Page 113 - Physics

Sinking and fl oating

Upthrust in kerosene = weight of kerosene
displaced Upthrust in water = w − w = 8.6 N − 6.0 N = 2.6 N
1
0
= 8.6 N − 6.0 N = 2.6 N
w − w
Upthrust in kerosene = w − w 0 1
1 3
Upthrust in water = Weight of water By Archimedes’ principle
displaced Upthrust = weight of the displaced fl uid
= w − w 2
1
Note that, 1 g = 0.01 N,
Since an object immersed in a fl uid w w
displaces its volume of the fl uid, and Mass of displaced water = g
considering the relation for the relative = 2.6 g = 260g
density of a liquid, 0.01
w
density of a substance Volume V of water displaced = w
weight of any given volume of liquid
RD ,
R.D = =
densityof water equal volume of water
weight of an ρ w
it follows, m = 260 g 3 = 260 cm 3
weight of the displaced kerosene ρ 1g/cm
R.D =
weight of the displaced water Mass of liquid displaced = w l
Therefore, the relative density of w 3.2 N g
w −w = =320 g
kerosene (R.D) = 1 3 g 0.01N/g
w −w
1 2
Then,
Example 5.5 w

In an experiment to determine the Density of liquid = v l
relative density of a liquid, a solid Q l
weighed as follows: m 320 g = 1.2 g / cm .
3
=
v 260 cm 3
Weight in air, w = 8.6 N
0
Relative density of liquid =
Weight in water, w = 6.0 N density of liquid
1 = 1.2.
density of water
Weight in liquid, w = 5.4 N.
2
Alternatively,
Calculate the relative density of the Relative density of liquid =
liquid. Upthrust in liquid w − w
= 0 2
Solution Upthrust in water w − w 1
0
Upthrust in liquid = w − w = 8.6 N − 5.4 N = 3.2 N
2
0
w − w = 8.6 N − 5.4 N = 3.2 N 3.2 N
2 Relative density of liquid = = 1.2.
0
2.6 N
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Physics Form 1 Final.indd 107 16/10/2024 20:56