Page 34 - Pressure 10 class

3. Weight of a stone in air, water and salt solution is given in the table shown below. Answer

the following questions. Medium Weight
a. Identify the mediums A, B and C.
A 20N
b. Calculate the upthrust of water.

c. Find the mass of the stone(use g=9.8m/s2) B 14N
d. Find the mass of water displaced. C 16N

e. Identify the mediums with the highest and lowest density. Give reason.

Solution : a. Medium A is Air, Medium B is Salt solution and Medium C is Water.
b. Upthrust (U) = Weight of stone in air – Weight of stone in water = 20N – 16N = 4N

c. Mass of stone ( m) = ? d. Mass of water
displaced( m) = ?

we have, weight of stone in air ( W) = 20N. Ans; Weight of water
displaced(W) = U = 4N

Then ,We know that Weight (W ) = m x g Then , Weight ( W ) = m x g
or, 20 = m x 9.8 or,4 = m x 9.8

or, 20/9.8 = m or, 4/9.8 = m
Mass of stone is 2.04kg. Or, m = 0.408kg

Therefore, mass of water displaced is
0.408kg

e. Medium B has highest density and Medium A has lowest density, because body
losses its more weight on the liquid with more density and vice versa. As Upthrust
is directly proportional to the density of liquid. Due to more upthrust stone loses

its more weight in salt solution and less in air.

July 30, 2020 Taranath Baral/GC Shiba/Suraj Thapaliya 34