Ametal block of density 9000kgcm3 weighs 70n in air. find its weight when it is immersed in paraffin wax of density 800kgm3? (take g=10ms-2)

Note: the text says that the density of the block is (not , which not a plausible value)

63.9 N

Explanation:

We want to find the apparent weight of the block when it is in water.

First of all, we know its true weight:

W = 70 N

So we can find the mass of the block:

where is the acceleration of gravity.

From the mass and the density, which is

we find the volume of the block:

We know that when the block is immersed in paraffin, it is acted upon the buoyant force, which acts upward, and whose magnitude is

where

is the density of paraffin

V is the volume of paraffin displaced, which corresponds to the volume of the block

Substituting,

Therefore, the apparent weight of the block in paraffin will be:

63.788 N

Explanation:

Density of a metal block  =  9000 ×〖10〗^(-6)  kgm^(-3)

Mass of the metal block = 70/10 = 7 kg

Volume = Mass/ Density

Volume of the metal block = 7/9000 ×(10)^(-6)  kgm^(-3)

      = 777.777 m^3

When it’s immersed in water up thrust is acted on a metal block then the weight is reduced due to up thrust, Let’s take W as a New measurement,

W + U = 70

W = 70-U

W = 70 -Vρ_l g

W= 70 – 777.77×800×(10)^(-6)×10

W = 63.778 N

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