Fluids Flashcards
How is density measured?
P=m/v
Units are
kg/m^3
g/mL or g/cm^3
Remember ml and cm^3 are equivalent
What is the density of water?
1g/cm^3= 1000kg/m^3
How is specific gravity measured? What does it tell you?
Specific gravity is measured as the density of a fluid divided by the density of water at 1atm and 4ºC
Specific gravity allows you to determine what percentage of an object will be submerged under water. You simply multiply it by 100. If the specific gravity of an object is >1 it will sink
What is atmospheric pressure and how is it measured?
pressure of air (on the surface of Earth)
P=F/A
N/m2= 1 Pa
1.013x10^5 Pa=760mmHg=760 torr=1 atm
Neglecting gravity what happens when you add an object to a closed container filled with a gas?
Pascal’s principle: Because the molecules are moving randomly within the space, it will exert pressure that is the same at all points along the container and within the space of the container.
What’s the difference between Work and pressure?
Work is a force applied over a distance. Pressure is the force applied by fluids.
What happens to the boiling point of liquids as atmospheric pressure changes with altitude?
The boiling point decreases when atmospheric pressure decreases. This is because a low pressure means less resistance from air molecules when a boiling liquid is entering the air. Because vapor pressure reduced, the temperature needed to boil the liquid is also reduced.
How does atmospheric pressure change with altitude?
The atmospheric pressure decreases as altitude increases (inversely related)
What is absolute (hydrostatic) pressure? The pressure of a fluid
The total pressure on an object that is submerged in a fluid
P=Pº + pgz
Where Pº is the pressure at the surface of the fluid
p= density
g= acceleration due to gravity 9.8m/s^2
Z= depth of the object
What is gauge pressure?
Gauge pressure is the difference between the absolute pressure in a closed space and the atmospheric pressure
P gauge= P absolute- P atmosphere
Pg= (Pº+pgz)-Patm
What happens to a liquid if you try to compress it?
Pascal’s principle: The pressure exerted is the same at all points throughout the liquid.
P1=P2 where p1 is the pressure exerted or put into the liquid and p2 is the pressure output.
This is true to the law of conservation of energy (energy is not created nor destroyed but changes from one form to another)
So if you try to compress it the pressure moves through the liquid. If in a closed container, the pressure will cause the container to explode.
What is Pascal’s principle?
Pascal’s principle says that if an external pressure is applied to a confined fluid (fluid in some sort of container) the pressure at every point in that fluid increases by that amount.
How does a hydraulic lift demonstrate Pascal’s principle?
Hydraulic lift is a device that allows a small output force to convert into a large output force by changing the area. Remember according to Pascal’s principle, the pressure put into a system is distributed evenly throughout the system. This means the the pressure put in = pressure put out.
P1=P2 or F1/A1=F2/A2
We can rearrange this equation to F1/F2=A1/A2. And
How do we get mechanical advantage?
When we take Pascal’s principle P1-P2 or F1/A1=F2/A2 we can rearrange force and area so that they are ratios. F1/F2=A1/A2.
This ratio of forces F1/F2 is the mechanical advantage.
For a fluid at rest, how does the fluid exert pressure on an object?
The fluid exerts a force that is perpendicular to the surface of the object.
Remember, if the fluid is at rest, the velocity is 0 and the net force is also 0. This means the object is exerting the same amount of force on the fluid, that the fluid is exerting on it.
