PHYSICS Flashcards
1
Q
What are the base units of a Newton
A
1 N = 1 (kg · m) / (s^2)
2
Q
What are the base units of a Joule
A
1 J = 1 N · m = 1 (kg · m^2) / (s^2)
3
Q
What are the base units of a Watt
A
1 W = 1 J/s = 1 (kg · m^2) / (s^3)
4
Q
If the newton is the product of kilograms and meters/second^2 , what units comprise the pound
A
Since F = m·a –> lb = ((slug) · ft ) / s^2
5
Q
What are vectors and what are some examples of vector quantities
A
Vectors are numbers that have both magnitude and direction
- some examples are force, displacement, velocity, and acceleration
6
Q
What are scalars and what are some examples of scalar quantities
A
Scalars are numbers that have only magnitude and no direction
- some examples are distance, speed, energy, pressure, and mass
7
Q
The sum or difference of two or more vectors is called the ________ of the vectors
A
resultant
8
Q
What is cos 30˚
A
(root 3)/2
9
Q
What is sin 30˚
A
1/2
10
Q
what is sin 60˚
A
(root 3)/2
11
Q
what is cos 60˚
A
1/2
12
Q
what is the difference between vector A being multiplied by scalar 3 and vector A being multiplied by scalar -3
A
both resultant vectors are 3 times bigger than vector A but the first one is parallel (goes in same direction) while the second one is perpendicular (goes in opposite direction)
13
Q
what is the dot product
A
multiplication of magnitude of two vectors and the cosine of the angle between the two vectors
OR
(x1 · x2) + (y1 · y2)
- generates a scalar product
14
Q
what is the cross product
A
multiplication of magnitude of two vectors and the sine of the angle between the two vectors
- generates a vector product that will always be perpendicular to the plane created by the two vectors
- use right hand rule to find direction of product (thumb = vector A , pointer = vector B , palm = resultant)
15
Q
what are the differences between distance and displacement
A
distance is a scalar quantity and refers to the total pathway traveled
displacement is a vector quantity and connects the initial position to the final position
16
Q
what are the differences between speed and velocity
A
velocity is a vector quantity that measures change in displacement over time
speed is a scalar quantity that measures change in distance over time
17
Q
what is the relationship between instantaneous velocity and instantaneous speed?
A
instantaneous speed is the magnitude of the instantaneous velocity vector (lim of delta x/t)
18
Q
what is the relationship between average velocity and average speed?
A
no necessary relationship because velocity is change of displacement over time while speed is change in distance over time
19
Q
the magnitude of the gravitational force between two objects is
A
Fg = (Gm1m2) / r^2
20
Q
what is the acceleration due to gravity near Earth’s surface
A
approximately 10 m/s^2
21
Q
the magnitude of the gravitational force is _________ related to the square of the distance and _________ related to the masses of the objects
A
inversely (if r is halved, Fg is quadrupled)
directly (if m1 is tripled, Fg is tripled)
22
Q
What is static friction
A
force of friction that exists between a stationary object and the surface upon which it rests
23
Q
What is the inequality that describes the magnitude of static friction
A
0 ≤ fs ≤ usN
- minimum value is 0 and maximum value is the coefficient of static friction times the normal force
24
Q
what is the coefficient of friction
A
a unitless quantity that is dependent on the two materials in contact
25
what is kinetic friction
force of friction that exists between a sliding object and the surface over which the object slides
26
what type of friction does a wheel rolling across the road experience
it experiences static friction as the tire maintains an instantaneous point of contact with the road
it does not experience kinetic friction because it is not sliding against the road
27
what is the equation for kinetic friction
fk = uk · N
28
what are the two major differences between the equations for kinetic and static friction
1. kinetic friction equation has an equals sign because it is always a constant value; static friction is represented by an inequality because it can be a range
2. the coefficient of friction is different ; coefficient of static friction will always be larger than that of kinetic friction because it always requires more force to get an obejct to start sliding than to keep it sliding
29
What are the differences between mass and weight
Mass is a scalar quantity represented in kilograms that represents how much matter is in the object and is independent of gravity
Weight is a vector quantity represented in Newtons that is a measure of the gravitational force acting on an object
Fg (weight) = m · g
30
What is Newton's 1st Law
Fnet = m · a = 0
law of inertia
A body that is at rest or in motion with constant velocity (acceleration of 0) will remain that way until a net force acts upon it
31
What is Newton's 2nd Law
Fnet = m · a
an object of mass m will accelerate when a nonzero net force acts on it
32
What is Newton's 3rd Law
F (A,B) = - F (B,A)
law of action and reaction
To every action, there is always an opposite but equal reaction
33
What are the 4 equations for linear motion with constant acceleration
v = v0 + at
x = v0t + (at^2)/2
v^2 = v0^2 + 2ax
x = vt
34
what is terminal velocity
the constant velocity an object in free fall will experience once the drag force (air resistance) becomes equal in magnitude to the weight of the object
35
T or F: when air resistance is negligible, the time it takes for an object to get to its max height is the same it takes for it to fall back to its starting height
T
36
for objects in projectile motion, how will vx and vy change
vx will remain constant and vy will experience acceleration due to gravity
37
what is the velocity of an object that reached its max height
0
38
what is kinetic energy and what is its equation
the energy of motion
K = 1/2 mv^2
39
is kinetic energy related to speed or velocity
speed because the direction of the velocity vector does not affect KE
40
what is gravitational potential energy and what is its equation
energy that depends on the object's position with respect to some 'ground zero'
U = mgh
41
what is elastic potential energy and what is its equation
potential energy in a spring that is stretched or compressed from equilibrium point
U = 1/2kx^2
42
What is an object's total mechanical energy
sum of its potential and kinetic energies
43
what is the conservation of mechanical energy
law that energy cannot be created or destroyed, it is only transferred between forms
44
does an object's total mechanical energy always remain constant?
no, mechanical energy only includes potential and elastic energy
- if friction is present, some energy is lost as heat (thermal) and so total mechanical energy decreases
45
what are conservative forces
forces that are path independent (change in energy between endpoints is equal despite path taken) and do not dissipate energy
46
what are examples of conservative vs nonconservative forces
conservative: gravitational potential energy, electrostatic potential energy, (sometimes elastic potential energy)
nonconservative: friction, air resistance, fluid drag
47
what are the two methods to tell if a force is conservative
1. consider the change in energy of a system if the system is brought back to its original setup
- if the net energy change is 0, it is conservative
2. consider the change in energy of a system moving from one setup to another
- if the energy change is equal despite path taken, it is conservative
48
what is the equation for total mechanical energy if nonconservative forces are present
W(nonconservative) = ∆E = ∆U + ∆K
W(nonconservative) is the work done by these nonconservative foorces
49
work is not a form of energy itself but a _________________
process by which energy is transferred from one system to another
50
what are the two ways energy can be transferred
work and heat
51
what is the work equation
W = Fdcos𝛉
52
what kind of forces can do work
forces that are either parallel or antiparallel to the displacement vector
53
when work is done by a system, it has a __________ value
when work is done on a system, it has a ___________ value
positive ; negative
54
how can you calculate work done on a system using pressure and volume
calculate the area under a pressure-volume curve
55
what is an isovolumetric or isochoric process
process where pressure changes but volume stays constant --> no work is done
56
what is an isobaric process
process where pressure remains constant as volume changes --> work is calculated as W = P∆V
57
what is the definition and equation of power
power is the rate at which energy is transferred from one system to another
P = W/t = ∆E/t
SI unit: Watt (J/s)
58
what is the work-energy theorem
the net work done by forces acting on an object will result in an equal change in the object's kinetic energy
Wnet = ∆K = Kf - Ki
59
what is the zeroth law of thermodynamics
if one object is in thermal equilibrium with another object, and the second object is in thermal equilibrium with a third one, then the first and third object are also in equilibrium
- transitive property in thermal systems: a=b and b=c; a=c
- no net heat flows between objects in thermal equilibrium
60
what is temperature versus heat
temperature is the quantitative value of the average kinetic energy of the particles of a substance
heat is the transfer of thermal energy from a hotter object to a cooler one
61
what is the third law of thermodynamics
the entropy of a perfectly organized crystal at absolute zero K is 0
62
what is the equation for length change due to thermal expansion
∆L = ɑL∆T
alpha - the coefficient of linear expansion (a constant based on materials)
mnemonic - when the temperature of an object changes, its length changes (a lot)
63
what is the formula for volumetric thermal expansion
∆V = βV∆T
β=coefficient of volumetric expansion
64
T or F: volumetric thermal expansion is applicable to both liquids and solids
True
65
how does the coefficient of volumetric expansion relate to the coefficient of linear expansion of the same material
β=3ɑ
66
what are the units of the coefficients of linear or volumetric expansion
K^-1
67
what is a state function and what are the known state functions
a thermodynamic property that is a function of only the current equilibrium state of a system (path-independent)
pressure, density, temperature, volume, enthalpy, internal energy, Gibbs free energy, entropy
68
what are process functions
properties such as work and heat that describe the path/process taken to get from one state to another
69
what is the first law of thermodynamics
the change in a system's total internal energy is equal to the amount of energy transferred in the form of heat minus the amount of energy transferred in the form of work
∆U = Q - W
70
the first law of thermodynamics tells us that an increase in the total internal energy of a system is caused by
transferring heat into the system or performing work on the system
71
what is the second law of thermodynamics
objects that are in thermal contact but not in thermal equilibrium will exchange heat energy such that the object with a higher temperature will give off heat energy to the object with a lower temperature until they are equal
72
what are the three means by which heat can transfer energy
conduction, convection, and radiation
73
what is the specific heat of a substance
the amount of heat energy required to raise one gram of a substance by one degree Celsius or one unit Kelvin
74
what is the specific heat of water in calories
1 cal/g·K
75
what is the equation that relates the heat lost or gained by an object
q = mc∆T
c=specific heat
76
what equation is used to calculate the amount of heat added or removed during a phase change
q = mL
L = heat of transformation or latent heat of the substance
77
both fluids and solids can exert forces ___________ to their surface, although only solids can withstand ________ forces
perpendicular ; shear (tangential)
78
what is the density formula
p = m/V
SI unit : kg/m^3
79
what is the formula for calculating weight of substance with a known density
Fg = pVg
80
What is specific gravity
ratio of a substance's density compared to the standard one of water - can be used to determine if an object will sink or float in water
SG = p / (1 g/cm^3)
81
what is pressure
ratio of the force per unit area
P = F/A
F= refers to only magnitude of normal force vector
SI units: pascals (Pa) or N/m^2
82
Is pressure a scalar or a vector
scalar
- no matter the direction, the pressure exerted on a surface is the same
83
what is hydrostatics
the study of fluids at rest and the forces and pressures associated with standing fluids
84
what is Pascal's principle
for fluids that are incompressible, a change in pressure will be transmitted undiminished to every portion of the fluid and the walls of the container
- example: squeezing a closed container of milk distributes pressure to the whole liquid
P = (F1/A1) = (F2/A2)
85
explain the mechanics of a hydraulic lift
the lift has two columns filled with incompressible liquid topped with a piston. when the left piston pushes down on the left column with a cross-sectional area of A1 and a force of F1 it generates a pressure of P1. This liquid must then also be displaced on the right side of the lift so the liquid pushes up on the right piston which has a much larger A2. Since P1 must be equal to P2, F2 has to be larger than F1.
- a small force exerted over a small area through a large distance generates a much larger force over a larger area through a smaller distance
86
what is absolute pressure
the total pressure that is exerted on an object that is submerged in a fluid
P = P0 + pgz
P0 = incident or ambient pressure (pressure at the surface)
87
what is gauge pressure
difference between absolute pressure and atmospheric pressure
P(gauge) = P - P(atm)
88
what is Archimedes' principle
89
90
91
92
can the kinetic energy equation be used when solving problems with charged particles?
yes! even though they are very tiny, they still have mass
93
what are the differences between insulators and conductors
Insulators will not easily distribute charge over its surface and will not transfer that charge to another neutral object
- tend to have electrons that are closely linked to nuclei
- most nonmetals are insulators
Conductors will distribute a charge evenly across its surface and are able transfer/transport charges
- often used in circuits
- electrons are usually 'free' and can move around rapidly
- generally metals or ionic solutions
94
what is Coulomb's Law
quantifies the magnitude of the electrostatic force Fe between two charges
Fe = (kq1q2) / r^2
95
what is Coulomb's constant
k
- also known as the electrostatic constant
- k = 8.99 x 10e9 (N·m^2)/C^2
96
what is the fundamental unit of charge
e = 1.60 x 10e-19 C
- charge of protons (positive) and electrons (negative)
97
what is a test charge vs source charge
test charge (q) is the charge placed in the electric field and source charge (Q) is the charge that actually creates the electric field
98
how do you calculate the magnitude of an electric field
E = (Fe/q) = (kQ)/r^2
- 2 ways
99
what is the convention for drawing the electric field vector
drawn in the direction that a positive test charge would move in the presence of the source charge
- represented by field lines
100
T or F: electrostatic force vectors and electric field vectors can go in opposite directions
T
- if the test charge is negative, they will be in opposite directions
101
what is electric potential energy
form of potential energy dependent on the relative position of one charge with respect to others
U = (kQq)/r
102
what is current
current is considered the flow of positive charge (even though only negative charge is moving)
103
what is conductivity
the reciprocal of resistance
SI unit: siemens (S)
104
what are the two categories of conductivity
metallic conductivity (solid metals and molten salts) and electrolytic conductivity (solutions)
105
what is metallic conductivity
the free flow of electric charge in metallic materials that makes them good electrical conductors
- metal atoms easily lose their outer electrons so they form a free sea of moving electrons
106
what is a generalized model for visualizing the metallic bond
a sea of electrons flowing over and past a rigid lattice of metal cations
107
what is electrolytic conductivity
conductivity that depends on ion concentration in a solution
108
T or F: electrolytic conductivity also includes strength of nonionic concentration
T, even though this contribution is much less significant than ionic concentratioon
109
what is the equation for current
I = Q / ∆t
SI unit: ampere (C/s)
110
T or F: the direction of current is opposite the direction of actual current flow
T
Electrons are negatively charged and so move from a point of lower electric potential to higher electrical potential. Current (flow of positive charge) flows in the opposite direction
111
What are the two patterns of current flow
1. direct current
- the charge flows in one direction only
2. alternating current
- the flow changes direction periodically
112
What is the electromotive force (emf)
the voltage (potential difference) between the two terminals of a cell that are at different potential values when no charge is moving between them
113
T or F: EMF is a force
no, it is a voltage! has units of volts = joules/coulomb
114
what is an electric circuit
a conducting path that usually has one or more voltage sources (such as a battery) connected to one or more passive circuit elements (such as resistors)
115
what is Kirchoff's junction rule
the sum of currents directed into a point or junction is equal to the sum of currents directed away from that point (conservation of charge)
I (into junction) = I (out of junction)
116
what is Kirchoff's loop rule
around any closed-circuit loop, the sum of voltage sources will always be equal to the sum of voltage (potential) drops (conservation of energy)
- all the electrical energy supplied by a source gets fully used up by the other elements of the loop
V (source) = V (drop)
117
T or F: The sum of the voltage sources in a circuit is equal to the sum of the voltage drops in that circuit
F: While the voltage sources and drops are equal in any closed loop, this is not necessarily true for the entire circuit.
example: a 9V battery that powers 10 lightbulbs in parallel has a 9V voltage source and a 9V drop across each lightbulb (90V for whole circuit)
118
what is resistance
the opposition within any material to the movement and flow of charge (electrical version of friction)
119
materials that offer almost no resistance are called __________ and materials that offer very high resistance are called ___________
conductors ; insulators
120
what are resistors
conductive materials that offer amounts of resistance between the two extremes of conductors and insulators
121
what is the equation for resistance
R = (𝜌L) / A
𝜌 = resistivity ; L = length of resistor ; A = cross-sectional area
122
T or F: appliances function as resistors in circuits
T - most common for MCAT will be lightbulb
123
what is resisitivity
a number that characterizes the intrinsic resistance to current flow in a material
SI unit : ohm · meter
124
what are the relationships between resistance and length vs cross-sectional area
resistance is directly proportional to length
resistance is inversely proportional to cross-sectional area
125
why is resistance inversely proportional to cross-sectional area
increase in area leads to increase in number of pathways through the resistor (known as conduction pathways) - the wider the path, the more current that can flow, the less the resistance
126
T or F: most conductors have greater resistance at higher temperatures
T
127
What is Ohm's Law
V = IR
the voltage drop across the resistor will be proportional to the magnitude of the current
128
what is internal resistance
r(int)
the weak resistance found within conductive materials themselves
- causes the voltage supplied to a circuit to be reduced from its theoretical emf by a small amount
V = E(cell) - i·r(int)
E(cell) = emf of cell
i = current through cell
*if the cell is not driving any current, then the internal resistance is 0 and V = E(cell)
129
what is a dielectric material
another way of saying insulation ; when a dielectric material is introduced between the plates of a capacitor it increases the capacitance by a factor called the dielectric constant (k)
130
what are transverse waves
waves in which the direction of particle oscillation is perpendicular to the propagation (movement) of the wave and direction of energy transfer
- think of 'the wave' at a stadium : people move up and down but wave moves to the side
131
what are examples of transverse waves
electromagnetic waves (visible light, microwaves, X-rays)
132
what are longitudinal waves
waves in which the particles of the wave oscillate parallel to the direction of propagation and energy transfer
- think of a slinky flat against a table being pushed back and forth
133
longitudinal waves cause air molecules to oscillate through cycles of ______________ and _______________ along the direction of the motion of the wave
compression ; rarefaction (decompression)
134
what is one example of a longitudinal wave
sound
135
what is the equation to calculate the propagation speed of a wave
v = fλ
f = frequency
λ = wavelength
136
what is the period of a wave
period (T) is the inverse of frequency (number of cycles per second) or the number of seconds per cycle
T = 1/f
137
what is the equation for angular frequency in relation to frequency and period of waves
ω = 2π f = 2π / T
138
what is the displacement (x) of a wave
how far a particular point on the wave is from the equilibrium position, expressed as a vector
139
what is the phase difference between two waves traveling in the way that the crests of one wave coincide with the troughs of the other
one-half of a wave ; λ/2 ; 180˚
140
what is the principle of superposition
when waves interact with each other, the displacement of the resultant wave at any point is the sum of the displacements of the two interacting waves
141
what is constructive interference
when the waves are perfectly in phase and the amplitude of the resultant wave is equal to the sum of the amplitudes of the two waves
142
what is destructive interference
when waves are perfectly out of phase and the amplitude of the resultant wave is the difference of the amplitudes of the interacting waves
143
T or F: waves can be partially constructive or destructive
T
144
what is the relationship between traveling and standing wave
traveling waves are 'moving' waves. if a string fixed at one end is moved up and down, a traveling wave will form and propagate down towards the fixed end. this wave then gets inverted at the fixed end and travels back but interferes destructively with the original traveling wave. since these waves are perfectly out of phase, the resultant wave seems stationary except for fluctuation of amplitudes at fixed points. this is a standing wave
145
what are nodes versus antinodes
nodes are points long standing waves that remain at rest (where amplitude is constantly 0)
antinodes are points midway between the nodes that fluctuate with maximum amplitude
146
what is the range of frequencies commonly audible to young adults
20 - 20,000 Hz
147
what is forced oscillation
if a periodically varying force is applied to a system, the system will then be driven at a frequency equal to the frequency of the force
148
what does it mean when a system is said to be resonating
if the frequency of a periodic force is equal to the natural (resonant) frequency of the system, then the system is said to be resonating and the amplitude of the oscillation is at a maximum
149
what is damping or attenuation
the decrease in amplitude of a wave caused by an applied or nonconservative force
150
what is the FINER method for evaluating a research question
feasible; interesting ; novel ; ethical ; relevant
151
what is the use of controls or standards in research
a way of verifying results ; help establish causality
152
what are positive vs negative controls
positive controls ensure a change in the dependent variable when it is expected (using HIV positive samples to test a new HIV detection method)
negative controls ensure no change in the dependent variable when no change is expected (using negative samples) - can be used to assess for the placebo effect
153
when is a relationship said to be causal
when the change in the independent variable always precedes the change in the dependent variable and the change in the dependent variable does not occur in the absence of the experimental intervention
154
what is the difference between accuracy and precision
accuracy (validity) is the ability of an instrument to measure a true value while precision (reliability) is the ability of the instrument to read consistently, or within a narrow range
155
does an inaccurate or an imprecise tool introduce bias?
an inaccurate tool introduces bias (systematic error in data) while an imprecise tool will just introduce error
156
what are single-blind vs double-blind experiments
in single-blind experiments, only the patient or assessor do not know in what group the patient is in
in double-blind experiments, neither the patient nor the researcher know
157
what are the three kinds of variables used by software programs in regression models?
binary (yes or no, better or worse)
continuous (amount of weight lost, percent improvement)
categorical (state of residence, economic status)
158
what are the three kinds of observational studies in medicine
cohort, cross-sectional, and case-control
159
observational studies do not demonstrate ___________ and can only be said to show ________
causality ; correlation
160
what are cohort studies
subjects are sorted into groups based on differences in risk factors (exposures) and then assessed at various intervals to determine which subjects had a certain outcome
- form of longitudinal study (same subjects over time)
- ex: smokers and nonsmokers being followed for 20 years and seeing how many develop lung cancer
161
what are cross-sectional studies
categorization of patients into different groups at a single point in time
- ex: survey determining how many people out of smokers and nonsmokers have lung cancer
162
what are case-control studies
identify the number of subjects with or without a particular outcome and then look backwards to assess how many subjects in each group had exposure to a particular risk factor
163
what are Hill's criteria
the components of an observed relationship that increase the likelihood of causality in a relationship (necessary but not sufficient)
- the more criteria satisfied, the likelier it is that the relationship is causal
164
what are the 9 Hill's criteria
temporality, strength, dose-response relationship, consistency, plausibility, consideration of alternative explanations, experiment, specificity, coherence
165
what is the difference between bias and confounding
bias is a result of flaws in the data collection phase while confounding is an error during analysis
166
what is selection bias
bias where the subjects used for a study are not representative of the target population
167
what is detection bias
bias resulting in educated professionals using their knowledge in an inconsistent way
- ex: screening obese patients for diabetes more frequently
168
what kind of images do diverging lenses produce
virtual and reduced images for objects that farther than the focal length
- focal length is negative
169
in a blood pressure reading, which is the systolic and which is the diastolic
the systolic pressure is in the numerator, the diastolic is in the denominator
- systolic pressure is the max blood pressure during contraction of the vesicles
- diastolic pressure is the min pressure in between heartbeats
170
as wavelength increases, frequency and energy _______
decrease
171
what is the conversion between atm and mmHg
1 atm = 760 mmHg
