Physics chap 4 Flashcards
What is work and how do you calculate it?
- A force does work acting on an object and displace it in the direction of force
W= F x D x cos (. )
W=work done
F=magnitude of the force
d= magnitude of displacement
.= angle between the force and displacement
Work has what unit
SI units of joule
One joule of work is used when a force of 1 Newton acts over a displacement of 1 meter.
1 J= 1N X m
Work is the
act of force of an object, to displace the object in the direction of the force (direction/vector)
- work is not done if the object does not move over a distance
Mass is the
total of all matter in an object (sum of all electrons, protons, and neutrons). Mass only has magnitude and is a scalar quantity.
measured in kilograms
mass=volume x density
Weight is the
total effect of gravity pulling on all these electrons, protons, and neutrons of an object. Mass remains the same but weight decreases at moon surface
Measure of the amount of force acting on a mass due to acceleration due to gravityHas both magnitude and direction and is a vector quantity
measured in newtons
weight = mass x acceleration due to gravity
SVR
900-1200 dynes/cm ^5
((MAP-CVP)/CO) x 80
What is compliance? How is it related with elasticity?
Inversely related.
What happens to lung compliance in emphysema?
- emphysema destroys elastic tissue
- compliance goes up
What happens to lung compliance in pulmonary fibrosis?
Too much elastic tissue. Too tight. Stiff. Increased elastic tissue decreases compliance.
Work=
pressure X volume
Both inspiratory and expiratory work of breathing is performed by
diaphragm
Energy is
exertion of force (kinetic) or the capacity (potential) to do work.
Can be expressed as mechanical work, chemical reaction or heat.
Energy is neither created nor destroyed, but only converted to other kinds of energy
Kinetic energy
KE= 1/2mv^2
KE=
m=mass
v^2= velocity
KE=energy of motion/momentum
Potential energy
is stored energy by virtue of position, waiting to be used
PE=mgh
(mass, gravity, height)
PE of a mass connected to an ideal string:
PE= kx^2
PE= stored energy/energy from gravity
k= spring constant and depends on the specific spring used
Law of energy conservations states
the amount of energy in the universe is constant and is constantly being converted from one form to another
1 calorie is needed to
raise the temperature of 1 gram of water by 1 degree Celsius
1 kcal= 4184 J
W total=
change in KE= KE final-KE initial =mv^2 - mv^2 initial
Entropy is the
universe’s trend to equilibrate all things. It is the process that allows: everything from ice melting to gas expansion and induction of general anesthesia by diffusion
Power is the
rate of doing work or, conversaely, the rate of expending energy. Unit is watt
Watt is the
capacity to do work
Temperature is the
measurement of the thermal state of an object
Heat is thermal energy, temperature is the quantitative measurement of that energy
Endothermic process
heat flows from the surroundings into the system
Exothermic process
heat flows from the system out into the surroundings
first law of thermodynamics
law of conservation of energy. energy cannot be created or destroyed.
second law of thermodynamics
heat spontaneously flows from a hot body to a cold body when the two bodies are brought into thermal contact
third law of thermodynamics
it is not possible to lower the temperature of an object to absolute zero
Radiation is the
most significant mechanism of heat
Convection is
heat loss by air current.
Conduction
is transfer of heat by physically touching the objects
Evaporation means
when water converts into gas form
- ex cleaning solution
How much are you doing if you hold a 20 lb weight 3 ft above the floor?
no work
How much are you doing if you lift a 20 lb weight 3 ft above the floor?
20 X 3 = 60 lbs
Restrictive lung diseases
(pulmonary fibrosis; stiff lungs_ patients learn to minimize work of breathing by rapid and shallow breathing
Obstructive lung diseases
COPD, resistance to flow;
patietns learn to minimize work of breathing by slowing and deep breathing. their problem is blowing the air out due to obstruction
Minimize work of breathing by:
PEEP to keep lung volume at FRC (incentive spirometer)
-positioning
-surfactant
-optimizing respiratory rate
-increase laminar flow by heliox
-bronchodilators
During inspiration,
about 1/2 the energy used is stored as PE in the elastic tissue fo the lungs and chest wall; active process.
this energy is then used during expiration to overcome airway resistance. this makes expiration a passive process
-
resting membrane potential
makes nerve/muscle ready for action
-70 to 90 mV
Joule (J) = ____ cal
0.239 cal
Calorie (cal)= ____ J
4.184 J
Watt hours (Wh) =_____ J
3,600 J
Heat loss from greatest to least
1- Radiation
2- convection
3- evaporation
4- conduction
Isotonic
work was done
