Lecture 1: Basics Of Physics Flashcards
Newton’s First Law of Motion
An object at rest remains at rest until a force acts upon it
AKA – law of inertia
What is Newton’s first law of motion also referred to as?
Law of inertia
The greater the mass of an object… The ___ force is required to get it moving
More
Velocity
Describes how the position of an object changes with time
Velocity is a ___ quantity
Vector quantity
Is mass a vector quantity?
No–mass is a scalar quantity
What are vectors?
Vectors have both magnitude and direction
What is a resultant vector?
When you add two vector quantities together…for example, if you are walking 5 mph on a train going 30 mph (both in the same direction), then the resultant vector quantity is 35 mph.
Acceleration
Describes how velocity changes over time
Acceleration is a ___ quantity
Vector quantity–has both magnitude and direction
Newton’s second law of motion
Force = mass X acceleration
Acceleration is dependent upon what two variables?
1) the net force acting upon the object
2) the mass of the object
F = ma (Newton’s second law of motion)
What is the unit of measure for acceleration?
Meters/second ^ 2
What is the estimated force of gravity?
9.8 m/s^2
What is force?
A push or a pull; related to mass
Force =
Mass X acceleration (Newton’s second law of motion)
What is gravity?
Universal attraction between all objects; related to Newton’s third law of motion
What is Newton’s third law of motion?
For every action, there is an equal and opposite reaction
What is weight?
Gravitational force exerted on an object by another larger object
Weight =
Mass X gravity (9.8 m/s^2)
What is pressure?
Force per unit area
Pressure =
Force/area
How can you increase pressure?
1) Increase the applied force (push down more)
2) Decrease the area that force is applied in
How can you decrease pressure?
1) Decrease applied force
2) Increase area
Units of pressure–PSI
Pounds per square inch
What is atmospheric pressure (1 atm)?
Standard temperature and pressure
1 atm =
=760 torr
=760 mm Hg
What is an Aneroid gauge?
- Gauge seen on old oxygen tanks
- Greek in origin–aneroid means “without water/liquid”
- Change in dial relies on expansion and contraction of bellow system
What is a Bourdon gauge?
- Aneroid style gauge–no liquid inside
- Measures gas pressures
- Seen on oxygen, air tanks
What does the Bourdon gauge measure?
It measures the pressure difference between the pressure exerted by the gas in the tank versus the pressure exerted by the gas in the atmosphere.
When the Bourdon gauge reads ‘0,’ is there any pressure left in the tank?
YES–there is still gas in the tank that is exerting the same amount of pressure as atmospheric pressure. Once it reads 0, it still has the equivalent of atmospheric pressure in there (14 psi = atmospheric pressure).
A tank of gas has a gauge that reads 45 psi. If the atmospheric pressure at that time is 14 psi, how much gas is really in the tank?
P total = P gauge + P atmosphere
45 + 14 = 59
Oscillometry
- Basis behind non-invasive BP technology
- Relies on measurement of blood pressure oscillations
Piezoelectric technology
- Non-electric pressure changes impact transducer, creating a voltage that is proportional to the pressure change
- Based on the voltage received by the transducer, specific algorithms calculate the actual pressures that we can monitor
What is work?
The expenditure of energy
Work =
Force X distance
What is the unit of measure for work?
Joules
What is kinetic energy?
Energy of a mass in motion
What are state functions?
Mathematical functions that describe the “state” of a system
What are 3 examples of state functions?
- Volume
- Pressure
- Temperature
What is energy?
The capacity to do work
What is Newton’s law of conservation of energy?
Energy is neither created or destroyed; energy can only be converted into other kinds of energy
Two types of energy
- Kinetic energy
- Potential energy
What is kinetic energy?
Energy of a mass in motion
What is potential energy?
Stored energy
What are examples of potential energy?
- Rock at the top of a hill
- A spring
- Sugar or fat
- Thermal energy
What is the unit of measure for energy?
-Joule
Calories
Big C = kilocalorie, or 1000 calories
-calories from the food that we eat
calories
Little C = an older unit of energy
Internal energy
The sum of all energies (kinetic and potential energies) in a system
What is thermodynamics?
The study of energy, how it is converted from one form to another, and how it flows into and out of thermodynamic systems.
Zeroth law of thermodynamics
If A is the same temperature as B, and B is the same temperature as C, then the temperature of A must equal the temperature of C (thermal equilibrium), and no heat will flow between A and C.
First law of thermodynamics
A change in the internal energy of a system is equal to the sum of heat flow of the system and then work done by or on the system.
Endothermic
Energy flows INTO the system
Exothermic
Energy flows OUT of the system
Expansion
Work done BY the system
Compression
Work done ON the system
Second law of thermodynamics
Heat flows spontaneously from a hot body to a cold body when two bodies are brought into thermal contact. Heat will flow until the two temperatures are equal.
Third law of thermodynamics
It is an impossible to lower the temperature of an object to absolute 0–there’s always some energy in the system.
Entropy
Measure of randomness or disorder in a system
What is heat capacity?
The amount of heat required to raise the temperature of a given material– mass X specific heat
What is specific heat?
The amount of heat needed to raise the temperature of 1 g of a substance by 1 degree Celsius
Water and specific heat
Water has a very high specific heat – lots of energy must flow into water before its temperature will significantly change.
Good thermal insulators are materials with…
high specific heats (because large amounts of heat will cause small changes in temperature)
Good thermal conductors are materials with…
Low specific heats–i.e.: metal pots for cooking
Four types of heat transfer:
- Convection
- Conduction
- Radiation
- Evaporation
What is convection?
- Heat transfer by movement of a liquid or gas
- Examples: air above a heat source, cold air blowing over patient in the OR
How much heat (%) is transferred through convection?
-30%
What is conduction?
- Transfer of heat by direct interaction of molecules in a hot area with molecules in a cooler area
- Examples: moving patient onto cold table, covering patient with warm blanket
How much heat (%) is transferred through conduction?
-20%
What is radiation?
- Energy emitted from an object
- Requires no physical medium or contact
How much heat (%) is transferred through radiation?
-40%
What is evaporation?
- Heat lost through respiration
- Surgical prep left on patient’s skin to dry (Betadine, alcohol prep)
How much heat (%) is transferred through evaporation?
-10%
What is thermal expansion?
An increase in heat will cause an object to expand
Thermal expansion is ___ for a given material and occurs ___
- constant for a given material
- occurs in all directions equally
What is power?
The rate of doing work or expending energy
What is the unit of measure for power?
Watt
