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physics eq's 2 Flashcards

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1
Q

The formula for: average velocity?

A

v = displacement / time

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2
Q

The formula for: average acceleration?

A

a = velocity / time

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3
Q

The formula for: uniform accelerated motion –> solved for d (3)

A 
d = 1/2 (Vo + V)t     missing a 
d = Vot + 1/2at^2   missing V 
d = Vt - 1/2at^2      missing Vo

notice the difference in +/-

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4
Q

The formula for: solved for final velocity (2)

A 
V^2 = Vo^2 + 2ad   missing t
V = Vo + at missing d
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5
Q

the area under a velocity vs. time graph gives?

A

displacement

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6
Q

newtons second law

A

Fnet = ma

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7
Q

if an object has constant velocity what is true of Fnet?

A

no acceleration (constant v) so Fnet = 0 (i.e. dynamic equilibrium)

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8
Q

formula for: weight?

A

w = mg (g is 10 unless on different planet)

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9
Q

formula for: gravitational pull between two objects

A

Fg = G x Mm / r^2

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10
Q

formula for g (force of gravity)?

A

we can combine w = mg with Fg = G x Mm / r^2
(note w = Fg)

we get: g = G x M/r^2

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11
Q

formula for static and kinetic friction

A

Fk = Fn x μk

Fsmax = Fn x μs

μs > uk always

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12
Q

what is the equation for the parallel force of gravity on an object sitting on an inclined plane?

A

sin slides down the slope

mgsinθ

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13
Q

the formula for: the centre of mass for a multi-mass object

A

Xcm = m1x1 + m2x2 +m3x3 / m1 + m2 + m3

x is the distance from a set point

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14
Q

the formula for: centripetal acceleration

A

a = V^2 / r

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15
Q

if r increases what happens to centripetal a?

A

it actually increases since r is proportional with v and v is squared in a = V^2 / r

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16
Q

the formula for: centripetal force

A

Fc = m x V^2 / r

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17
Q

formula for: torque (2)

A

T = F x d x sinθ

or

T = F x L 
L = lever arm
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18
Q

what decreases rotational inertia?

A

making the mass closer to the axis of rotation

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19
Q

the formula for? work?

A

W = F x d x cosθ
measured in joules

note: this opposes torque which is
T = F x r x sinθ
measured in Nm

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20
Q

the formula for? power?

A

P = W / t

P = F x v
if force is parallel to velocity

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21
Q

the formula for? kinetic energy and gravitational potential energy

A

KE = 1/2mv^2

PEgrav = mgh

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22
Q

t or f, ΔKE = total Work

A

true - work energy theorem

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23
Q

the formula for? conservation of mechanical energy

A

KE1 + PE1 = KE2 + PE2

in friction is involved

KE1 + PE1 + Work = KE2 + PE2

Work = Ff x d

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24
Q

the formula for? mechanical advantage

A

F needed without machine / F needed with machine

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25
Q

the formula for? momentum and impulse

A

p = mv

J = Δp = Δ(mv) = FΔt

I = ΔM = FΔt
I am fat

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26
Q

what occurs in an inelastic collision

A

KE is not conserved
p is conserved
if perfectly inelastic, objects stick together

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27
Q

first law of thermodynamics equation?

A

ΔE = Q - W

Q - heat - this is positive when heat flows into the system
W - work - this is positive when the system does work (e.g. a gas expanding and increasing volume)

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28
Q

The work done by a gas?

A

W = PΔV

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29
Q

what is an adiabatic process?

A

when Q=0

therefore ΔE = -W

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30
Q

formula for density ?

A

ρ = mass / volume

measured in kg/m^3

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31
Q

what is the density of water?

A

1000 Kg / m^3
1g / cm^3
1kg / L

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32
Q

what is specific gravity?

A

s.g. = ρ / ρH2O

density relative to gravity

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33
Q

weight of a fluid?

A

ρ = m / V
therefore, m = ρV

weight (w) = ρVg

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34
Q

formula for pressure?

A

P = F / A measured in N / m^2 = Pa

Force must be perpendicular to object

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35
Q

formula for hydrostatic gauge pressure

A

Pgauge = ρfluid x g x D

this is proportional to depth, total pressure is not

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36
Q

formula for total pressure ?

A

P total = Pgauge + Psurface

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37
Q

buoyant force formula? (Archimedes principle)

A

Fb = ρfluid x g x Vsubmerged

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38
Q

for a floating object, what is true of the buoyant force?

A

w = Fb

mg = Fb

ρobject x Vobject x g = ρfluid x Vsubmerged x g

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39
Q

for a floating object what is the relationship between the density of fluid and the object?

A

w = Fb

mg = Fb

ρobject x Vobject x g= ρfluid x Vsubmerged x g

Vobject / Vsub = = ρfluid / ρobject

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40
Q

Formula for apparent weight of a submerged object?

A

Wapp = Wtrue - Fb

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41
Q

Pascals law on fluids distributing external pressure?

A

F1 / A1 = F2 / A2

fluids perfectly distribute external pressures if they are confined

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42
Q

list what makes an ideal fluid

A
  1. incompressible (ρ is constant)
  2. negligible viscosity
  3. laminar flow
  4. constant flow rate
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43
Q

Bernoulli’s equation ?

A

P1 + 1/2ρv1^2 + ρgy1 = P2 etc…

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44
Q

flow rate equation?

A

f = Av

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45
Q

continuity law?

A

A1v1 = A2v2 if the fluid runs through the same pipe

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46
Q

what is true of two fluids are at the same height?

A

the faster running fluid has less pressure

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47
Q

Torcelli’s result for v-efflux?

A

this equation is used when a hole has been punctured in a container allowing fluid to leak from the bottom area. This equation explains velocity of efflux

v-efflux = (2gD)^1/2

square root of 2gD

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48
Q

stress equation?

A

stress = F / A but force does not need to be perpendicular like it does in pressure

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49
Q

what is the value of the elementary charge?

A

1.6 x 10^-19

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50
Q

What is Coulomb’s Law?

A

Felec = kQq / r^2

K = 9 x 10^9

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51
Q

formula for electric field due to a point charge?

A

E = KQ / r^2 where Q produces the field

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52
Q

which direction does a negative charge move in an electric field produced by a source charge?

A

negative charge will move opposite the direction of the field

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53
Q

formula for the force of an electric field?

A

F=qE where q feels the field.

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54
Q

formula for electric potential (φ)?

A

φ = kq / r

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55
Q

for electric potential (φ), where do positive charges move?

A

positive charges move to area’s of lower φ

negative charges move to area’s of higher φ

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56
Q

change in electrical potential energy is equal too?

A

ΔPE = qΔφ where q is the charge that is moving through the electric potential

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57
Q

work done by an electric field?

A

W = -ΔPE

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58
Q

kinetic energy of a particle in a field

A

ΔKE = -ΔPE

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59
Q

what is basic the formula for current?

A

I = Q / t

and note that often Q = # of electrons times e

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60
Q

the formula for resistance relative to the wire?

A

R = p L/A

p = resistivity, not density

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61
Q

the formula for Ohms law

A

V = IR

where R is equivalent resistance

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62
Q

the formula for connecting two resistors in parallel to get Req?

A

R1R2 / R1 + R2

can’t do this with more than two at a time

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63
Q

t or f, current is the same for resistors in series whereas voltage is the same for resistors in parallel.

A

true

64
Q

what are the two main Kirchhoff rules

A
  1. junction rule –> current into a junction must equal current out
  2. voltage rule –> voltage drop of all resistors must sum up to the voltage gain of the battery
65
Q

the formula for power dissipated by a circuit element.

where P = x = y = z

A

P = IV = I^2R = V^2 / R

just remember P = IV and then use V = IR to switch the terms

66
Q

t or f, total power supplied to the circuit is equal to total power dissipated by the R’s?

A

true

67
Q

true or false, the ground is at a potential of 0

A

true

68
Q

the basic formula for a parallel plate capacitor?

A

Q = CV

Note: C is a constant therefore you can’t find it with this equation.

69
Q

the formula for capacitance of a capacitor

A

C = K ε0 A / d

where K is the dielectric number
ε0 is the permittivity of free space constant

70
Q

t or f, K can be less than 1

A

false. K is always greater than 1 and therefore, when a dielectric insulator is present, it increases the capacitance always
C = K ε0 A / d

71
Q

what occurs when

  1. keep battery attached, insert dielectric
  2. disconnect the battery, insert dielectric
A
  1. keep battery attached, insert dielectric –> keeping it connected means voltage is constant. Since the dielectric is added, C increases. According to Q = CV, if C increases, but V stays the same, Q must increase.
  2. disconnect the battery, insert dielectric –> disconnecting it Q is constant. Since the dielectric is added, C increases. According to Q = CV, if C increases, but Q stays the same, V must decrease.
72
Q

the formula for an electric field produced by a capacitor (which is uniform)

A

V = Ed

73
Q

the formula for potential energy stored in a capacitor

A

PE = 1/2 QV

using Q = CV we can rearrange to

PE = 1/2 QV = 1/2CV^2 = Q^2 / 2C

74
Q

t or f, the work done by a battery to charge a capacitor is equal to PE

A

true

75
Q

t or f, capacitors have the same rules for capacitor equivalence (Ceq) as resistors do for equivalent resistor (Req)

A

false –> they are opposite

e.g. capacitors in series are added by their inverses

76
Q

the formula for magnetic force

A

Fb = qvBsinθ

θ is in between v and B
if v and B are parallel, sinθ is 0, no force felt

if the charge is not moving, no force felt either

77
Q

t of f, Fb is always perpendicular to B and v

A

true

78
Q

t or f, in a solenoid, B is proportional to I and N/L

A

true

79
Q

what is B proportional to when created by a long straight wire

A

B varies with I / r

r is distance from the wire

80
Q

can a magentic force do work?

A

no!!! therefore is does not change the speed of the charge ever - only the direction

81
Q

what is hookes law?

A

F = -kx

x = displacement 
k = spring constant
82
Q

what is the elastic potential energy of a spring equation?

A

PE = 1/2kx^2

83
Q

simple pendulum formula for frequency?

A

f = 1/2pi x squareroot (g / L)

84
Q

wave equation?

A

v = f x λ

85
Q

true or false, speed is dependent on λ and f

A

false!! although v = f x λ, speed depends on the medium it travels through and NOT on f or λ

therefore, if we change f then λ changes in the opposite way

86
Q

how does v, f, and λ change when a wave changes media?

A

recall: wave speed is dependent on the medium

therefore v changes

NOTE: frequency always remains constant for a media change.

if frequency remains constant but v changes, λ must be proportional to v

v = f x λ

87
Q

the equation for the wavelength of a standing wave?

A

λn = 2L / n

where n = the # of nodes - 1
where n = the number of harmonics (1/2 wavelengths)

88
Q

what is the fundamental wavelength?

A

this is the wavelength of one harmonic, i.e. when n of λn = 2L / n is equal to 1.

if we know this value then we can simply multiply this wavelength by any integer to find any other harmonic

89
Q

t or f, we can take λn = 2L / n and combine it with v = f x λ to get the harmonic frequency

A

true

90
Q

t or f, λn = λ1 / n

and

fn = f1 /n

A

false,

λn = λ1/n is correct since if we extend the number of nodes over a distance L, the wavelength must be decreasing

(fn = f1 /n is incorrect) –> fn = f1 x n is correct since if wavelength is decreasing (above) then frequency must be increasing.

91
Q

What is the formula for the harmonic wavelength for sound waves in an open pipe?

A

Each end of an open pipe is considered an anti-node

therefore, this is similar to a transverse standing wave.

λn = 2L / n

where n is the number of half wave lengths

92
Q

What is the formula for the harmonic wavelength for sound waves in an closed pipe?

A

the closed en of the pipe is a node while the open side is an anti-node.

λn = 4L / n

BUT n can only be odd numbers (1,3,5, etc.)

93
Q

what is beat frequency?

A

fbeat = f |f1 - f2|

absolute value is necessary

94
Q

the formula for sound intensity

A 
I = P / A 
I = j/s / m^2
95
Q

what 2 important factors does sound intensity vary by?

A

since most sources produce sound that permeates a sphere, A = 4 pi r^2

therefore I varies with 1/r^2

I = P / A

power is a measure of energy and wave energy increases with amplitude
therefore, intensity varies with amplitude

96
Q

what is the formula for sound level / intensity level?

A

B = 10 log (I / Io)
measured in decibels (remove the multiple of 10 and its just bels)
Io = the threshold of hearing = 10^-12 W / m^2

97
Q

what two rules govern the equation B = 10 log (I / Io) in terms of manipulating I?

A

If we multiply I by 10 we add 10 to B

If we divide I by 10 we subtract 10 from B

98
Q

if the intensity of a sound increases by 100, how did the sound level change?

A

sound level = intensity level

if intensity increased by 100 then it was multiplied by 10 twice (10 x 10 = 100). therefore B must have increased by 20dB

99
Q

Doppler effect: when the source and the detector are..

a. approaching
b. receding

how does the perceived frequency change?

A

a. approaching –> when the distance between them is getting smaller the perceived frequency increases
b. receding –> when the distance between them is getting larger the perceived frequency decreases

100
Q

what is the doppler equation?

A

(v +/- vd)
fd = fs ———-
(v -/+ vs)

fd = perceived frequency of detector
fs = source frequency 
vd = speed of detector 
vs = speed of source
v = speed of wave (340 m/s for sound)
101
Q

explain the logic for when the source and the detector are both moving away from each other using the equation.

A

(v +/- vd)
fd = fs ———-
(v -/+ vs)

if relative motion is away, then we know fd < fs
therefore the fraction must be as small as possible for this to hold true

therefore: v - vd
and
v + vd

note also the way the signs are positioned.
also may think top sign means toward

102
Q

when a detector moves relative to a stationary source what changes out of
v
f
λ

A

when the detector moves, he’s changing his relative speed. Since the source is still, the wavelength fronts are the same

for v to change but λ to stay the same f must change too

e. g.
approaching: detector approaches the sound then the relative speed increases and so does the perceived frequency.

103
Q

when a source moves relative to a stationary detector what changes out of
v
f
λ

A

when a source moves, the speed must stay the same. However, the moving source changes the wavelengths.

for wavelength to stay change while speed stays the same f must change too.

approaching: source approaches the detector then the wavelength is decreasing and so the frequency must increase

104
Q

which waves require a medium out of

electromagnetic
sound
rope

A

electromagnetic - does not need a medium to propagate
sound - needs media
rope - needs media

105
Q

t or f, sound waves are longitudinal and EM waves are transverse

A

true

106
Q

t or f, the speed of an EM wave is the same regardless of the frequency in a vacuum and in a medium

A

false

the speed of an EM wave is the same regardless of the frequency in a vacuum

however, the speed is slightly different for each frequency in a medium. this accounts for dispersion of waves (prism)

107
Q

what is the order from shortest to longest wavelength of EM waves

A

gamma rays < x rays < UV light < VBGYOR < IR waves < microwaves < radiowaves

108
Q

EM waves: when is energy proportional to amplitude and when is it proportional to frequency?

A

as a wave - amplitude squared

as a particle / photon - frequency

109
Q

what is the energy of a photon equation

A

E = hf

E = h c/λ

h = 6.6 x 10^-34

110
Q

law of reflection: where is the angle measured

A

between the incidence ray and the normal (perpendicular line from the surface the ray is hitting)

111
Q

t or f, the angle for refraction is also measured from the normal

A

true

112
Q

t or f, media slows down EM waves

A

true

113
Q

what is a mediums index of refraction

A

this is a measure of how much the medium slows down the EM wave.
speed in vacuum
IoR = ———————–
speed in medium

n = c / v

the bigger the n value, the more the medium slows down light

114
Q

what is Snells law (equation)

A

n1sinθ1 = n2sinθ2

115
Q

If n1 > n2 what is true about the θ’s? draw it.

A

if n1 > n2, and n1sinθ1 = n2sinθ2

then θ1 must be less than θ2 by Snell’s law

therefore when light travels from a slower medium (n1 in this case) to a faster medium (n2 in this case) then θ of refraction must be bigger then θ of incidence and therefore light bends away from the normal

116
Q

when can total internal reflection occur?

A

ONLY when the second medium has a lower n value then the first medium. Think of when light tries to leave water into air.

117
Q

what is the critical angle

A

the angle of incidence at which total internal reflection is about to occur. at the critical angle, light refracts along the media boundary making θ = 90 degrees with the normal. (draw it). if the angle of incidence exceeds the critical angle, then TIR will occur

118
Q

what is the formula for the critical angle?

A

sinθ = n2 / n1

θ = critical angle

119
Q

what is diffraction?

A

when light passes through a slit of similar size to the lights wavelength. the light will bend

120
Q

what is polarization

A

when light has a restricted direction of electric fields

121
Q

what is dispersion

A

when light is refracted through a medium in which the individual colours are refracted slightly differently due to slightly different speeds (since it is in a medium).

122
Q

what colour is refracted (bent) the least in dispersion?

A

red

123
Q

what is the equation for the focal length?

A

f = 1/2r

r = radius of the theoretical circle that a mirror / lens creates

124
Q

mirrors: objects very distant from the mirror will have light rays converging?

A

at the focal point

125
Q

mirrors: for a concave mirror, if the object is close but further away then the focal point the image will be real and the rays will intersect behind the focal point. If the object is within the focal point and the mirror, the image is virtual since lines intersect behind the mirror. t or f

A

true

126
Q

mirrors: what is a real image? what is the value of i? virtual images?

A

if the rays actually intersect then the image is real and i is positive. if the rays theoretically intersect (like a convex mirror) then the image is virtual and i is negative.

127
Q

what is the mirror equation?

A

1/f = 1/o + 1/i

note: o is always positive - distance the object is from mirror

i - distance of image from mirror

128
Q

when is i and f positive for mirrors and lenses?

A

when the observer is on the same side as the image, the image is real and positive.
draw a mirror and lens to see

129
Q

magnification equation?

A

m = -i / o

think: if i is positive, then the image is real, which means the observer is on the same side as the image.

real image then must be inverted since m is negative

130
Q

t or f virtual images are upright images

A

true, since i of a virtual image is negative and

m = -i/o

131
Q

how can we find the height of the image?

A

multiply the height of the object by the magnification number

132
Q

concave mirrors
concave lenses
convex mirrors
convex lenses

list whether the focal length is +/- for each.

A

a focal length is positive if the image results from the actual intersection of rays

concave mirrors –> positive
concave lenses –> (diverging lens) –> negative
convex mirrors –> negative
convex lenses –> (converging lens) –> positive

133
Q

plane mirrors produce what kind of image?

A

a virtual image (therefore a negative i value, upright image)

134
Q

t or f, the equations for mirrors apply to lenses

A

true

135
Q

what is lens power and what is its equation?

A

lens power explains how strong a lens bends light. the more it bends light the more power has

P = 1 / f

focal length (f) must be in meters

unit = diopters (D)

136
Q

what unit for focal length do we use for lens power

A

meters

137
Q

t or f, for consecutive lenses we add the powers

A

true and note that negative power does exist. for example, a diverging/concave lens has a negative focal length and thus negative power

138
Q

what is myopia?
what do they see
where do rays converge
how do we correct it

A

myopia = shortsightedness

people can see nearby things
the rays converge before the retina
corrected with a diverging lens

139
Q

what is hyperopia?
what do they see
where do rays converge
how do we correct it

A

hyperopia = farsightedness

people can see far away things
the rays converge after the retina
corrected with a converging lens

140
Q

Stats: what is the mean?

A

the average of a sample. here you sum up all the values and divide by the number of components.

the mean is not necessarily a number seen in the sample

141
Q

Stats: what is the median?

A

the middle number in the data set. put the numbers in consecutive order and find the one literally in the middle.

If there is an even amount of numbers, we then average the two closest to the middle

XXYYXX –> we average the Y’s

142
Q

Stats: what is the mode?

A

the most frequently recurring number in a data set.

32, 65, 66, 67, 68, 68, 69, 70, 70, 70, 70 ,71

70 is the mode

143
Q

Stats: what is the mode for a sequence of numbers that never repeat?

A

if no numbers occur more than once, there is no mode!!

144
Q

Stats: what is the standard deviation?

A

it is a measure of how much each individual number differs from the mean

145
Q

Stats: for standard deviation, what is a normal distribution?

A

large sets of data form a symmetrical, bell shaped curve when graphed by frequency (# of instances).

the measure is on the y axis (weight, grades, etc) and the frequency is on the x

146
Q

Stats: what is a low standard deviation?

A

most data points are close to and similar to the mean

147
Q

Stats: what is a high standard deviation?

A

data is more spread out

148
Q

Stats: what is the significance of the values 34%, 68%, and 13.6%?`

A

a normal distribution has a set structure. We can therefore break up the graph into chunks of certain meaning.

34% of components fall 1 S.D. above the mean
34% of components fall 1 S.D. below the mean
thus, 68% of components fall within 1 S.D. of them mean.

13.6% of components fall between 1 and 2 S.D.’s and so on.

149
Q

Stats: t or f, for a normal distribution, essentially all data falls within 3 standard deviations of the mean

A

true

150
Q

Stats: what is an independent and dependent variable?

A

dependent variable is a function of the independent variable.

151
Q

Stats: what is statistical power?

A

statistical power is the likelihood that you have enough subjects to accurately prove your hypothesis is true within an acceptable margin of error

small sample sizes influence this

152
Q

Stats: what is sampling bias?

A

when a group of people being tested was not randomly selected and therefore may unintentionally skew results.

153
Q

Stats: what is

specific real area bias
self-selection bias
pre-screening / advertising bias
healthy user bias

A

these are all forms of sampling bias

specific real area bias –> when you select people close in proximity. (like standing in the arc where you get extrovert answers but no introvert answers)

self-selection bias –> when the study allows people to choose to participate or not (like surveys which may only reach out to highly opinionated people on the topic)

pre-screening / advertising bias –> volunteers how succumb to advertising of a research may acquire only people highly motivated in the research. e.g. smoking cessation may only get people who are v serious about quitting

healthy user bias –> when the study population is likely healthier than the general population.

154
Q

Stats: t test measures what? whats important about it?

A

t test measures significance of a correlation between stats.

significant findings have a p value of less than 0.05

155
Q

Stats: what is inter-rater reliability?

A

when two separate raters (researchers) examine someone, they should have similar findings for the same study.

156
Q

what are confounding factors?

A

these are hidden variables not directly tested for, that correlate in some way with either the independent or dependent variable and thus may impact results.

this may effect internal validity –> can we prove a causal relationship between the two variables being tested

157
Q

Stats: what is external validity?

A

this is asking if we can take the info of the study and generalize it to other situations.

MCAT chem (11 decks)

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