PHY 102 Final Exam
Why is light such an important tool for astronomers?
Because light is how we learn about distant objects without travelling there. It is also a measuring took of astronomy. Light is a wave and a particle.
Why do all the planets in our solar system orbit the sun in the same plane and in the same direction?
Because of conservation of angular momentum, which is when the original rotation that formed the solar system continues due to gravity after the solar system was created.
Why do stars, Sun, Moon and planets all appear to rise and set in our sky?
Because of the way the Earth rotates on its axis. Depending on where you are on Earth, the movements of the stars appear somewhat different.
How are the tides affected by the gravity of the Moon and Sun?
Because the gravitational force gets weaker with distance, as r increases, f decreases. The gravitational forces from the Moon and Sun pull harder on the "near oceans" which causes 2 high tides and 2 low tides every day. When the Sun, Earth, and Moon are 90 degrees apart, there is a "neap tide" (first or last quarter phase). When the Sun and Moon are both in line with the Earth (new or full phase) it causes a "spring tide."
What is a black hole? How are they created?
A black hole is the remnant core of a very massive star (M> 25 Msun) after exploding as a supernova. The name black hole comes from the fact that these objects' gravity is so strong, light cannot escape. The boundary of which light cannot leave is called the event horizon. They are created by the collapse of a very massive star. The book definition of a black hole is an object whose gravity is so strong that the escape velocity from it exceeds the speed of light.
What are the blackbody radiation laws?
A blackbody is an idealized object which absorbs and emits all frequencies. Classical physics can be used to derive an equation which describes the intensity of blackbody radiation as a function for a fixed temperature. A blackbody is defined as a hypothetical perfect radiator that absorbs and re emits all radiation falling upon it. The laws are: 1. As an object heats up, it gets brighter, emitting more electromagnetic radiation at all wavelengths. 2. The brightest color (most intense wavelength) of the emitted radiation changes with temperature.
What is meant by a "frame of reference"?
A framework that is used for the observation and mathematical description of physical phenomena and the formulation of physical laws, usually consisting of an observer, a coordinate system, and a clock of clocks assigning times at positions with respect to the coordinate system.
What are Kepler's 3 Laws? How are they used?
A line joining the planets and the Sun out equal areas in equal intervals of time. That means the planets move faster when it closer to the Sun and slower when it is further from the Sun. Perihelion=when planet is closest to the Sun. Aphelion-when planets are farther from the Sun. The orbit of a planet around the Sun is an ellipse with the Sun at one focus. The squares of a planet's sidereal period around the Sun is directly proportional to the cube of its semi-major axis. That means 1 AU=the average distance between the Earth and the Sun. These laws are used to explain planetary motion around the Sun.
What is a main sequence star? What is hydrostatic equilibrium?
A main sequence star is in the process of converting hydrogen into helium by the process of nuclear fusion (this produces energy E=mc^2).. Nuclear fusion is converting mass into energy. Main sequence stars exist in a state where outward forces (pressure resulting from energy production) and inward forces (gravity) are in balance. This state is known as hydrostatic equilibrium.
What is electrical resistance? What does a resistor do?
A resistor is a device that uses current to do work. Resistance, R, is measured in ohms, and depends on the geometry and materials used to make the resistor. The bigger R is, the harder it is to push charge around the circuit. Temperature also changes resistance--higher temperatures usually increase the resistance of a resistor. High resistance materials are called insulators, low resistance materials are called conductors.
What is the definition of acceleration? How is it related to velocity, distance, and time?
A=V/t Acceleration is defined as "a charge in the direction or magnitude of a velocity." It is related to velocity, distance, and time because the equation for acceleration is a=(delta) v/t, meaning that acceleration is the change in velocity (and distance factors into velocity) divided by time.
What causes magnetic forces? What direction do magnetic forces act?
All magnets have 2 varieties called the North and South poles. Similar to electric charges, like poles repel, and opposite poles attract. Unlike electric charges, you cannot separate magnetic poles; they always exist in pairs. For example: if you cut a magnet in half, the side you cut will turn into the oppositely charged magnet (so you won't have one large magnet, you will have a smaller bar magnet)
What are the stages of a star's life? How long do stars "live"?
As stars evolve, they change their properties (luminosity and temperature) and therefore change their position on the H-R Diagram. Young stars are cool and dim, and start in the lower right portion of the H-R Diagram, before moving toward the main sequence. After a main star sequence star runs out of hydrogen in the core, forces inside the star become unbalanced and start to change. Pressure no longer pushes against the force of gravity, so the star starts to collapse under the weight of its outer layers. This collapse heats the core up to even higher temperatures than before, and triggers the nuclear fusion of helium into carbon. This heat produced pushes the outer layers outward, which causes it to expand and cool and become a Red Giant. Mass determines how long a star lives.
Where are supermassive black holes found?
Astronomers believe supermassive black holes exist at the center of most, if not all, large galaxies (including the Milky Way).
What force is responsible for the behavior and structure of galaxies?
Basically gravity. Gravity creates and shapes the galaxies. Gravity is strongest near the most mass. In our galaxy, the most mass is located in the middle.
How is it related to the gravity we feel at the surface of the Earth?
Because G gravity measures the gravity between 2 objects while g gravity measures falling motion.
How is work related to Force?
Because force x distance makes up work, also force must act along the direction of motion for work to be done. Work is only done on an object when the FF is changed.
What does a capacitor do? What does a battery do?
Capacitors store charge temporarily for later use (even after the battery has been disconnected). The most common type is a parallel plate capacitor with equal and opposite charge on the two plates, and a uniform electric field in between the plates between the plates so charge cannot jump across. A battery pumps charge onto the plates and pushes charge around. Batteries are like the "charge pump" because their job is to push charge around the circuit.
What causes electric fields?
Charges exert forces on other charges which are separated from it in space. Charge fills space with an electric field and when another charge is in the electric field, electric forces act on it. The fields fill all space, but are strongest near the source (near the charge).
How are galaxies classified? What type of galaxies are there?
Classified by Edwin Hubble by how big they were through a telescope. Elliptical, Spiral, spiral barred, and irregular
What is the relationship between frequency, color, wavelength, and energy?
Color is how our eyes distinguish frequency. Speed of light equals frequency times wavelength. If frequency gets big then wavelength gets smaller and vice versa. E=hf means if energy gets larger so does frequency (because h is a constant). Frequency and wavelength are connected by speed of light. If you know one of c=f(lambda) then you are able to calculate them all.
What are some real-life natural examples of magnetism?
Compasses is the biggest example of magnetism, but motors, magnets on the refrigerator, maglev trains, and many new roller coasters are other examples of magnets.
What is electric charge? Where is it found?
Electric charge can be positive or negative, and like mass, it is conserved. Charge comes from the particles in an atom (negative charge from the electrons, and positive charge from the protons). Every electron carries the exact same amount of electric charge (e), and every proton has the same positive amount.
What causes magnetic fields?
Electric currents cause magnetic fields. Electric currents and changing electric currents will create a magnetic field. The electrons in each atom have a certain pattern that work like a current, so they have mini magnetic fields within each atom. So when a lot of atoms are doing the same way, you can get a magnetic field.
What is electric potential (Voltage)?
Electric potential is a relationship that allows us to define a new quantity which is the amount of EPE per charge. Electric Potential equation is V=EPE/q
What is the correct explanation for the seasons on Earth?
Earth's axis is tilted 23.5 degrees with respect to its orbit around the Sun. The tilt changes the seasons.
What does the Law of Conservation of Energy state?
Energy cannot be created or destroyed, only changed. Etotal=constant+KE+PE. Total energy in the system stays the same so we can measure it at 2 separate times and Einitial=E total.
What is kinetic energy?
Energy that a body possesses by virtue of being in motion. Symbol: KE, Equation=½ mv^2. Simply put, it is the energy of motion.
What is gravitational potential energy?
Energy where nothing is moving but there is energy because of where the object is located on Earth's gravitational field. Symbol: GPE. Equation: GPE=(mg)h. Potential energy is energy possessed by an object because of it's position.
What were Galileo's contributions to the areas of astronomy and physics?
Galileo made many observations about falling motion that led to Newton figuring out gravity. He also figured out the equation for distance (d=½ at^2). He also figured out gravity was 9.8 m/s^2. He also discovered velocity changing is caused by force, if there is no force than an object will keep in a uniform, straight line motion. Lastly, when the force of gravity=air resistance, the object is in free fall.
What does relativity say about space and time?
General Theory of Relativity was published in 1915, and some of Einstein's conclusions were: Space and time are connected. Mass actually curves (or warps) spacetime and this is the true explanation for gravity.Light can bend around massive objects as it passes through the "curved spacetime." The force of gravity arises from the curvature of space and time.
What are the characteristics of a good scientific theory?
Good science involves building upon existing knowledge, can be modified when new information is found, has predictive power, develops step-by-step, is objective, and can be tested and disproved. Scientific method steps: observe, hypothesize, predict, test, modify, and simplify. It has predictability, it can be done repeatedly, and should be objective.
What types of atoms are most important in studying astronomy?
Hydrogen and helium because they are most abundant. 90% of the universe is hydrogen and 9% is helium.
What might cause a scientific theory to be changed or abandoned?
If the theory is not testable or if it has been disproved numerous times. It would also be abandoned if it is a pseudoscience which means it is based off of non-developing facts or it is unable to be tested.
What is Faraday induction? What does it tell us about the relationship between electricity and magnetism?
In 1831, English physicist and chemist Michael Faraday proved that moving magnets can induce electric currents. This general rule is known as Faraday's Law: a changing magnetic field will produce a current in a nearby loop or circuit, if any part of the field is perpendicular to the loop.
What happens when stars "die"?
In a low mass star (M<8 Msun), after the Red Giant stage, helium fusion into carbon stops. The core collapses again, and heats up, but this time, there is not a high enough temperature to start the nuclear fusion of carbon into something else. The carbon core contracts, becoming very hot and the outer layers of hydrogen/helium drift away. The core cools off as a White Dwarf, with a bubble of gas surrounding it (planetary nebula). In a mid mass star (8 Msun <M< 25 M sun) after the red giant stage, helium fusion into carbon stops. The core collapses again, heating up and the core temperature rises and starts the nuclear fusion of carbon into neon. When that's done, the cycle repeats, fusing neon into oxygen, oxygen into silicon, etc, creating many layers in the star's core like an enormous onion. This is what goes on inside a supergiant star. Eventually silicon undergoes fusion into iron, and at this point, no more energy can be produced from nuclear fusion. No more energy can be produced so gravity takes over and collapses the star, creating a violent explosion called a supernova. In a high mass star (M> 25 Msun) after the silicon fusion into iron stops no more energy can be produced so gravity takes over, collapsing the star. The core of the star completely collapses in on itself and becomes a black hole.
What are some of the differences between the inner and outer planets?
Inner planets--called the Terrestrial Planets, are closer to the sun (and therefore warmer) and have solid surfaces. The outer planets--called the Jovian planets), have similar atmospheres, no solid surface, are larger and lower in density, have Earth sized, rocky cores, circled by rings of ice and rock, and they all have moons (while the Terrestrial planets do not).
What is the free fall acceleration due to gravity?
It is 9.8 m/s^2 and was discovered by Galileo and is based on the idea that there is no air resistance.
What is Ohm's Law? Where is it used?
It is a relationship created by George Ohm that states: current, i, equals voltage, v, divided by resistance, R. The higher the voltage, the more current flows through a given resistance. V=IR. As V changes, so does I, and the constant of proportionality is the resistance of the material, the resistor does work--it changes the EPE into other forms of energy (usually heat or light).
What is the age of the Solar System?
It is about 4.6 billion years old.
What property makes an atom unique, as opposed to other divisions of matter?
It is because it is the smallest chemical properties? Each chemical element has it's own type of atom, and if you break an atom up more it would not be that element anymore.
What is a supermassive black hole?
It is believed that supermassive black holes exist at the centers of remnant black holes (supermassive means mass equivalent to millions or billions of stars: 10^6 to 10^10 MSun). Astronomers believe they exist at the centers of most, if not all, large galaxies (including ours).
. What is OUR galaxy called? What type of galaxy is it?
It is called the Milky Way and it is a barred spiral galaxy. In the center of our galaxy is a supermassive black hole.
What does this equation express? y=½ g t^2
It is the same as distance and measures acceleration due to gravity (i.e. falling motion)
What is meant by the "total force" in one direction or dimension?
It means there is a net force (the vector sum of all the forces that act upon the object) moving all in one direction with enough to cancel out the other forces.
What are some historical examples (using the scientific method) of observations combined with a theoretical model?
Kepler's combination of Copernicus's model and Brahe's observations. Galileo's use of Kepler's information for Gravity. Newton's use of Galileo's information to figure out gravity ("If I have seen any further it is because I stood on the shoulders of giants.")
What are Kirchhoff's laws?
Kirchhoff's law is for current and voltage and it lies at the heart of circuit analysis. It states that 1: a solid, liquid, or dense gas produce a continuous spectrum (called a continuum)--a complete rainbow of colors without any spectral lines. This is a blackbody spectrum. 2. A rarefield (opposite of dense) gas produces an emission line spectrum-- a series of bright spectral lines against a dark background. 3. The light from an object with a continuous spectrum that passes through a cool gas produces an absorption line spectrum--a series of dark spectral lines among the colors of the rainbow.
What are Newton's 3 Laws? How are they used?
Law of inertia. An object in motion stays in motion with the same speed and direction unless acted on by an unbalanced force. Acceleration of an object is directly proportional to the force applied to it, and inversely proportional to its mass. F=ma. For every force, there is an equal and opposite reaction. Weight is a force, mass is the amount of matter in an object. Newton was credited for discovering gravity and his biggest contribution was unifying 2 kinds of theories of motion.
What is the speed of light?
Light can travel enormous distances under short periods of time. It is faster than any other phenomenon. It takes about 8 minutes for light to travel from the Sun to Earth. The speed of light in a vacuum is c=3x10^8 m/s.
How are different kinds of light waves arranged in the EM spectrum?
Light is arranged on the electromagnetic (EM) spectrum from shortest wavelength (highest energy) to longest wavelength (lowest energy). The longer the wavelength the safer it is for people to be around. Gamma rays have the shortest wavelength and are used for cancer radiation. X-Rays are used for medical examinations. Infrared radiation is used in a TV remote, microwaves are used in microwave ovens, and the radio waves are used in mobile phones. They are arranged by frequency.
Why are light waves called electromagnetic waves?
Light waves are waves of energy and light moving all around us in the form of TV and audio transmissions, gamma radiation from space, and heat in the atmosphere. The waves of energy are called electromagnetic because they have oscillating (varying in magnitude or position in a regular manner around a central point) electric and magnetic fields.
What property of a star determines its "life"?
Mass is the biggest thing that will determine how long a star will live. The more massive a star is, the longer it will live.
What is the basic theory of how the solar system formed?
The best current theory of the origin of our solar system is known as the Solar Nebular Hypothesis. Our Sun (and solar system) started as a cloud of cold, rotating gas and dust. After some initial disturbance, gravity slowly collapses this cloud, and it rotates, naturally forming a rotating disk. Important process were accretion and collisions. The original rotation shows up in the orbit and spin of current planets and objects (conservation of angular momentum).
What is the definition of momentum? How is it related to Force? What is impulse?
Momentum is the quantity of mass x volume, and force depends on the rate of change of momentum. Impulse is the quantity of force x time. Impulse is the change in momentum.
How do stars form? What is their energy source?
Most stars form with another star, or as part of a group (our Sun as a solitary star is less common). Stars form inside relatively dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold and at these temperatures, gases become molecular meaning that atoms bond together. When atoms of light elements are squeezed under enough pressure for their nuclei to undergo fusion. All stars are the result of a balance of forces: the force of gravity compresses atoms in interstellar gas until the fusion reactions begin. Basically, stars are formed from gas and dust.
Is our solar system with planets the only one?
No. Most solar systems have some type of planets.
How do normal frictional tension forces and weight work?
Normal (perpendicular, requires contact with a surface) force has the symbol N or FN and uses Newton's Laws to function because it is based off the idea they are reacting with a surface. Frictional force (FF) occurs during contact between objects, it always acts in the opposite direction of motion, the equation is FF=mu x N (with mu representing the coefficient of friction). FF is a constant, and the rougher the surface the higher the coefficient of friction. Kinetic friction is easier to overcome than static friction. Tension (in a rope) friction is T and it also uses Newton's laws. Weight (W) is W=mg with m being mass and g being gravity (9.8 m/s^2).
How old is our Sun? How much longer will it last?
Our sun is about 4.6 billion years old. In about 5 billion years, our sun will run out of hydrogen in the core, and become a Red Giant star (meaning it will swell up to about 100 times its current size). It will swallow up Mercury, Venus, and probably Earth.
What is Power? How is it related to energy?
Power is defined as energy per unit of time. It measures how fast energy is produced or consumed. Power applies also to mechanical systems, as in a powerful car, which can accelerate rapidly. A high-powered light bulb puts out a low of light per second. Watt is the unit of power. Power is the rate at which energy is converted. 1 Watt=1 Joule/second. 1 watt=(1 ampere) x (1 volt)
What observations of planetary motion helped shape the theories and models of our solar system?
Pythagoras noticed that the planets move differently than the stars, Plato and Aristotle observed that all objects have a "natural state" which was the start of the theory of gravity. Aristotle noticed retrograde motion of Mars which is that Mars appeared to move "backward" compared to constellations in a path that was clearly not circular. Ptolemy used geometry to observe that the planets move in epicycles. Copernicus made the heliocentric model of the Sun and measured the planet's distance from the Sun. Brahe made careful observations on Planet positions that Kepler used to create the correct model.
How did the contributions of various astronomers/scientist shape the modern theory of astronomy and the nature of our solar system?
Reference Slides 1-14 on physics exam 2.
What are some real-life natural examples of static electricity?
Rubbing your feet on the carpet, running a rubber comb through your hair, not putting a dryer sheet in the dryer when you dry your clothes, when we were younger and used to rub our head on Nana's carpet.
What is the difference between a science and a pseudoscience?
Science is a process and is testable and falsifiable, while a pseudoscience is usually impossible to disprove and rarely has new developments. A pseudoscience has no test-ability, therefore it is not a science.
What units, and what size scales are needed to measure the universe?
Science is generally done in the metric system, and different units are used for different measurements?
What is the Celestial Sphere? How is the coordinate system set up? What are some of the major features on the celestial sphere?
The celestial sphere is a fixed coordinate system to model and map the sky: an imaginary sphere surrounding the Earth in which all objects in the sky can be located. It has 2 axis points, the north and south celestial poles (located directly above Earth's poles). There is also a celestial equator (directly above Earth's equator). Longitude is measured in "right ascension" (in hours), latitude is "declination" (in degrees, minutes, and seconds), and zero is the celestial equator.
What is the correct model of our solar system? Geocentric or heliocentric?
The correct model is a heliocentric (with the Sun in the middle) and elliptical planetary orbits. This was discovered by Kepler after he combined Copernicus's model with Brahe's data.
What do Maxwell's equations predict the existence of?
The predict the existence of light waves. Combine some Maxwell's equations mathematically, and the result is a "wave equation," meaning E and B fields move outward as a wave. Lightwaves. You can predict the formulas that can produce a cosine function that forms these equations.
How do we observe black holes?
Since no light comes from inside the event horizon, black holes are difficult for astronomers to observe. We detect them indirectly by observing their effect on visible objects nearby. Black holes presence has been observed by their effects on the orbits of other stars and on gas and dust near them.
What is electric potential energy?
Since there is an electric force, there is the potential to do work (the force can move, and change the energy of a test charge). Electric potential energy (EPE) is measured in Joules (J). EPE=(Coulomb's Law Electric Force) x (distance).
What are some of the effects of special relativity?
Special Theory of Relativity was published in 1905 by Einstein and the conclusions were: He realized that the perspective (the Frame of Reference) makes a difference in observations. Different frames of reference (moving with respect to one another) observe the same event, but with different descriptions. Within one's own reference frame, the descriptions of physical reality is consistent, regardless of the relative constant velocity between frames. The speed of light, c, is the same for all observers (for all frames of reference). The speed of light is a constant, and no physical object can go at or faster than c.
What other types of energy are there?
Spring (elastic), energy (SPE), chemical (CPE), electric (EPE), heat (Q), Light (Electromagnetic) energy (E), and waves (including sound and water) (E).
What is Coulomb's Law of Electric Force? What direction does it act?
The electrical force between two objects is proportional to the charge (q) of each object and inversely proportional to the square of the distance (r) between the centers of the charged objects: F=(kq1q2)/r^2. It is a force of attraction or repulsion between 2 charges. This force is nearly identical in forms to Newton's Universal Law of Gravitation, but there are 2 important differences: Gravity only attracts, Coulomb's law can be attractive or repulsive, and the strength of the electric force is much stronger than Gravity.
What are galaxies made of?
They are made of hydrogen, helium, simple carbon compounds, and most importantly gas and dust. These form stars and clouds of gas and dust that are lit up by dust or will obscure the light from the stars.
What is the Doppler Effect and what does it do?
The Doppler Effect occurs when a wave source is moving with respect to an observer (or when the observer is moving with respect to the source). The effect results in an observed change in frequency of the original wave--for light waves we call this change a "redshift" or a "blueshift. It works for sound too.
What is an H-R Diagram and what does it tell us about stars?
The H-R Diagram (Hertzsprung-Russell diagram) is a graph of stellar luminosity or absolute magnitude against surface temperature or spectral type. It is a graph of stars based on the quantities listed above, it compares luminosity and temperature to indicate what stars share in common. It tells us how stars are going to die, for example: red giants are high in luminosity, and low in temperature, white dwarfs are low in luminosity and high in temperature, main sequence stars are the typical mature star and can be any brightness or temperature, but the two values are related.
What happens with forces in "static" situations?
The acceleration is zero.
What does this equation express? v=vo +at
This equation means: velocity=intial velocity +constant x time.
What is the electromagnetic spectrum? How is it characterized?
The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength. The sun, earth, and other bodies radiate electromagnetic energy of varying wavelengths. Electromagnetic energy passes through space at the speed of light in the form of waves.
What is electric current? How is it related to charge?
The flow of charge around a circuit is called the electric current (like the flow of water through a pipe). Direction of current is defined to be the direction of flow of positive charges.
What is the Newton's Universal Law of Gravitation?
The gravitational force between 2 objects is proportional to the mass of each object and inversely proportional to the square of the distance between the centers of the masses. F=(Gm1m2)r^2. The universal gravitational constant is G=6.67x10^-11 Nm^2/kg^2.
What can happen when galaxies interact or collide?
The gravity from both will affect both galaxies, spiral arms can get distorted, they can move through each other because there is so much space; however, since they get close enough the gravity can ruin the setup of a galaxy.
What is the structure of an atom? What are its constituent parts? What are the main features of the Bohr model of an atom?
The modern view (Bohr model) has energy levels that are very rigid and unique, energies in electrons are quantized meaning they can only have certain energy levels. Nucleus has protons and neutrons and the number of protons tells the chemical element while the number of neutrons tells the isotopes. Farthest electron has maximum energy on the KLMN. Electrons can jump to different levels if turned on
What is wave superposition and interference?
The principle of superposition may be applied to waves whenever two (or more) waves travelling through the same medium at the same time. The waves pass through each other without being disturbed. Wave interference is the phenomenon that occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium.
What are the quantities used to describe a wave?
The quantities used to describe waves are frequency (f)--the number of peaks or troughs of a wave that pass a fixed point each second. Equivalently, the number of complete vibrations or oscillations per second, wavelength (lambda)--the distance between two successive peaks in a wave, period (T)--the time needed for one complete cycle of vibration to pass a given point, velocity (v)--a quantity that specifies both direction and speed of an object, amplitude (A)--the maximum extend of a vibration or oscillation, measured from the position of equilibrium.
What is the correct explanation for the phases of the Moon?
The relative angle between the Sun, Moon, and Earth changes, illuminating the Moon's face differently.
What do Maxwell's equations state (in words)?
There are 4 calculus formulas that summarize all of electromagnetism, they are: Stationary electric charges produce electric fields (Coulomb's Law)--"the divergence of electric fields equals the charge inside" Magnetic fields form closed loops--"the divergence of magnetic fields equals zero" Changing magnetic fields produce electric currents and electric fields "Faraday's Law"--electric fields curl around changing magnetic fields"Moving electric charges (currents) produce magnetic fields (Oersted's discovery)-"magnetic fields curl around currents and the amount of magnetic fields equals the current inside"Changing electric fields produce magnetic fields--"magnetic fields curl around changing electric fields"
What sorts of quantities are used to classify stars?
There are 4 things to consider when classifying stars. Luminosity (L)--the energy output rate, surface temperature (T)--related to color, spectrum--the fingerprint of starlight, spectral class--O (blue-violet), B (blue-white), A (white), F (yellow-white), G (yellow), K (orange), and M (red-orange), and mass (M)--perhaps the most important quantity because it determines the star's fate.
How many planets are there in our solar system?
There are 8 planets in our solar system. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus.
What is the cause of an eclipse? What kinds of eclipses are there?
There are lunar eclipses (when the moon enters the shadow of the Earth). There are 3 types of lunar eclipses. There is the penumbral eclipse (when the moon enters the penumbra of the Earth's shadow) which is not very noticeable, a partial eclipse (when the moon is partially in the umbra), and the moon is half dark, and a total lunar eclipse (when the whole Moon is in the Earth's umbra) and the moon looks red. There are also solar eclipses (when the moon completely surpasses the sun). There are partial solar eclipses (when the sun is only partially covered by the moon), and Annular solar eclipses (when the Moon's umbra falls short of the Earth, the moon appears too small to cover the Sun), these leave a thin ring, "annulus" of light around the moon.
What other types of forces are there?
There is general force (F0, gravitational force (FG), centripetal force (FC), which are central forces that always keep an object in a circular motion. There are also four fundamental forces which are gravitation (attracts all objects with mass) the weakest of the 4, electromagnetism (either attracts or repels objects with electrical charge), weak nuclear force (acts only on particles of the atomic nucleus. Is responsible for radioactive decay), and strong nuclear force (acts only on particles of the atomic nucleus. Is responsible for holding the nucleus together).
What does this equation express? x=x0+v0t+½ at^2
This is a kinematics equation meaning: distance=initial displacement + initial velocity x time + constant x time squared. X is a distance or position X0 is initial position, V0 is initial velocity. This equation figures out where an object will be after certain time, velocity and with its initial position.
What is an energy level in an atom? How do electrons move between them?
This is part of Bohr's model, and the energy level is how much energy an electron has. Physicists used to care about the placement of an electron, but lately they decided that placement does not matter as much as energy level. Electrons can only move energy levels if the exact amount of energy needed comes along. It was described like stairs, where you can't stand between 2 stairs, you either have to be on one or the other.
What is a perfectly elastic collision? Perfectly inelastic?
Totally elastic is when a ball bounces back to the original height after being dropped, perfectly inelastic is when a ball doesn't bounce at all after being dropped.
What is the difference between transverse and longitudinal waves?
Transverse waves velocity is perpendicular to amplitude, and in longitudinal waves velocity is parallel to amplitude.
What is the definition of velocity? How is it related to distance and time?
Velocity is defined as "a quantity that specifies both direction and speed of an object." It is related to distance and time because the equation for velocity is velocity=distance/time, meaning that distance divided by time make up velocity.
Where are we (the sun and the Earth) located within our galaxy?
We are 2/3 the way out in the galaxy, in the disc. Not in one of the bright spiral arms. We are located nowhere special, basically.
What happens to momentum in a collision?
Within a system, momentum is not lost or gained, just changed. So in a collision the momentum is not changed it is just changed into different types of energy. Also, keep in mind Newton's 3rd law which states, "every action has an equal and opposite reaction."
What is conservation of momentum?
Within a system, the total momentum does not change.
How are work and energy related to each other?
Work is force x distance, and energy is the capacity to do work. If work is done on an object, the object gains energy. That means work is change in energy is a system.
What do these equations express? c=f(lambda) and E=hf?
c=speed of light, f=frequency, lambda=wavelength, C=f(lambda) is the equation of speed of light. For E=hf, E=photon's energy, h=Planck's constant (6.67x10^-34 J) and f=frequency, This is the equation for measuring a photon's energy.
