Page 151 - Physics

Pressure

The difference in pressure = Pressure at the bottom – Pressure at the top
2
=1 027 N/m −821.6 N/m 2

= 205.4 N/m 2
So, the difference in pressure between the bottom and the top is 205.4 N/m .
2

Force
(b) Pressure =
Area
Difference in force
Difference in pressure =
Area
Difference in force = difference in pressure × area

(
Area for a cube = length) 2
(
2
Area = 0.02 m) = 0.0004 m 2
2
2
Difference in force = 205.4 N/m × 0.0004 m = 0.0822 N
This is the upthrust acting on the cube.

(c) The weight of water displaced = massof water displaced×acceleration due to gravity.

The weight of water displaced =
density × volume of water displaced × acceleration due to gravity
But the volume of water displaced = volume of the cube
The length of the cube = width = height of the cube.

Then, Volume of the cube = L 3

L = (2 cm) = 8 cm = 0.000008 m 3
3
3
3
The volume of water displaced is equal to the volume of a cube = 0.000008 m 3
Mass of water displaced
M ( ) = Densityof water × Volume of water displaced = ρV
water water
Then,

weight of water = Mass of water × acceleration due to gravity = M water × g

3
3
3
3
Weight of water = 1027 kg/m × 0.0008 m ×10 N/kg = 0.0822 NWeight of water = 1027 kg/m × 0.0008 m ×10 N/kg = 0.0822 N
3
0.000008 m
Therefore, weight of displaced water is 0.0822 N.
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Physics Form 1 Final.indd 145 16/10/2024 20:57