physics Flashcards
if a net force is zero, will the velocity change?
it will be constant and there will be no greater force that needs to be applied
what type of force is a gravitational force?
pulling force
if accel is 0 what does that tell u about velocity?
it is either constant or zero
unbalanced force impacts direction of acceler and?
velocity direction
t or f ? unbalanced force will always change dir?
no bc it could be going on same dir as accell
when there’s a force that hits the center of mass, the forrce will cause?
the object to move in the direction of the force
what happens when force is applied on the object away from the center of mass?
object will then rotate around the center of mass bc of the force that was applied at one of the ends and not the center
when it comes to pulleys. each one has the same or different forces?
same forces
when thinking about the formula for work, what happens to cosine when the force and distance is in the same direction?
cosine will become cosine of 0 degrees or 180 which will become one
normal force means what
normal force is perpendicular to floor/surface making cos 90 deg
gravitational force is perpendic or parallel to surface
perpendicular
how do u increase and decrease the normal force of an object
to increase, you push down on the object
to decrease, you lift up the object like using a tension force which will reduce the stress
why are the weight force/ normal force and the centripetal/centrifugal not part of action reaction pairs?
they cannot be bc together they act on the same object. action reaction means one force acts on one pair of the object while the other force will act on the other object
why are the car tires for a car turning static friction and not kinetic?
it is still driving smoothly to make that turn (friction bc not going straight anymore) but not sliding off of the road which will be kinetic
type of angle btwn accel and velocity in ucm?
perpendicular
why is there change in velocity in circular motion?
constantly changing in direction around the circle
why do u set centripetal force equal to the other forces?
its not a physical force independently but the result of the other forces so it is equal to net force
define closed sys
only exchange energy like earth still getting energy from sun
isolated sys
doesn’t exchange matter or energ
open sys
free to interact with environment
heat vs temp
temp measures thermal energy
heat transfers thermal energy btwn sys and environ
center of mass
the balance point of an object (usually in the moddle)
ignores the rotation of an object
torque and why does it occur
effect of a force (not a force itself) and causes rotation and can measure how fast it rotates
cannot occur when static or without any acceleration
pivot
point that the object will start rotating around
when is torque maximized ?
when force is perpendic to radius bc sin will be 90 deg
T = F * r * sin(theta)
angular acceleration means?
object is not rotating
difference between l and radius of the torque
L is the distance btwn where u apply the force and the axis of rotation
r is the distance from the axis to the line of arm which is parallel to the force???
why is gravity a conservative force?
it is path indep
why is the work for the normal force and the grav force zero?
bc they are perpendic to the surface and cosine of 90 deg is 0
If work is present, what happens to ME
me is not conserved so that means non conserve forces like friction and drag are present
work
energy generated/ transferred by a force
energy
ability to do work
when it comes to an elevator, lmk the tension when its moving up down or not moving
up = tension > force
dwn = tension < force
not moving = tension = force
when it comes to work when will it be zero
when the cos is perpendic (equals 0) so when force and distance make a perpendic
cos goes in same dir of displacement
when finding work with diff cos ang;es and forces
normal force and gravitational force has works of zero becausev cos 90
friction work is neg 1 bc opp dir of cos that aligns with distance being moved
not in all cases bc can change vice versa with elevators
forcs vs displacement graph has slope representing
k the spring constant
work formula for spring
1/2 k (x^2)
conservative force
path independent
ex: gravitational, energy , spring
what does power measure and what is its formula?
it measures the rate of the work that is being done
power= work / time WATTS = J/s
when does the instantaneous power = avg power
when given powers were the same during each time period
instantaneous power
fdcoso / t
force (cos angle btwn force and speed) ( speed )
if force is in same dir as the speed, cos will be 1
mechan advantage formula
work in = work out
fd = fd
when lose polarity or pos charges move to neg what happens to the voltage
dec
avg sodium and potassium level in extracellular fluid
150 mg/L sodium
5mg/L potassium
2 types of fluid
gas and liquid
pressure formula
force/ area = n/m^2
volume of sphere formula
V=4/3 (πr^3)
area of circle
pi r^2
volume of fluid
area x distance
pascal principle formula
for fluids with external pressure meaning a pressure of external force was applied :
pressure in = pressure out
work in = work out
unit for pressure is pascals
ex: applies to finding pressure volume etc
F1/ A1= F2 / A2
the deeper u dive in water, what happens to pressure
it incr
internal pressure of fluid
pressure = density of water x height x gravity
density of h20
1000 kg / m^3
spec gravity
density of substance / density of water
no units bc ratio of density
u use spec grav bc it tells u how much of object will be submerged while floating in the water
if value is > 1 then obj will sink so 100% of it will submerge
OR to float, its density has to be less than that of air or water density
how to get density from specific gravity
multiple specif density of substance by the density of water which is 1000 kg / m^3
1 atm = how many pascals and kpascals
1 atm = 101 kPa
1 atm = 100,000 Pa
buoyant force
F= mg F= density x volume that is submerged (water displaced) x gravity
F= wt of substance out of water - wt inside of water
has an upward force in water to counteract the downward wt of the substance
laminar flow vs turbulent
During turbulent flow ,first of all, the velocity of fluid flow will be higher. Turbulence is induced by roughness of the pipe surface. With the higher velocity at outlet than at inlet you will have different volume of liquid in and out. That’s why Sal mentions that for equal volumes to come in and out the flow should be laminar.
laminar is even so volume in = volume out
A1V1 = A2V2
viscous fluid
turbulent flow with friction or resistance
flux meaning and formula
how much of volume crosses in an amount of time
input volume/ second
m^3 / sec
when dealing with burnoili equation,
what will happen to potential energy if the heights are even?
what would happen to pressure when there is no potential energy, higher velocity?
with equal height, potential energy cancels out
the pressure will decrease
compare viscosity of liquid vs gas
viscosity is resistance to flow
so gas will have less viscosity than liquid because it has less order and more random movement
unit: pa x second
= pouise which = 1/10 of pa x sec
no viscosity means no force needed to continue flow but usually not the case bc viscos is seen all the time and will cause pressure diff to help continue flow
3 things to keep in mind with Pouseille’s law volume blood flow rate (Q)
pir^4(Pressure1 - pressure 2) /8nL = Q
increasing the blood vessel’s radius by let’s say a factor of 2 would increase it’s blood flow (Q) by a factor of 16
increases the length decreases the blood flow rate
increasing the pressure change increases the bllod flow rate bc keep in mind things with high pressure in fluids will have low speed bc harder to move through
if u increase viscosity (which connects to resistance) what happens to volume blood flow?
decreases
what to remember with pressure and fluids
that within a horizontal flow of fluid, points of higher fluid speed will have less pressure than those with slower fluid speed
Reynolds number
the speed number that shows that if u go higher than this number, the flow becomes turbulent
unitless
surface tension and its formula
when water can hold things up (tension of water equal the gravity force) without the object sinking because water at the surface is less restricted compared to bottom water molecules by using stronger intermolec forces like hydrogen bonds to work together to hold
adhesion
water molecules are attracted to other things as well like the container that it is in so can form meniscus (or capillary action)
smaller the tube, the greater effect of adhesion which is known as capillary action
when it comes to fluid, the more pressure what happens to speed
speed decreases
venturi effect and the formula
for a constriction in pipe, u want a lower pressure so that speed can increase
v1 / t1 = v2/ t2
bernoilli equation
what happens if height is the same?
cancel pou
arteries vs veins pressure/ volume flow rate
The rate, or velocity, of blood flow varies inversely with the total cross-sectional area of the blood vessels. As the total cross-sectional area of the vessels increases, the velocity of flow decreases.
arteries have most pressure because closest to the pump
even though an individual capillary has a smaller cross-sectional area, you have to take the entire capillary system into account, which has a much larger cross-sectional area. You just gotta keep in mind that pressure is lowest in the veins and highest in the aorta, so it’s going to decline as you go from aorta to arteries to arterioles to capillaries, etc.
arteries have greater resistance because the low blood flow means high viscosity
blood flow rate is slowest in capillaries bc so many of them which makes sense because it should be slow for best gas exchange results
volume blood rate/flow
change in pressure / resistance
(resistance is proportional to r^4)
stroke volume x heart rate
(vol / beat) x (beat/min) and beats will cancel out
formula that uses force and tension
T – mg = ma
to keep it upward and not going down, the tension has to be stronger than gravitational force so that is why tension is bigger
moves 50% faster than means what
means moves 1.5 faster because its an additional 50% of the original one
when will buoyant force of two objects be equal?
when the volumes are the same for each and when they both are fully submerged (aka sink)
adiabatic formula
the process is adiabatic, Q = 0, so ΔE = –W = –(PatmΔV).
work formula on relationship with thermodynamics
(PatmΔV)
PV = nRT
electrical fields flow from
Electric field lines move from positive to negative charges
how many horse power equals watts
1 horsepower = 745.7 W)
Each individual in a group of teenagers is asked to estimate the height of a tree. One individual estimates the height to be 25 feet, but after discussing with the group is convinced that the height is likely closer to 40 feet. Which type of conformity is seen here?
Internalization refers to the type of conformity in which an individual changes her outward opinion to match the group and also personally agrees with those ideas.
what is the charge for protrons and electrons?
1.6 x 10^-19
force formula for electrostatics
F = K (q)(q) / r^2
k = 8.99 x 10^9
gravitational force formula
F = G M1 M2/ r^2
insulators vs conductors
insulators have more resisitance, cannot move freely, but can still attract other charges within it to have a force
cant really repel each other bc it cant move around freely
ex: glass wood and plastic
charge of induction
gain, steal, or give away electrons
electromotive force across an electrical conductor in a changing magnetic field
if gas is being compressed is work pos or beg
pos for compress and - for expand
calorimeters are used for what kind of systems?
they are used for isolated systems
convection
deals with fluid heat transfer
diff btwn conduction convection and enthalpy
enthalpy does no heat transfer
conduction is from cold to hot in contact
convection is heat transfer between fluids
heat of fusion?
the amount of heat needed to melt something
current formula other than the v=ir
charge/ second so coulm/t
series vs parallel resistance
in series, the current are constant so each never change in value
when in series, the path never diverges in another path
parallel is when they branch off
How does the inner mitochondrial membrane differ from the outer mitochondrial membrane?
The inner mitochondrial membrane is less permeable and lacks cholesterol.
electrical field formulas
N/C
volts per meter
kq/r^2
what is 1 volt equal to (in other units)
1 J/C
what bare the degrees of constructive and destructive interference?
0 and 360 for constructive
90 and 180 for destructive but 90 is partially destructive
shortest period means what in waves?
Short period = high frequency. Period is proportional to 1/f. The first harmonic = lowest frequency/highest period. Therefore, the third harmonic will have the shortest period/highest frequency
Shortest period (displacement/time graph as in this passage) is equivalent to shortest displacement, which could be given by an amplitude vs displacement.
Harmonic calculation for a closed string or open (both end) air coumn:
lambda = 2L/n, v = f*lambda, Therefore, f = nv/2L, n = 1 = first harmonic, n=2 = first overtone (for strings). Also know that sound is a longitudinal wave. When n=3 you get shortest wavelengh/longest period (third harmonic)
freq of 1rst second and third harmonic
1/f = T so
- 1/f
- 1/2f
- 1/3f
capacitors store current and what else?
electrical pot energy
electrical pot energy formula
vs energy
q (V) = pot
1/2 q (VOLTAGE OF CAPAC) = energyregular
= 1/2Capac(V^2)
capacitance formulka
Q/V
all capacitors will have the same what when in a series
charge
when it comes to sound, what happens when u decrease the period?
well period is measured in time (seconds) to be exact so when u decr period, u will decrease the time it takes to complete the cycle so the sound will be highernote that we perceive
frequency formula for sound
1/ second so f = 1/t(as in period)
the lower the sound, the lower the freq
wavelength vs period of a sound wave
wavelength measures the distance btwn two compressed units whereas the period is the tine it takes for the sound to oscillate (move) back and fourth for one cycle
each measures the point from one hill to the next but u have to know which grapgh u are looking at… distance as x axis will measure the wavelength.. but if it is time, then it will be period that will be measuring
sound wave has what axis
displacement vs time graph … displacement will be y axis …. sometimes instead of time, x axis could be position (distance)
speed of sound in m/s and mph
340 m/s
760 mph
what type of wave is sound
longitudinal
formula for speed of sound
usyally 343 m/s but keep in mind it is wavelenghh times the freq
speed only changes when properties or its materials change but never bc of freq or amplitude… ex: person screams at u will sound louder but u wouldn’t hear them faster than not screaming at u
what does density have to do with speed of sound in materials
more dense the material is, slower the sound
also keep in mind that more stiff something is (bulk modulus) the faster it will be
order of speed of sound for properties
speed of sound in solid > liquid > air because the bulk modulus is a lot higher, even though the density is higher as well its less of an impact because the bulk modulus is much larger so it leads to a higher speed. And yep bulk modulus is resistant to compression. Gases are easily compressed so they have low resistance to compression = lower bulk modulus = lower speed of sound. Solids are difficult to compress = higher bulk modulus = faster speed of sound. And liquids are in between obviously.
keep in mind if choosing btwn two gases, warmer one is faster bc less dense in humid air than in cold air
intensity formula
power/ area
note that if area incr, u hear the sound even less than b4
significance of 10^-12 W/ m^2
lowest intensity sound that a person can hear so anything louder, the person can def hear
decibel scale formula
beta = 10log_10 (I/ 10^-12 W/m^2)
why is diffraction bad for ultrasounds?
diffraction causes images to be less clear but if u have high fre (low wavelength) u will have less diffraction
resonance for sound means?
standing wave
narcolepsy
cataplexy (a sudden loss of muscle tone and intrusion of REM sleep during waking hours, usually in response to a startling or emotional trigger) and sleep paralysis (an inability to move despite being awake, usually when waking up in the morning). These symptoms are highly suggestive of narcolepsy; in fact, some consider cataplexy to be pathognomonic for (absolutely indicative of) the disorder.
beat frequency
diff btwn two freq
Angular frequency (w):
the rate, in how many radians per second.
w = 2πf
w is also called angular velocity.
constructive vs destructive waves
- –When in phase waves add, the resulting wave has a greater amplitude.
- –When out of phase waves add, the resulting wave has a smaller amplitude.
- –Constructive interference: addition of waves resulting in greater amplitude. (bright spots)
- —Destructive interference: addition (cancellation) of waves resulting in diminished amplitude. (dark spots)
describe the type of wave phases and the degrees that associate with them
In phase: the waves are 0 or 2π radians (0 or 360°) apart. The resulting amplitude (sum of the waves) is twice the original.
Completely out of phase: the waves are π radians (180°) apart due to being in opposite directions so 180 makes sense. The resulting amplitude is zero.
Out of phase: resulting amplitude is between 0 and twice the original.
double slit formula
dsinθ=mλ for m=0,1,−1,2,−2,…(constructive).
dsinθ=(m+ 1/2)λ, for m=0,1,−1,2,−2,…(destructive),
d= distance btwn double slits
Huygens principle
if u got a wave coming in, u could treat every point on the wave as a infinite source of another wave and cause interference
everytime a reflection hits, what happens ?
pi shift may occur and the half integers of lambda can be constructive
reflected off of a liquid if going to a slower speed due to another medium
no pi shift when going into a faster medium
So since the velocity of light in a medium will be v = c/n..can we say that light reflected off a substance with a higher index of refraction will have a pi shift?
yes
what to know about freq of wave interference
stays the same
index of refraction formula
c/ speed in the certain vacuum or material
what is unique about parallel rays
they reflect at the same point (focus point) of the parabolic mirror
How can you distinguish whether an image is real or virtual?
I just want to add one thing to the talk about virtual images versus real images. The virtual image is construct of our brains. The virtual image is the way our brain interprets the light it is receiving (or better yet the signals from our optic nerves which receive the light). While this could be said about the real image as well, there actually is light at the spot of the real image. A virtual image is like a mirage; while a real image is…well…real.
center of curvature relationship to focal length
c = 2f
center of curvature relationship with ceratin points b4 after, at c , and at focal point of concave parabolic mirrors
keep in mind that convex lens will be the same too
b4 c = smaller real inverted
at c = same size but real inverted
btwn c and f = bigger real inverted image
at focal point = no image at all, not even real nor virtual
closer to the mirror than the focal point = larger virtual image
diverging vs converging points
diverging means rays are going separate ways but converging means that they are coming together
concave vs convex parabolic mirrors
concave is like the inside of the spoon… think of it pointing inward like going into a “cave”
convex is the outer part of the spoon like this -> (
so is the convex mirrors are always form smaller and upright virtual image ?
Yes. Since they are diverging mirrors, they’ll form virtual image for real object.(They’ll produce real images for virtual objects though).
And since,
1/v=1/f-1/u
=>f is positive, u is negative, So, 1/v is greater than 1/u. So, v is lesser than u and v is positive,
=>Magnification=m=-v/u=> Positive but less than 1.=>Smaller image.
acronym for schizoid vs schizotypal?
Schizoid means emotionally DISTANT, can spell as DiZtant. D and Z in schizoid and D and Z in distant (credit: premed95’s Kahn Academy doc)
Schizotypal means having odd beliefs/ magical thinking. Weird thinking like that is TYPICAL of a SCHIZO. (side note, I know that being emotional detachment is also typical of schizophrenics, but when I think of schizophrenia, the positive Sx come to mind before negative Sx do, at least for me)
Without my lenses near I would virtually die in a cave” .
The useful portions are those in bold: Without my lenses near I would virtually die in a cave.
This mnemonic tells you Concave Lenses are divergent and produce virtual images, which correct for nearsightedness.
Due to the oppositional nature of mirrors/lenses , virtual/real, convergent/divergent, convex/concave, near/farsighted, having this information allows you to conclude the other necessary facts, e.g. if I tell you a concave lens is divergent, then a convex lens must be convergent, and a concave mirror must be convergent as well.
UV and IR meanings for mirror/ lenses
upright (same side) for virtual image
inverted (opp side) real images
conVEX MIrror –> DIvergent
conVEX LENS –> CONvergent
conVEX MIrror –> DIvergent (vex me and die. That’s a negative thing, so r and f are negative)
conVEX LENS –> CONvergent (vex Lenny and CONtinue to live. Thats a positive thing, so r and f are positive)
Then by default, you know concave mirrors are convergent (with positive r and f), and concave lenses are divergent (with negative r and f).
do = always pos for single lens
di lens = pos when on opp side of object
endoderm ectoderm mesoderm mnonic
ENDODERM- “end-ternal organs” most internal organs..
ECTODERM- “attracto-derm” brains(NS) and looks(skin and sense organs)
(this one is my favorite) MESODERM- “means to get around/movement” skeletal/musculature, cardiovascular, gonads and kidneys(bc you need to move to go pee)
Which of the following is the halflife of a first-order reaction with a rate constant of 1.4 x 10-5?
A
0.7 x 10-2 seconds
B
5 x 10^4 seconds
C
2 x 10^5 seconds
D
3 x 10^2 seconds
B
For a first-order reaction, the halflife can be calculated as 0.7/k, where k is the rate constant. Thus 0.7/1.4 x 10-5 = 0.5 x 105 = 5 x 104 seconds.
relationship btwn distance of object/image to its respective heights
do/di = ho/ hi
magnification formula
M = -di / do
- di = upright
+di = inverted
do =
distance from object to lens NOT FOCAL POINT
how to solve multiple lens questions
solve for the first lens while ignoring the second one..
then use the distance image as the object of the second lens and find the distance of it from the lens to get the actual object distance
power relationship with focal length
shorter focal length = more power= more impact
not power as j/s but rather a diopter = 1/meters
power = 1 /f makes sense bc larger the diopter, smaller the focal length
spherical aberration
not all parallel light rays do not all go through the focal point so can cause cause a blurry image that can be inherited …. light at top get bent more than the light rays in the middle…
incident ray
light ray that approaches the reflective surface which will then bounce off at the same angle to make the reflective ray
angle of incid = angle of reflect
What basically is Refractive Index?
The refractive index tells you the speed of light in a given material. it is defined as n = c/v
where c is speed of light in vaccum, and v is velocity of light in the material.
The refractive index is used in (not defined by) Snell’s law, which relates the angle of incidence to the angle of refraction when light passes from one material into another.
Since the speed of light in vacuum is a universal speed limit, the refractive index is greater than 1.
refraction def
refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium. which will basically cause a bend
snells law
n1 sin () = n2 sin ()
n1 = incident index
n2 = refracted index
sin 1 theta= incident angle
sin 2 theta= refracted angle
if n is bigger than the angle must be smaller (vice versa)
dispersion
separation of light of the wavelengths visible spectrum
index refraction of air and water
air = 1.00 water = 1.33
relationship between wavelength and index of refraction /. dispersion
smaller the wavelength the more light will bend
magnetic field formulas
F = q v B (sin theta)
when it comes to the electric field, will dir of electron be going in same or opp dir?
opp bc they are both neg charge bc they will repel
venturi effect
Venturi effect is that, for a pipe/tube/container thingy, increased velocity of a fluid causes a decrease in pressure (btw gas is considered a fluid).* In the gas mask, when the person breathes in, the pressure exerted on the walls of the tube decreases. A negative change in pressure causes the air to enter the tube. Think of negative pressure as a vacuum: it is a force that pulls in (as opposed to positive pressure, which exerts force outwards).
reflection vs refraction vs critical angle
An important special case occurs when light moves into a medium with a smaller index of refraction (that is, when n2 > n1). A classic example of this is when light is moving from water to air. As this happens, the angle θ with the normal will increase—in other words, the ray of light will bend further away from the normal. As the angle of the incident ray (θ1) increases, there will come a point where the angle of the refracted ray (θ2) reaches 90°. This is known as the critical angle. If we increase the angle beyond the critical angle, the light can no longer refract at all. Instead, all the light rays are reflected within the original medium. This is known as total internal reflection.
