AST101 Exam 2 (Ch. 4, 5, 6)

How is mass different from weight? Use the Moon to give example [pwp question] (113)

-Mass of object depends only on the amount of matter in object and is the same anywhere -Weight of object can very because the forces acting on the object can vary -Objects are weightless in free-fall. -EX: my mass would be the same on the Moon as on Earth, but I would weigh less on the Moon because of its weaker gravity

What are the four major ways light and matter can interact? Give an example of each from everyday life (pwp, 139)

-Matter can emit light, absorb light, transmit light, and reflect (or scatter) light. -Interactions between light and matter determine the appearance of everything around us. • Emission • Absorption ~Opaque objects block (absorb) light. • Transmission ~Transparent objects transmit light. • Reflection/scattering • Emission: the process by which matter emits energy in the form of light -EX: a light bulb emits visible light ; the energy of the light comes from electrical potential energy supplied to the light bulb • Absorption: the process by which matter absorbs radiative energy ~Opaque objects block (absorb) light. - EX: when you place your hand near an incandescent light bulb, your hand absorbs some of the light, and this absorbed energy warms your hand • Transmission: the process in which light passes through matter without being absorbed -(glass or air) ~Transparent objects transmit light. • Reflection/scattering: -Reflection- light bounces off matter all in the same general direction (EX: A mirror reflects light in a particular direction) -Scattering- when the bouncing is more random (EX: A movie screen scatters light in all directions) -Red glass transmits red light but absorbs other colors -A green lawn reflects (scatters) green light but absorbs all other colors

What do we need to know if we want to measure an object's mass with Newton's version of Kepler's third law? (pwp)

-Newton's version of Kepler's third law allows us to calculate the masses of orbiting objects from their orbital periods and distances between the two

Define speed

-Rate at which object moves (pwp) -tells us how far an object will go in a certain amount of time (111) -Formula: speed = distance/time (units of m/s)

What does a force acting on an object do to that object's motion? (Ch.4 quiz)

A force changes an object's momentum.

If you heat a rock until it glows its spectrum will be....

A thermal Spectrum -(look at chegg ch.5 #33)

A plasma is a..... (Ch.5 quiz)

gas of ions and electrons ions: atoms with a positive or negative electrical charge -interacts with light differently bc it has lots of charged particles in it

A car is accelerating when it is.... -traveling on straight flat road at 50mph -traveling on straight uphill road at 30mph -going around a circular track at a steady 100mph (ch.4 hw)

going around a circular track at a steady 100mph -its direction is always changing since its not moving along a straight line and direction is a type of acceleration

The gravitational potential energy of a contracting interstellar cloud....

gradually transforms into other forms of energy

When a ball is dropped, some of the ball's energy changes from.... (Ch.4 quiz)

gravitational potential energy to kinetic energy.

A photon with a longer wavelength... (Ch.5 quiz)

has a lower frequency than a photon with a short wavelength.

Compared to red light, blue light has higher frequency and... (ch.5 hw #28)

higher energy and shorter wavelength

A red chair appears red to the eye because.... (Ch.5 quiz)

it reflects red light.

The energy of Earth's rotation is an example of what kind of energy? (Ch.4 quiz)

kinetic energy

The higher the photon energy.... (pwp thought question)

the shorter its wavelength.

A molecule is.... (Ch.5 quiz)

two or more atoms linked together (O^2 [oxygen -> made of 2 oxygen molecules]) [quiz answer] [notes] -compound: molecule with two or more types of atoms (H^2O [water -> 2 hydrogen atoms 1 oxygen atom] -chemical properties of molecule are different from those of its individual atom (ex: molecular oxygen [O^2] behaves differently from atomic oxygen [O] -Molecules have additional energy levels because they can vibrate and rotate. -The large numbers of vibrational and rotational energy levels can make the spectra of molecules very complicated. • Many of these molecular transitions are in the infrared part of the spectrum.

How does light tell us the temperatures of planets and stars? (pwp overview question)

we can determine temperature bc of the two laws of thermal radiation: -Hotter objects emit more light at all frequencies per unit area. -Hotter objects emit photons with a higher average energy (which means shorter average wavelength) • Nearly all large or dense objects (stars, planets, me) emit a thermal radiation spectra (most common type of continuous spectra) that depends only on the object's temperature. -bc a dense object absorbs most light and doesn't allow photons to escape easily so they bounce and interact a lot with those atoms/molecules that they end up with energies that match the kinetic energies of the object's atoms/molecules

Define atomic number and atomic mass number. Under what conditions are two atoms different isotopes of the same element?

ATOMIC NUMBER: = # of protons in nucleus ATOMIC MASS NUMBER: = # of protons + neutrons in nucleus CONDITIONS FOR DIFFERENT ISOTOPES SAME ELEMENT: -same # of protons but different # of neutrons (EX carbon-13: 13^C (6 protons + 7 neutrons)

Which of the following is not changing for someone driving a car in a circle at 30 miles per hour? (Ch.4 quiz) A. position B. velocity C. acceleration D. momentum E. none of the above (all are changing)

Acceleration

Define temperature and thermal energy. How are they related? How are they different? (pwp, 120-121)

TEMPERATURE: -the average kinetic energy of the many particles in a substance. -higher temperature: particles on average have more kinetic energy so they're moving faster THERMAL ENERGY: -subcategory of kinetic energy -The collective kinetic energy of many individual particles (atoms/molecules) moving randomly within a substance (ex:in a rock, in air, in water) -all objects have thermal energy even when sitting still because the particles within them are always moving -depends on temperature and density bc higher average (temperature) = higher total energy / higher density = higher total energy DIFFERENT: -Thermal measures the total kinetic energy of the particles -temperature measures the average kinetic energy of the particles

How does visible light compare to radio waves? (Ch.5 quiz)

Visible light waves have a shorter wavelength than radio waves.

Explain why orbits cannot change spontaneously, and how a gravitational encounter can cause a change. How can an object achieve escape velocity? (ch.4 hw)

WHY ORBITS CAN'T CHANGE: Law of conservation of energy says total orbital energy (gravitational + kinetic) stays constant if there is no external force to cause the planet to gain or lose orbital energy so it's orbit stays the same. GRAVITAIONAL ENCOUNTER: two objects exchange orbital energy when they pass close enough that each feel the effects of the other's gravity -EX: a comet (with an unbound orbit) passes by a planet, they exchange energy, the comet's orbit changes to bound ESCAPE VELOCITY: If an object gains enough orbital energy, it may escape (change from a bound to unbound orbit).

list the phases of matter in order of increasing temperature (Ch.5 quiz)

solid, liquid, gas, plasma

Waves / three basic properties of waves (wavelength, frequency, speed) (pwp, 141)

-A wave is a pattern of motion that can carry energy without carrying matter along with it. WAVELENGTH: is the distance between two wave peaks. FREQUENCY: the number of peaks passing by any point each second (the number of times per second that a wave vibrates up and down) -units of hertz or cycles per second SPEED: how fast the peaks travel / how fast the energy travels from one place to another -Wave speed = Wavelength × Frequency RELATIONSHIP: -energy is proportional to frequency -wavelength is inversely proportional to its frequency • High frequency ↔ short wavelength ↔ high energy • Low frequency ↔ long wavelength ↔ low energy EX: A wave has a wavelength of 1cm and a frequency of 3 hertz. -wavelength tells us that each time a peak passes by, the wave peak has traveled 1 cm -frequency tells us that three peaks pass by each second -the speed of the wave is 3cm per second

Describe the conditions that lead to each of the three basic types of spectra. Which type is the Sun's visible light spectrum and why? (ch.5 hw)

-CONTINUOUS SPECTRUM -EMISSION LINE SPECTRUM -ABSORPTION LINE SPECTRUM CONTINUOUS SPECTRUM: -The spectrum of a common (incandescent) light bulb spans all visible wavelengths, without interruption (shows full rainbow). EMISSION LINE SPECTRUM: -A thin or low-density cloud of gas emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines against black background. ABSORPTION LINE SPECTRUM: -A cloud of gas between us and a light bulb can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum. SUN'S visible light spectrum: -absorption line spectrum bc Earth's atmosphere is between us and the sun. The atmosphere absorbs lights of certain wavelength

Compared to the sun, a star whose spectrum peaks in the infrared is.....

-Cooler -The sun's spectrum peaks at visible light -an infrared photon has lower frequency than a visible light photon and thus less energy ->so the photons emitted from infrared spectrum have less energy than Sun's spectrum -temperature corresponds to energy ->lower temperature lower energy -the star that emits photons with less energy must be at a lower temperature

How can we use emission or absorption lines to determine the chemical composition of a distant object?

-Each type of atom has a unique spectral fingerprint. They emit and absorb light at specific wavelengths -observing the absorbed lines or emitted lines in a spectrum tells us which kinds of atoms are present. • Each type of atom has a unique set of energy levels. -emission or absorption lines occur only at specific wavelengths that correspond to particular energy level transitions • Downward transitions produce a unique pattern of emission lines. • upward transitions produce a pattern of absorption lines at the same wavelengths because those atoms can absorb photons with those same energies.

-Electromagnetic Spectrum -Electromagnetic radiation List the different forms of light in order from lowest to highest energy. Is the order the same from lowest to highest frequency? From shortest to longest wavelength? Explain.

-Electromagnetic Spectrum: the complete spectrum of light / The entire range of wavelengths of light -Electromagnetic radiation: another name for light of all types • Trends on the electromagnetic spectrum: • High frequency ↔ short wavelength ↔ high energy • Low frequency ↔ long wavelength ↔ low energy Lowest to highest energy / frequency -RADIO WAVES -MICROWAVES -INFRARED -VISIBLE LIGHT -ULTRAVIOLET -X-RAYS -GAMMA RAYS Shortest to longest wavelength: -gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves, radio waves EXPLANATION: - energy&frequency the same bc energy is proportional to frequency -Wavelength different bc wavelength is inversely proportional to its frequency RADIO WAVES: -longest wavelength and lowest frequency -useful for radio communication bc they make electrons move up&down in an antenna -carry so little energy that they don't noticeably effect our bodies MICROWAVES: -wavelength range from micrometers to centimeters -considered a subset of radio waves INFRARED: -lies beyond the red end of the rainbow -light with wavelengths somewhat longer than red light -molecules moving in a warm object emit infrared light (why we associate it w/heat) VISIBLE LIGHT: -light that our eyes can see -the particular frequencies that our eyes happen to be capable of detecting (Human eyes cannot see most forms of light.) -wavelengths range from 400 nanometers at the blue/violet end of the rainbow to 700 nanometers at the red end -nanometer (nm) is a billionth of a meter -vision's possible bc receptors in our eyes respond to visible light photons ULTRAVIOLET: -lies beyond the blue/violet end of rainbow -wavelengths somewhat shorter than blue/violet light -ultraviolet photons carry enough energy to damage skin cells, cause sunburn/cancer X-RAYS: -shorter wavelengths than ultraviolet -can be used to make images of bones/teeth bc x-ray photons have enough energy to penetrate through skin/muscle but is blocked by bones/teeth GAMMA RAYS: -shortest wavelength / highest frequency -astronomers seek to observe light of all wavelengths bc certain types of matter tend to interact more strongly with certain types of light so each light carries different information about distant objects in the universe

What is tidal friction? What effects does it have on Earth? How does it explain the Moon's synchronous rotation?

-Friction that's the result of tidal forces stretching earth EFFECT TO EARTH: -Tidal friction gradually slows Earth's rotation (and makes the Moon get farther from Earth) -Earth's rotation tries to pull bulges with it -the moon's gravity tries to pull the bulges back into line, slowing Earth's rotation HOW IT EXPLAINS MOON'S SYNCHRONOUS ROTATION: -The Moon once orbited faster (or slower); tidal friction caused it to ''lock'' in synchronous rotation. - as a result of tidal friction, the moon rotated through its tidal bulges because the earth's gravitational pull was much stronger, causing it to rotate and orbit synchronously

Where do objects get their energy? (pwp overview)

-From other objects • Conservation of energy: energy is always conserved it cannot be created or destroyed but only transformed from one type to another. • Energy comes in three basic types: kinetic, potential, radiative.

Define acceleration. What are the units of acceleration?

-Rate of change in velocity -measured in units of speed/time (m/s^2) ->in meter per second per second -object has an acceleration if its velocity is changing in any way, whether in speed (speeding up/slowing down) or direction (turning) or both -Slowing: negative acceleration, causes velocity to decrease -Turning: change in direction, causes change in velocity (represents acceleration even if speed remains constant) -when an object accelerates there is a net force -planets are always accelerating when they orbit the sun, because their direction of travel constantly changes as they go around their orbits [112]

What keeps a planet rotating and orbiting the Sun? (pwp question) Define Angular momentum and torque [pwp, 113]

-Rotational momentum of a spinning or orbiting (moving in circles) object [pwp] -an object that is either spinning or moving along a curved path has angular momentum [113] -FORMULA: m x v x r (m=mass ; v=velocity ; r=radius) -Earth has angular momentum due to its rotation (rotational angular momentum) and due to its orbit around the sun (orbital angular momentum) -object's angular momentum can change only when a torque is applied to it TORQUE: -twisting force -amount of torque depends not only on how much force is applied, but also where it's applied What keeps a planet rotating and orbiting the Sun? (pwp question) Conservation of Angular momentum -as long as there is no external torque, the total angular momentum of a set of interacting objects cannot change -an individual object can change its angular momentum only by transferring some angular momentum to or from an object. -Earth experiences no twisting force as it orbits the Sun, so its rotation and orbit will continue indefinitely. -also explains why objects rotate faster as they shrink in radius.

compared to its angular momentum when it is farthest from the Sun, Earth's angular momentum when it is nearest the sun is......(ch.4 hw) -greater -less -same

-Same -angular momentum can only be changed by a torque

A compact car and a Mack truck have a head-on collision. What happens? (pwp thought question) (add bug vs. truck story 112)

-The force of the car on the truck is equal and opposite to the force of the truck on the car. -The momentum transferred from the truck to the car is equal and opposite to the momentum transferred from the car to the truck.

Spectrum / Colors of Light / White light (138, pwp)

-Visible (white) light is actually a combination of colors (the rainbow) -EX: light from the sun or a light bulb is often called white light SPECTRUM: -Passing visible light through a prism separates it into its "component" colors -> a spectrum -You can produce a spectrum with a prism OR a diffraction grating (a piece of plastic or glass etched with many closely spaced lines)

Why do we say that light is an electromagnetic wave? Describe the relationship among wavelength, frequency, and speed for light (Ch. 5 HW)

-We say that light is an electromagnetic wave bc a light wave is a traveling vibration of electric and magnetic fields. -the vibrations of the electric field in an electromagnetic wave will cause any charged particle (electrons) to bob up and down, which is how we tell wavelength, frequency, and speed RELATIONSHIP: -because all light travels at the same speed, the longer the wavelength the lower the frequency and vice versa -energy is proportional to frequency -wavelength is inversely proportional to its frequency • High frequency ↔ short wavelength ↔ high energy • Low frequency ↔ long wavelength ↔ low energy

Describe the phase changes of water as you heat it, starting from its solid phase, ice. What happens at very high temperatures? (ch.5 hw)

-as a substance is heated, the average kinetic energy of its particles (temperature) increases enabling the particles to break the bonds holding them to their neighbors -As temperature rises, a substance transforms from a solid to a liquid to a gas, then the molecules can dissociate into atoms. -Stripping of electrons from atoms (ionization) turns the substance into a plasma. -Chemical Bond: name for the interactions between electrons that hold the atoms in a molecule together -Phase of a substance depends on both temperature and pressure. -Phase changes occur when one type of bond is broken and replaced by another BELOW FREEZING • Solid (ice): -atoms/molecules are held tightly in place & tightly bound to neighbors (low avg. kinetic energy AT MELTING POINT (0C): • Liquid (water): -Melting: molecules have enough energy to->breaking of rigid chemical bonds, changing solid into liquid -atoms/molecules remain together but move relatively freely ABOVE BOILING POINT (0C) • Gas (water vapor) -Evaporation: molecules have enough energy to->breaking of flexible (all) chemical bonds, changing liquid into solid -atoms/molecules move essentially unconstrained • Molecular Dissociation: -molecules in gas violently collide together which breaks chemical bonds holding individual molecules together -molecules break apart into component atoms AT TEMPS OF THOUSANDS DEGREES: •Plasma Ionization: -stripping of electrons, changing atoms into plasma->free electrons move among positively charged ions -collisions break the bonds holding electrons around the nuclei

Briefly describe the structure and size of an atom. How big is the nucleus in comparison to the entire atom? (ch.5 hw) What is electrical charge? Will an electron and a proton attract or repel each other? How about two electrons? Explain

-atoms come in different types. Each type corresponds to a different chemical element -very very small millions could fit end to end across a period (".") -number of atoms in single drop of water may exceed the number of stars in the observable universe -consist of a tiny nucleus that has protons and neutrons in it and i the nucleus is surrounded by a cloud of electrons -held together by the attraction between the positively charged protons and negatively charged electrons -properties of atom mainly depend on electrical charge in its nucleus (electrically neutral if same # of protons&electrons) NUCLEUS: -is small compared to the atom as a whole but contains most of atoms mass (bc protons and neutrons are 2000times as massive as an electron) PROTON: -positive charge (+1) NEUTRON: -no charge (electrically neutral) ELECTRON: -negative charge (-1) -form smeared out cloud around nucleus->this gives atom its big size -if nucleus is size of my fist the electron cloud is many kilometers wide ELECTRICAL CHARGE: physical property that describes how strongly an object will interact with electromagnetic fields -total electrical charge is always conserved -oppositely charged particles attract -similarly charged particles repel

If Earth were twice as far from the sun, the force of gravity attracting Earth to the sun would be.....(ch.4 hw) -twice as strong -half as strong -one quarter as strong

-one quarter as strong -Universal law of gravitation-> Attraction is inversely proportional to the square of the distance between their centers.

What is the acceleration of gravity (g)? The acceleration due to gravity of an object on the surface of Earth depends on what? (Ch.4 quiz)

-the acceleration of a falling object -All falling objects accelerate at the same rate, regardless of their mass (not counting friction of air resistance) -On Earth, air resistance causes the difference in acceleration between a feather and a rock [112] -On Earth the acceleration of g ≈ 10 m/s2 (this is 10 meters per second per second or 10 meters per second squared): -speed increases 10 m/s with each second of falling. -Galileo showed that g is the same for all falling objects, regardless of their mass. The acceleration due to gravity of an object on the surface of Earth depends on what? (Ch.4 quiz) A. the radius of Earth. B. the mass of Earth.

Define velocity

-the combination of an objects speed and its direction (111) -EX: 10 m/s, due east -can change velocity by speed up slow down, change direction [pwp my notes]

the statement "there's no gravity in space." is false because.... (ch.4 hw)

-universal law of gravity says that one object will always experience an attractive force from other objects. So no matter where a person is in the universe it will experience gravity from the rest of the things in the universe even if it's a very small amount.

For each of the following is there a net force on the object described? Y/N 1. A car coming to a stop 2. A bus speeding up 3. An elevator moving up at constant speed 4. A bicycle going around a curve 5. A moon orbiting Jupiter (pwp thought question)

1. A car coming to a stop: Y 2. A bus speeding up: Y 3. An elevator moving at constant speed: N (the upward speed is being canceled out by the downward force of gravity) 4. A bicycle going around a curve: Y 5. A moon orbiting Jupiter: Y

What determines the strength of gravity? (pwp overview question) Summarize the universal law of gravitation both in words and with an equation

1. Every mass attracts every other mass through the force of gravity. 2. Attraction is directly proportional to the product of their masses. 3. Attraction is inversely proportional to the square of the distance between their centers. 1. Every mass attracts every other mass through the force of gravity. 2. Attraction is directly proportional to the product of their masses. ----the strength of the gravitational force attracting any two objects is directly proportional to the product of their masses. (doubling the mass of one object doubles the force of gravity between the two objects) 3. Attraction is inversely proportional to the square of the distance between their centers. -----the strength of gravity between two objects decreases with the square of the distance between their centers (doubling the distance between two objects weakens the force of gravity by a factor of 2^2) SEE NOTE CARD FOR FORMULA Fg=Force of gravitational attraction G= gravitational constant (number given) M1 and M2= the masses of the two objects D=the distance between their centers

Does statement make sense or not make sense? (ch.4 hw) 16. Suppose you could enter vacuum chamber on Earth. A feather would fall at the same rate as a rock. 19. If the sun were replaced by a giant rock that had precisely the same mass, Earth's orbit would not change. 20. The fact that the moon rotates once in precisely the time it takes to orbit earth once is such an astonishing coincidence that scientists probably will never be able to explain it 24. Someday soon scientists are likely to build an engine that produces more energy than it consumes

16. Makes sense; there wouldn't be air resistance 19. Makes sense 20. Doesn't make sense; The moon's synchronous rotation can be explained by tidal friction 24. Doesn't make sense; law of conservation of energy says energy can't be created or destroyed into nothingness. Can only exchange or transform so an engine will at most produce as much energy as it consumes

Does the statement make sense or does it not make sense? 17. the walls of my room are transparent to radio waves 19. if you could see infrared light, you would see a glow from the backs of your eyelids when you close your eyes 20. if you had x-ray vision you could read this entire book without turning any pages 21. two isotopes of the element rubidium differ in their number of protons

17. Makes sense; the various portions of the electromagnetic spectrum interacts in different ways w/matter. A brick wall can transmit radio waves 19. Makes sense; The backs of eyelids are at a temp. that can emit thermal radiation, which is mostly infrared. If our eyes could see infrared light we'd be able to the glow from thermal radiation when we close our eyes 20. Doesn't make sense; 21. Doesn't make sense. Isotopes have same # of protons different # of neutrons

Does statement make sense or not make sense? 18. I used newtons version of Kepler's third law to calculate Saturn's mass from orbital characteristics of its moon titan. 21. Venus has no oceans, so it could not have tides even if it had a moon (which it doesn't) 22. If an asteroid passed by Earth at just the right distance, Earth's gravity would capture it and make it our second moon 23. When I drive my car at 30mph it has more kinetic energy than it does at 10mph

18. Makes sense 21. Doesn't make sense; land can experience tidal friction too 22. Makes sense; use explanation of how unbound can become bound 23. Makes sense; kinetic energy depends on mass and speed of car. Mass of car wouldn't change

Does the statement make sense or does it not make sense? (ch.5 hw) 18. because of their higher frequencies, X-rays must travel through space faster than radio waves

18. doesn't make sense; In space light always travels at the same speed

Does the statement make sense or does it not make sense? 24. If you could view a spectrum of light reflecting off a blue sweatshirt, you'd find the entire rainbow of color (looking the same as a spectrum of white light) 26. If a distant galaxy has a substantial redshift (as viewed from earth) then anyone living in that galaxy would see a substantial redshift in a spectrum of the Milkyway galaxy

24. Doesn't make sense; -It'd be impossible to see the entire rainbow bc the other colored photons are absorbed -If we could see blue light reflecting off a blue sweater that means all the other colored photons are absorbed instead of reflected by the blue sweater. 26. Makes sense; if from our point of view we see a distant galaxy with a red shift (its moving away from us) then the people from the distant galaxy will would see a redshift bc we'd be moving away from them

Does the statement make sense or does it not make sense? (ch.5 hw) 25. Galaxies that show redshifts must be red in color

25. doesn't make sense; -when wavelength becomes longer when the object moves away it is called redshift which has nothing to do with the color of the galaxy; it only tells us that the galaxy is actually moving away from us

When two objects collide what happens...(Ch.4 quiz) -Momentum -Forces -Angular momentum -energy

A. their combined momentum remains unchanged. B. they exert equal and opposite forces on each other. C. their combined angular momentum remains unchanged. D. their combined energy remains unchanged.

!!!!!!!!!SEE 163!!!!!!!!!!!!! Energy level transitions. The following labeled transitions represent an electron moving between energy levels in hydrogen. Answer the following A. Which transition could represent an atom that absorbs a photon with 10.2 eV of energy? B. Which transition could represent an atom that emits a photon with 10.2 eV of energy? C. Which transition represents an electron that is breaking free of the atom? D. Which transition shown is not possible? E. Would transition A represent emission or absorption of light? How would the wavelength of the emitted or absorbed photon compare to that of the photon involved in transition C? Explain. (ch.5 hw #43)

A. Transition B (absorb=gain) B. Transition C (emit=lose) C. Transition E D. Transition D E. Transition A represents emission of light. The photon in transition A is more energetic than the photon in transition C bc the photon in transition A is making more of a jump than transition C. So, the wavelength of the photon in transition A is shorter than the wavelength of the photon in transition C

Which is hottest? (pwp question) A. a blue star B. a red star C. a planet that emits only infrared light

A. a blue star

Light with a short wavelength..... (Ch.5 quiz)

A. has a higher frequency than light with a long wavelength. B. is bluer than light with a long wavelength. C. has more energy than light with a long wavelength.

The acceleration due to gravity of an object on the surface of Earth depends on what? (Ch.4 quiz)

A. the radius of Earth. B. the mass of Earth.

Objects on bound orbits do what? (Ch.4 quiz) What is the difference between a bound and an unbound orbit? What orbital shapes are possible?

BOUND: A. follow elliptical orbits. B. orbit the center of mass of the system. C. stay in orbit around the object they are orbiting. UNBOUND: paths that bring an object close to another object just once Shape: parabola or hyperbola

What is the difference between a bound and an unbound orbit? What orbital shapes are possible?

BOUND: object goes around another object over and over again Shape: ellipses UNBOUND: paths that bring an object close to another object just once Shape: parabola or hyperbola

If the moon were closer to earth high tides would.... (ch.4 #34)

Be higher than they are now bc the gravitational force of the moon would be stronger

Describe the laws of conservation of momentum, of angular momentum, and of energy. Give an example of how each is important to astronomy

CONSERVATION OF MOMENTUM: - states the total momentum of interacting objects cannot change unless an external force is acting on them -Interacting objects exchange momentum through equal and opposite forces. -an individual object can gain or lose momentum only if some other object's momentum changes by a precisely opposite amount CONSERVATION OF ANGULAR MOMENTUM: -as long as there is no external torque, the total angular momentum of a set of interacting objects cannot change -an individual object can change its angular momentum only by transferring some angular momentum to or from an object. -also explains why objects rotate faster as they shrink in radius. CONSERVATION OF ENERGY: -energy cannot be created or destroyed but only transformed from one type to another or be exchanged between objects. -The total energy content in an isolated system is always the same. -objets can gain/lose energy only by exchanging energy with other objects

Why do objects move at constant velocity if no force acts on them? (pwp question)

Conservation of momentum - states the total momentum of interacting objects cannot change unless an external force is acting on them -Interacting objects exchange momentum through equal and opposite forces. -an individual object can gain or lose momentum only if some other object's momentum changes by a precisely opposite amount

Describe the doppler effect for light and what we can learn from it. What does it mean to say that radio waves are blue shifted? How does light tell us the speed of a distant object? (pwp overview question) Why does the doppler effect widen the spectral lines of rotating objects?

DOPPLER EFFECT: -is a change in the frequency and wavelength of a wave, as measured by an observer, due to the motion of the source or observer. -Doppler shift tells us ONLY about the part of an object's motion toward or away from us (not moving across our line of sight or diagonally from us) BLUESHIFT: -doppler shift of an object coming toward you -the light waves bunch up between us and the object, so its entire spectrum is shifted to shorter wavelengths -Increase in observed wave frequency (decreased wavelength) -name is bc shorter wavelengths of visible light are bluer REDSHIFT: -doppler shift of an object moving away from us -light is shifted to longer wavelengths -Decrease in observed wave frequency (increased wavelength) -name bc longer wavelengths of visible light are redder WHAT WE CAN LEARN/HOW IT TELLS US SPEED: -by comparing the rest wavelength/normal spectrum of an element to its shifted spectrum we can find speed -The amount of blue shift or red shift tells us an object's speed toward or away from us. • Greater speed → Greater blue (or red) shift • Lower speed → Less blue (or red) shift ROTATION: -doppler effect also tells us information about motion within the object -looking at spectral lines of a rotating object: light from the part of the object rotating toward us will be blue shifted -light from the part rotating away from us will be redshifted -light from center won't be shifted at all -net effect is to make each spectral line appear wider than it would if the object were not rotating -the faster the object is rotating the broader in wavelength the spectral lines become -this means we can find the objects rotation rate by measuring the width of its spectral lines

Does the statement make sense or does it not make sense? (ch.5 hw) If the sun's surface became much hotter (while the sun's size remained the same) the sun would emit more ultraviolet light but less visible light than it currently emits

Doesn't make sense; -the intensity-wavelength curve for a hotter object is everywhere above the curve for a colder object. -This means if the sun became much hotter, then it would emit more ultraviolet AND emit more visible light

How does the force the Earth exerts on you compare with the force you exert on it? (pwp question)

Earth and you exert equal and opposite forces on each other.

According to the universal law of gravitation what would happen to Earth if the sun were somehow replaced by a black hole of the same mass? (ch.4 #33)

Earth's orbit would not change -the strength of gravitational force attracting two objects is directly proportional to the product of their masses

Ionization is the process by which....

Electrons escape from atoms

How do electrons in an atom change energy? (Ch.5 quiz)

Electrons move between discrete energy levels, or escape the atom if given enough energy.

State Newton's three laws of motion. For each law, give an example of its application (Ch.4 hw) [pwp, 115-117]

FIRST LAW: An object moves at constant velocity unless a net force acts to change its speed or direction. (objects at rest [0 velocity] remain at rest, objects in motion remain in motion with no change to speed/direction) EX: A spaceship needs no fuel to keep moving in space b/c there's no friction or air resistance SECOND LAW: Force = mass x acceleration OR Force = rate of change in momentum EX: a baseball accelerates as the pitcher applies a force by moving his arm. (once the ball is released, the force from the pitcher's arm ceases, and the ball's path changes only bc of the forces of gravity and air resistance) THIRD LAW: For every force, there is always an equal and opposite reaction force. EX: a rocket engine generates a force that drives hot gas out the back, which creates an equal and opposite force that propels the rocket forward

What is free-fall, and why does it make you weightless? Briefly describe why astronauts are weightless in the Space station (pwp, 113-114)

FREE-FALL: falling without any resistance to slow you down / wherever there is nothing to prevent you from falling -When in free fall you are floating above the scale so you are not exerting force on the scale or anything else so you are weightless -> there's nothing below you to exert force on. -Remember that weight is the force applied to an object so you're weightless until you hit the ground ASTRONAUTS: -There is gravity in space -Astronauts are in a constant state of free fall -(Need more info see chegg ch.4 #3 and 114)

(ch.5 #11) How do we convert a spectrum shown as a band of light (like a rainbow) into a graph of the spectrum?

In the intensity wavelength graph the relative amount of energy received from an object in each wavelength of light is shown. -the intensity given at a certain wavelength is proportional to the product of the number of photons observed at that wavelength

Explain how the moon creates tides. Why do we have two high and low tides each day? How do the tides vary with the phase of the moon? (ch.4 hw)

HOW THE MOON CREATES TIDES: Gravitational attraction of each part of Earth to the Moon gets weaker as we go from the side of earth facing the moon to the side facing away. -The Moon's gravity creates a tidal force that stretches Earth and its oceans, causing earth to bulge both toward and away from the moon. WHY WE HAVE 2 HIGH AND LOW TIDES: Earth's rotation carries us through the two bulges each day, giving us two high and low tides each day Low tides: occur when location is halfway between the tidal bulges High tides: occur every 12 hours 25 min because reaches its highest point in the sky every 24 hours 50 minutes HOW THE TIDES VARY WITH PHASE OF MOON: Size of tides depends on phase of Moon bc The Sun also has a small tidal effect on Earth. -New/Full Moon: Tidal forces add up and increase tidal effect -Third/First Quarter Moon: Tidal forces counteract and decrease tidal effect

Some nitrogen atoms have seven neutrons and some have 8 neutrons. These two forms of nitrogen are... ((ch.5 hw #31)

Isotopes of each other

How does the force of gravity between two objects depend on the distance between the objects? (Ch.4 quiz)

It increases in proportion to 1/distance squared.

I measure a line in the lab at 500.7 nm. The same line in a star has wavelength 502.8 nm. What can I say about this star?

It is moving away from me.

What was Newton's insight about gravity? (ch.4 quiz) How did Newton change our view of the universe? (pwp overview)

It is responsible for the motion of the Moon around Earth. • He discovered laws of motion and gravitation. • He realized the same laws of physics were identical in the universe and on Earth (he unified things).

How do the cornea and lens affect light entering the eye? (ch.6 quiz)

Light travels slightly slower moving through them, causing the direction of the incoming light to change and focus on the retina.

What do we mean by mass-energy? Explain the formula E = mc^2 [Ch.4 hw] (pwp, 122)

MASS-ENERGY: -Mass itself is a form of potential energy -energy can be transformed into mass -Concentrated energy can spontaneously turn into particles (for example, in particle accelerators). EXPLAIN E = mc^2: E= the amount of potential energy contained in mass, m= the mass of the object, c= the speed of light -The equation tells us that a small amount of mass contains a huge amount of energy and can release a great deal of energy (for example, an H-bomb). -tells us that mass can be converted into other forms of energy -and tells us energy can be transformed into mass

Mass / Weight

MASS: -a measure of the amount of matter in an object (how much stuff there is in an object) -it's the same anywhere WEIGHT: -the force that an object applies to its surroundings -the force that a scale measures when you stand on it (force acting on mass) -depends on object's mass and the forces (including gravity) acting on objects mass. Weight can vary because the forces acting on object can vary -can vary because the forces acting on object can vary

Define momentum; what do we mean when we say that momentum can be changed only by a net force? Define force / net force

MOMENTUM: -an objects momentum is the product of its mass and velocity -Formula: Momentum = mass x velocity OR p = mv P=momentum ; m=mass ; v=velocity -only way to change an object's momentum is to apply a force to it WHAT DO WE MEAN: -A change in momentum occurs only when the net force is not zero (A net force that is not zero causes an object to accelerate) -changing object's momentum produces acceleration (means changing its velocity), as long as its mass remains constant FORCE: -Anything that can cause a change in momentum -EX: gravity / electromagnetic forces acting between atoms NET FORCE: -the overall force acting on an object; -represents the combined effect of all the individual forces put together -if two forces cancel each other out then there is no net force [my pwp notes] -equal to the rate of change in the object's momentum FORMULA: F=ma (F=force ; m=mass ; a=acceleration)

Does the statement make sense or does it not make sense? 22. a white hot object is hotter than a red hot object

Makes sense; -A "white hot" object looks white bc the light emitted is a mixture of colors, which means the thermal radiation spectrum of this object peaks somewhere in the middle of the invisible light range. -A "red hot" object looks red bc the light emitted is mostly red or infrared, which is a longer wavelength than the "white hot" object's thermal radiation spectrum peaks. -The hotter the temp of an object the shorter wavelength its thermal radiation spectrum will peak at. -Thus, "white hot" is hotter than "red hot"

Gravitational Potential Energy (pwp, 121-122) On earth / space

On Earth, depends on: -object's mass (m) -strength of gravity (g) -distance object could potentially fall as a result of gravity / the higher it is the more gravitational potential energy IN SPACE: -In space, an object or gas cloud has more gravitational energy when it is spread out than when it contracts. -A contracting cloud converts gravitational potential energy to thermal energy.

What is a photon? In what way is a photon like a particle? In what way is it like a wave? (Ch. 5 HW)

PHOTON: -an individual particle ("piece") of light -each photon of light carries a specific amount of radiative energy. -the shorter the wavelength/ higher its frequency the higher the energy of the photons LIKE PARTICLES: -can be counted individually LIKE WAVES: -each photon is characterized by a wavelength and a frequency

Special Topic: Polarization / Polarized Sunglasses (from pwp)

POLARIZATION: describes the direction in which a light wave is vibrating • Reflection can change the polarization of light. • Polarized sunglasses block light that reflects off of horizontal surfaces.

What is the difference between energy and power? What units do we use to measure power? (138, pwp, chegg Ch.5 #1)

POWER: -is the rate of the energy flow -measured in units of watts: 1 watt = 1 joule/s. -power can only tell us how fast energy has been transferred, not the total amount -bc the amount of energy transferred from one object to the other object does not only depend on the rate of the energy flow, which is power, but also depends on how long it has been transferring. EX: a 100-watt light bulb requires 100 joules of energy for each second it's turned on

Why don't we glow in the dark? (pwp question)

People only emit light that is invisible to our eyes.

A spectral line that appears at a wavelength of 321nm in the laboratory appears at a wavelength of 328nm in the spectrum of a distant object. We say that the object's spectrum is.... (ch.5 hw #36)

Redshifted

Describe two ways in which the thermal radiation spectrum of an 8000 K star would differ from a 4000 K star. (ch.5 hw)

The 8000K star would 1. have a shorter wavelength of peak emission, and 2. would emit more light at all wavelengths -Hotter objects emit more light at all frequencies per unit area. -Hotter objects emit photons with a higher average energy (which means shorter average wavelength)

How does light tell us the speed of a distant object? (pwp overview question)

The Doppler effect tells us how fast an object is moving toward or away from us.

How does the Doppler effect affect an emission line spectrum if the emitting object is moving toward you? (Ch.5 quiz)

The emission lines move to shorter wavelengths.

Why can cameras see objects too faint to be seen by the eye? (ch.6 quiz)

They can record light for a longer period of time.

What keeps a planet rotating and orbiting the Sun? (pwp question)

What keeps a planet rotating and orbiting the Sun? (pwp question) Conservation of Angular momentum -as long as there is no external torque, the total angular momentum of a set of interacting objects cannot change -an individual object can change its angular momentum only by transferring some angular momentum to or from an object. -Earth experiences no twisting force as it orbits the Sun, so its rotation and orbit will continue indefinitely. -also explains why objects rotate faster as they shrink in radius.

How do we describe motion? (pwp question)

With the concepts of speed, velocity, and acceleration. -Speed = distance/time • Speed and direction => velocity • Change in velocity => acceleration

All of Newton's laws of motion express the concept that....(Ch.4 quiz)

a force (and only a force) always changes the momentum of an object.

Radio waves are....

a form of light

The set of spectral lines that we see in a star's spectrum depends on the star's..... (ch.5 hw #34)

chemical composition

The spectrum from an incandescent (witha filament) light bulb is a(n) (Ch.5 quiz)

continuous spectrum.

How does Newton's law of gravity extend Kepler's laws? (pwp overview question)

• Applies to other objects, not just planets • Includes unbound orbit shapes: parabola, hyperbola • Objects orbit their common center of mass • Can be used to measure mass of orbiting systems • Applies to other objects, not just planets -> Newton showed that any object going around another object will obey Kepler's first two laws • Includes unbound orbit shapes: parabola, hyperbola -> Newton showed elliptical bound orbits are not the only possible orbit shape orbits can also be unbound in shape of parabolas or hyperbolas -BOUND: object goes around another object over and over again Shape: ellipses -UNBOUND: paths that bring an object close to another object just once Shape: parabola or hyperbola • Objects orbit their common center of mass-> Newton showed that two objects attracted by gravity both orbit around their common centers of mass -It's the point where the two objects would balance if they were connected -Equal Mass: center of mass is halfway between them -Different Masses: center of mass lies closer to the more massive one -Hugely different masses: center of mass lies inside the more massive one • Can be used to measure mass of orbiting systems -> Newton's laws of gravity and motion showed that the relationship between the orbital period and average orbital distance of a system tells us the total mass of the system. --Newton's version of Kepler's third law allows us to calculate the masses of orbiting objects from their orbital periods and distances between the two --EX: • Earth's orbital period (1 year) and average distance (1 AU) tell us the Sun's mass. • Orbital period and distance of a satellite from Earth tell us Earth's mass. • Orbital period and distance of a moon of Jupiter tell us Jupiter's mass.

Define Kinetic energy, radiative energy, and potential energy, and give two examples of each (ch.4 hw) [pwp, 119-123]

• Kinetic (motion): Energy of motion -EX: Falling rocks, orbiting planets • Radiative (light): Energy carried by light -EX: sunlight warms surface of earth, light can alter molecules in our eyes • Potential (stored): energy stored for later conversion into kinetic energy -EX: A rock on ledge has gravitational potential energy, Gasoline has chemical potential energy

Centers of Mass (pwp slide) -equal mass -different masses -hugely different masses

• Objects orbit their common center of mass-> Newton showed that two objects attracted by gravity both orbit around their common centers of mass -It's the point where the two objects would balance if they were connected Equal Mass: center of mass is halfway between them Different Masses: center of mass lies closer to the more massive one Hugely different masses: center of mass lies inside the more massive one

How is energy stored in atoms? (pwp overview question) Describe the energy levels that we find for electrons in atoms. Under what circumstances can energy level transitions occur? (ch.5 hw)

• The energies of electrons in atoms correspond to particular energy levels. -energies between those special few are not possible • Atoms gain and lose energy only in amounts corresponding to particular changes in energy levels. ENERGY LEVELS: -Lowest level: ground state / level 1 / 0 electron volts -Higher levels: excited states / labeled w/the extra energy of an electron in that level compared to an electron in the ground state -amount of energy separating levels gets smaller at higher levels -if electron gains enough energy to ionization level it'll escape atom completely CIRCUMSTANCES FOR TRANSITIONS: -The only allowed changes in energy are those corresponding to a transition between energy levels. -can only occur if electron gain/loses the specific amount of energy separating the levels

What is light? (pwp overview question) [142]

•Light can act either like a wave or like a particle -it's an electromagnetic wave but it also comes in individual "pieces" or particles called photon -each photon has a precise wavelength, frequency, and energy (the energy depends on its frequency) -the wavelength, frequency, and energy of light are simply related because no matter what the frequency, wavelength, or energy of an electromagnetic wave, ALL types of electromagnetic radiation (light) travel at the EXACT SAME SPEED! (the speed of light) -energy is proportional to frequency -wavelength is inversely proportional to its frequency • We call this the "Wave-Particle Duality of Light" • Particles of light are called photons