Physics Flashcards
Intensity
Intensity refers to the amount of energy over area. for the same area, more energy is higher intensity and less energy is lower intensity
SI Base Unit: Length
Meter (m)
SI Base Unit: Mass
Kilogram (kg)
SI Base Unit: Time
Second (s)
SI Base Unit: Current
Ampere (A)
SI Base Unit: Substance
Mole (mol)
SI Base Unit: Temperature
Kelvin (K)
SI Base Unit: Luminous Intensity
Candela (cd)
SI Derived Units: Force
Newton (N) kg*m/s2
F = ma
SI Derived Units: Energy
Joule (J) kg*m2/s2
J = N*m
SI Derived Units: Power
Watt (W) kg*m2/s3
W = J/s
Vectors
magnitude & direction
ex: velocity, acceleration, displacement
denoted with v or v with arrow, magnitude is |v|
Scalars
magnitude only
ex: speed, distance, time
denotes with italics
Normal Force on Inclined plane
F = mgcos(theta)
Friction
Static Friction: Us is the coefficient of static friction, the object will start moving with force greater than coefficient* force applied
Kinetic Friction: Uk is coefficient of kinetic friction, fK = Uk*N
Static friction is always greater than Kinetic friction
Acceleration
delta v / delta t
Friction
Static Friction: Us is the coefficient of static friction, the object will start moving with force greater than coefficient* force applied
Kinetic Friction: Uk is the coefficient of kinetic friction, fK = Uk*N
Static friction is always greater than Kinetic friction
Newton’s First Law
A motion at rest has a net force of 0
Newton’s Second Law
Every action has an equal & opposite reaction
Linear Motion: “The Kinematics Equations”
- v = v0 + at
The final velocity is the initial velocity plus acceleration multiplied by time
MISSING x (displacement) - x = v0 * t + at2/2
The displacement is the initial velocity multiplied by time plus acceleration multiplied by time squared divided by two. The first part of the equation is what displacement would be without any acceleration
MISSING v (final velocity) - v2 = (v0)2 + 2ax
The final velocity squared is the initial velocity squared plus two times acceleration and displacement
MISSING t (time) - x = vt
The displacement is equal to the average velocity multiplied by time
MISSING a (acceleration)
Projectile Motion
You need to think about velocity in the x and y plane.
Vx = vcos(theta)
Vy = vsin(theta)
The vertical and horizontal velocity components are independent. The verticle decreases by 9.8 m/s2. The horizontal stays the same
Inclined plane
Force parallel to the plane: Fg(parallel) = mg*sin(theta)
Force perpendicular to the plane: Fg(perpendicular) = mg*cos(theta)
Circular Motion
The only force that can act in this was is centripetal force, where is always points towards the inside of the circle
Fc = mv2/radius
Mechanical Equilibrium
This is when all the forces cancel each other out, and you can draw a free-body diagram to make sure things cancel out
Rotational Motion (think seesaw)
Object moving around a fixed point, the fixed point if the fulcrum
Torque T = r * F = rFsin(theta), where r is the distance from the fulcrum and theta is the between the lever and force
Kinetic energy
kinetic energy is the energy of motion
The value is given by k=1/2mv2
Potential energy
energy related to the position in space
two types:
gravitational - U = mgh
m is for mass, g is 9.8m/s2, h is height in meters
elastic potential E (springs)
U = 1/2 * k * x2 where x is displacement from equilibrium, k is the spring constant
Total Mechanical Energy
(E) = KE + PE
Conservative Forces
The total mechanical energy remains the same, so there is no change in the total mechanical energy
Nonconservative energy
When there are forces like friction or heat, energy can get lost in a system
Work
Energy transfers from one system to another through movement
W = Fd = Fdcos(theta)
The cos theta term is there when the work applied is not linear to the movement. Think applying a diagonal pressure to a 1 kg box on a flat surface
Pressure and Volume with Work
Think of a piston, where changes in pressure or volume makes the lid more up or down
W = Pressure * Volume
Power
This is the amount of work over time. Think of cars and cell phone batteries.
P = W/t = change in energy / time
This is in Watts
Work Energy Theorem
Work is the change of energy, so it does mean that the change in KE is the final kinetic energy - initial kinetic energy
Mechanical Advantage: Simple Machines
Offers a mechanical advantage without electricity
Mechanical Advantage = Fout/Fin
Efficiency = Wout/Win = (load)(load distance)/(effort)(effort distance)
Examples:
Wedge
Lever
Pulley
Zeroth Law of Thermodynamics
transitive property in a thermal system. If a(object) = b(object) = c(object)
NO net heat flow
It can be contact across space or physical
Third law of Thermodynamics
absolute zero (0 K) has an entropy of zero with perfectly organized crystals, there is no thermal energy
Thermal Expansion
A change in length or volume due to temperature change. Think of gaps in a bridge for the size of the bridge to change
(delta) L = aL(delta) T
a is the coefficient of linear expansion
(delta) V = beta * V * (delta) T
applicable to both liquid and solid
beta = coefficient of volumetric expansion
V = volume
Systems
Systems vs. Surrounding
System Types:
Isolated = no transfer in matter or energy
Closed = transfers energy, but not matter
Open = transfers matter and energy
State function vs. Process function
process function is the method that a system for to its state, whereas a state function, is when variables do not depend on the path taken
Process functions:
Heat (Q)
Work (W)
State functions: PaPa HUGS TV
Pressure (P)
Density (p)
Enthalpy (H)
Internal Energy (U)
Gibbs Free Energy (G)
Entropy (S)
Temperature (T)
Volume (V)
First Law of Thermodynamics
The change in energy is heat minus work
(delta) E = Q - W
Second Law of Thermodynamics
Uneven temperature will cause heat to transfer between objects until it reaches thermal equilibrium, generally means that energy will continue to move until an equilibrium is met, endorses Entropy (S)
Heat Transfers:
Conduction
Convection
Radiation
Specific Heat (c)
Property that is intrinsic to a material that is the amount of energy that is needed to increase 1 gram of substance by 1 degree
cal/gK or J/gK
Isothermal
Constant temperature, so delta E is 0
Q = W
Adiabatic
No heat change, so Q is 0
(delta) E = -W
Isobaric
Constant pressure
Isovolumetric
No volume change, so W = 0,
(delta) E = Q
Entropy
measure of the spontaneous dispersal of energy at a specific temperature
S = Q/T
Greater than zero is SPONTANEOUS - INCREASE in entropy
Fluids
Weak-to-shear (tangential) forces
density (rho) = m/v = kg/m3 = g/cm3
Specific gravity
Comparing the density to the density of water
SG = density / 1 g/cm3
Pressure
This is the amount of force over area in Pascals Pa
1.013X105 Pa = 760 mmHg = 760 Torr = 1atm
Absolute pressure
the total amount of pressure on an fluid at any given time
Atmospheric pressure
the amount of pressure from the atmosphere
Hydrostatic pressure
the amount of pressure from being submerged in a fluid not air
P = P0 +rho *gh
Gauge pressure
all of the pressure without the atmospheric pressure
Archimedes’ Principle
Displacement of a liquid depending on the volume that is placed in water
F (buoyancy) = density (fluid) * V (submerged) * g
F (buoyancy) = F (gravity)
Molecular forces in liquids: surface tension = cohesion; meniscus = adhesion
Viscosity
(n) resistance to flow
Pa*s
Laminar flow
orderly and predictable
Turbulent flow
chaotic flow because velocity is too high to remain laminar
Poiseulle’s Law
the radius is to the fourth, so any changes is significant changes
Bernoulli’s Principle
The metrics at one point of the fluid will be the same at another point of the fluid
Dynamic pressure: 1/2 * density * v2
Static pressure = P + density * g * h
You would add the dynamic and status pressure together and equate to the dynamic and static pressure at another point
Unit Charge
1 unit charge = 1.6 x 10 -19 Coulombs = e
Coulomb’s Law
this is the electrostatic force Fe between 2 charges:
Fe = (k * q1 * q2)/ r2
k = 8.99 x109 Nm2/c2
Electric Potential Energy
E = kQq/r
This is in Nm or Joules
This is the work required to move a charge there from infinity
Electric Potential
sounds similar to Electric Potential Energy, right, where is kinda is but not. This is the potential for only the electric field, so there is no one particle or two particles. This is in Volts or Joules/Coulomb.
V = E/q = kQ/r
Voltage is the potential difference between 2 points
Dipole moment
instead of one source charge, there is 2, so makes the field more interesting
Magnetic Field
In an electrical field where the charges are examined prior to moving, the magnetic field is what is created when the charges do move.
The SI unit is T (tesla) (Ns/mC)
1 G (gauss) is 10-4 T
Diamagnetic substance
-no unpaired electrons
-has no magnetic field
-doesn’t interact with magnetic fields
-hydrocarbons, organic materials
Paramagnetic substance
-has unpaired electrons
-interacts weakly with magnetic forces
-ex: oxygen, gold
Ferromagnetic substance
-interacts strongly
-ex: iron
Current
The movement of positive charges; is a measurement of conductivity (siemens, S, 1/(omega)). Resistance is the opposite of current. How much charge is moving in a time
Two Types of Conductivity:
Metallic Conductivity - sea of electrons, think metals
Electrolyte Conductivity - concentration based, think sodium, chlorine
Types of Current:
Direct
Alternating
Electron motive force
A type of potential difference, which is in voltage
Kirchoff’s Junction Rule
The amount of the current going into the junction is the same as the ones that is leaving the junction
Kirchoff’s Loop Rule
All circuits will be loops. The whole loop has to add to 0 V
Resistance
This is rho, that is resistivity, which is essentially the strength of a filter given a material.
R = (rho * L)/ A
rho = resistivity
L = Length
A = cross-section area
Ohm’s Law
I = V / R
I = Current
V = Voltage
R = Resistance
Power in circuits
We typically think about power in the context of doing something, but with circuits, we think about it as the power dissipated by the resistor
Typical:
P = W/t = change in E / t
Circuits:
P = IR = I^2 * R = V^2/R
Capacitance
The ability to hold a charge
C = Q/V in farad (C/V)
Capacitor
A material that has capacitance. Not to be confused with a battery, capacitors do not have energy on their own and can only hold a charge for a certain amount of time. A capacitor needs to be charged by a battery.
C = (epsilon)0 * A/d
C = capacitance
Epsilon 0 = E not, constant, 8.85 x 10^-12
A = Area
d = distance between plates
Meters
ammeters - measures current in amps, circuit on
voltmeter - measures voltage drops in volts, circuit on
ohmmeter - measures resistance in ohms, circuit off
General Wave Characteristics
MCAT only cares about sinusoidal waves, smooth periodic waves
Types:
Transverse wave - particle movement is perpendicular to the movement. Ex: electromagnetic waves, microwaves, lights
Longitudinal waves - particles move parallel to the propagation of the wave. Ex: sound waves
Propagation speed = v = frequency * wavelength
Angular frequency (think springs and pendulums (harmonic motion)) = w = 2 * pi * f = radians/ second
Principle of superposition
displacement of the resultant wave at any point is the sum of displacement of two interacting waves
Destructive interference
two waves that cancel out each other
Constructive interference
two waves that amplify each other
Sound production
Mechanical disturbance of particles in a material along the sound wave’s direction of movement (propagation)
Speed of sound = v = sqrt (B/rho)
Doppler Effect
(applies to all waves) the difference between the actual frequency of the sound and the perceived frequency when the sound and the sound detector are moving relative to one another
Attenuation (damping)
The presence of a nonconservative force causes the system to decrease in amplitude during each oscillation
Harmonic
number of half-wavelengths of this standing wave supported by the string
Harmonic Series: for Closed/Closed pipe
wavelength = 2L/n
Length of string/pipe
n = number of nodes
Ultrasound
high-frequency sound waves outside the range of human hearing to compare the relative densities of tissues in the body
Doppler Ultrasound
determine the flow of blood within the body by detecting the frequency shift that is associated with movement toward or away from the receiver
Electromagnetic Spectrum
These are transverse waves. The speed of light is 3X10^8 m/s, which is denoted as c.
c= frequency * wavelength
Rectilinear propagation
goes in a straight line when in a homogenous medium
Law of Reflection
The angle that light hits the surface is equal to the angle of the reflection based on the normal straight up line
Plane Mirror Images
Real-light converges where the image appears and can be projected to a screen
Virtual- converges somewhere else, looks like its somewhere where it is not
Spherical Mirror
center of curvature C
radius of curvature r
half of the radius is the focal length
o is the object distance, WILL ALWAYS BE POSITIVE
i is the image distance
concave from the inside - converging
convex on the outside - diverging, will only ever form virtual, upright, and reduced images
1/f = 1/o + 1/i = 2/r
i > 0 real image
i < 0 virtual image
Magnification
m = -i/o
if it is positive, then the image is upright
if it is negative, then the image is inverted
Refraction
When light goes into a different medium and therefore reduces speed
n = c/v
n = index of refraction
c = speed of light
v = speed in medium
Snell’s Law
Defines the refraction in changing mediums
n1sin(theta1) = n2sin(theta2)
n1<n2 = towards normal
n1>n2 = away from normal
Total Internal Reflection
For this case, n1 must be greater than n2 and the critical angle must be less than 90 degrees
Critical angle - the point where the reflection brings the ray back within itself
Lenses
These operate under refracting light, unlike mirrors that work under reflecting light. They have 2 different surfaces.
Two types -
thin spherical lens (important for MCAT), where the thickness of the lens is negligible, the same snells law, real and virtual are opposite, sign for convex and concave are opposite
real lenses (not important for MCAT) lensmaker’s equation
Myopia
-Near-sightedness
-Caused by the rays of light converging too early, because the lens is too strong
-Want a diverging lens or a concave lens
Hyperopia
-Far-sightedness
-Caused by the rays of light converging way to far, so it does not hit the retina
-Wants a converging lens or a convex lens
Power in lenses
Think about power of reading glass at a drug store, usually negative, because its mostly for nearsightedness, which needs diverging lenses
Power = 1/f in diopters (1/m)
Spherical aberration
lenses aren’t perfect and sometimes the rays don’t converge at the same spot, makes the image blurry
Dispersion
When the light goes through a lens, and the colors can separate, chromatic aberration
Diffraction - not tested often
The process in which a beam of light is spread out as a result of passing through a narrow hole.
Single-slit:
asin(theta) = n*wavelength
a = slit width
theta = from slit to dark spot
n = fringe #
Double-slit:
dsin(theta) = (n +1/2)* wavelength
d = distance between two slits
theta = from midpoint of 2 slits
Diffraction grading - formed when there are more than 2 slits
Polarization
Can manipulate the waveform of the light, by either linear or circular.
The application of the MCAT is to deal with stereoisomers in organic chemistry. The idea is that you want to hit the center of the stereoisomer with linearly polarized light to see the light that comes back out. You would be able to see the angle of reflection, where it shows if the stereoisomer is chiral and the specific rotation of the stereoisomer.
The Photoelectric Effect
When high frequency light strikes on a metal, then the metal will emit an electron, electrons that were emitted will produce a charge flow. The incident frequency must be larger than the threshold frequency
Threshold frequency (fT)
the minimum amount of frequency that will result in emitting electrons (all or nothing)
Photon
light quanta that light consists of, which is proportional to the frequency of light
Energy of a photon:
E = hf
h = Planck’s constant 6.626 x 10-34 J
f = frequency
Work function is the minimum energy required to eject an electron, so if you remove this from the initial incident energy, you can find the leftover energy
Absorption
absorb precisely enough energy to jump between orbits
Emissions
When the electron falls from higher energy level to lower energy level, while emitting a photon (the light energy is equivalent to the energy difference between the two orbits)
Infrared (IR) spectroscopy
determine chemical structure (each bond emits different wavelength)
UV-Vis spectroscopy
examine the absorption of light invisible and UV range
Fluorescence
the excitement of fluorescence substance with UV radiation, which causes it to glow with visible light
Mass defect
The phenomenon that the actual mass of the nucleus is slightly less than the sum of all the protons and neutrons (excluding hydrogen). This is due to some matter being converted into energy.
E = mc2
m = amount of mass missing
E = nuclear binding energy
Fusion
a small nuclei combine to form a large nucleus (example sun)
Fission
a large nucleus splits into smaller nuclei (example: nuclear power plants), will be written in isotopic notation, can cause chain reactions of fission
Alpha Decay
-Radioactive decay
-emits alpha particle, which is basically a helium atom
-atomic number = -2 (two protons)
-mass number = -4 (two protons, two neutrons)
Beta-negative decay
-Radioactive decay
-emits an electron by taking a neutron and making it a proton
-atomic number = +1
-mass number same
Beta-positive decay
-Radioactive decay
-emits a positron, by taking a proton into a neutron
-atomic number = -1
-mass number same
Gamma decay
-Radioactive decay
-emits only energy
-atomic number and mass number same
Electron capture
-Radioactive decay
-electron is taken from the surrounding
-atomic number = -1
-mass number same
Half-life
the time is takes for half of the sample to decay, exponential decay
The resistance of an object acting as a resistor is directly proportional to its:
resistivity and length
