: The Nature of Fluids and the Study of Fluid Mechanic

Question 1

Fluid?

Answer 1

A substance that deforms continuously under application of of a shear stress.
Gas or liquid

Question 2

Pressure (P)

Answer 2

P=F/A
P=N/m^2 or Pascals
1 bar= 100kPa

Question 3

Pascals law

Answer 3

Pressure acts uniformly in all directions on a small volume of fluid.
Pressure acts perpendicular to boundary where fluid is confined.

Question 4

Compressibilty?

Answer 4

Change in volume due to change in pressure.
Measured by bulk modulus of elasticity (E)

Question 5

Density (p)

Answer 5

Mass density is the amount of mass per unit volume of a substance.
p=m/V
kg/m^3
Water at 4 degrees is 1000kg/m^2

Question 6

Specific weight/weight density (y)

Answer 6

y=w/V or y=pg
N/m^3
Water at 4 degrees= 9.81kN/m^3

Question 7

Specific gravity(sg)

Answer 7

sg= ps/pw or sg=ys/yw

Question 8

Surface tension

Answer 8

Tensile force acting on the surface of a liquid in contact with a gas (or immisicible liquids in contact) such that the contact surface behaves like a membrane.
It is why water droplets assume spherical shape (capillary effect).

Question 9

Gas and liquid difference

Answer 9

Unlike a liquid, a gas does not form a free surface, and
it expands to fill the entire available space