phy/chem week 1 review guide questions Flashcards
what is work
Work is the expenditure of energy
Work is defined as a force acting through a distance
W = F • d
what is the unit of measurement of work? SI unit?
joules
W= F x D
work = force x displacement
If there is no force, no work is done. Likewise, if the magnitude of the displacement is zero, no work is done.
You can push with all your might and effort, but if the stretcher doesn’t move, you haven’t done any work!
1 joule
One joule of work is expended when a force of 1 N acts over a displacement of 1 m.
what is kinetic energy
Kinetic energy is also called energy of motion because one way to define it is one-half the product of mass times the square of the speed.
We thus see that work and kinetic energy both have units of joules.
Kinetic Energy is the energy a mass has by virtue of being in motion
KE = ½ mv2
The units of KE are joules
what are kinetic energy’s units
We thus see that work and kinetic energy both have units of joules.
does breathing require work?
yes
what are State functions
State functions are mathematical functions that describe the “state” of a system. The state of a given system can be described using one or more variables such as volume, pressure, or temperature.
what is energy
Capacity for doing work
Cannot be lost but converted
1. Kinetic Energy
2. Potential Energy
what does a joule = in reference to energy
1 calorie.
what is one calorie
One calorie was defined to be the amount of energy necessary to raise the temperature of 1 g of water from 14.5°C to 15.5°C.
Today, one calorie (thermochemical calorie) is defined to beexactly4.184 J.
The ubiquitous food Calorie (note the capitalization) is a kilocalorie or 1,000 cal.
You use one joule of energy when you accelerate what?
a 1 kg mass by 1 m/s2 over a distance of 1 meter.
Giving this 1 kilogram mass 1 J of energy also requires that you expend 1 joule of work
Law of Energy Conservation
The amount of energy in the universe is constant and is constantly being converted from one form to another. Alternatively, we can say, energy is neither created nor destroyed, but only converted to other kinds of energy.
Potential Energy is what
Potential energy is stored energy A rock at the top of a hill PE = mgh Spring (expanded lungs) PE = ½ kx2 Sugar or fat, thermal energy, light
The units of PE are joules
can potential energy be stored and used later?
yes
review slide 18 chapter 2
Let’s examine the gravitational potential energy of a ball, which is thrown straight up into the air. The ball starts at rest in your hand, then goes up, slows down, stops, and then falls back to you. The instant you release the ball, it has a maximum amount of kinetic energy. As it travels upward, though, the velocity decreases and, therefore, the kinetic energy decreases. The kinetic energy is not destroyed, however, but converted into potential energy. At the top of the flight, the kinetic energy is zero, because the ball is not moving, and the potential energy is at a maximum. Then, as the ball begins to fall, the potential energy is converted back into kinetic energy.
The potential energy of the system is large when the ball is high in the air, and it is low when the ball is near the ground.
what is internal energy
The internal energy of a system is the sum of all the kinetic and potential energies of the particles comprising the system.
Imagine a cylinder of a compressed gas in an airplane;
What kinds of energy does this sample have?
Airplane and cylinder are moving = KE
Elevation relationship to Earth = PE
Molecules inside tank are moving = KE
Compressed gases are like springs pressure > atm. Pressure = PE
Thermodynamics is?
Loosely defined as the study of energy, how it is interconverted from one form to another, and how it flows into and out of thermodynamic systems.
Zeroth Law of Thermodynamics:
2 objects A/B are same temperature. B/C are same temperature; therefore A/C are equal temperature (thermal equilibrium) and no heat will flow between A/C.
First Law of Thermodynamics
Change in internal energy = energy transferred to object from a higher temp body + work done on the object
ΔU = Q + W
Second Law of Thermodynamics
Heat spontaneously flows from a hot body to a cold body when 2 bodies are brought into thermal contact.
Entropy Law is ?
Entropy is a measure of randomness or disorder in a system.
Example – Give a liter of iv fluid, it does not remain separated, it is equally mixed into blood. Will not separate out.
Systems that are more randomized, chaotic, or evenly mixed have more entropy.
The Second Law states the entropy of the universe is constantly increasing. One clear implication of the Second Law is that the universenever,and a system almost never, spontaneously becomes more organized.
Third Law of Thermodynamics
It is not possible to lower the temperature of an object to absolute 0.
Temperature is
(at first glance) a rather arbitrary numerical ranking of “hot” or “cold”
Temperature is a measurement of the tendency to gain or loose heat
Heat is
is energy that is transferred as a result of a temperature difference. In one sense, it can be viewed as an energy flow. In another sense, it can be viewed as a process.
When two bodies of unequal temperature are brought into contact, a flow of heat occurs until the two temperatures are equal (from hot to cold)
Heat is energy which can be transferred
what is the measure of heat?
Calorie is the unit of measurement
Calorie is the heat required to raise 1g of water 1o C
Kinetic Energy and Temperature
For now, a sample of an ideal gas will have a temperature that is proportional to the kinetic energy of the molecules in the sample.
The Boltzmann constant (k)
Heat Capacity what is it
Heat required to raise the temperature of a given material
HEAT Capacity = Mass x Specific heat
Heat capacity is defined to be the ratio between the amount of heat added to or taken away from an object and the change in temperature of the object.
Specific Heat is
Specific heat is the amount of heat (Q) needed to raise the temperature of 1 gram of material by onedegree Celsius
Heat Transfer
Convection 30%
Conduction 20%
Radiation 40%
Evaporation 10%
Convection is
Heat transfer caused by the movement of a liquid or gas
Air above a heat source or flame. = natural
Cold air blowing over a patient in the OR! = forced
Conduction is
Transfer of heat by the direct interaction of molecules in a hot area with molecules in a cooler area.
Does not involve motion of the body.
Thermal conductivity of material is a measure of efficiency.
Moving a patient onto a cold table = Cools patient.
Covering the patient with warm blankets = Warms the patient
Radiation
Energy emitted from an object.
Requires no physical medium or physical contact between the objects.
Evaporization
Heat lost through respiration.
Surgical prep (betadine) left on the patients skin to dry.
Thermal Expansion
An increase in heat will cause an object to expand
Expansion is constant for a given material
Expansion is constant in all directions
Power and Breathing
slide 40
Power
Power is the rate of doing work or, conversely, the rate of expending energy. The average power delivered during a timetwhen an amount of workWis done is given by: p= W/T
The watt (W), which is defined as joules per second
The average power is equal to the force involved times the speed.
Different power example
You know gas cylinders are very dangerous! Yes, those little O2 tanks we use with patients!
How much work can 200 L of gas at an initial pressure of 2,000 psi accomplish if the cylinder ruptures and the gas expands to a new volume of 27,000 L?
If the release occurs over a period of, say, 10 s, the power production is 18.5 megawatts (MW), comparable to a small nuclear reactor.
