Question

Question 3
(1) A solid of relative density 5.5 is found to weigh 70 gf in a liquid of relative density 0.7. find its weight in
air and apparent weight in water.​

Answer 1

Answer:

Weight of solid in air = 80.2 gf

And, Apparent weight in water = 65.6 gf

Explanation:

Given,

Relative density of solid = 5.5

Apparent Weight in liquid = 70 gf

Relative density of the liquid = 0.7

Let, the weight of the solid in air (Real Wt.) = W

We know that,

Loss of weight in liquid (Upthurst) = W - 70

And, R.D. of a solid is given by

$\frac{real \: weigt}{upthurst} \times \: r.d. \: of \: liquid$

Substituting all the values, we have

$5.5 = \frac{w}{w - 70} \times 0.7$

=> 5.5 × ( W - 70) = 0.7 × W

or, 5.5W - 385 = 0.7W

or, 5.5W - 0.7W = 385

Now, Wt. of the solid in air

W = 385/4.8 = 80.2 gf

Relative Density of water = 1

Let, Apparent weight of the solid in water = A

Again, upthurst due to water = Real wt. - Ap. Wt.

= 80.2 - A

Now,

$5.5 = \frac{80.2}{80.2 \: - \: a} \times \: 1$

[R.D. of water = 1]

=> 5.5 × (80.2 - A) = 80.2 × 1

or, 441.1 - 5.5A = 80.2

or, 5.5A = 441.1 - 80.2 = 360.9

Apparent wt. of the solid in water :

A = 360.9/5.5 = 65.6 gf

Presented By : MR. VIVAAN

B.Sc. PHY. Hons.