physics flashcards 1
kinematics equations
vf2=vi2+2ax x=vit+½at2 v=vo+at vavg=(vo+v)/2 x=vt=((vo+v)/2)*t
Newton’s Laws
1st: Law of inertia - objects in motion (or at rest) will stay in motion (or at rest) unless acted on by a nonzero net force 2nd: F=ma 3rd: Fa=-Fb Every action has an equal and opposite reaction
Friction equations
force of friction opposes motion kinetic: ff=μkFN static fs<μsFN
Gravitation
two masses will exert an attractive force on one another inversely proportional to the square of the distance b/w them. F=(Gm1m2)/r2
mnemonic for trig values
sin0=√0/2=0 sin30=√1/2=½ sin45=√2/2 sin60=√3/2 sin90=√4/2=1 cos0=√4/2=1 cos30=√3/2 cos45=√2/2 cos60=√1/2=½ cos90=√0/2=0
centripetal motion
net force on an object at a constant speed on a circular path points toward center of circle Fc=(mv2)/r ac=v2/r
torque
always greatest at 90o to object trying to move τ=rFsinΘ units: N*m
Work
W=FdcosΘ units: N*m=Joules
Kinetic energy
KE=½mv2 units: J
Work energy theorem
Wnet=∆KE and W=∆PE
Gravitational potential energy
U=mgh units: J
Average Power
P=W/t = ∆E/∆t units: Watts
momentum
p=mv
types of collisions
elastic collisions: KE and momentum conserved inelastic collisions: KE not conserved, momentum conserved totally inelastic collisions: KE not conserved, momentum conserved
Impulse
force applied to an object over time I=∆p=Fav∆t units: N*s
Hooke’s Law
F=-kx x=displacement of spring from unstrained length k=proportionality constant units: N/m - = restoring force always opposite to displacement of spring amplitude is max displacement from equilibrium
period in SHM
time required to complete one cycle
angular frequency
ω=2π/t = 2πf=√(k/m) frequency at which object at mass m vibrates on a string units: radians
frequency
f=1/T units: Hz = 1/s the number of cycles of motion per second
Elastic Potential energy
-energy a spring has because of being stretched or compressed. -at max displacement from equilibrium, potential energy of spring is at max and KE is 0 PEelastic=½ kx2 units: J = kg*m2/s2
Total mechanical energy
½mv2+mgh+½kx2
angular frequency of pendulum
ω=2πf=√(g/L) L=length (m)
restoring force of pendulum
F=-mgsin
properties of electromagnetic waves
-transverse, can trave through vacuum -all move through vacuum at speed of light (c)=3.0*108 m/s
speed of electromagnetic waves
v=fλ
λ=wavelength (m)
Electromagnetic spectrum
longest wavelength, lowest frequency and energy:
radio waves, microwaves, infrared, visible (red (700 nm) -violet (400 nm)), ultra-violet, xrays, gamma rays -
shortest wavelength, highest frequency, highest energy
transverse vs. longitudinal waves
material transmitting the wave…
longitudinal - particles are parallel to the direction of motion (think slinky)
transverse - particles are perpendicular to the direction of motion (piece of string moving).
interference
- 2 waves of same frequency have different “phases” - one complete cycle = 360 or 21 radians - in phase if crest of one wave coincides with crest of the other - 90i out of phase - wave is ¼ wavelength ahead of other - 180i out of phase - wave is ¼ wavelength ahead of other
speed of a wave
v=f(lambda)=(angular frequency)/k=(lambda)/T
k=2π/(lambda) –> wavenumber
angular frequency =2πf=2π/T
constructive interference
2 crests of waves in phase meet at same point in space and the amplitude of the resulting wave is the sum of individual amplitudes
destructive interference
a crest and trough meet at the same point in space; amplittude of the resulting wave is difference of individual amplitudes - complete destructive when amplitudes are equal and 180 out of phase
charged particles
exert a force on one another. unlike charges attract, like charges repel
Coulomb’s Law
The electric force that charged objects exert on each other is called the electrostatic force. this depends on the amt. of charge and the distance between objects. the greater the chargers and the closer they are, the greater the force. Fe=k((q1q2)/r2) k=9*109 N*m2/C2 q1 and q2 = charges (C)
Electric Field
E=F/q0 units: N/C - the E at a point is the electrostatic force (F) experienced by a small test charge placed at that point divided by the charge itself - E is a vector, direction is the same as the direction of the force F on a positive test charge. opposite directions if negative test charge
Electric field produced around a point charge q
E=kq/r2 electric field lines point in direction positive charge would move pos - move away from neg - move towards
Electric Potential
- a positive charge accelerates from a region of higher potential (positive) to a region of lower potential (neg) and a neg. charge does the opposite. V=electric potential energy/q0= Wab/q0 = kq/r units: J/C = Volt Wab=work done to move charge from point A to point B
Electric Current
- flow of positive charge - opposite the actual movement of electrons (e- generally the charge carriers in a current) I=q/t unites: Ampere (A)
Ohm’s Law
V=IR V = voltage or potential drop across a piece of material I = the current through the material R = resistance
Electric Power
P=IV units: Watts
Resistors in series
same electric current through each device V=IRt RT =R1+R2+R3+…
Resistors in parallel
same voltage across each device V=IRP 1/RP=1/R1+1/R2+…
Capacitor
- stores electric charge - 2 conductors or any shape that are placed near each other w/out touching q=CV q=charge on each plate V= potential difference b/w the plates or Voltage C= capacitance units: C/V = farad (F)
parallel plate capacitors
C=(eoA)/d e0 = 8.85*10-12 F/m
Capacitors in parallel
q=CpV where Cp=C1+C2+… U=½ CpV2
Capacitors in series
q=CsV 1/Cs=1/C1+1/C2+1/C3+…
temp. and kinetic energy
temp of an object is directly proportional to the avg. kinetic energy of its constituents - temp is degree to which atoms and molecules in substance are agitated
thermal equilibrium
2 objects with different temperatures will, over time, reach the same temp if they are brought into contact.
linear thermal expansion
when a solid increases in temp. its length also increases L=LT L=length = coefficient of linear expansion units: (Ko)-1 T = temperature
volumetric thermal expansion
V=VT V= volume = coefficient of volumetric expansion = 3
zeroth law of thermodynamics
transitive property of thermal equilibrium. if a is in thermal equilibrium with b, and b is in thermal equilibrium with c, then a is in thermal equilibrium with c and when brought into contact, no heat will flow between them.
specific heat
-the amount of heat energy required to raise 1 kg of a substance by 1 degree C or 1K -a Calorie (C) is the amt. of heat required to raise 1 kg of water 1 oC Q=mcT Q=heat gained or lost by an object units: J
phase change heat equation
Q=mL L= heat of transformation of substance
sublimation
solid to gas
deposition
gas to solid
fusion
solid to liquid
freezing
liquid to solid
condensation
gas to liquid
vaporization
liquid to gas
units for pressure
1 atm =1.013*105 Pa= 760 torr = 760 mmHg
work on vs. in a system
- work done by a system - positive, internal energy of system decreases - work done on a system - negative, internal energy of system increases
work in thermo
W=PV P= pressure V = volume
1st law of thermodynamics
an increase in the total internal energy of a system is caused by transferring heat to the system or performing work on the system. the total internal energy of a system will decrease when heat is lost from the system or work is performed by the system. U=Q-W U = change in system’s internal energy Q = energy transferred through heat to the system W = work done by the system units: J
special cases of 1st law of thermodynamics
adiabatic (Q=0) — first law becomes: U=-W constant volume (W=0) — first law becomes: U=Q closed cycle (constant internal energy) (U=0) — first law becomes Q=W
2nd Law of thermodynamics
energy spontaneously disperses from being localized to becoming spread out if it is not hindered from doing so
entropy
measure of spontaneous dispersal of energy at a specific temp. – how much is it spread out or how widely dispersed is it? S=Q/T S=change in entropy units: J/K T= temp in K Q= heat gained or lost - entropy increases when energy is distributed into a system at a given temp. decreases when distributed out of a system - the entropy of the universe is always expanding because it is a closed system that is expanding
Magnetic field
created by any moving charge unit: Tesla (T) = 1 N*s/m*C
diamagnetic
atoms with no unpaired electrons and that have no net magnetic field. will be repelled by either pole of a bar magnet. “nonmagnetic” - ex. wood, skin, plastic
paramagnetic
“weakly magnetic” atoms have unpaired electrons. have a net magnetic moment dipole. atoms are usually randomly oriented so material doesn’t create a net magnetic field will become weakly magnetized in presence of external magnetic field will be attracted to the pole of a bar magnet
current carrying wires and mag. field
create a magnetic field. configuration of field depends on shape of wire
electric current
the flow of charge i=qt i = current units: Amps = C/s q= amt. of charge
mag. field of straight current carrying wire
B=i2r B = magnetic field units: T o=permeability fo free space = 1.26*10-6 T*m/A i=current r= distance from magnetic field to wire
right hand rule
to determine the direction of the field vectors right thumb points in the direction of the current, right hand fingers mimic the circular mag field lines curling around thumb fingers=direction of magnetic field lines and direction of B at any point ** works for straight line wire and circular loop wire**
mag. field of circular loop of current carrying wire
B=i2r B = magnetic field units: T o=permeability fo free space = 1.26*10-6 T*m/A i=current r= radius of circular loop magnitude of field at the center of the circular loop with radius r.
magnetic force on a moving charge
F=qvBsin units: N q=charge (include sign) v=velocity of charge B=magnetic field =smallest angle b/w any vector qv and B ** charge must have perpendicular component of velocity to experience force - if charge moving parallel or antiparallel to B vector - no mag force.
right hand rule for moving charge
right thumb in direction of qv - accounts for direction of velocity and sign of charge. if q is positive - thumb will point in direction of v, negatve=opposite. fingers point in direction of magnetic field palm faces in direction of magnetic force vector F
magnetism and circular motion
when a charged particule moves perpendicular to a constant, uniform mag. field, the resulting motion is circular with a constant speed in plane perpendicular to magnetic field. F=qvB=mv2/r changing the strength of the magnetic field will change radius of the circular pathway, but not the magnitude of charge’s velocity
Force of current carrying wire in magnetic field
F=iLBsin
right hand rule for current carrying wire in an external magnetic field
same as others, right-hand thumb points in direction of current/ fingers on right hand point in direction of b palm faces direction of magnetic force vector.
**capacitors added
parallel- increases overall capacitance - 1/CT=1/C1+1/C2+… (opposite resistance) series: CT=C1+C2+… total capacitance decreases in similar fashipn to the decrease in resistance for resistors in parap;;e Voltage is the sum of the individual voltages
dielectric materials
“insulation” when placed between capacitors, voltage across capacitors decreases. -shields the opposite charges from each other - capacitance of capacitor increases C’=KC
Intensity of sound
I=P/A units: W/m2
Sound level
=10logII. = sound level (decibels) Io= reference intensit at threshold of hearing= 1*10-12 W/m2
beat frequency
fbeat=f1-f2
wavelength of string and pipe vibration
=2Ln = wavelength L= length of string n= interger
frequency of wave in strings and pipes
f=nv2L for strings attached at both ends, the number of antinodes present will tell which harmonic it is
electric dipole and electric potential
electric potential is zero anywhere on any perpendicular bisector of the axis and at infinity
work done on a charge
W=V*qo potential is directly proportional to the amount of work done which is equal to the amt of energy exerted by the particle/
isobaric work done on a gas
Wisobaric=PV
conversion between gauss and Tesla
1 gauss = 0.0001T 1T=10^4 gauss
