Class Project Physics 1010-042, Physics 1010-048 Fall 2012 The Project Parts Part 1: Star Identification: The photo below is of the centaurus/southern cross region of the milky way. This is not visible in our sky as our latitude on the Earth is too far north. These are starfields seen generally in the southern hemisphere and some of the tropical latitudes of the northern hemisphere. Centaurus is a large constellation in terms of the area it covers. The easiest markers in this constellation are the two brightest stars, alpha and beta centauri. These are the two brightest stars in the photo and are located just under the center of the photo. Alpha Centauri is yellow and Beta Centauri is blue. Alpha Centauri is the nearest star system to our own. Were we living in the Alpha Centauri system, looking back towards the Sun, the Sun would look much like Alpha Centauri does from here. If you draw a line from Alpha Centauri through Beta Centauri and move, from Beta Centauri about 2.5 times the Alpha Centaure/Beta Centauri distance you will see a bright red star. That bright red star is one of the stars of the Southern Cross. Pick 3 of the stars in the photograph below. Label each of these stars on the photo. Then tell me the following things about each star: 1) Its name * Alpha Centauri * Beta Centauri * Gamma Crux (in the Southern Cross) 2) Distance from Earth in light years (a light year is how far light can travel through the vacuum of space moving at 670 million miles per hour for a year. By everyday standards a light year is an enormous distance) * Alpha Centauri- 4.37 light years * Beta Centauri- 352+/- 13 light years * Gamma Crux (in the Southern Cross)- 88.6 light years 3) When the light from the star now visible in the skies of Earth actually left the star (if a star is 10 light years away its light now visible in the skies of Earth left that star 10 years ago in 2002) * Alpha Centauri- 4.37 years ago (2008 AD) * Beta Centauri- 352+/- 13 years ago (1647-1673 AD) * Gamma Crux (in the Southern Cross)- 88 years ago (1924 AD) 4) Its size compared to the Sun (you can do the comparison using the star’s radius to the Sun’s radius or the star’s volume to the Sun’s volume) * Alpha Centauri- has a 1.227 solar radius compared to the suns 1 solar radius. *Beta Centauri- The radius of beta Centauri has an 8 solar radius compared to the sun which has a solar radius of 1. * Gamma Crux (in the Southern Cross)- Gamma Crux has an 84 solar radius compared to the sun which has a solar radius of 1. 5) The star’s luminosity compared to the Sun (luminosity is a measure of brightness) *Alpha Centauri- has a solar luminosity of 1.519 compared to the sun’s solar luminosity which is 1. *Beta Centauri- has a solar luminosity of 41,700 compared to the sun’s solar luminosity which is 1. *Gamma Crux (in the Southern Cross)- has a solar luminosity of 1,500 compared to the sun’s solar luminosity which is 1. You can list this information in tabular form star by star. A little extra credit will be available for identifying the coal sack in the photo. A good way to proceed is to use the star chart (also attached) to identify the stars by their greek letters or proper name and then do a net search on the names to find information. . Southern Cross Gamma Crux Beta Centauri Alpha Centauri Coal Sack Below: photo of the Centaurus/Crux (Southern Cross) sector of the milky way Australian flag with the Southern Cross on the Centaurus/Southern Cross right and Beta Centauri in the lower left star chart with Alpha and Beta Centauri on the left Part 2: Equation Analysis: These equations are in your textbook so that should be a good source of accurate information about them. Equation 1: E = mc2 Answer or do the following: Question 1: Find out what the things in this equation (using your book or a net search will do it) are and identify them as either variables or constants. *E- energy (variables) *m- mass (variables) *c^2- speed of light (constant) Question 2: What is the size of c2? 300,000 kilometers per second squared or 2.9979 x 10^8 m/s squared or (9 x 10^16) J/kg. Question 3: Are mass and energy related? Answer yes or no and then provide a brief explanation of your answer based on the analysis of the equation. *Yes- Energy and mass are the same thing. Mass is congealed energy. If you want to know how much energy is in a system, measure its mass. For an object at rest, its energy is its mass. Energy, like mass, exhibits inertia. Shake a massive object back and forth; it is energy itself that is hard to shake. Question 4: Analyze the statement: “if it is possible to change mass into energy a little bit of mass could produce a lot of energy”. Is it true or not? Provide a brief explanation based on your analysis of the equation *False- if mass and energy are basically the same, which would mean it takes a lot of mass to produce a lot of energy. Less energy would require a smaller mass. Equation 2: d = gt2/2 …where: d = distance an object falls when released from rest (no air resistance) g = acceleration of gravity at the Earth’s surface t = time the object has been falling Question 5. Which of the following statements do you agree with and why? Use the equation to support your answer (you can also refer to the learning from equations module files). a) heavy objects fall faster than lighter objects * False (disagree) - weight has nothing to do with how fast something falls. The only things that matter is acceleration of gravity at the Earth’s surface, time the object has been falling, and distance an object falls when released from rest. b) objects fall at the same speed (if no air resistance) and weight doesn’t matter. * True (agree) - weight has nothing to do with how fast something falls. The only things that matter is acceleration of gravity at the Earth’s surface, time the object has been falling, and distance an object falls when released from rest. Equation 3: v = gt …where: v = velocity of a falling object if released from rest (no air resistance) g = acceleration of gravity at Earth’s surface t = time the object has been falling Question 6: Which of the following statements do you agree with and why? Use the equation to support your answer (you can also refer to the learning from equations module files). c) heavy objects fall faster than lighter objects * Disagree d) objects fall at the same speed (if no air resistance) and weight doesn’t matter. * Agree- weight doesn’t matter because all that matters is we know what the acceleration of gravity at Earth’s surface is, time the object has been falling, and the velocity of a falling object if released from rest. Now go online and view this link. If the link is inoperable go to google video and do a search on “Galileo hammer feather experiment”. http://www.youtube.com/watch?v=4mTsrRZEMwA Question 7: For most of recorded history, people thought that heavy objects naturally and under all conditions fall faster than lighter objects. Why did it take us so long to realize the true state of affairs? *We never thought of forces such as air resistance and things of the same sort that would give inaccurate results. On the moon there is no air resistance and no forces besides gravity acting on the hammer and feather. Because of that, regardless of weight, they fall at the same speed. Question 8: The Earth’s gravity DOES exert a greater force on heavier objects than lighter ones (these forces are called weight). However, with no air resistance objects fall at the same speed in a given gravity field. The weight difference can be thousands of pounds to one and the objects still fall at the same speed. What physical property of mass compensates for the difference in applied forces? *Acceleration Equation 4: e = 1 – Tcold/Thot …where: e = efficiency of energy use Tcold = the temperature of the environment surrounding the heat engine Thot = the internal operating temperature of the engine This is the equation for the efficiency of a heat engine (your car is a heat engine unless you have an electric model). An e = 1 is 100% efficiency, meaning 100% of the energy gets used to do what you want to do with no “wasted”, unrecoverable energy. An e = 0 is an efficiency of zero with none of the energy going to what you want to do and all of the energy being “wasted” or in unrecoverable forms. The temperatures in this equation are in the Kelvin scale where the lowest temperature is 0 degrees. There are no negative temperatures in the Kelvin scale. A temperature we might encounter on Earth would be about 300 degrees Kelvin. Question 9: Is it possible to achieve 100% efficiency, in theory, by lowering the temperature of the environment surrounding the heat engine (Tcold)? Why or why not? *In theory yes. If you were able to lower the temperature of the environment surrounding the heat engine (Tcold) until it was 0 (absolute zero). Than the following the formula, e=1 would be 100% efficiency. Question 10: Is it possible, in practice, to achieve 100% efficiency by lowering the temperature of the environment surrounding the heat engine (Tcold)? Why or why not? *It is not possible because it is impossible to remove all of the heat of the environment surrounding the heat engine (Tcold) to reach absolute zero. Question 11: Is it possible to achieve 100% efficiency, in theory, by raising the internal operating temperature of the heat engine (Thot)? Why or why not? *It is possible to achieve 100% efficiency in theory by raising the internal operating temperature of the heat engine to infinity. If you raise Thot to infinity, according to the formula, you will achieve 100% efficiency. Question 12: Is it possible to achieve 100% efficiency, in practice, by raising the internal operating temperature of the heat engine (T hot)? Why or why not? * It is not possible because no matter how much you raise the internal operating temperature of the heat engine (Thot) as long as the environment surrounding the heat engine (Tcold) is greater than 0, you will never achieve 100% efficiency. It is also impossible to raise the internal operating temperature of the heat engine to infinity. Question 13: If your car is not electric, it is a heat engine and is subject to the efficiency equation. Is it possible to build a car, using any kind of burning fuel, that is 100% efficient? Explain. *It is not possible. In some way heat will be released into the environment and you will never be able to remove all of the heat of the surrounding environment. In that sense you will never be able to build a car that is 100% efficient. Part 3: Learning about a Law of Physics Pick any Law or Principle of Physics in your textbook and: Newton’s Third Law of Motion 1. Give me an explanation of what it is and what it means. *Newton’s third Law of Motion states that whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. It means that when things hit the force they exert on each other is the same and opposite. 2. Give me 3 examples in the real world involving the law or principle. *Bug hitting a windshield *Pool balls hitting one another *Me punching my brother in the face Part 4: Explanation of Fermi’s Paradox and possible resolution This involves the possible existence of alien life in the Universe. A net search should bring up some immediate information on the subject. 1. Clearly explain what this paradox involves and why it is a paradox. *What this paradox involves is there are planets similar to ours in different galaxies. Because our sun is young and there are much older suns with planets like ours it is probable that there is intelligent life on these other planets. Since their sun is older than ours if there has been intelligent life they must be way more advanced than we are. If they are a lot more advanced than us they could probably travel to us. Why this is a paradox is because if those intelligent life forms are more advanced and can travel through space “where are they?” 2. List and briefly explain (like in a paragraph for each) 4 possible resolutions to the paradox. There may be a few possible resolutions to Fermi’s Paradox about alien life. First of all, maybe they haven’t advanced as fast as we have. Even though the life form may be much older than us, maybe they are very slow at advancing. Another reason may be is that there really aren’t any other intelligent life forms in other galaxies. We might be alone. Maybe they have studied a small portion of their galaxy and they realize that they don’t have any reason to travel through space or to us. Perhaps the alien life forms know we are here but they don’t want us to know that they can reach us. If we make connection with them and receive some of their technology, maybe we will advance dangerously fast. Last of all, maybe these aliens are all around us but we have no idea of knowing.