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Would you use a physical model or a conceptual model to describe the following: a gold coin, a dollar bill, a car engine, air pollution, a virus, the spread of sexually transmitted disease? Suppose that a pancake recipe designed to feed three people calls for 600 mL of flour. How many milliliters of flour would you use if you wanted to extend the recipe to feed five people? The centripetal acceleration depends upon the square of the speed rather than just being proportional to the speed. Why does the speed enter twice? Explain. Estimate how many solar panels or wind turbines are needed to produce the same amount of electrical energy as the 10 kt of coal that can be extracted in a long wall mining operation in one year by... Compute the fraction of Carnot efficiency realized by a coal plant operating at 600 C and 45% efficiency (assume ambient temperature of 300 K). If another plant operates at the same fraction of... Compute and compare the amount of carbon released per GJ of delivered energy by (a) a coal plant operating at 35% efficiency, (b) a natural gas combined cycle plant operating at 60% efficiency, (c)... Assume that 1% of a net radiative forcing of 3.7 W/m 2 world wide goes to melting ice over land. Estimate the rate of sea level rise from this melting. Assume that the rate of carbon emission at 10 Gt/year increases at a constant rate to a maximum of 20 Gt/year in 2050, and then decreases at the same rate. Assume that ocean and land biomass together... Thomas Edisons first DC power plant on Pearl St.in New York City produced roughly 100 kW at 110 V(DC), which was distributed over two copper wires spanning distances of order 1 km. Suppose resistive... A homeowner is trying to decide whether to heat with a furnace rated at 95% efficiency or by an electrically powered heat pump. She lives in a town where electricity is produced by a coal-fired power... A force of 40 N pushes down on the movable piston of a closed cylinder containing a gas. The pistons area is 0.5 m 2 . What pressure does this produce in the gas? If 200 cal of heat are added to a system, how much energy has been added in joules? If 600 J of heat are added to 50 g of water initially at 20C, a. how much energy is this in calories? b. what is the final temperature of the water? Is it possible to produce a longitudinal wave on a rope? Explain. When two waves on separate ropes reach the spliced junction out of phase with one another, they interfere destructively producing no wave beyond the splice. What happens then to the energy carried by... What is the beat frequency that results when an 880-Hz note is played with a 660-Hz note? If this beat frequency is heard as a musical tone, how is this tone related to the original two notes? What... A fish lies 80 cm below the surface of a clear pond. If the index of refraction of water is assumed to be 1.33 and that of air is approximately 1, how far below the surface does the fish appear to a... A rock appears to lie just 24 cm below the surface of a smooth stream when viewed from above the surface of the stream. Using the indices of refraction given in exercise 2, what is the actual... A positive lens has a focal length of 6 cm. An object is located 24 cm from the lens. a. How far from the lens is the image? b. Is the image real or virtual, erect or inverted? c. Trace three rays... A positive lens has a focal length of 12 cm. An object is located at a distance of 3 cm from the lens. a. How far from the lens is the image? b. Is the image real or virtual, erect or inverted? c.... A negative lens has a focal length of -10 cm. An object is located 20 cm from the lens. a. How far from the lens is the image? b. Is the image real or virtual, erect or inverted? An object is located at the focal point of a positive lens with a focal length of 12 cm. a. What is the image distance predicted by the object image distance formula? b. Trace two rays to confirm the... How many more electrons can fit within the valence shell of a fluorine atom? Some bottled water is now advertised as containing extra quantities of Vitamin O, which is a marketing gimmick for selling oxygen, O 2 . Might this bottled water actually contain extra quantities of... For every question we can answer with our space telescopes, there are more questions that arise. Why, then, should we continue looking for answers? Describe the connection between special and general relativity Compare and contrast the Big Bang and a black hole? If we cant even predict the weather, how can we ever expect to predict the fate of the universe? If there are so many stars and galaxies, why do we see so much darkness in the clear night sky? Mass can transform into energy, and energy can transform into mass, in accordance with Einsteins equation E = mc 2 . If the amount of massenergy in the universe remains constant, what happens to the... If the universe were unchanging and there were an infinite number of stars, what effect might this have on the darkness of a clear night sky? Why is dark energy not called the dark force? What is one important difference between dark matter and dark energy? Is space just the absence of matter? What is the relationship between dark energy and Einsteins cosmological constant? If dark matter is affected by gravity, might there be lots of it surrounding us here on the surface of Earth? The y-axis in the largest graph of Figure 28.27 is given in units of redshift, z. How is this related to velocity, as given in the y-axis of the smaller graph above it? Original Hubble data 50 100... Why doesnt dark matter clump together as effectively as ordinary matter? What force allows dark matter to clump? Early astronomers such as Kepler and Newton developed the laws of gravity on the basis of the motion of the planets around the Sun. How might these laws be different if our solar system were set... What might we assume about the distribution of dark matter if the planets in our solar system all orbited the Sun at about the same speed? If we are made of stardust, what are stars made of? How do the distances in Exercise 73 compare as seen in the frame of reference of an observer on a stationary planet (Figure 28.19)? Inside the moving compartment of Figure 28.18, light travels a certain distance to the front end and a certain distance to the back end of the compartment. How do these distances compare as seen in... Astronomers view light coming from distant galaxies that are receding from us at very high speeds, greater than 10% of the speed of light (that is, at about 30,000 km/s). How fast does this light... Assume the onboard light in Figure 28.18 is fixed to the front wall. For whom does this light hit the back wall first: the onboard observer or the observer at rest on a planet as shown in Figure... When do clocks move slowest on Mercury? A man leaves his identical twin brother behind to live on another planet that is half as massive. After living apart for many years, the two brothers are reunited on the original planet. According to... Being ultra-sensitive, should a person who wants to live a long life live at the top or at the bottom of a tall apartment building? Several billion years in the future, our Sun will grow in size to become a red giant, whose surface will extend to the present orbit of Earth. After this happens, will the slowing of time on the Suns... Where does a clock run slower: at the front end or the back end of an accelerating spaceship? Assume the onboard light in Figure 28.18 is fixed to the back wall. For whom does this light hit the front wall first: the onboard observer or the observer at rest on a planet as shown in Figure... You are free-floating in a spaceship that is in uniform motion deep in outer space. A ball is hovering in front of you. Suddenly the ball starts moving to the floor. What is happening to the... You toss a tennis ball up and down in front of you as you sit in a jet airplane that is cruising at a constant velocity of 500 miles per hour. Why is the tennis ball easy to catch, despite the fact... You toss a tennis ball up and down in front of you as you sit in a jet airplane that is accelerating down the runway for takeoff. Why is the tennis ball difficult to catch? Explain how weight can be caused by both gravity and acceleration. Is cosmic inflation a cause or an effect? How about dark energy? What if there were symmetry to cosmic background radiation such that the pattern of temperature fluctuations in one direction was exactly the same as the pattern of temperature fluctuations in the... The average temperature of the universe right now is about 2.73 K. Is this temperature likely to go up or down over the next billion years? Astronomers tell us that the average temperature of the universe is a rather homogeneous 2.73 K (+/- 0.0001 K). But how can this be when we know that stars are ultra-hot? A helium balloon here on Earth pops, releasing direct remnants of the Big Bang. True or False? Explain. Are astronomers able to point their telescopes in the direction of where the Big Bang occurred? If the initial universe had remained hotter for a longer period of time, would there probably be more helium or less helium? A police officer pulls you over for speeding. He tells you that his radar tracked you moving at a rate of 45 mph away from his parked police car. Were you really speeding away from him, or was the... What does the expansion of space do to light passing through it? When was most of the helium in the universe created? Rank the following in order of increasing duration: One minute on the surface of (a) Earth. (b) Mercury. (c) The Moon. Rank the following in order of longest ago to most recent: (a) Star formation. (b) Inflation. (c) Big Bang Rank the following in order of increasing abundance in the universe: (a) Dark matter. (b) Ordinary matter. (c) Dark energy Rank the following in order of increasing abundance in the universe: (a) Helium. (b) Hydrogen. (c) Carbon. What scenario for the fate of the universe proposes that cosmic inflation is not a one-time event? What does the Big Rip scenario assume about dark energy? According to the heat death scenario, about how long will it take for the black holes of the universe to evaporate? Which is more abundant: dark matter or ordinary matter? What is probably the major constituent of our universe? What does WMAP stand for? According to recent evidence, how long ago did the expansion of the universe start accelerating? What did Einstein refer to as the greatest blunder of his life? Did Einstein first believe that the universe was static or dynamic? In a huge cloud of ordinary matter and dark matter, the two are uniformly mixed together. Over time, the ordinary matter becomes concentrated toward the center of this cloud. Why? The closer a planet is to the Sun, the faster it orbits. Is it also true that the closer a star is to the center of the galaxy, the faster it orbits? Is dark matter found mostly within a galaxy or just outside a galaxy? If we cant see dark matter, how do we know it is there? What type of matter is visible? Why is the essence of a coffee table best captured with a video camera, rather than with a still camera? Within a spaceship moving at 99% the speed of light, what do you notice about the onboard clocks? What happens to starlight as it passes close to the Sun? What did general relativity predict about the orbit of Mercury? You release a ball while standing on the floor of an accelerating spaceship. What happens to the ball? Can an accelerated frame of reference be distinguished from a gravitational field? In what year did Einstein publish his general theory of relativity? How many dimensions are there in spacetime? At what point did the universes temperature even out? According to cosmic inflation theory, how long did it take for the universe to increase its size by a factor of 10 30 ? Judging by the cosmic background radiation, what is the average temperature of the universe today? What is the approximate age of the universe? Which depends on distance: a stars brightness or its luminosity? What is a Cepheid? Why is it important to have a science-based understanding of the structure of our universe? Try condensing your answer into a single philosophical sentence. It takes an infinite amount of time to watch an object fall through a black holes event horizon. In what sense, therefore, can it be said that black hole singularity does not exist?
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