Week 1 & 2 Basics of Physics Flashcards
What is 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 velocity?
- describes how the position of an object changes with time.
- its a vector.
- also has to do with position of origin. If end point same as starting point, velocity is zero
-generally m/s
What are vectors?
- have both magnitude and direction
- vectors can be added to give the resultant vector.
- mass is not a vector
What is acceleration?
- describes how velocity changes with time
- a vector quantity
- generally m/s2
What is force?
- a push or pull
- related to Newton’s second law: F=ma
What is gravity?
- it is the universal attraction between all objects.
- Newton’s third law: for every action there is an equal and opposite reaction
- 9.8m/s2
What is weight?
- Weight is the gravitational force exerted on an object by another larger object such as the earth
- W=mg
What is pressure?
-pressure is force per unit area.
Pressure = force/area
- unit is pounds per square inch (psi)
- pressure increases by either increasing the applied force, or decreasing the area the force is applied
- pressure decreases by either decreasing the applied force, or increasing the area the force is applied
What is atmospheric pressure?
Air pressure results from gravity pulling on the atmospheric, and the resulting force is spread over the earth’s surface
- the weight of the air above us
- roughly 14 psi = 1 atmosphere = 760mmHg
What is a barometer?
Measures absolute pressure or atmospheric pressure.
-
What is a Bourdon gauge?
- measure gauge pressure, but is affected by changes in atmospheric pressure.
- use on gas cylinders
- measures the differences between the pressure in the tank an atmospheric pressure.
- Ptotal = Pgauge + Patmosphere
-even if gauge reads zero, still pressure in the tank
What are scalar quantities?
- they have magnitude only.
- They can be additive
Distance, height, weight, speed
What is an aneroid bellow?
- doesn’t need liquid.
- relies on expansion and contraction of a bellow as pressure changes
What is barometric pressure?
-The measure of atmospheric pressure
What is work?
The expenditure of energy
Measured in joules
W = F x d
F: force
D: distance
Can also be W = P x change of volume
P: pressure
What is power?
- the rate of doing work, or the amount of energy transferred per unit of time
- measured in watts
What is a machine?
- device for multiplying force
- does not supply energy, but provides an advantage
- mechanical advantage = force output/force input
What is energy?
Capacity for doing work
What are 2 types of engery?
Kinetic energy
Potential energy
What is kinetic energy?
Energy that a body possesses by being in motion
What is potential energy?
Energy possessed by an object by virtue of its position relative to other objects
What is the law of conservation of energy?
Energy can not be created or destroyed
-it can be changed from one form to another
What is the SI standard unit of energy?
Joules
What is internal energy?
The sum of kinetic and potential energies of a system
What is thermodynamics?
Branch of physics concerned with heat and temperature and their reaction to energy
What is the 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
What is the First Law of Thermodynamics?
- heat is a form of energy, and thermodynamics states that heat is a form of energy. Therefore, thermodynamic processes are subject to the principle of conservation of energy.
- Heat can not be created or destroyed
- from slide: a change in the internal energy of a system is equal to the sum of the heat flow of a system and the work done by/on the system
What does exothermic mean?
Gives off heat
What does endothermic mean?
Absorption of heat
What is the Second Law of Thermodynamics?
Heat spontaneously flows from a hot body to a cold body when 2 bodies are brought into thermal contact
-AKA: entropy law
important for keeping pt warm in OR
What does entropy mean?
A measure of randomness or disorder in a system.
Systems can be randomized, chaotic, or evenly mixed. A system will never become more organized
What is Third Law of Thermodynamics?
It is not possible to lower the temperature of an object to absolute zero
What is the difference between heat vs. temperature?
- Heat is a process, not a product
- heat is energy which can be transferred
- temperature is a numerical ranking of “hot” or “cold”
- temperature is an arbitrary number
- temperature is a measurement of the tendency to gain or loose heat
What is thermal expansion?
-the tendency of matter to change in shape, area, and volume in response to a change in temperature.
- an increase in heat will cause an object to expand
- expansion is constant for a given material
- expansion is constant in all directions
What is the unit of measurement for heat?
Calorie
Calorie is the heat required to raise 1g of water 1 degree C
What is specific heat?
The amount of heat needed to raise the temperature of 1 gram of material by 1 degree C
- materials with a high specific heat make good insulators
- materials with a low specific heat make good thermoconductors
What is heat capacity?
Heat required to raise the temperature of a given material
Heat capacity = mass x specific heat
What factors affect the rate of change of heat of an object?
- heat capacity (inv proportional)
- temperature gradient (dir proportional)
- surface area (dir proportional)
- forced convection (dir proportional)
What are the different types of heat transfer?
how heat is lost
- radiation: 40%
- convection: 30%
- conduction: 20%
- evaporation: 10%
What is convection?
Heat transfer caused by a liquid or gas
What is conduction?
Transfer of heat by the direct interaction of molecules in a hot area with molecules in a cooler area
What is radiation?
Energy emitted from an object
Requires no physical medium or physical contact between the objects
What is evaporation?
Heat loss primarily through respiration
What are the 4 fundamental forces?
- Strong nuclear force
- Electromagnetic force
- Weak nuclear force
- Gravitational force
