Week of Feb 1st Astronomy Notes
Week of Feb 1st Astronomy Notes Phys 1055
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Popular in Physics 2
This 7 page Class Notes was uploaded by Julia Jones on Tuesday February 23, 2016. The Class Notes belongs to Phys 1055 at Virginia Polytechnic Institute and State University taught by Astronomy Staff in Spring 2016. Since its upload, it has received 20 views. For similar materials see Introduction to Astronomy in Physics 2 at Virginia Polytechnic Institute and State University.
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Date Created: 02/23/16
Feb 1 2016 Speed distance time Acceleration change in velocity Velocity speed amp direction All objects are affected identically by gravity Yet our atmospheric pressure on Earth acts upon objects so unless we are in a vacuum with no pressure at all objects will fall at different speeds Ex hammer and feather experiment by Myth Busters Momentum is a measure of the motion of particular objects the multiplication of mass and velocity What is Force Change in momentum change in velocity acceleration Net force the sum total of all forces acting on an object simultaneously Centrifugal force is an inward force that creates acceleration by a change in momentum Ex even if your driving your car in a circle at a constant speed Angular Momentum is tangent velocity x mass the motion of an object as they rotate or move Torque is the same as angular velocity Mass is a measure of how much an object is willing or unwilling to change is motion to accelerate inertia is the same thing Weight is a force forces are masses that are moving When you weigh yourself on a scale you are measuring your net force Weightlessness ex free fall in space is when an object is constantly going through acceleration without any forces acting upon it Newton39s Three Laws of Motion First Law objects at rest remain at rest objects in motion remain in motion in a straight line unless acted upon by an unbalanced force Velocity is zero when sti When the velocitymomentum stays constantly in motion am object will travel in a straight line until an outside force causes the momentum to change Second Law force equals mass X acceleration the change Third Law for every action there is an equal and opposition there are interactions between things equal action and reaction forces Food for thought from class Acceleration If you are driving in a car that is going 60 mph and you throw an apple FORWARD out of the window in the direction that the car is traveling then the apple will be going 61 mph If you throw it BACKWARDS in the opposite direction that the car is traveling it will go 59 mph Net force If you put a scale in the elevator and you weigh yourself as the elevator is not in motion the scale will display your net weight When the elevator starts to go up your weight will increase in the moments that the elevator is accelerating upward When the elevator starts to go down your weight will decrease in the moments that it is accelerating downwards Weightlessness If we re the canon ball so far out into our atmosphere that it is falling at the same rate as the earth is falling spinning with the exact same curvature then it is free falling Newton s Third Law Action Force Earth pulls an object down with a force equal to it s weight Reaction force the object pulls the Earth up with an equal force to it s own weight Astronomy Feb 03 2016 Clicker question 2 Kepler s Third Law objects orbiting closer to the sun will travel faster and object orbiting farther from the sun will travel slower Recap from Post Ouiz 21 question 1 Astronauts are weightless because they are free falling There IS gravity in space that is how Earth holds on to the moon how the Sun holds on to Earth While in space Terminal Velocity the net force acting upon their body is zero Recap from Post Quiz 21 question 3 dump truck and bicycle moving 10 mph in opposite directions they have the same speed 10 mph But they have different momentum because it has velocity which depends upon direction Recap from Post Ouiz 21 question 4 it must experience a non zero net force because when there is zero net force they you are not moving at all Recap from Post Quiz 21 question 5 objects move in a circle becayse a center pointing force is acting on the object making it change direction Not because centrifugal force is pushing out the object not because gravity or because a center pointing force is acting on the object making it change speed Sections 33 amp 43 in the book below In 15001600 5 Johannes Kepler the apprentice trying to learn as much as possible and used Tycho Brahe s data and would make predictions draw pictures gure out where they would be in a year by math amp physics and Tycho Brahe the master lost his nose in a duel battle he was brilliant scientist he had the best naked eye observation of the planets During this time everyone thought that planets revolved around the Earth and that the Earth was atthey thought everything was an in nite regression of little circles and big circles Kepler nally stood up to the heavenly beliefs because he found an eightminute discrepancy between the predicted and actual orbit of Mars He discovered that the planet s orbits in ellipses instead of perfect circles and the math came out perfectly so he was able to make that huge jump not made up of perfect circles Kepler came up with Three Planetary Rules 1 Orbits are ellipses with the sun at one of the two foci focuses 2 Planets sweep out in equal areas in equal amounts of time if we try to cut a pie but its not a perfect circle we have to make each piece a weird shape in order to have each piece be the same amount the time intervals between each piece are the same 3 More distance planets orbit the sun at a slower average speed obeying a precise mathematical relationship the orbital period of the Earth is one year there is a relationship between between pquot2 aquot3 aaverage porbita period Conservation Laws Newton s theories his revelation that the Heavens are not some separate thing he said that the laws of physics apply to the entire universe how gravity works on Earth is the same how they work in the galaxy Conservation of momentum says that if we have a system of anything pool table tennis balls the momentum that they have to begin with must be the same amount of momentum that they have throughout time Momentum is the measurement of objects moving through space Conservation of Angular Momentum Ang Mom mass velocity radius the total amount that an angular momentum has will always stay the same until there is an external outside force will use a lot in this class Clicker question angular momentum conversation gives us Kepler s 2nCI law of planetary motion Conservation of Energy energy cannot be created or destroyed only transferred or transformed Types of energy in a general sense energy is something that makes matter move it is not a substance nor does it have a mass Kinetic energy the energy of motion 12mvquot2 Potential energy ex gravitational potential energy It comes from somewhere else could be gravity could be elastic a spring could be chemical like eating radiative energy is light itself Energy of astronomy thermal energy depends upon temperature and how many particles we are actually talking about total energy of all the particles in a substance or room VERSUS temperature average motion of the particles in this room make it feel like ex 70 degrees Food for thought Energy of astronomy you have an oven that is 400 degrees Fahrenheit and a pot of hot water at 200 degrees Fahrenheit yet the pot feels hotter because Mass Energy Mass is stored energy Emcquot2 energy is related to mass Mass can be turned into energy Hydrogen bombs are the strongest type of bombs if the mass of a paperclip was turned into energy it would explode all of Virginia tech Emcquot2 is how the sun works Astronomy Feb 08 Clicker When you look at a red chair it is re ecting red in order for you to see it Student made PowerPoints NASA Spacecraft Juno heads to Jupiter to study the planets origin NASA is building the James Webb Space Telescope to study the formation of galaxy this telescope with orbit around the Earth just like a planet looking at infrared stuff Post Quiz Question recap two objects with different masses and I m holding them a certain distance apart from each other I double one of the masses and double the distance between the masses What happens to the force of gravity Decreases by a factor of 2 Light the messenger of the Cosmos Allows us to determine what things are made ofwhat is the composition hydrogen Mercury how hot things are the temperature how fast they are movingthe universe is always expanding Light is energy radiative energy The rate of change of energy is how we determine the power of say a light bulb power the rate of change of energy unit of Watts 1 Joule per second 1 Watt A certain amount of average power x time Light and Matter light interacts throudh matter bV Emission light bulbs your laptop the sun Absorption the chairs are red because all of the other colors are absorbed Re ecti0nscattering mirrors essentially a perfect re ection while scatter happens with almost every other object how we see other people Transmissi0n windows or glass or water or air What is light Particles are quotthingsquot we can locate them in a particular location in space amp time Waves are the transition of energy through space and time a transmitter of energy no particular location they are patterns revealed by interaction with particles 2 types of waves only transfer energy no matter waves in the sea vibrations are perpendicular to the wave s direction quottransversequot sound waves vibrations are parallel to direction of travel wave length full cycle from one point to same next point symbolized by lambda 7 crest top of wave trough bottom of wave frequency total number of peaks passing a point each second is measured in hertz f using speed frequency x wavelength light is something that can behave as a wave or a particle We don t exactly know what light is How can it act like a wave How can light travel through space it makes electric and magnetic elds so light is an electromagnetic wave all light travels through space at the exact same speed The speed of light symbol quotcquot always a constant value 299792458 miles persecond Light does not have mass so it can travel this fast nothing else can Light with bigger wavelengths has smaller frequencies Light with smaller wavelengths have higher frequencies Clicker question39s lesson X rays visible light radio waves and ultraviolet light are all light so they travel at the same speed Photons are light acting as a particle or pieces we can count them individually But protons can also be waves if they have a frequency or wavelength associated with them And protons can have energy associated with them They re energy can be different depending upon the frequency higher freq higher energy Blue light has a higher frequency than red light Visible light does not burn your skin ultraviolet light can destroy your skin cells Wavelengthfrequencyspeed of light From left to right on the spectrum radio waves have the least frequency they are the biggest then infrared planets and humans emit them then visible light in the middle then ultra violet more energetic higher frequency then xrays penetrate through skin but not bones then gamma rays are the most energetic light in the universe extremely dangerous Matter Atoms are the building blocks of matter atoms are protons neutrons and electrons Mass versus size mass is stuff packed in there but size is speci cally volume The atom is tremendously small protons are positive neutrons are neutral electrons are negative Similar to the way that the Moon and Earth are connected with gravity and orbit Atomic number is the number of protons what sort of element you have Atomic mass number is the combined number of protons and neutrons Isotope is atoms with the same atomic number but different atomic mass number Molecule a combination of 2 or more atoms bonded together in some way ex H20 2 hydrogens and 1 oxygen bonded together How does matter change It changed between solid liquid and gas states Its all the same molecule but differing in the strength of glue holding the molecules close together But enough energy can be given to molecules where we start to break the apart and now they are individual molecules when the temperature increases We can ionize the atoms completely rip all of the electrons out
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