Margins Study Assistant

Chapter 1

What is Physics?

Summary

Modern physics involves the theory of relativity, which describes how time, space and gravity are not constant in our universe can be different for different observers, and quantum mechanics, which describes the… Physics is the most fundamental of the sciences, concerning itself with energy, matter, space and time, and their interactions Physics is the basis for all other sciences, such as chemistry, biology and geology, because physics describes the fundamental way in which the universe functions The processes of science include observation, hypothesis, experiment, and conclusion

Key terms

physics: science aimed at describing the fundamental aspects of our universe—energy, matter, space, motion, and time
theory: explanation of patterns in nature that is supported by much scientific evidence and verified multiple times by various groups of researchers
theory of relativity: theory constructed by Albert Einstein which describes how space, time and energy are different for different observers in relative motion
scientific law: pattern in nature that is true in all circumstances studied thus far
modern physics: physics as developed from the twentieth century to the present, involving the theories of relativity and quantum mechanics
science: the study or knowledge of how the physical world operates, based on objective evidence determined through observation and experimentation
quantum mechanics: major theory of modern physics which describes the properties and nature of atoms and their subatomic particles
observation: step where a scientist observes a pattern or trend within the natural world

Chapter 2

Motion in One Dimension

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Summary

Average speed is a scalar quantity that describes distance traveled divided by the time during which the motion occurs Displacement is the difference in the initial and final positions of an object Average velocity is displacement over the time period during which the displacement occurs. A description of motion depends on the reference frame from which it is described

Key terms

reference frame: a coordinate system from which the positions of objects are described
distance: the length of the path actually traveled between an initial and a final position
scalar: a quantity that has magnitude (and possibly sign) but no direction
average speed: distance traveled divided by time during which motion occurs
average velocity: displacement divided by time over which displacement occurs
displacement: the change in position of an object against a fixed axis
position: the location of an object at any particular time
vector: a quantity that has both magnitude and direction

Chapter 3

Acceleration

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Summary

The kinematic equations in this section are valid only for constant acceleration The kinematic equations show how time, displacement, velocity, and acceleration are related for objects in motion Acceleration is the rate of change of velocity. Its magnitude is expressed in units of m/s 2

Key terms

kinematic equations: the five equations that describe constant acceleration motion in terms of time, displacement, velocity, and acceleration
constant acceleration: acceleration that does not change with respect to time
kinematic equations in this section: valid only for constant acceleration
acceleration due to gravity: acceleration of an object that is subject only to the force of gravity; near Earth’s surface this acceleration is 9.80 m/s 2
negative acceleration: a component of acceleration in the negative direction of the component axis
average acceleration: change in velocity divided by the time interval over which it changed
instantaneous acceleration: rate of change of velocity at a specific instant in time

Chapter 4

Forces and Newton’s Laws of Motion

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Summary

Dynamics is the study of how forces affect the motion of objects and systems A free-body diagram is a drawing of all external forces acting on a body Newton’s first law states that a body at rest remains at rest or, if moving, remains in motion in a straight line at a constant speed, unless acted on by a net external force. External forces are any forces outside of a body that act on the body.

Key terms

force: a push or pull on an object with a specific magnitude and direction; can be represented by vectors; can be expressed as a multiple of a standard force; the SI unit of force is…
system: one or more objects of interest for which only the forces acting on them from the outside are considered, but not the forces acting between them or inside them
inertia: the tendency of an object at rest to remain at rest, or for a moving object to remain in motion in a straight line and at a constant speed
law of inertia: Newton’s first law of motion: a body at rest remains at rest or, if in motion, remains in motion at a constant speed in a straight line, unless acted on by a net external force…
external force: a force acting on an object or system that originates outside of the object or system
dynamics: the study of how forces affect the motion of objects and systems
net external force: the sum of all external forces acting on an object or system
free-body diagram: a diagram showing all external forces acting on a body

Chapter 5

Motion in Two Dimensions

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Summary

Next, use the head-to-tail method as for vector addition to obtain the resultant vector R The graphical method of adding vectors A and B involves drawing vectors on a graph and adding them by using the head-to-tail method. The resultant vector R is defined such that A + B = R . The head-to-tail method of adding vectors involves drawing the first vector on a graph and then placing the tail of each subsequent vector at the head of the previous vector.

Key terms

head-to-tail method: a method of adding vectors in which the tail of each vector is placed at the head of the previous vector
tail: the starting point of a vector; the point opposite to the head or tip of the arrow
graphical method: drawing vectors on a graph to add them using the head-to-tail method
magnitude and direction of R: then determined with a ruler and protractor
resultant: the sum of the a collection of vectors
resultant vector: the vector sum of two or more vectors
vector addition: adding together two or more vectors
resultant vector R: defined such that A + B = R

Chapter 6

Circular and Rotational Motion

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Summary

The angle of rotation Δ θ is defined as the ratio of the arc length to the radius of curvature The arc length Δ s is the distance traveled along a circular path and r is the radius of curvature of the circular path The direction of angular velocity is along the axis of rotation, away (toward) from you for clockwise (counterclockwise) motion The angle of rotation Δ θ is measured in units of radians (rad), where 2 π rad = 360 ° = 1 revolution

Key terms

rotational motion: the circular motion of an object about an axis of rotation
arc length Δ s: the distance traveled along a circular path and r is the radius of curvature of the circular path
direction of angular velocity: along the axis of rotation, away (toward) from you for clockwise (counterclockwise) motion
angular velocity: ( ω ) the rate of change in the angular position of an object following a circular path
tangential velocity: the instantaneous linear velocity of an object in circular or rotational motion
angle of rotation: the ratio of the arc length to the radius of curvature of a circular path
arc length: ( Δ s ) the distance traveled by an object along a circular path
radius of curvature: the distance between the center of a circular path and the path

Chapter 7

Newton's Law of Gravitation

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Summary

Newton’s law of universal gravitation provides a mathematical basis for gravitational force and Kepler’s laws of planetary motion Einstein’s theory of general relativity shows that gravitational fields change the path of light and warp space and time An object’s mass is constant, but its weight changes when acceleration due to gravity, g , changes

Key terms

Einstein’s theory of general relativity: the theory that gravitational force results from the bending of spacetime by an object’s mass
Kepler’s laws of planetary motion: three laws derived by Johannes Kepler that describe the properties of all orbiting satellites
object’s mass: constant, but its weight changes when acceleration due to gravity, g , changes
Copernican model: the model of the solar system where the sun is at the center of the solar system and all the planets orbit around it; this is also called the heliocentric model
Newton’s universal law of gravitation: states that gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Ptolemaic model: the model of the solar system where Earth is at the center of the solar system and the sun and all the planets orbit around it; this is also called the geocentric model
aphelion: the point farthest from the sun in the path of an orbiting planet (called apoapsis for other celestial bodies)
perihelion: closest distance between a planet and the sun (called periapsis for other celestial bodies)

Chapter 8

Momentum

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Summary

Impulse is the average net external force multiplied by the time this force acts, and impulse equals the change in momentum, Δ p = F net Δ t Newton’s second law of motion in terms of momentum states that the net external force equals the change in momentum of a system divided by the time over which it changes, F net = Δ p Δ t The law of conservation of momentum is written p tot = constant or p tot = p ′ tot (isolated system), where p tot is the initial total momentum and p ′ tot is the total momentum some time later In an isolated system, the net external force is zero

Key terms

law of conservation of momentum: when the net external force is zero, the total momentum of the system is conserved or constant
isolated system: system in which the net external force is zero
change in momentum: the difference between the final and initial values of momentum; the mass times the change in velocity
impulse: average net external force multiplied by the time the force acts; equal to the change in momentum
linear momentum: the product of a system's mass and velocity
net external force: zero, within the defined system
impulse-momentum theorem: the impulse, or change in momentum, is the product of the net external force and the time over which the force acts
perfectly inelastic collision: collision in which objects stick together after impact and kinetic energy is not conserved

Chapter 9

Work, Energy, and Simple Machines

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Summary

The work-energy theorem states that an amount of work that changes the velocity of an object is equal to the change in kinetic energy of that object.The work-energy theorem states that an amount of work that changes… Doing work on a system or object changes its energy Mechanical energy may be either kinetic (energy of motion) or potential (stored energy)

Key terms

simple machine: a machine that makes work easier by changing the amount or direction of force required to move an object
work: force multiplied by distance
mechanical advantage: the number of times the input force is multiplied
power: the rate at which work is done
velocity of an object: equal to the change in kinetic energy of that object.The work-energy theorem states that an amount of work that changes…
work-energy theorem: states that the net work done on a system equals the change in kinetic energy
mechanical energy: kinetic or potential energy

Chapter 10

Special Relativity

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Summary

One postulate of special relativity theory is that the laws of physics are the same in all inertial frames of reference The other postulate is that the speed of light in a vacuum is the same in all inertial frames Einstein showed that simultaneity, or lack of it, depends on the frame of reference of the observer Time dilates, length contracts, and momentum increases as an object approaches the speed of light

Key terms

special relativity: the theory proposed to explain the consequences of requiring the speed of light and the laws of physics to be the same in all inertial frames
relativity: the explanation of how objects move relative to one another
postulate: a statement that is assumed to be true for the purposes of reasoning in a scientific or mathematic argument
frame of reference: the point or collection of points arbitrarily chosen, which motion is measured in relation to
other postulate: that the speed of light in a vacuum is the same in all inertial frames
simultaneity: the property of events that occur at the same time
laws of physics: the same in all inertial frames of reference
relativistic: having to do with modern relativity, such as the effects that become significant only when an object is moving close enough to the speed of light for γ to be significantly…

Chapter 11

Thermal Energy, Heat, and Work

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Summary

Heat is transferred by three different methods: conduction, convection, and radiation The transfer of heat Q that leads to a change Δ T in the temperature of a body with mass m is Q = m c Δ T , where c is the specific heat of the material Absolute zero is the temperature at which there is no molecular motion There are three main temperature scales: Celsius, Fahrenheit, and Kelvin

Key terms

heat: transfer of thermal (or internal) energy due to a temperature difference
thermal energy: average random kinetic energy of a molecule or an atom
Kelvin: unit on the Kelvin temperature scale; note that it is never referred to in terms of “degrees” Kelvin
specific heat: amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 °C
absolute zero: lowest possible temperature; the temperature at which all molecular motion ceases
conduction: heat transfer through stationary matter by physical contact
radiation: energy transferred by electromagnetic waves
convection: heat transfer by the movement of fluid

Chapter 12

Thermodynamics

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Summary

The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C The ideal gas law relates the pressure and volume of a gas to the number of gas particles (atoms or molecules) and the absolute temperature of the gas Systems are in thermal equilibrium when they have the same temperature Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy

Key terms

thermal equilibrium: condition in which heat no longer transfers energy between two objects that are in contact; the two objects have the same temperature
zeroth law of thermodynamics: states that if two objects are in thermal equilibrium, and a third object is in thermal equilibrium with one of those objects, it is also in thermal equilibrium with the other…
ideal gas law: physical law that relates the pressure and volume of a gas to the number of gas molecules or atoms, or number of moles of gas, and the absolute temperature of the gas
pressure: force per unit area perpendicular to the force, over which the force acts
entropy: measurement of a system's disorder and how much energy is not available to do work in a system
cyclical process: process in which a system is brought back to its original state at the end of every cycle
Boltzmann constant: constant with the value k = 1.38×10 -23 J/K, which is used in the ideal gas law
first law of thermodynamics: states that the change in internal energy of a system equals the net energy transfer by heat into the system minus the net work done by the system

Chapter 13

Waves and Their Properties

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Summary

Mechanical waves must travel through a medium A periodic wave is a wave that repeats for several cycles, whereas a pulse wave has only one crest or a few crests and is associated with a sudden disturbance A transverse wave has a disturbance perpendicular to its direction of propagation, whereas a longitudinal wave has a disturbance parallel to its direction of propagation Sound waves, water waves, and earthquake waves are all examples of mechanical waves

Key terms

wave: disturbance that moves from its source and carries energy
periodic wave: wave that repeats the same oscillation for several cycles and is associated with simple harmonic motion
transverse wave: wave in which the disturbance is perpendicular to the direction of propagation
longitudinal wave: wave in which the disturbance is parallel to the direction of propagation
wave velocity: speed at which the disturbance moves; also called the propagation velocity or propagation speed
medium: solid, liquid, or gas material through which a wave propagates
pulse wave: sudden disturbance with only one wave or a few waves generated
mechanical wave: wave that requires a medium through which it can travel

Chapter 14

Sound

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Summary

Sound intensity level in decibels (dB) is more relevant for how humans perceive sounds than sound intensity (in W/m 2 ), even though sound intensity is the SI unit The energy of a sound wave is also proportional to its amplitude squared Sound intensity level is not the same as sound intensity—it tells you the level of the sound relative to a reference intensity rather than the actual intensity Sound is a disturbance of matter that is transmitted from its source outward in the form of longitudinal waves

Key terms

sound: a disturbance of matter that is transmitted from its source outward by longitudinal waves
amplitude: the amount that matter is disrupted during a sound wave, as measured by the difference in height between the crests and troughs of the sound wave
sound intensity level: the level of sound relative to a fixed standard related to human hearing
sound intensity: the power per unit area carried by a sound wave
decibel: a unit used to describe sound intensity levels
speed of sound v: the same for all frequencies and wavelengths
energy of a sound wave: also proportional to its amplitude squared

Chapter 15

Light

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Summary

Calculations can be based on the relationship among the speed, frequency, and wavelength of light, and on the relationship among luminous flux, illuminance, and distance All frequencies of EM radiation travel at the same speed in a vacuum and consist of an electric field and a magnetic field. The electromagnetic spectrum is made up of a broad range of frequencies of electromagnetic radiation The types of EM radiation have different frequencies and wavelengths, and different energies and penetrating ability

Key terms

luminous flux: rate at which light is radiated from a source
magnetic field: the directional lines around a magnetic material that indicates the direction and magnitude of the magnetic force
electric field: a field that tells us the force per unit charge at all locations in space around a charge distribution
electromagnetic spectrum: made up of a broad range of frequencies of electromagnetic radiation
illuminance: number of lumens per square meter, given in units of lux (lx)
lux: unit of measure for illuminance
Maxwell’s equations: equations that describe the interrelationship between electric and magnetic fields, and how these fields combine to form electromagnetic radiation
interference: increased or decreased light intensity caused by the phase differences between waves

Chapter 16

Mirrors and Lenses

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Summary

The angle of reflection equals the angle of incidence Plane mirrors and convex mirrors reflect virtual, erect images. Concave mirrors reflect light to form real, inverted images or virtual, erect images, depending on the location of the object The index of refraction for a material is given by the speed of light in a vacuum divided by the speed of light in that material

Key terms

convex mirror: a mirror with a reflective side that is curved outward
concave mirror: a mirror with a reflective side that is curved inward
angle of incidence: the angle, with respect to the normal, at which a ray meets a boundary between media or a reflective surface
angle of reflection: the angle, with respect to the normal, at which a ray leaves a reflective surface
index of refraction: the speed of light in a vacuum divided by the speed of light in a given material
Snell’s law: the law of refraction expressed mathematically as n 1 sin θ 1 = n 2 sin θ 2
convex lens: a lens that causes light rays to converge toward the central axis
critical angle: an incident angle that produces an angle of refraction of 90°

Chapter 17

Diffraction and Interference

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Summary

Characteristics of diffraction patterns produced with diffraction gratings can be determined Diffraction gratings have been incorporated in many instruments, including microscopes and spectrometers Slits produce a diffraction pattern if their width and separation are similar to the wavelength of light passing through them Interference bands of a single-slit diffraction pattern can be predicted

Key terms

diffraction: bending of a wave around the edges of an opening or an obstacle
resolution: degree to which two images can be distinguished from one another, which is limited by diffraction
diffraction grating: many of evenly spaced slits having dimensions such that they produce an interference pattern
laser: acronym for a device that produces light amplification by stimulated emission of radiation
differential interference contrast (DIC): separating a polarized light source into two beams polarized at right angles to each other and coherent with each other then, after passing through the sample, recombining and…
Huygens’s principle: Every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself; the new wavefront is a line tangent to all of…
Rayleigh criterion: two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other
iridescence: the effect that occurs when tiny, fingerlike structures in regular patterns act as reflection gratings, producing constructive interference that gives feathers colors not solely…

Chapter 18

Static Electricity

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Summary

Objects can be charged in three ways: by contact, by conduction, and by induction Electric charge is a conserved quantity, which means it can be neither created nor destroyed Electric charge comes in two varieties, which are called positive and negative Charges with the same sign repel each other.

Key terms

induction: creating an unbalanced charge distribution in an object by moving a charged object toward it (but without touching)
Coulomb’s law: describes the electrostatic force between charged objects, which is proportional to the charge on each object and inversely proportional to the square of the distance between the…
proton: subatomic particle that carries the same magnitude charge as the electron, but its charge is positive
law of conservation of charge: states that total charge is constant in any process
test charge: positive electric charge whose with a charge magnitude so small that it does not significantly perturb any nearby charge distribution
electric field: defines the force per unit charge at all locations in space around a charge distribution
capacitor: arrangement of objects that can store electrical energy by virtue of their geometry
inverse-square law: law that has the form of a ratio, with the denominator being the distance squared

Chapter 19

Electrical Circuits

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Summary

Direct current is constant over time; alternating current alternates smoothly back and forth over time Circuit diagrams are schematic representations of electric circuits The equivalent resistance of a group of N identical resistors R connected in parallel is R / N Electrical resistance causes materials to extract work from the current that flows through them

Key terms

in parallel: when a group of resistors are connected side by side, with the top ends of the resistors connected together by a wire and the bottom ends connected together by a different wire
in series: when elements in a circuit are connected one after the other in the same branch of the circuit
circuit diagram: schematic drawing of an electrical circuit including all circuit elements, such as resistors, capacitors, batteries, and so on
resistance: how much a circuit element opposes the passage of electric current; it appears as the constant of proportionality in Ohm’s law
alternating current: electric current whose direction alternates back and forth at regular intervals
electric circuit: physical network of paths through which electric current can flow
path: proportional to the current that runs through the path
direct current: electric current that flows in a single direction

Chapter 20

Magnetism

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Summary

A charged particle moving through a magnetic field experiences a force whose direction is determined by the right-hand rule All magnets have two poles: a north pole and a south pole. If the magnet is free to move, its north pole orients itself toward the geographic North Pole of Earth, and the south pole orients itself toward the geographic South Pole of Earth A repulsive force occurs between the north poles of two magnets and likewise for two south poles.

Key terms

magnet: free to move, its north pole orients itself toward the geographic North Pole of Earth, and the south pole orients itself toward the geographic South Pole of Earth
right-hand rule: rule involving curling the right-hand fingers from one vector to another; the direction in which the right thumb points is the direction of the resulting vector
magnetic field: directional lines around a magnetic material that indicates the direction and magnitude of the magnetic force
north pole: part of a magnet that orients itself toward the geographic North Pole of Earth
south pole: part of a magnet that orients itself toward the geographic South Pole of Earth
electric motor: device that transforms electrical energy into mechanical energy
electromagnet: device that uses electric current to make a magnetic field
force whose direction: determined by the right-hand rule

Chapter 21

The Quantum Nature of Light

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Summary

The maximum kinetic energy KE e of ejected electrons (photoelectrons) is given by K E e = h f - B E , where hf is the photon energy and BE is the binding energy (or work function) of the electron in the particular… Analysis of blackbody radiation led to the field of quantum mechanics, which states that radiated energy can only exist in discrete quantum states As Einstein explained, all characteristics of the photoelectric effect are due to the interaction of individual photons with individual electrons A blackbody will radiate energy across all wavelengths of the electromagnetic spectrum

Key terms

quantum: discrete packet or bundle of a physical entity such as energy
blackbody: object that absorbs all radiated energy that strikes it and also emits energy across all wavelengths of the electromagnetic spectrum
photon energy and BE: the binding energy (or work function) of the electron in the particular…
photoelectric effect: phenomenon whereby some materials eject electrons when exposed to light
photoelectron: electron that has been ejected from a material by a photon of light
photon: a quantum, or particle, of electromagnetic radiation
particle-wave duality: property of behaving like either a particle or a wave; the term for the phenomenon that all particles have wave-like characteristics and waves have particle-like characteristics
ultraviolet catastrophe: misconception that blackbodies would radiate high frequency energy at a much higher rate than energy radiated at lower frequencies

Chapter 22

The Atom

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Summary

Described as an electron cloud, the quantum model of the atom is the result of de Broglie waves and Heisenberg’s uncertainty principle The structure of the nucleus is defined by its two nucleons, the neutron and proton Rutherford’s gold foil experiment provided evidence that the atom is composed of a small, dense nucleus with electrons occupying the mostly empty space around it The Bohr model of the atom describes electrons existing in discrete orbits, with discrete energies emitted and absorbed as the electrons decrease and increase in orbital energy

Key terms

atom: composed of a small, dense nucleus with electrons occupying the mostly empty space around it
quantum model of the atom: the result of de Broglie waves and Heisenberg’s uncertainty principle
structure of the nucleus: defined by its two nucleons, the neutron and proton
nucleons: particles found inside nuclei
decay constant: quantity that is inversely proportional to the half-life and that is used in the equation for number of nuclei as a function of time
radioactive dating: application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs
nuclear fusion: reaction in which two nuclei are combined, or fused, to form a larger nucleus
half-life: time in which there is a 50 percent chance that a nucleus will decay

Chapter 23

Particle Physics

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Summary

There are three types of fundamental particles—leptons, quarks, and carrier particles Known particles can be divided into three major groups—leptons, hadrons, and carrier particles (gauge bosons) Quarks come in six flavors and three colors and occur only in combinations that produce white Hadrons are thought to be composed of quarks, with baryons having three quarks and mesons having a quark and an antiquark

Key terms

particle physics: the study of and the quest for those truly fundamental particles having no substructure
quark: an elementary particle and fundamental constituent of matter that is a substructure of hadrons
antimatter: matter constructed of antiparticles; antimatter shares most of the same properties of regular matter, with charge being the only difference between many particles and their…
four fundamental forces: gravity, the electromagnetic force, the weak nuclear force, and the strong nuclear force
color: a property of quarks the relates to their interactions through the strong force
hadron: particles composed of quarks that feel the strong and weak nuclear force
carrier particle: a virtual particle exchanged in the transmission of a fundamental force
lepton: fundamental particles that do not feel the nuclear strong force