UNIT 4
Density and Pressure
Example 1
Example 2
Example 3
Example 4
Example 5
Example 6
Example 7

 

Density and Pressure in Fluids
Example 1

example1

A room has dimensions of 5.0 m X 4.5 m X 4.0 m.
(a) What weight of air occupies the room when the air pressure is 1.01 X 105 Pa and the density is 1.15 kgm-3?
(b) A typical scuba tank with volume 1.1 X 10-2 m2 can be pressured up to 2.0 X 107 Pa. How many scuba tanks will it take to store this amount of air?
(b) What is the magnitude of the atmosphere’s downward force on your phone, which we take to have an area of 4.0 X 10-3 m2?

Density of air = 1.15 kgm-3
Volume of room = 5.0 m X 4.5 m X 4.0 m
Volume of room = 90 m3
Volume of scuba tank = 1.1 X 10-2 m2
Weight = mg
Mass = ρV
Weight = ρVg

(a) Weight of air in room = 1.15 kgm-3 X 90 m3 X 9.8 m3s-2
Weight of air in room = 1014N

(b) P1V1 = P2V2 if T is constant.
Volume of air in room if compressed to scuba tank = [(1.01 X 106 Pa) X (90 m3) / (2.0 X 107 Pa)]
Volume of air in room if compressed to scuba tank = 4.545 m3
No of scuba tanks required = [(1.01 X 105 Pa) X (90 m3) / (2.0 X 107 Pa)] / [1.1 X 10-2 m2]
No of scuba tanks required = 42 tanks.

(c) Force = Pressure X Area
Force on phone face = (1.01 X 105 Pa) X (4.0 X 10-3 m2)
Force on phone face = 404N

   
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Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.