Physics Flashcards
what is kinetic energy? how is it calculated? and what is the SI unit?
K= 1/2mv^2
SI unit is J or Joules
what is Joule (J) equal to?
kg x m^2 divided by seconds squared
Kinetic energy is a function of the _______ of speed. If speed doubles, the kinetic energy will ________, assuming the mass is constant.
square
quadrupled
How is gravitational potential energy calculated?
U=mgh
U is potential energy, m is the mass in kg and h is the height
tripling the height or tripling the mass of the object, will do what to the gravitational potential energy?
increase it by a factor of 3
what is elastic potential energy? what is it determined or calculated with?
when springs are stretched or compressed from its equilibrium length, the spring has elastic PE
U= 1/2kx^2
k is the spring constant, x is the measure of displacement from equilibrium
how is total mechanical energy calculated?
E=U+K
U is potential energy and K is kinetic energy
what does the first law of thermodynamics account for?
energy can neither be created nor destroyed- it can only be transfered from onw form to another
what are conservative forces?
path dependent and do not dissipate energy
most commonly they have potential energy associated with them ex: gravtiational and electrostatic forces
what are examples or conservative forces? non conservative forces?
conservative forces: gravity and electrostatic forces. they conserve mechanical energy
nonconservative forces: friction and air restistance. they dissipate mechanical energy as thermal or chemical energy
what is work?
the process by which energy is transferred from one system to another
what forces are capable of doing work?
only forces parallel or antiparallel to the displacement vecotr will do work (that is transfer energy)
work and energy are not the same thing. work is the process by which a quantity of energy is moved from one system to another
when do we say that work was done by the gas and the work is positive?
when a gas expands
when do we say that work was done on the gas and the work is negative?
when a gas is compressed
how do you calculate the work done on or by a system?
by finding the area under the pressure-volume curve
If the volume stays constant as pressure changes then how much work is done?
no work is done because there is no area to calculate
what is the work done on a system in an isovolumetric or isochoric process?
no work is done because the volume is constant as pressure changes
If pressure remains constant as volume changes ( isobaric processes), then how is the area under the curve calculated?
the length of P and the width change in V so with isobaric processes where pressure is constant work is calculated as
W=P x change in V
what is Power? and what are the SI units for it?
a measure of the rate of energy consumption, transfer or transformation per unit time
P= W/t= change in E/t
SI unit is watt (W), which is equal to J/s
power can also be calculated in circuits, resistors and capacitors and it is known as electric power. what is the equation for electric power?
P= IV
I is current and V is electrical potential difference (voltage)
what is the relationship between work and energy?
there is a direct relationship between the work done by all the forces acting on an object and the change in kinetic energy of an object
when one calculates the change in kinetic energy, experieinced by an object, then what is the net work done on or by an object?
the same as the change in kinetic energy
how is the first law of thermodynamics expressed?
the change in systems internal energy (U) is equal to the heat transferred into the system (Q) minus the mechanical work done by the system (W)
change in U= Q - W
when is Q ( heat transferred into the system) positive? and when is it negative?
positive when heat flows into the system
negative when heat flows out of the system
when is W (work done by the system) positive and when is it negative?
positive when work is done by the system (expansion)
negative when work is done on the system (compression)
what does it mean when the change in internal energy is a positive value? when it is a negative value?
positive value: increasing temperature
negative value: decreasing temperature
what is Heat?
the process of energy transfer between two objects at different temperatures and will continue until the two objects come into thermal equilibrium at the same temperature
what is conduction?
the direct transfer of energy from molecule to molecule through molecular collisions. two things need to come in contact in order for energy to be transferred
what is convection?
the transfer of heat by the physical motion of a fluid over a material.
since it involves flow, only liquids and gases can transfer heat by these means
what is radiation?
the transfer of energy by electromagnetic waves. transfer of energy through a vacuum.
how can you determine the heat gained or lost by an object and the change in temperature of that object?
q=mc(delta)T
m is mass, c is specific heat, and delta T is change in temp in C or K
specific heat of water is 4.184 J/g x K
when do phase changes occur?
at a constant temperature and the temperature will not begin to change until all of the substance has been converted from one phase to the other
what are phase changes related to?
changes in potential energy
how do you calculate the amount of heat added or removed for a system experiencing a phase change?
q=mL
q is the amount of heat gained or lost, m is the mass of substance, L is the heat of transformation or latent heat of the substance
what is the corresponding heat of transformation with the phase change of liquid to solid or solid to liquid?
heat of fusion
what is the corresponding heat of transformation with a phase change from liquid to gas or gas to liquid?
heat of vaporization
what is an isothermal process? how does it relate to the equation of the first law of thermodynamics?
change in U = 0 (constant temperature so no change in internal energy)
first law reduces to Q=W
heat equals Work
What is an Adiabatic process? how does it relate to the first law of thermodynamics?
Q= 0 ( no heat exchange)
first law reduces to change in U = -W
what is an Isobaric process?
constant pressure
the normal equation is used: change in U = Q - W
what is an isovolumic process and how does it relate to the first law of thermodynamics?
no change in volume and therefore no work accomplished
also called isochoric
so the change in U= Q
How are the processes indicated on a Pressure-Volume graph?
- isobaric
- isothermal
- adiabatic
- isovolumic (isochoric)
isobaric: horizontal line
isothermal: less steep of a hyperbola
adiabatic: more steep of a hyperbola
Isovolumic: vertical line
***pressure is on the Y axis and Volume is on the X axis
what is density and how is it calculated? what are the SI units for it?
what is the density for water?
p=m/V
p(rho) represents density, m is mass and V is volume
kg/m^3, g/mL, or g/cm^3
waters density is 1 g/cm^3
how is the weight of any volume of a substance with a known density calculated?
by multiplying the substance’s density by it’s volume and its acceleration due to gravity
what is specific gravity and how is it calculated?
when the density of a fluid s compared to that od pure water at 1 atm and 4 degrees C
calculated by p(rho) / 1g/cm^3
what is pressure? how is it calculated and what is the SI unit for it?
pressure is the ratio of the force per unit area
P=F/A
SI unit is the pascal (Pa) which is equivalent to 1 N/m^2
what is absolute (hydrostatic) pressure? and what is the equation for it?
the total pressure that is exerted on an object that is submerged in a fluid. (could be either iquids or gases)
P=Po + p(rho) x g x z
P is absolute pressure, Po is pressure at the surface, p(rho) is the density of the fluid, g is acceleration due to gravity, z is the depth of the object
what is gauge pressure?
the amount of pressure in a closed space above and beyond atmoshperic pressure
Pgauge= P - Patm or absolute pressure - atmospheric pressure
when applying pascals principles, what is important to remember when there is a large area? small area?
the larger the area, the larger the force, although this force will be exerted through a smaller distance
a small force over a small area through a large distance to generate a much larger force over a large area through a smaller distance
what is the equation for work as the product of constant pressure and volume change as in an isobaric process?
W=P x (delta V)= F1d1=F2d2
how is the buoyant force magnitude calculated?
density of fluid times the Volume submerged times gravity.
or
density of fluid times the Volume of fluid displaced time gravity
when will an object float?
if its average density is less than the average density of the fluid it is immersed in
what does surface tension result from?
cohesion, the attractive force that a molecule of liquid feels toward other molecules of the same liquid
cohesion occurs btwn molecules with the same properties
when does a convex (backwards) meniscus occur and when does a concave meniscus occur?
backwards: when cohesive forces are greater than adhesive forces
concave: when adhesive forces are greater than cohesive forces
what is the SI unit for viscosity? those with lower viscosities behave more like _______
Pascal x sec (Pa x s or Nxs/m^2)
ideal fluids which have no viscosity and have very little resistance to flow. the more viscous something is the more energy is lost during flow
what is laminar flow?
smooth and orderly and is often modeled as layers of fluid that flow parallel to each other
During laminar flow, what is the relationship between pressure and gradient?
a very slight change in radius has a significant effect on the pressure gradient
what is turbulent flow?
rough and disorderly and can arise when the speed of the fluid exceeds a certain critical speed.
what is the flow rate for a closed system?
the volume per unit time is constant for a closed system and is INDEPENDENT of changes in cross-sectional area
what is linear speed and how is it related to the flow rate?
linear speed is a measure of the linear displacement of fluid particles in a given amount of time
Linear speed will increase with decreasing cross sectional area but flow rate is constant regardless of the cross-sectional area
the product of linear speed and cross-sectional area is equal to the flow rate
what does the continuity equation say about fluids?
that they will flow more quickly through narrow passages and more slowly through wider ones.
*** flow rate is the same at all points but the linear speed can differ at all points dependingon the cross sectional area
Bernoulli’s equation can be related to what concept?
the conservation of energy. the parts are similar to kinetic energy calculations and potential energy calculations besides the fact that instead of mass, it has density in the equation.
the absolute pressure of the fluid + the KE of fluid 1 + the PE of fluid 1 = the absolute pressure of the fluid 2 + the KE of fluid 2 + the PE of fluid 2
*** PE is mgh but in this equation it is p(rho)gh
what is dynamic pressure?
1/2p(rho)v^2
the pressure associated with the movement of a fluid (ex: kinetic energy of a fluid) just remember that density is m/V. so it really is kinetic energy divided by volume
Pressure has many units, what are some examples
N/m^2 and J/m^3 and Pa and torr and mmHg and atm
what is static pressure the same concept as?
absolute pressure although h is used to imply height while z was used to imply depth
P + p(rho)gh
what is the Bernolli equation basically stating?
that the more energy dedicated toward fluid movement means less energy dedicated toward static fluid pressure.
and inverse is true too. the less movement, the more static pressure
As blood flows away from the heart, each vessel has a progressively higher resistance until the capillaries, however the total resistance of the system decreases, how does this happen?
the total resistance of the system decreases because the increased number of vessels are in parallel with each other.
what does Coulomb’s law do?
quantify the magnitude of electrostatic force between two charges
Fe= kq1q2 divided by r^2
Fe is magnitude of electrostatic force, k is Coulmb’s constant, q1 and q2 are the magnitudes of the 2 charges and r is the distance between the two charges
As distance between the two charges is doubled, how has the force of attraction between them changed?
the force is reduced to 1/4th of what it was originally.
how is the electric field calculated?
electric fields are produced by the source of charges (Q). when a test charge (q) is placed in an electric field (E), it will experience and electrostatic force equal to qE
E=Fe/q= kQ/r^2
What is the SI unit for Magnetic field strength
tesla (T) 1 T= 1 N x s / m x C
what are diamagnetic materials?
made up of atoms with no unpaired electrons and that have no net magnetic field. These materials are slightly repelled by magnets.
wood, plastic, water, glass, and skin
what are paramagnetic materials?
have a net dipole moment
become weakly magnetized in the presence of an external magnetic field, aligning the magnetic dipoles of the material with the external field.
copper, aluminum, gold
What are ferromagnetic materials?
have unpaired electrons and permanent dipoles that are normally oriented randomly so that the material has no net magnetic dipole (similar to paramagnetic)
They become strongly magnetized when exposed to a magnetic field or under certain temperatures
Ni, Fe, Co
How is Current calculated? what are the SI units of it?
the amount of charge (Q) passing through a conductor per unit time (delta t)
I=Q/delta t
ampere (1 A= 1 C/s)
the amount of current that enters a junction point equals _________________
the sum of currents directed away from that point
what is the equation for resistance?
Resistance = resistivity x length divided by the cross-sectional area
what is the SI unit for resisitivity?
ohm-meter
what is the relationship between resistance and cross-sectional area of a resistor?
what about the relationship between resistance and length?
inversely proportional, if a resistor’s cross-sectional area is doubled, the resistance will be cut in half
if a resistor i doubled in length, it will also double its resistance
how does temperature affect resistance in conductors?
conductors have higher resistance at higher temperatures
what is Ohm’s law?
the basic law of electricity bc it states thatfor a given magnitude of resistance, the voltage drop across the reisistor will be proportional to the magnitude of current
And for a given resistance, the magnitude of the current will be proportional to the magnitude of the voltage impressed apon the circuit
V=IR
how is the voltage provided by a cell calculated?
the actual voltage supplied by a cell to a ciruit can be calculated by V= Ecell - ir
Ecell is the emf of the cell, i is the current through the cell and rint is the internal resistance
What is the Power of a resistor?
the rate at which energy is dissipated by a resistor
calculated by P=IV=I^2R= V^2/R
How is capacitance calculated?
capacitance of a parallel plate?
C=Q/V
SI unit is the farad (1F=1C/V)
capacitance of a parallel plate: C= 8.85x10^-12 F/m times (area of overlap of the two plates divided by the separation of the two plates
how is the magnitude of a uniform electric field calculated?
E=V/d
how is the Potential energy stored on a capacitor calculated?
U= 1/2CV^2
how are capacitance and voltage related?
inversely. increase in capacitance results in a decrease in voltage
What do Voltmeters do? Ammeters?
Voltmeters measure the voltage drop across two points in a circuit and need to be wired parallel between these two points in a circuit
Ammeters used to measure the current at some point within a circuit
what is the speed of sound fastest in and what is it slowest in?
the speed of sound is fastest in a solid with low density and slowest in a very dense gas
what is the normal range of human hearing?
20 Hz to 20,000 Hz
what are sound waves with frequencies below 20 Hz called? and what are sound waves with frequencies above 20,000 Hz called?
infrasonic
ultrasonic
what is intensity? what are the SI units of intensity? and how is it calculated?
the average rate of energy transfer per area across a surface that is perpendicular to the wave
SI units: watts per square meter (W/m^2)
I=P/A
I is intensity, P is power and A is area
how would you determine the power delivered across the tympanic membrane?
P = IA
how is intensity related to the amplitude of a sound wave
intensity is proportional to the square of the amplitude
therefore doubling the amplitude produces a sound wave that has 4 times the intensity
how is intensity related to the distance from the source of the sound wave?
Intensity is inversely proportional to the square of the distance from the source
what is the equation that relates a standing wave and the length of a string that supports it?
wavelength= 2L/n
n is a positive nonzero interger (1,2,3,4 etc) called the harmonic
what does the harmonic correspond to? what are the possible frequencies?
the harmonic corresponds to the number of half wavelengths supported by the string
f= nv/2L
n is harmonic and v is wave speed
for strings attached at both ends how do you determine which harmonic it is?
the number of antinodes (those that allow maximum osscillation) present will tell you.
1 antinode: first harmonic
2 antinodes: second harmonic
3 anti nodes: third harmonic
for open pipes, how do you determine which harmonic it is?
the number of nodes present
1 node: first harmonic (L= lambda/2)
2 nodes: second harmonic (L=lambda)
3 nodes: third harmonic (L=3lambda/2)
what is the equation that relates the wavelength of a standing wave and the length L of a closed pipe that supports it?
how is the harmonic given?
wavelength= 4L/n
n can only be odd integers harmonic is given by the number of quarter wavelengths supported by the pipe first harmonic: L= wavelength/4 second harmonic: L= 3wavelength/4 third harmonic: L= 5wavelength/4
what is the frequency of the standing wave in the closed pipe?
f= nv/4L
n can only be odd integers and v is the wave speed
what are standing waves?
produced by the constructive and destructive interference of two waves of the same frequencies traveling in opposite directions in the same space
what is destructive interference?
constructive interference?
destructive interference occurs when waves are exactly out of phase with each other. the amplitude of the resultant wave is equal to the difference in amplitude between the two interfering waves
constructive interference occurs when waves are exactly in phase with each other. the amplitude of the resultant wave is equal to the sum of the two interfering waves
what is snell’s law?
when light is in any medium besides a vacuum, its speed is less than c. For a given medium:
n=c/v
c is the speed of light in a vacuum, v is the speed of light in the medium and n is the index of refraction of the medium
according to snell’s law what happens when light enters a medium with a higher index of refraction (n2>n1)?
it bends toward the normal, angle two is less than angle one
according to snell’s law, what happens if the light travels into a medium where the index of refraction is smaller (n2
the light will bend away from the normal (theta 2 > theta 1)
when does total internal reflection occur?
what is the refracted angle equal to at the incident angle of theta c?
what happens at incident angles above 90 degrees?
as light moves from a medium with a higher refractive index to a medium with a lower one
equal to 90 degrees
total internal reflection occurs
what is reflection?
the reboundng of incident light waves at the boundary of a medium
what are plane mirrors and how do light rays reflect off of them? is a real or virtual image produced?
are flat reflective surfaces that neither cause convergence or divergence of reflected rays.
because the light does not reflect at all, plane mirrors always create VIRTUAL images.
What image is formed from a convex mirror regardless of the position of the object?
A virtual, upright, and reduced image
In a concave mirror, when an object is placed beyond the focal point (F), what image is produced?
Real, inverted, and magnified
In a concave mirror, when the object is placed at the focal point what happens to the image?
No image is formed because the rays are parallel to each other. Thus the image distance will be infinity
With a concave mirror, when the object is placed between the focal point and the mirror then the image produced will be ______
Virtual upright and magnified
Concave mirrors are also called ______
Convex mirrors are also called ________
Converging mirrors
Diverging mirrors
Angles in optics are always measured from the _______. A line drawn _________ to the boundary of the medium
Normal; perpendicular
If the image has a positive distance then it is a _______ image
If the image has a negative distance then it is a _______ image
Real
Virtual
What is magnification?
Magnification can determine if the image is upright or inverted. If the magnification is negative, the image is ________
If the magnification is positive, the image is ________
The ratio of the image distance to the object distance
Inverted
Upright
The absolute value of the magnification can determine whether the image is reduced or enlarged. If the absolute value of m is less than 1 then image is _______
If the absolute value of m is greater than 1 then image is _______
If the absolute value of m = 1 then the image is _______
reduced
enlarged
the same size as the object
The focal length of converging mirrors (and converging lenses) will always be ________
The focal length of diverging mirrors will always be ______
Positive
Negative
Concave mirrors and ______ lenses have similar properties and are both converging
Convex mirrors and ______ lenses are both diverging and therefore have similar properties
Convex
Concave
Image types with a single lens or mirror, assuming o (object is positive): inverted images are always \_\_\_\_\_\_\_\_\_\_
and Upright images are always ___________
real
virtual
what happens when light enters a medium with a higher index of refraction?
when light enters a medium with a lower index of refraction?
bends toward the normal
bends away from the normal
how is the power (P) of a lens determined?
P=1/f
f is the focal length
how do you correct farsightedness (hyperopia)
how do you correct nearsightedness (myopia)?
a lens that causes the convergence of light
a lens that causes divergence of light
what is dispersion? what are effects of it?
when various wavelengths of light separate from each other chromatic abberation (results in rainbow effect)
if theta is zero,
what is the sin of zero, cos of zero, and tan of 0?
sin 0 = 0
cos 0 = 1
tan 0 = 0
if theta is 30 degrees, what is the
sin of 30
cos of 30
tan of 30
sin 30 = 1/2
cos 30 = root3/2
tan 30= root3/3
if theta is 45 degrees, what is the
sin of 45
cos of 45
tan of 45
sin 45= root2/2
cos 45= root2/2
tan 45= 1
if theta is 60 degrees, what is the
sin of 60
cos of 60
tan of 60
sin 60= root3/2
cos 60= 1/2
tan 60 = root 3
if theta is 90, what is the
sin of 90
cos of 90
tan of 90
sin 90= 1
cos 90= 0
tan 90= undefined
if theta is 180, what is the
sin of 180
cos of 180
tan of 180
sin 180= 0
cos 180= -1
tan 180= 0
