object, m = W/g

= 8/9.8

= 0.8163 kg

lrt V is the volume of the object.

from the given data,

buyont force = 8 - 6

= 2 N

weight of the dispalced water = 2 N

rho*V*g = 2

V = 2/(rho*g)

= 2/(1000*9.8)

= 2.041*10^-4 m^3

so, density of the object = mass/volume

= 0.8163/(2.041*10^-4)

= 4000 kg/m^3

b) 22 N

c) before submerged = 20 + 8 = 28 N

after submerged = 22 + 6 = 28 N

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