Fluids & Pressure 1.1

Question 1

Convert 1m^3 to 1cm^3

Answer 1

1m^3 = 10^6 cm^3

Question 2

Describe relationship between density and mass, and what is the SI unit

Answer 2

ρ = m/V ; m=ρV ; kg/m^3

Question 3

Describe the relationship between Pressure and Force, and what is a pascal

Answer 3

P = F/A ; F = PA ; 1Pa = 1N/m^2

Question 4

What are the two contributors to Pressure?

Answer 4

Gravitational Contribution: Forces exerted on the bottom and sides of the container
*Dependent on strength of gravitational force

Thermal Contribution: Due to collisions of freely moving particles
*Dependent on absolute temperature of gas

Question 5

What is the hydrostatic pressure equation, what assumption does it make

Answer 5

P = Po + ρgd ;

Assumes fluid is incompressible

Question 6

What percentage of pressure change occurs between the top and bottom of a 100m tall column of gas?

Answer 6

1%

Question 7

List 5 key features of fluids

Answer 7

1: Pressure is equal whether pointed up, down, left or right
2: Liquid Pressure increases with depth
3: Gas Pressure is nearly constant everywhere
4: A connected liquid in hydrostatic equilibrium rises to the same height in all open regions of the container
5: The pressure is the same at all points on a horizontal line through a connected liquid in hydrostatic equilibrium

Question 8

What is the relationship between Gauge Pressure & Absolute Pressure?

Answer 8

Pg = P - 1atm
P  = Pg + 1atm

Gauge Pressure reads the pressure in excess of atmosphere

Question 9

What are the 5 steps to solving Hydrostatics Problems

Answer 9

1: Draw a diagram
2: Determine pressure at surfaces: Open to air, covered by a gas, closed surface: P=F/A
3: Use the horizontal line rule
4: Consider Gauge pressure: Pg = P - 1atm
5: Hydrostatic Pressure Equation: P = Po + ρgd

Question 10

Describe the two pressure measuring instruments

Answer 10

Manometer: U-shaped tube connected to gas at one end, and open to air at the other end.

Barometer: A tube filled with liquid, sitting in a puddle of its own blood. The ambient pressure pushes down on the puddle, supporting the column of liquid up the tube.

Question 11

Convert the from 1atm to the following:
Pa
mm of Hg
in of Hg
Psi

Answer 11

1atm =
101,300Pa
760mm of Hg
29.92in of Hg
14.7 Psi

Question 12

What is Pascal’s Principle

Answer 12

A pressure exerted at any point on an enclosed fluid is transmitted undiminished throughout all points of the fluid

Question 13

What is archimedes principle

Answer 13

A fluid exerts a buoyant force on an object that is floating or immersed in the fluid. The magnitude is equal to the weight of the fluid displaced by the object