Kaplan Math and Physics Unknown Concepts Flashcards
What are the vector quantities? Scalar?
vector: displacement, velocity, acceleration, force
- cross product results in vector
- AB * sine(theta)
- RHR determines direction of resultant vector
scalar: speed
- dot product results in scalar
- AB * cos(theta)
What is the difference between mass and weight?
mass: amount of material
weight: force experienced by a given mass due to its gravitational attraction to earth
What are Newton’s Laws?
object will remain at rest or move with a constant velocity if there is no net force on the object
any acceleration is the result of the sum of the forces acting on the object and its mass
any two objects interacting with one another experience equal and opposite forces
What is the total mechanical energy of a system?
KE + PE (gravitational, elastic, electrical, chemical)
What are conservative forces?
path independent and do not dissipate the mechanical energy of a system
- gravity, electrostatic forces
What are nonconservative forces?
path dependent and cause dissipation of mechanical energy as thermal or chemical energy
- friction, air resistance, and viscous drag
What is work?
process by which energy is transferred from one system to another
- area under PV curve
What is power?
rate at which work is done or energy is transferred
What is the work-energy theorem?
when net work is done on or by a system, the system’s KE will change
What is mechanical advantage?
factor by which a simple machine multiplies the input force to accomplish work
- inclined plane, wedge, wheel and axle, lever, pulley, screw
What is load? what is effort?
output force of a simple machine, which acts over a load distance
input force of a simple machine
What is efficiency?
ratio of machine’s work output to work input when nonconservative forces are taken into account
What is the zeroth law of thermodynamics?
objects are in thermal equilibrium when they are at the same temperature
- no net exchange of heat energy
heat is the process of energy transfer between two objects at different temperatures until they are at thermal equilibrium
What are state functions? process functions?
state: pathway independent and are not defined by a process
- pressure, density, temperature, volume, enthalpy, internal energy, entropy, Gibbs free energy
process: pathway from one equilibrium state to another
- work, heat
What is the first law of thermodynamics?
conservation of energy: total energy can never increase or decrease
What is the second law of thermodynamics?
in a closed system, energy will spontaneously and irreversibly go from being localized to being spread
- entropy = measure of how much energy has been spread out
What is conduction, convection, and radiation?
conduction: direct transfer of energy from molecule to molecule through molecular collisions
convection: transfer of heat by the physical motion of fluid over a material
- liquids and gases
radiation: transfer of energy between electromagnetic waves
What are the phase changes?
solid to liquid: fusion, melting
- melting point; heat of fusion
liquid to gas: boiling, evaporation, vaporization
- boiling point
solid to gas: sublimation
gas to liquid: condensation
liquid to solid: freezing or solidification
gas to solid: deposition
What is the difference between gas and liquid if they’re both fluids?
liquids retain their shapes regardless of their containers and are incompressible
gasses are compressible and take the shape of their containers
What is pressure?
measure of force per unit area; exerted by fluid on the walls of a container and on objects placed in a fluid
- scalar quantity
P = F/A
What is absolute pressure? absolute hydrostatic pressure?
sum of all pressures at a certain point within a fluid
- equal to the pressure at the surface of the fluid plus the pressure due to the fluid itself
P = P0 + pgz
What is gauge pressure?
difference between absolute pressure and atmospheric pressure
- in liquids, caused by the weight of the liquid above the point of measurement
P = P0 + pgz - Patm
What is Pascal’s principle?
pressure applied to an incompressible fluid will be distributed undiminished throughout the entire volume of fluid
P = F1/A1 = F2/A2
- hydraulics
V = A1d1 = A2d2
W = F1d1 = F2d2
What is buoyant force?
when an object is placed in a fluid, the fluid generates a buoyant force against the object that is equal to the weight of the fluid displaced by the object
- opposite direction of gravity
- if the buoyant force is larger than gravity, it will float and average density of object < average density of fluid
What is viscosity?
fluid’s internal friction
- low-viscosity fluids has low internal resistance
How do fluids flow?
laminar: smooth and orderly
- incompressible fluids; low viscosity
- R= 8ηL / πr^4; capillaries have small r, larger R, slow flow
turbulent: rough and disorderly
What is the continuity equation?
flow rate is constant for a closed system and is independent of changes in cross sectional area
- linear speed DOES change
Q = v1A1 = v2A2
velocity increases with decrease in area
pinching a garden hose
What is Bernouli’s equation?
sum of static pressure and the dynamic pressure will be constant between any two points in a closed system
similar to the conservation of energy equation, substitute in density for mass
What is the Venturi effect?
inverse relationship between pressure and speed and there is a direct relationship between cross-sectional area and pressure
how do you draw electric field lines?
radiate outward from positive charged, inward to negative charges
- positive charges moves in the direction of the field lines
How is current defined?
movement of positive charge from high potential to low potential
- in reality, electrons move from low to high
What are the effects of parallel and series resistors in a circuit?
parallel: decrease overall resistance
series: increase overall resistance
What are the characteristics of ammeters, voltmeters and ohmmeters?
ammeters: in series to measure current; negligible resistance
voltmeters: parallel into circuit to measure voltage drop; very large resistances
Ohmmeters: around resistive elements to measure R; negligible
What is the difference between transverse and longitudinal waves?
transverse: have oscillations of wave particles perpendicular to the direction of wave propagation
- electromagnetic waves
- sine function
longitudinal: have oscillations of wave particles parallel to the direction of wave propagation
- sound waves
What is wavelength? frequency?
distance between two crests or troughs
number of cycles per second (Hz)
- angular frequency is in radians = 2(pi)f
- T = 1/f
What does sound propagate fastest through?
all forms of matter, but not vacuum
not dense solids > liquids > dense gases
- as density increases, speed of sound decreases
What is the Doppler effect?
shift in perceived frequency of a sound compared to the actual frequency
- higher when source and detector are moving towards each other
- lower when source and detector are moving away from each other
- when source is moving at or above the speed of sound, shock waves can form
What are pitch and volume of sound?
pitch: frequency
volume: intensity
- wave’s amplitude
How does ultrasound work?
uses high frequency sound waves to compare relative densities of tissues
- speed of wave and travel time is known
List the energy waves from lowest to highest.
radio waves, microwaves, infrared, visible light (400 nm violet - 700 nm red), ultraviolet, X-rays and gamma rays
consist of oscillating electric field and magnetic field
What is the law of reflection?
the incident angle will equal the angle of reflection
What is the difference between real and virtual images created by mirrors?
Real Image
- Formed when light rays converges at the position of the image
- Can be projected onto a screen
- Always inverted (flipped upside down).
Ex) Formed by concave mirrors when the object is placed beyond the focal point
Virtual Image
- Formed when light rays appear to diverge from a point.
- Cannot be projected onto a screen
- Always upright (same orientation as the object).
Ex) Formed by plane mirrors and convex mirrors, or by concave mirrors when the object is placed between the mirror and its focal point.
What are concave and convex mirrors? plane mirrors?
concave: converging systems and can produce real, inverted images or virtual, upright images, depending on the placement of the object relative to the focal point
- inside of a sphere; center of curvature and radius in front of mirror
convex: diverging systems and will only produce virtual, upright image
- center of curvature and radius are behind the mirror
lenses are opposite
plane: flat, reflective surfaces that produce virtual, upright images; images are always the same size as the object
What is the formula for focal length? what is the formula that combines focal length, object distance, and the image distance?
f = r/2
1/f = 1/o + 1/i = 2/r
What is important to know about the image distance (i)?
if image has i>0, it is REAL and the image is in front of the mirror
if the image has i < 0, it is VIRTUAL and located behind the mirror
What is the magnification?
m = -i/o
negative: inverted image
positive: upright image
m<1, the image is smaller than the object
m>1, the image is larger than the object
What does a single diverging mirror form?
only virtual, upright and reduced image, regardless of the position of the object
- grocery store mirror
What does a concave mirror form?
1) when the object is beyond the focal point, image is real, inverted, and magnified
2) when the object is at the focal point, no image is formed because the reflected rays are parallel to each other
3) when the object is between F and the mirror, the image is virtual, upright, and magnified
What is the law of refraction?
refraction: bending of light as it passes from one medium to another
inverse relationship between index of refraction and the sine of the angle of refraction
- n = c/v
n = index of refraction
v = speed of light in the medium
c = speed of light
What happens when light enters a medium with a higher index of refraction?
n2>n1, sin02 < sin01, therefore light will bend towards the normal
- pencil in water appears bent because it has a higher refractive index
What is total internal reflection?
all the light incident on a boundary is reflected back into the original material
What is the difference between lenses and mirrors?
lenses refract light while mirrors reflect it
What is dispersion?
various wavelengths of light separate
- splitting of white light in a prism
What is diffraction?
bending and spreading our of light waves as they pass through a narrow slit
What is plane-polarized light?
light in which the electric fields of all the waves are oriented in the same direction
- chiral centers cause plane-polarized light to rotate counterclockwise or clockwise
unpolarized: random orientation of its electric field vectors
What is the photoelectric effect?
ejection of an electron from the surface of a metal in response to light
What is the threshold frequency?
minimum light frequency necessary to eject an electron from a given metal
- work function: minimum energy necessary to eject an electron from a given metal
- the greater the kinetic energy of an incident photon above the work function, the more kinetic energy the ejected photon can possess
What is nuclear binding energy?
amount of energy that is released when nucleons (protons and neutrons) bind together
- the more binding energy per nucleon released, the more stable the nucleus
What is the mass defect?
difference between mass of the unbonded nucleons and the mass of bonded nucleons within the nucleus = amount of mass converted to energy during nuclear fusion
- unbonded have more energy and therefore more mass
E = mc^2
What are the different types of radioactive decay?
alpha: emission of alpha particle = helium nucleus
beta negative: decay of a neutron into a proton = emission of an electron
beta positive: decay of a proton into a neutron = emission of positron
gamma: emission of gamma ray
What are the most important questions in the scientific method?
F: feasible
I: interesting
N: novel
E: ethical
R: relevant
What is the difference between independent and dependent variable?
independent: manipulate this (x-axis)
dependent: observe changes in this (y-axis)
What is the difference between positive and negative controls?
positive: ensure that a change in the dependent variable occurs when expected
- development of new assay for HIV – testing blood known to have HIV
negative: ensure that no change in dependent variable happens when none is expected
- development of new assay for HIV – testing blood without HIV
What are the types of observational studies?
cohort: records exposures throughout time and then assess the rate of a certain outcome
cross-sectional studies: assess both exposure and outcome at the same point in time
prevalence
case-control: outcome status and then assess for exposure history
What are Hill’s criteria?
determine if causality is there
1) temporality: exposure before outcome
2) strength: more variability in outcome variable is explained by variability in the study variable
3) dose-response relationships: as independent variable increases, there is a proportional increase in the response
4) consistency: similar in multiple settings
5) plausibility: reasonable mechanism
6) consideration of alternative explanations: all other plausible explanations have been eliminated
7) experiments
8) specificity: change in outcome variable is only produced by an associated change in independent variable
9) coherence: new data and hypothesis are consistent with current scientific knowledge
What is selection bias, detection bias, and the Hawthorne effect?
selection: sample differs from population
detection: educated professionals using their knowledge in an inconsistent way by searching for an outcome disproportionately in certain populations
Hawthorne: changes in behavior that occur as a result of knowledge that the subject is being observed
What is a confounding variable?
unmeasured third variable that influences both the cause and effect
what are the four principles of ethics?
1) beneficence: px best interest
2) nonmaleficence: avoid things where harm outweighs benefits
3) patient autonomy: informed consent, confidentiality
4) justice: treat px with similar care
What is the difference between internal and external validity?
internal: identification of causality
external: ability of study to be generalized
What is the difference between independent and dependent events?
independent: probability does not change based on the outcomes of other events
- rolling a dice
- both: multiply the probabilities together to get the probability of them occurring together
- or: add the probabilities of each then subtract the probably of both happening together
dependent: probability changes depending on the outcomes of other events
mutually exclusive outcomes CANNOT occur simultaneously
What is the statistical measure of outlier?
more than 3 SD from the mean
result from
1) true statistical anomaly
2) measurement error
3) distribution that is not approximated by the normal distribution
What is a confidence interval?
the probability that a population parameter will fall between a set of values for a certain proportion of times
- 95 % is standard
