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 mechanic uses a grease gun which has a cylindrical piston of radius 0.25 cm. If the handle is 25cm long and the fulcrum is 1 cm from the piston (a) calculate the pressure in the fluid grease when he applies a force of 20N.
(b) what is the force that the grease is expelled from the nozzle if it has a radius of 1mm?

Let FP be the force on the piston
Radius of piston = 0.25cm
Cross-sectional Area of piston = 1.96 X 10-5 m2
Length of handle = 0.25m
Distance of piston from fulcrum = 0.01m
Radius of nozzle = 1mm
Cross-sectional Area of piston = 3.14 X 10-6 m2

When the piston is about to move Στ = 0
Clockwise torque + Anticlockwise torque = 0
[-(0.25m X 20N)] + (0.01m X F) = 0
F = 500N

Pressure = Force / Area
Pressure by piston = P / Area
Pressure by piston = 500N / 1.96 X 10-5 m2
Pressure by piston = 25.5 MPa.

Pressure is transmitted throughout all part of the fluid
Pressure on nozzle = FN / Area
2.55 X 107 = FN / 3.14 X 10-6 m2
FN= 2.55 X 107 X 3.14 X 10-6 m2
FN= 80.1 N

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