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the physical universe

Questions and Answers of The Physical Universe

What are the two postulates from which Einstein developed the special theory of relativity?
What physical quantity will all observers always find the same value for?
The potential energy of a golf ball in a hole is negative with respect to the ground. Under what circumstances (if any) is the ball’s kinetic energy negative? Its rest energy?
A certain walking person uses energy at an average rate of 300 W. All of this energy has its ultimate origin in the sun. How much matter is converted to energy in the sun per hour to supply this
When 1 g of gasoline is burned in an engine, about 48 kJ of heat is produced. How much mass is lost in the process? Do you think this mass change could be directly measured?
Approximately 4 × 109 kg of matter is converted into energy in the sun per second. Express the power output of the sun in watts.w
Even if the developed countries stabilize or reduce their energy consumption in years to come, worldwide energy consumption will increase. What are the two main reasons for this?
List the fossil fuels in the order in which they will probably be used up.
What energy sources cannot be traced to sunlight falling on the earth?
When a mercury-in-glass thermometer is heated, its mercury column goes down briefly before rising. Why?
Would it be more efficient to warm your bed on a cold night with a hot water bottle that contains 1 kg of water at 50°C or with a 1-kg gold bar at 50°C? Why?
Every body of matter radiates light. What is characteristic of light radiated by something very hot, such as the sun? Of light radiated by something at ordinary temperatures, such as the earth’s
List the chief greenhouse gases in the atmosphere. What property do they share?
(a) Why is deforestation so important in global warming?(b) In round numbers, which proportion of worldwide greenhouse gas emissions is due to deforestation:5 percent, 10 percent, 20 percent, 40
What fuel liberates the most energy per gram when it burns? What is produced when it burns?
How do the oil reserves in tar sands compare with the reserves of ordinary crude oil? What are some of the disadvantages of tar sands oil?
What is the chief reason why the average fuel efficiency of cars in the United States is the lowest in the world?
Why is natural gas rarely used as a vehicle fuel?
What are the chief advantages of coal as a fuel? The chief disadvantage?
Coal smoke contains sulfur and mercury. Why are they harmful?
(a) List the desirable aspects of coal gasification, the process in which coal is turned into a mixture of gases called syngas.(b) Is there any way to prevent the CO2 emitted when coal is burned from
What role does uranium play in nuclear energy production? What is the uranium supply situation?
Explain why no nuclear power plants were planned in the United States between 1979 and 2012 but are currently being considered for construction.
What stands in the way of the immediate use of nuclear fusion as a commercial energy source?
Give examples of clean sources that can supply energy continuously and examples of others whose output varies with time of day and weather conditions.
Give several reasons why fossil-fuel energy is cheaper than energy from most renewable sources.
What advantages do photovoltaic panels have for installation in remote regions?
Explain how tide and wave energies can be captured.
List four practical ways to store energy from noncontinuous energy sources.
What are the advantages and disadvantages of hydrogen fuel cells?
Why are algae so interesting as a way of producing biodiesel fuel?
A major obstacle to a worldwide agreement on reducing greenhouse gas emissions is that the developing countries want the developed ones to do what three things?
Why do you think the Celsius temperature scale is sometimes called the centigrade scale?
What is the Celsius equivalent of a temperature of 160°F?
You have a Fahrenheit thermometer in your left hand and a Celsius thermometer in your right hand. Both thermometers show the same reading in degrees. What is the temperature?
A 150-L water heater is rated at 8 kW. If 20 percent of its heat escapes, how long does the heater take to raise the temperature of 150 L of water from 10°C to 60°C?
The specific heat of granite is 0.80 kJ/kg · ° C. If 1.6 MJ of heat are added to a 100-kg granite statue of James Prescott Joule that is originally at 18°C, what is the final temperature of the
Ninety kilojoules of heat were added to a 2.0-kg piece of wood whose temperature then rose from 20°C to 48°C. What was the specific heat of the wood?
An essential part of a home solar heating system is a way to store heat for use at night and on cloudy days. In a certain system, the water used for storage is initially at 75°C and it is required
Why do tables of densities always include the temperature for which the listed values hold? What would be true of the densities of most solids and liquids at a temperature higher than the quoted one?
A 156-kg coil of sheet steel is 0.80 mm thick and 50 cm wide. How long is the steel in the coil?
A 1200-kg concrete slab that measures 2 m × 1 m × 20 cm is delivered to a building under construction. Does the slab contain steel reinforcing rods or is it plain concrete?
A cube of gold 30 mm long on each edge (the size of an ice cube) is usually worth at least $18,000. If that is its value, how much is a gram of gold worth?
Some water is boiled briefly in an open metal can. The can is then sealed while still hot. Why does the can collapse when it cools?
The three containers shown in Fig. 5-55 are filled with water to the same height. Compare the water pressures at the bottoms of the containers.
A 60-kg swami lies on a bed of nails with his body supported by 4000 nails. The area of the point of each nail is 1 mm2. If the threshold pressure for pain is 1 MPa, how unpleasant is the experience
A nail whose cross-sectional area is 3 mm2 is embedded in a tire in which the air pressure is 1.8 bar. How much force tends to push the nail out?
The smallest bone in the index finger of a 75-kg circus acrobat has a cross-sectional area of 0.5 cm2 and would break under a pressure of 1.7 × 108 Pa. Is it safe for the acrobat to balance his
At the distance of the earth from the sun, the pressure exerted by sunlight is about 1025 Pa. How much force does this pressure exert on a 10-m2 array of solar cells on a satellite when the array is
Two balls of the same size but of different mass are dropped from a tower. If the air resistance is the same for both, will they reach the ground together? If not, which will arrive first? Why?
A jar is filled to the top with water, and a piece of cardboard is slid over the opening so that there is only water in the jar. If the jar is turned over, will the cardboard fall off? What will
A bridge in Sweden carries the Göta Canal over a highway. What, if anything, happens to the load on the bridge when a boat passes across it in the canal?
An ice cube with an air bubble inside it is floating in a glass of water. Compare what happens to the water level in the glass when the ice melts with what would happen if the cube had no bubble in
An aluminum canoe is floating in a swimming pool. After a while it begins to leak and sinks to the bottom of the pool. What, if anything, happens to the water level in the pool?
A 40-kg girl dives off a raft whose area is 3 m2 and which is floating in a freshwater lake. By how much does the raft rise?
As global warming proceeds, sea level is rising, partly because of thermal expansion and partly because of meltwater from disappearing icecaps and glaciers. Coastal cities are expected to be flooded
What are the equivalents of 0 K, 0°C, and 0°F in the other temperature scales?
A tire contains air at a pressure of 2.8 bar at 10°C. If the tire’s volume is unchanged, what will the air pressure in it be when the tire warms up to 35°C as the car is driven?
A weather balloon carries instruments that measure temperature, pressure, and humidity as it rises through the atmosphere. Suppose such a balloon has a volume of 1.2 m3 at sea level where the
The propellant gas that remains in an empty can of spray paint is at atmospheric pressure. If such a can at 20°C is thrown into a fire and is heated to 600°C, how many times atmospheric pressure is
Gas molecules have speeds comparable with those of rifle bullets, yet it is observed that a gas with a strong odor (ammonia, for instance) takes a few minutes to diffuse through a room. Why?
The pressure on a sample of hydrogen is doubled, while its temperature is kept unchanged. What happens to the average speed of the hydrogen molecules?
Temperatures in both the Celsius and Fahrenheit scales can be negative. Why is a negative temperature impossible on the absolute scale?
A 1-L tank holds 1 g of hydrogen at 0°C and another 1-L tank holds 1 g of oxygen at 0°C. The mass of an oxygen molecule is 16 times the mass of a hydrogen molecule.(a) Do the tanks hold the same
A tank holds 1 kg of nitrogen at 25°C and a pressure of 100 kPa. What happens to the pressure when 4 kg of nitrogen are added to the tank at the same temperature? Explain your answer in terms of the
You can safely put your hand inside a hot oven for a short time, but even a momentary contact with the metal walls of the oven will cause a burn. Explain.
A thermos bottle consists of two glass vessels, one inside the other, with air removed from the space between them. The vessels are both coated with thin metal films. Why is this device so effective
Why does evaporation cool a liquid?
A hydrogen molecule consists of two hydrogen atoms whose nuclei are single protons. Find the force between the two protons in a hydrogen molecule whose distance apart is 7.42 × 10−11 m. (The two
Two charges repel each other with a force of 0.1 N when they are 5 cm apart. Find the forces between the same charges when they are 2 cm and 8 cm apart.
Sensitive instruments can detect the passage of as few as 60 electrons/s. To what current does this correspond?
A 120-V electric coffeepot draws a current of 0.6 A. What is the resistance of its heating element?
A solar cell whose area is 80 cm2 produces a current of 2.1 A at 0.5 V in bright sunlight whose intensity is 0.1 W/cm2. Find the efficiency with which the cell turns solar energy into electric energy.
How many times stronger than the 60-dB sound of a person talking loudly is the 100-dB sound of a power lawn mower?
A radar sends out 0.05-μs pulses of microwaves whose wavelength is 24 mm. What is the frequency of these microwaves? How many waves does each pulse contain?
Under what circumstances, if any, will a converging lens form an inverted image of a real object? Under what circumstances, if any, will a diverging lens form an erect image of a real object?
The olive in a cocktail (n = 1.35) seems to be 30 mm below the surface. What is the actual depth of the olive?
How can constructive and destructive interference be reconciled with the principle of conservation of energy?
A radar operating at a wavelength of 3 cm is to have a resolving power of 30 m at a range of 1 km. Find the minimum width its antenna must have.
Find the number of neutrons and protons in each of the following nuclei: 36 Li; 13 6 C; 31 15 P; 9440 Zr.
How does the number of neutrons in a stable nucleus compare with the number of protons? Why is this?
The boron isotope 125 B decays into the carbon isotope 126 C. What kind of particle is emitted in the decay?
The helium isotope 62 He is unstable. What kind of decay would you expect it to undergo? What would the resulting nuclide be?
A 6429 Cu nucleus can decay by emitting an electron or a positron and also by capturing an electron. What is the final nucleus in each case?
A reaction often used to detect neutrons occurs when a neutron is absorbed by a 105 B boron nucleus, which then emits an alpha particle. What are the atomic number, mass number, and chemical name of
Old stars obtain part of their energy by the fusion of three alpha particles to form a 126 C nucleus, whose mass is 12.0000 u. How much energy is given off in each such reaction?
How does the speed of a photon compare with the speed of an em wave?
Find the frequency and wavelength of a 50-MeV gamma-ray photon.
A 1.2-kW radio transmitter operates at a frequency of 750 kHz. How many photons per second does it emit?
An electron needs an energy of 2.2 eV to escape from a potassium surface. If ultraviolet light of wavelength 350 nm falls on a potassium surface, what is the maximum KE of the emitted electrons?
What is the shortest wavelength present in the radiation from an x-ray machine whose operating potential difference is 40 kV?
In an old-fashioned TV picture tube, electrons are accelerated through voltages of about 10 kV. Find the highest frequencies of the em waves emitted when these electrons strike the screen of the
What voltage must be applied to an x-ray tube for it to emit x-rays with a maximum frequency of 2 × 1019 Hz?
Find the de Broglie wavelength of a 1500-kg car when its speed is 80 km/h. How significant are the wave properties of this car likely to be?
With the help of Fig. 9-29 find the frequency of the photon emitted when an electron in the n = 3 state of hydrogen falls to the ground state.
What is coherent light? Is the light from a lightbulb coherent? The light from the sun?
What kind(s) of particles make up (a) gaseous compounds, (b) liquid compounds, and (c) solid compounds?
Would you expect magnesium or calcium to be the more active metal? Explain your answer in terms of atomic structure.
What is the difference in atomic structure between the two isotopes of chlorine? How would you account for the great chemical similarity of the two isotopes?
(a) Would you expect N or Br to differ most in its chemical properties from F? (b) B or Si from C? (c) P or O from N?

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