Physics Flashcards
1 Å = ____ m
1 Å = 10-10 m
Prefix: giga
109 (G)
Prefix: mega
106 (M)
prefix: kilo
103 (k)
prefix: nano
10-9 (n)
prefix: pico
10-12 (p)
log(mn)=?
log(mn)=(n)log(m)
velocity
v=dx/dt
acceleration
a=dv/dt
Kinematic Equations
- vf=vi+at
- d=vit+½at2
- vf2=vi2+2ad
- vavg=½(vi+vf)
- d=vavgt=½(vi+vf)t
Weight
weight=mg
Newton’s Laws
- F=ma
- ΣF=ma
- FB=-FA
Gravitational Force Equation
F=(Gm1m2)/r2
Torque
τ=rFsinθ
- clockwise=neg
- r=distance between fulcrum and point of application
Uniform Circular Motion
F=(mv2)/r
Forces on Inclined Plane
Static friction
- between surface and stationary object
- 0≤fs≤μsFN
- fs,max> fk
Kinetic Friction
- Between sliding object and surface
- fk=μkFN
- less than static friction
Kinetic Energy
KE=½mv2
Types of potential energy
- Gravitational
- Electrical
- Mechanical
Potential Energy
U=mgh
First Law of Thermodynamics
Energy is never created or destroyed
What types of forces are conservative?
Gravitational and Electrostatic
Work
W=Fdcosθ
(J)
Power
P=W/t
(Watts)
Completely elastic collision
PE and KE conserved
Inelastic collisions
PE is conserved, KE is lost (to sound, light, heat, deformation)
Completely inelastic collisions
Objects stick together, PE is conserved
Work-Energy Theorem
Wnet=ΔKE
Momentum
p=mv
Impulse
I=FΔt=Δp=m(vf-vi)
What is mechanical advantage?
Work accomplished with reduced force via: inclinded plane, wedge, axel/wheel, lever, pulley, screw
Mechanical Advantage Eqn
Mech. Adv = Fout/Fin
Efficiency
Efficiency=Wout/Win
Center of Mass
x=(Σmixi)/(Σmi)
Density
ρ=m/v
Density of water
ρH2O=1g/mL=1kg/L
Pressure
P=F/A
Specific Gravity
SG=ρ/ρ<span>H2O</span>
Buoyant Force
FB=weight displaced
FB=(ρfluid)(Vsubmerged)(g)
Stress
σ=F/A
Strain
ε=ΔL/Lo
Young’s Modulus
Y=stress/strain
Y=σ/ε
Pascal’s Law
If you apply pressure on a liquid, the pressure is transmitted equally to all parts of the liquid.
Gauge pressure
P=ρgh
Absolute Pressure
P=ρgh+Patm
Continuity Equation
Q=AV=dV/dt
Q=A(dL/dt)
Bernoulli’s Equation
P + ½ρv2 + ρgh = constant
Thermal Expansion Equation
ΔL = αL0ΔT
What is adhesion?
Attraction of liquid molecules to another substance
What is viscosity?
- Resistance of a fluid to flow
- Ideal fluid is inviscid
critical velocity
vc=(Re*η)/(ρ*D)
- η=viscosity
- Re=Reynolds #
Bulk Modulus
B=(F/A)/(ΔV/V)
What is simple harmonic motion?
Periodic motion, particle oscillates about equilibrium, has a linear restoring force
Force of a spring? (Hooke’s Law)
F=-kx
Angular frequency of a spring?
ω=2πf (Hz)
Equation for spring displacement
x=Asin(ωt)
Kinetic and Potential Energy of a spring
KE=½mv2
U=½kx2
Force on a pendulum
F=-mgsin(θ)
Angular frequency of a pendulum
Longditudinal wave
Particles oscillate along direction of travel of the wave motion
Transverse wave
Particles oscillate perpendicular to energy
(ex. light, electromagnetic)
velocity of a wave
v=fλ
wave number
k=2π/λ
period related to frequency
T=1/f
2πf=ω
Standing waves
- f is constant, amplitude changes, nodes at rest
Natural frequency
- f at which object vibrates when disturbed
What is noise?
Natural frequencies are multiples but not whole # multiples
What is forced oscillation?
Periodically varying force applied to a system
Sound waves
- longditudinal
- can’t travel through a vacuum
- speed inversely proportional to (density)½
- Audible: 20-20,000 Hz
- Ultrasonic: > 20,000 Hz
- Infrasonic: < 20 Hz
Equation for sound intensity
I=P/A
(W/m2)
Equation for Sound Level
β=10log(I/Io)
[dB]
What parameter of a wave is associated with energy?
Amplitude
(Greater amplitude = greater energy)
(Higher amplitude = higher intensity)
What is resonance?
- Resonance is when things oscillate at its maximum amplitude.
- Resonance occurs at resonance frequencies.
Resonance of Standing Waves
λ=2L/n
Resonance in Open Pipes
λ=2L/n
Resonance in Closed Pipes
λ=4L/n
Dopper equation
fo=fs(v±vo)/(v±vs)
- vo is positive when observer moves towards source
- vs is negative when source is moving towards observer
What is a conductor?
Materials in which charges can move freely.
(ex. metal)
What is an insulator?
Insulators are materials in which charges can not move freely.
Coulomb’s law?
F=kq1q2/r2
(k=9E9 Nm2/C2)
Direction of an electric field?
Electric field goes from positive to negative
Unit: N/C
Electric field between a capacitor?
Electric field for wires?
Radially perpendicular to the wire
Absolute potential (V)
V=kq/r
V=U/qo
- V is absolute potential caused by q, or experienced by q0
- U is elec. potential energy posessed by q0
- Unit: Volts (V) = J/C
Potential Difference (ΔV)
ΔV=VB-VA
What are equipotential lines?
- Places where the potential is the same
- Always perpendicular to the electric field lines
What is a dipole?
- A positive charge and a negative charge separated by some distance
- In an electric field, it will align itself with electric field
Electrostatic Induction
- Where a charged object induces the movement/redistribution of charges in another object
- Static- charged species polarizes non-charged species by being there
- ex. comb rubbed against fur- pick up paper with comb
Gauss’s Law
ΦE=EAcosθ
ΦE=q/ε0
- ΦE = electric flux
- E = electric field
- θ = angle between field and normal of the area
- ε0 is the permitivity of free space
Faraday cage
Electric field inside a closed conducting cage is zero
(Charges on the conducting cage will rearrange to cancel out any external field)
What is the magnetic field?
- B
- Exists in a region of space if a moving charge experiences a force due to its motion in that region
- Unit: Tesla (T) or (N*s)/(m*C)
Equation for force on a charge moving in magnetic field
F=qVBsinθ
(RHR: thumb is direction of +q, fingers is direction of B, palm is F)
Current-carrying wire
F=iLBsinθ
- i = current
- L = length of wire
- Currens is direction of moving positive charge
- Two wires attract eachother if current is in same direction
- Two wires repel eachother if current is in opposite directions
Speed of light in a vacuum
c=3x108 m/s
Does light change speed in another medium?
Yes, light slows down when it travels in another medium
Equatino for index of refraction
n=c/v
Radiation of oscillating electric and magnetic fields are _____ to each other and to the ____.
Radiation of oscillating electric and magnetic fields are mutually perpendicular to each other and to the propagation direction.
Lower frequency waves have ____ wavelengths, and ____ energy.
Lower frequency waves have longer wavelengths, and less energy.
Radio waves
causes electronic oscillations in the antenna
Microwaves
cause molecular rotation
Infrared
Causes molecular vibration
Visible light…
Can excite electrons to orbits of higher energy.
Ranges from 400-700 nm.
400nm=violet, 700nm=red
Ultraviolet light
Can break bonds and excite electrons so much as to eject them, which is why UV is considered ionizing radiation
X-rays
Ionizing radiation, photoelectric effect
Types of waves from low frequency to high frequency
Lower Frequency, Longer wavelength, less energy
Radio
Microwave
Infrared
Visible
UV
X-ray
Gamma rays
Higher Frequency, Shorter Wavelength, More Energy
What conditions must hold for interference of light waves to occur?
- interfering light sources must be coherent (maintain same phase relationship)
- Light from 2 slits in Young’s double slit experiment are coherent
- Light source must be monochromatic (of single color/wavelength)
Young’s Double Slit Experiment (Include equations)
dsinθ=mλ
- Bright bands at m=0, +/-1, +/-2 …
- Dark bands at m= +/-0.5, +/- 1.5…
Thin films
- Thin films provide a means for interference to occur
- Light reflecting off the outer and inner boundary of a thin film interfere with eachother
- Film of oil on water appears like a swirly rainbow
Diffraction Grating
- Diffraction= light spreads out after passing through the slit, instead of going in a straight path
- Diffraction grating = a slap with many slits close together
- Bright and dark bands occur at same locations
Single Slit
- Light through a single slit has a central bright band and maximas and minimas
- The equation is different: asinθ=mλ (a= width slit)
Double slit vs Diffraction Grating vs. Single Slit
What happens to light shining through a pin hole?
Appears as a diffractino pattern of circular bright and dark bands, with a central bright band.
What happens to light shining past an opaque boundary?
Fringes of bright and dark bands appear above the boundary.
What happens to light shining past a penny?
Central bright spot, patterns of dark and bright rings.
What is unpolarized light?
Light with electric field oscillating in many planes
What is polarized light?
Light with electric field oscillating in only one plane
What is an optically active molecule?
Can rotate polarized light clockwise or counterclockwise
What is a red shift?
frequency decreases
(observer and source move away from eachother)
What is a blue shift?
Frequency increases
(source and observe moving towards each other)
What is a laser?
- Light Amplification by Stimulated Emission of Radiation
- Normal light emission = spontaneous
- Laser emission = stimulated emission
What is reflection?
- θi=θr
- mirrors completely reflect light
- Partial reflection when changing medium
Snell’s Law
n1sinθ1=n2sinθ2
Refraction
What is dispersion?
Dispersion is the change of index of refraction with wavelength
Does red or blue light refract more in a prism?
Blue light refracts mroe than red light in a prism.
Total internal reflection
- going from medium of high n to low n
- angle of incidence > critical angle
- Find the critical angle by:
- n1sinθc = n2sin90°
- n1 > n2
θc = critical angle
Concave mirror
Convex mirror
_____ mirrors focus light, so it’s converging.
_____ mirrors can’t focus light, so its diverging.
**concave **mirrors focus light, so it’s converging.
**convex **mirrors can’t focus light, so its diverging.
Focal length = ?
f=r/2
Converging mirrors have ____ focal length.
Diverging mirrors have ____ focal length.
Converging mirrors have positive focal length.
Diverging mirrors have negative focal length.
Mirror equation
(1/p) + (1/q) = 1/f
(1/o) + (1/i) = 1/f
- p is always positive
If q is positive, the image is ____.
If q is positive, the image is real.
For mirrors, real images are ____ the mirror.
For lenses, real images are ____ the mirror.
For mirrors, real images are in front of the mirror.
For lenses, real images are behind the mirror.
Focal length (f) is positive when the mirror/lens is _____.
This is when the mirror is ____ or the lens is ____.
Focal length (f) is positive when the mirror/lens is converging.
This is when the mirror is concave or the lens is convex.
Equation for magnification
M=i/o
Real vs. Virtual images
- Real images are inverted and can be cast on a screen
- Virtual images are always erect and can’t be cast on a screen.
For concave mirrors, real images, (positive q) are formed _______ the mirror.
For concave mirrors, real images, (positive q) are formed in front of the mirror.
For convex mirrors, images are always _______.
For convex mirrors, images are always virtual. (negative q)
_______ mirrors and lenses can never form real images.
Diverging mirrors and lenses (convex mirrors and concave lenses can never form real images.
Convex lenses are the same as _____ mirrors, both are _____. Except…
Convex lenses are the same as concave mirrors, both are converging.
Except:
- Real images are on the opposite side of the lens as the object because light travels through the lens and can focus on a screen behind the lens.
- Virtual images are on the same side of the lens as the object.
Concave lenses are the same as ____ mirrors (both are ____).
Except for…
Concave lenses are the same as convex mirrors (both are diverging).
Except:
- A virtual image formed by the lens is on the same side as the object because light can’t focus in front of a lens and be cast on a screen.
Converging lens is ____.
Converging lens is convex.
Is the focal length for a converging lens positive or negative?
positive
Is the focal length for a diverging lens positive or negative?
Negative
Diverging lens is _____.
Diverging lens is concave.
Formula for lens strength or lens power
P=1/f
(P in diopters)
Spherical aberrations
Not all light will focus at the focal point
Chromic aberration
Blue light gets refracted more than red light, so different colors focus differently.
Glasses are ____ for near-sightedness, and _____ for far-sightedness.
- Diverging (concave) for near-sightedness
- Converging (convex) for far-sightedness
What is the Bohr model?
- Electron orbits the pos nucleus
- Electrostatic attraction pulls electron to nucleus
- Electron orbits at high speed to prevent crashing into nucleus
- electron orbits at different energy levels (n)
- Higher energy level = larger radius
What happens when an electron transitions from a higher energy level to lower energy level?
It emits electromagnetic radiation. Emission spectrum of hydrogen consists of sharp, distinct lines.
Equation for energy levels of a hydrogen electron
E=-13.6eV/n2
(E is energy, n is energy level)
(All energies are negative- energy contributes to the stability of the system)
More negative energy of an electron means…
it is less stable in orbit and it is easier to knock out the electron
What is the highest energy of an electron?
0 eV, no binding energy, the electron dissociates
General equation for energy of an electron
Z is the atomic number. (Higher Z values give more negative, and more stable energies)
What is the Rydberg formula that gives the wavelength of emitted or absorbed radiation?
R is rydberg constant, nf and ni are final and initial energy levels
Energy of emitted or absorbed radiation
E=hf=hv=hc/λ
Energy is emitted for transitions to lower or higher energy levels?
Energy is emitted for transitions to lower energy levels.
What is the atomic number?
Number of protons. What defines an element.
What defines an element?
Number of protons.
What is the atomic weight?
The weighted average of the atomic mass for all isotopes.
Atomic mass = ?
Atomic mass = number of protons + neutrons
What is the standard notaiton for an atom?
What is a neutron?
Neutral particles in the nucleus
What are protons?
Positive particles in the nucleus.
What are isotopes?
Things with same # protons, different # neutrons.
What is a nucleon?
proton or neutron
T or F: Isotpes have similar chemical properties but different stabilities.
True
What force binds nucleons together and contributes to binding energy?
strong force
What causes electromagnetic force in the nucleus?
Due to electrostatic repulsion between positively charged protons in the nucleus.
How does the nucleus stay together?
The strong force or nuclear force is much stronger than electromagnetic repulsion.
What is alpha decay?
Ejection of a helium nucleus at a relatively low speed.
In a nearsighted individual, the image of a distance object is focused in front of/behind the retina, requiring divergent/convergent lens correction.
In a nearsighted (myopic) individual, the image of a distance object is focused in front of the retina, requiring divergent lens correction.
- Nearsighted person cannot clearly see objects far away
- Nearsighted eye has a shorter focal length
Equation for Specific Gravity
SG=ρsample/ρh2o
Avogadro’s number?
6.02x1023
Mechanical waves in a medium such as water function to transport:
a. matter only
b. energy only
c. matter and energy
d. neigher matter nor energy
Energy only.
Mechanical waves, such as sound and water waves, are a local oscillation of material. Only the energy propagates; the oscillating material does not move far from its initial equilibrium position.
What is beta decay?
Ejection of a high-speed electron/positron.
What is gamma decay?
Release of high energy electromagnetic wave.
What is an alpha particle?
Weakest form of radiation. Can be stopped by a sheet of paper. Essentially a low-speed helium nucleus.
What is a beta particle?
More energy than an alpha particle. Can be stopped by aluminum foil. High speed electron. (Or positron)
What is a gamma ray?
Strongest form of radiation. High Energy electromagnetic wave. Can be stopped by a hick layer of lead or concrete.
Equation for half life
When something is stable, does it decay?
No
The more unstable something is, the shorter/longer the half life
The more unstable something is, the shorter the half life
For exponential decay, a semi-log plot is a straight line with a ____ slope.
The semi-log plot intercepts the x-axis where the original y value is ___.
For exponential decay, a semi-log plot is a straight line with a negative slope.
The semi-log plot intercepts the x-axis where the original y value is 1.
What is fusion?
Two nuclei coming together.
(The sun works by fusion- hydrogen fuses to form helium)
Mnucleons=?
Mnucleons=Matom+binding energy/c2
Mnucleons>Matom because some is converted to binding energy
What is the equation for mass deficit?
ΔM=Mnucleons-Matom
(Also called mass defect)
Convert mass deficit into binding energy
Binding energy = ΔMc2
(Energy liberated is binding energy)
Equation for Energy with respect to mass and speed of light
E=mc2
Energy is liberated when mass is ___ during a reaction.
Energy is absorbed when mass is ___ during a reaction.
Energy is liberated when mass is lost during a reaction.
Energy is absorbed when mass is gained during a reaction.
Binding energy
- Nuclear binding energy (binds nucleons together)
- The Strong Force
Binding energy per nucleon is strongest for ___ and weakest for ___.
Strongest: Iron (Fe 56)
Weakest: Deuterium (2-nucleon isotope of hydrogen)
Equation for current?
Direction of current?
Unit?
I=ΔQ/Δt
Direction = flow of positive charge
Unit = C/s
What is emf?
- Electromotive force, a potential difference, unit: V
- Battery is a source of emf
- Battery w/o internal resistance has potential difference = EMF
- Battery w/ internal resistance: potential difference = EMF - voltage drop
What is terminal potential?
the voltage across the terminals of a battery.
Terminal potential = EMF -IRinternal
Ohm’s Law
V=IR
Resistors in SERIES
Iseries=I1=I2=I3
Vseries=V1+V2+V3
Resistors in Parallel
Vparallel=V1=V2=V3
Iparallel=I1+I2+I3
Resistivity
- ρ = RA/L
- Inverse of conductivity
- Greater resistivity = greater internal resistance
Resistance fo a wire
R = ρL/A
Capacitance
C=Q/V=εA/d
Equation for voltage across a capacitor
V=Ed
Energy of a charged capacitor
U = Q2/2C = ½QΔV = ½C(ΔV)2
Capacitors in series? in parallel?
Series:
1/Ceq = 1/C1 + 1/C2 + 1/C3
Parallel:
Ceq = C1+ C2 + C3
What is a dielectric?
Nonconducting material.
Inserting a dielectric between the plates of a capacitor increases the capacitance by either increasing Q, or decrasing V.
V = V0/κ
C = κC0
Charge a capacitor through a resistor
Discharge of a capacitor through a resistor
What is conductivity affected by?
- Electrolyte concentration
-
Temp
- conductivity decreases when metal temp increases, conductivity increases when semi-conductor temp increases
- Extremely low temperatures= superconductivity = 0 resistance
Conductivity (σ) is the inverse of ___.
Resistivity.
Power in circuits
P=IV=I2R
Root-mean-square current and voltage
Irms = Imax/√2 = 0.7 Imax
Vrms= Vmax/√2 = 0.7 Vmax
Vrms = IrmsR
