Physics Flashcards
What is potential energy?
Energy associated with position in space
What is the kinetic energy equation?
K = 1/2(m)(v^2)
What is the datum?
The zero potential energy position defined in a given problem
What is the gravitational potential energy eqn?
U = mgh
What is the eqn for elastic potential energy?
U = 1/2(k)(x^2)q
What is total mechanical energy?
Sum of the potential and kinetic energies
E = U + K
What is a conservative force?
A force that is path independent and does not dissipate energy.
EX: gravitational and electrostatic (and frictionless elastic)
What is the general equation for work done on a system?
W = [U final - U init.] + [K final - K init.]
Define work
the process by which energy is transferred from one system to another; NOT A FORM OF ENERGY, even though it is measured in joules
What is the eqn for work done by a force?
W = F (d) (cos theta) or W = F * d (dot product)
What is a P-V graph?
A graphical representation of gas expansion and compression w/ volume on x-axis and pressure on y-axis
What is a isovolumetric or isochoric process?
A process by which pressure changes but volume stays the same: no work is done.
What is a isobaric process?
A process by which volume changes but pressure stays the same: W = P(delta V)
Define power
rate of energy transfer from one system to another
What is the equation for power?
P = W/t = (delta E)/t
What is the unit for power?
Watt
J/s
What is a Joule in base units?
kg(m^2)/(s^2)
What’s the eqn for calc mechanical work without knowing displacement or forces?
W net = delta K
What is mechanical advantage?
the ratio of force input applied to machine to force output for machine
MA = F out/ F in
What is the efficiency eqn?
Efficiency = W out/ W in = [(load)(load distance)]/[(effort)(effort distance)]
define energy
the property that enables a system to enable to do something like do work
What is the zeroth Law of Thermodynamics?
In thermal systems, if a = b, and b = c, then a = c
Define temperature
Relative proportion of the average kinetic energy of the particles that make up the substance
How do you get K degrees from C degrees?
K = C + 273.15
What is the freezing point of water? Boiling point?
0 C (273.15 K) and 100 C (373.15 K) respectively
What is the 3rd Law of Thermodynamics?
the entropy of a perfectly organized crystal at 0 K is absolute zero
What is the formula for changing Celcius to Farenheit?
F = 9/5 (C) + 32
What is the eqn for linear thermal expansion? (used for thermometers or any rod shaped solids)
delta L = alpha(L)(delta T)
alpha is the coefficient of linear expansion of a specific material
What is the eqn for volumetric thermal expansion? (used for liquids and solids)
delta V = beta(V)(delta T)
beta is the coefficient of volumetric expansion of a specific material
Define isolated system
a system that is not capable of exchanging energy or matter with it’s surroundings
Define closed system
a system that can exchange energy, but not matter, with it’s surroundings
Define open system
a system that can exchange both energy and matter with it’s surroundings
What is a state function?
a thermodynamic property that is a function of the equilibrium state currently experienced, regardless of the path taken to get there
What are the 8 state functions?
pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, and entropy
What is a process function? What are 2 examples?
a thermodynamic property that is dependent on the path taken to get there
work and heat
What is the 1st Law of Thermodynamics?
The change in total energy of a system is equal to the heat transferred into the system minus the work done by the system
delta U = Q - W
What does a positive delta U mean in thermodynamics? What about a positive Q? What about a positive W?
+ U means temperature has increased
+Q means heat is flowing into the system
+ W means work is being done by the system on the surroundings
What is the 2nd Law of Thermodynamics?
Before equalibrium, objects in contact will experience heat transfer
How many joules are in a Calorie? How many BTU’s?
4184 J = 1000 cal = 1 Cal = 3.97BTU
Define conduction
direct transfer of heat through molecular collisions
Define convection
indirect transfer of heat through fluid flow (only liquids or gases)
Define radiation
the transfer of heat by electromagnetic waves (can be done through a vaccum)
What is specific heat?
the amount of energy required to heat 1 g of a substance 1 K or 1 C (same difference)
What is the specific heat equation?
q = sm(delta T)
What is the eqn for heat change during a phase change?
q = m(heat of transformation)
can’t use qsmAt because there is no temp change
Define an adiabatic process
a process where heat transfer is 0
Define an isothermal process
a process where temperature change = 0
define entropy
a measure of how widely dispersed the energy becomes at a certain temperature
What is the eqn for calculating entropy?
delta S = Qrev/T
Qrev is heat change in a reversible process
What are the units for entropy?
J/(mol*K)
Define an irreversible process
A process that does not spontaneously return to it’s previous state (also called a natural process)
Define a reversible process
A process that does spontaneously return to it’s previous state (also called an unnatural process because energy would have to be completely conserved in this process, which is not possible)
