Chapter 9 Flashcards
(23 cards)
what are the 4 states of matter?
which are fluids?
which cant be compressed?
solid- definite volume and shape, strong forces
liquid- definite volume, conforms the shape of a container
gas- no shape or volume, expands to fill a container, no forces except collisions
plasma- many of electrons have been separated from their atoms
positive ions and negative electrons interact via electric and magnetic forces
liquids and gases are fluids (flow)
liquids and solids are incompressible
How do you find specific gravity?
ρ/ρwater= specific gravity
What is pressure?
What happens in a static fluid?
Describes the effects of collisions between the atoms/molecules of a fluid itself and between the atoms/molecules of a fluid and its container
In a static (fluid at rest) fluid, the force of a surface due to collisions of molecules of the fluid must be perpendicular to the surface
If collisions are not perpendicular the fluid would flow along the surface
N/m^2 = Pa
Jan3 S7
Jan 3 S14
Why do we not feel the effects of atmospheric pressure?
The fluids inside our bodies are also at atmospheric pressure
How do we calculate how the pressure increases over atmospheric pressure over a certain depth?
P=Po + ρgh
Atmospheric pressure plus pressure increase over depth of submersion
P= absolute pressure
What is pascals principle on change in pressure applied to a fluid?
Change in pressure applied to a confined fluid is transmitted to every point of the fluid and its container
Principle behind hydraulic lifts
Example Jan 3 S18-19
What is pressure in a connected system (Jan 8 S3) at the same level of fluid?
How do you find gauge pressure?
Pressure is the same
Pa=Pb
Pb=Po + pgh
Pa=Po + pgh
Pgauge= Pabsolute-Patmospheric
Jan 8 S7 example
How does a sphygmomanometer work?
Does it use gauge pressure or absolute?
Inflatable cuff applies pressure until blood flow in arm is stopped
When pressure is reduced the blood just starts to flow is systolic pressure and the pressure when blood flows freely is diastolic
Gaige pressure because in order for blood to flow the absolute pressure must be greater than atmosphere
What are buoyant forces?
A fluid exerts an upward buoyant force on a wholly or partially submerged object
B = ρ(fluid) V(fluid) g
Pressure of the surrounding fluid is greater on the bottom of an object than the top
What is laminar or turbulent flow?
In laminar flow, the properties of the flow at a particular location do not change with time.
Every particle that passes a particular point moves along the same smooth path that was followed by previous particles
This path is the streamline
Jan 8 S16
What is viscosity?
What does non viscous mean?
In compressible?
Motion is steady?
Measure of the internal friction in a fluid, associated with the resistance between two adjacent layers of the fluid
Higher viscosity=harder to pour
Non viscous- no internal friction force between layers
Incompressible- density is constant
Motion is steady- velocity, density, and pressure don’t change with time
Is pressure greater in a bigger area tube or smaller area tube?
Jan 8 S21
Pressure is greater in the bigger area since the velocity will be lesser in the bigger area
What is non viscous flow compared to viscous flow?
Non viscous flow has a constant velocity profile
Viscous flow has a thin layer of liquid along the pie wall abreast and gradually increases velocity as you move to the centre of the tube
Jan 10 S15-17
What is the coefficient of viscosity?
Constant of proportionality of a property of fluid
Decreases with increasing temp
Symbol η
What is required to keep a viscous fluid moving through a horizontal pipe?
A pressure difference must be applied
Same way that a constant force must be applied to keep an object moving at constant velocity
Q (volume flow rate)= πR^4(P1-P2)/8ηL
Q=ΔV/Δt
ΔV/Δt=πR^4(P1-P2)/8ηL
Jan 10 S19
What is resistive force?
when object moves through a fluid, it exerts a resistive drag force around it
Fr=6πηrv
The effect of drag force is that an object will reach terminal velocity
If an object isn’t spherical then this doesn’t apply!!
Use Fr=kv
How do you find terminal speed?
Vt=m(obj)g/k (1-ρ(f)/ρ(obj))
Jan 10 S7-10
What is the deformation of solids (how shape and volume of a solid can change)?
It’s possible to change shape and volume of a solid by applying external forces
When forces are removed, the object tends to return to its original shape and size
This is called elastic behaviour
What is stress and strain?
What is the elastic modulus?
Stress is the force per unit area causing deformation in Pa (pascals)
Strain is the measure of the amount of the deformation
For small stresses, strain is proportional to stress
Stress= elastic modulus x strain
Elastic modulus is a measure of the stiffness of a material (large elastic modulus means very stiff and difficult to deform)
What is tensile stress?
The force per unit cross sectional area (F/A)
Jan 10 S15
A bar that is twice as long will stretch twice as much when subjected to an identical tensile force as a bar that is half as long
The increase distance between atoms is the same for the same force
F/A=Y (ΔL/Lo)
Tensile strain= ΔL/Lo
Y=Young’s modulus
What happens if applied stress is greater than the elastic limit?
What is ultimate strength and breaking point?
The material will not return to its original length
Ultimate strength is the maximum stress that the material can withstand
Breaking point is the stress at which the material breaks
Graph Jan 10 S24
What is shear modulus?
The elasticity of shape
F/A=S(Δx/h)
S is shear modulus
Jan 10 S25-26
What is bulk modulus?
The response of a substance to uniform squeezing (pushing equally from all sides)
Since pressure is force per unit are pushing perpendicular on all sides of an object:
ΔP=-B(ΔV/V)
B is bulk modulus and positive
ΔV is intrinsically negative because an object compresses in increased pressure
