BMS1031 (Fluids and Energy and Cardiovascular Weeks 1 to 5 (Energy, Work,…
Fluids and Energy and Cardiovascular
Weeks 1 to 5
Forces and Newtons Laws
Force - an interaction between two objects 1N = 1kg m/s2
The relationship between an objects mass
, its acceleration
and applied (net) force
For every action there is an equal and opposite reaction.
An object stays in its state of rest (or of uniform motion in a straight line) as long as no net force acts on it.
E.g. good example on page 65 of the text book.
Kinetic friction; sliding friction. An experimental relationship between the magnitude of the friction force which acts parallel to the two surfaces and the magnitude of the normal force. :red_flag:
Static friction; force parallel to the two surfaces that can arise even when they are not sliding. :red_flag:
Fluid and Density
Lecture 2 and 3
Hydrostatic Pressure in Fluids
The pressure in a fluid is proportional to the depth in the fluid.
Atmospheric Pressure at sea level =
absolute versus gauge pressure.
Pressure gauges measure the difference between two pressure, gauge pressure.
In a manometer pressure absolute = Patm + Pg
Mercury as a measurement tool:
1mm Hg = 133Pa = 133 N/m2
1 Pa = 1N/m2
Buoyancy force is equal to the weight of the fluid displaced. :red_flag:
For an object suspended in water:
Upward Force = Downward Force
T + F buoyancy = mg
Can be used to determine volume and density of an object.
Viscosity; a frictional force between adjacent layers of fluid as the layers move past one another.
Mass flow rate continuity:
pAv = pAv = Q
For two points in a flowing fluid.
Flow in tubes is a specific example of the concept of continuity.
Q = (change P.Pi.r^4)/(8.viscocity.length of tube) :red_flag:
For flow in a tube of uniform radius and assumes laminar and incompressible flow.
Bernoulli Equation and the conservation of flow energy
; the surface of a liquid acts like it is under tension and this tension acting along the surface arises from the attractive forces between molecules.
; a particle falling in a liquid / fluid experiences gravitational force down, a buoyant force Fb and a drag force D up due to viscosity.
Drag force = k.r.v where k is a constant :red_flag:
Sedimentation is faster for larger r, larger object
or larger g.
Energy, Work, Potential Energy
Ek = 0.5mv^2 :red_flag:
Gravitational Potential Energy
Ep = mgh :red_flag:
Power (J/s) = change in energy / change in time
A power limited activity is one where you require a large energy change over a small period of time.
Work = F.d (N.m) (J) :red_flag:
1 cal = 4.186J = amount of heat needed to raise the temp of 1g of water by 1 Celsius degree
Thermal energy = atoms and molecules kinetic and potential energy
Q = m.c.change in T :red_flag:
c (J kg-1K-1)
Storing heat in an object doesn't only depend on the specific heat but the mass as well
Energy is required for a material to change phase even though its temperature is not changing. The amount of heat required for a phase change is called latent heat = m
E.g. if you want to break the bonds of water molecules you have to put heat in to break the bonds.
Movement of heat flows by the mass movement of molecules. Natural convection is due to the lower density of hotter fluids.
E.g. main use of heat transfer by the body.
a form of electromagnetic wave due to oscillations of electrons / electric charges.
Stefan-Boltzmann Equation :red_flag:
Emission and absorbtion
E.g. cooking on a frying pan.
(change heat / change time) =
A (T1-T2)/l :red_flag:
heat transfer decreases by 1/l
First Law of Thermodynamics
Change in energy (Kinetic, Potential, internal energy) = Heat in - Work done
In a closed system the internal energy changes only as a result of heat flow or work done. In an open system (such as human) internal energy itself can flow into and out of the system.
Typical metabolic rates - the rate at which internal energy is transformed within the body.
Basal metabolic rate is the rate at which energy is produced when a person is totally resting
Torque, Levers, Circular Motion, Elasticity
= change in length / length (dimensionless) :red_flag:
= force / area :red_flag:
Force is directly proportional to elongation in the elastic region (this is reversible)
Beyond the elastic region is the plastic region where you get permanent deformation
v = change in distance / change in time
a = v2/r
F = mv2/r
Gases, Diffusion, Osmosis, Evaporation
D = diffusion constant for gas
Ideal Gas Laws
; V1/V2 = T1/T2
Ideal Gas law
; PV = nRT
Where R = 8.315 J mol-1 K-1
P1V1 = P2V2
number of moles of solute particles per litre of solution
Osmosis equalises water partial pressure
P water left + P solute left = P water right + P solute right
Hypotonic; water flowing out of solution
Hypertonic; water flowing into solution
Gas in solution
The equilibrium concentration of dissolved gas is proportional to the partial pressure of that gas in gas above the liquid.
Lecture 7 and 8
Electricity and Bio-electricity
Weeks 6 - 8
Waves and Optics and Bioimaging