Questions and Answers of Inquiry into Physics

In Jules Verne’s classical science fiction tale Journey to the Center of the Earth, a group of scientists and adventurers descend deep into the interior of Earth. Among the equipment they carry
The isotope plutonium-239 undergoes alpha decay. Write the reaction equation and determine the identity of the daughter nucleus.
What are the principal steps in neutron activation analysis? Why are neutrons used in this technique to probe the composition of objects instead of, say, protons or alpha particles?
1. The development of the Standard Model of elementary particles is one of the most significant achievements in physics in the 20th century. While refinements of this description of the subatomic
In a particular beam of protons, each particle moves with an average speed of 0.8c. Determine the total relativistic energy of each proton in joules and MeVs.
Analyze the following decays in terms of the quark contents of the particles: n+ (a) Σ~ → n + π (b) A → p + π 10 + (c) _K*+ → K° + π (d) Ω- → 1° + K- Κ
(a) A negatively charged iron ball (on the end of a plastic rod) exerts a strong attractive force on a penny even though the penny is neutral. How is this possible?(b) The penny accelerates toward
What is an electric field? Sketch the shape of the electric field around a single proton.
A defibrillator sends approximately 0.1 C of charge through a patient’s chest in about 2 ms. The average voltage during the discharge is approximately 3,000 V. Compute the average current that
Explain what an electrostatic precipitator is and how it works.
If electrons are flowing clockwise around an electric circuit, which way is the conventional current flowing in the circuit?
In winter, the amount of internal energy a heat pump delivers to a house is greater than the electrical energy it uses. Does this violate the law of conservation of energy? Explain.
A special glass thermometer is manufactured using a liquid that expands less than glass when the temperature increases. Assuming the thermometer does indicate the correct temperature, what is
An aluminum wing on a passenger jet is 30 m long when its temperature is 20oC. At what temperature would the wing be 5 cm (0.05 m) shorter?
The door of a refrigerator is left open. Assuming the refrigerator is in a closed room, will the air in the room eventually be cooled?
Explain what a bimetallic strip is and how it functions.
Which metal in the bimetallic strip has the larger coefficient of linear expansion: the metal on the outer side of the spiral or the metal on the inner side? How can you determine this?
The volume of an ideal gas enclosed in a thin, elastic membrane in a room at sea level where the air temperature is 18oC is 8 x 1023 m3. If the temperature of the room is increased by 10oC, what is
A certain engine part made of iron expands 1 mm in length as the engine warms up. What would be the approximate change in length if the part were made of aluminum instead of iron?
What is unusual about the behavior of water below the temperature of 4οC?
Air in a balloon does 50 J of work while absorbing 70 J of heat. What is its change in internal energy?
A company decides to make a novelty glass thermometer that uses water instead of mercury or alcohol.(a) The thermometer would include a warning informing the user that it should not be exposed to
You may have noticed warning labels in aerosol cans of spray paint or air freshener that caution the user: “Do not expose or store container to/in high temperatures.” Explain why the
A bottle containing 3 kg of water at a temperature of 20°C is placed in a refrigerator where the temperature is kept at 3°C. How much heat is transferred from the water to cool it to 3°C?
After sitting outside on a cold night, the pressure in the tires of your car is 26 psi. If you drive your vehicle to work, a distance of 25 miles, at highway speeds, would you expect the tire
What are the two general ways to increase the internal energy of a substance? Describe an example of each.
Aluminum is melted during the recycling process.(a) How much heat must be transferred to each kilogram of aluminum to bring it to its melting point, 660°C, from room temperature, 20°C?(b) About how
Air is allowed to escape from an inflated tire. Is the temperature of the escaping air higher than, lower than, or equal to the temperature of the air inside the tire? Why?
Is it possible to compress air without causing its internal energy to increase? If so, how?
A 0.02-kg lead bullet traveling 200 m/s strikes an armor plate and comes to a stop (Figure 5.46). If all of the bullet’senergy is converted to heat that it alone absorbs, what is its temperature
According to the first law of thermodynamics, under what conditions would it be possible for a system to absorb heat from its surroundings yet suffer no change in its internal energy?
Describe the three methods of heat transfer. Which of these are occurring around you at this moment?
Water flowing over the Lower Falls in Yellowstone National Park drops 94 m. If all of the water’s energy goes to heat it, what is its temperature increase?
A potato will cook faster in a conventional oven if a large nail is inserted into it. Why?
Double-paned thermal insulating windows consist of two glass panels separated by a narrow gap from which most of the air has been removed to create a near vacuum in the space between the panes.
On a summer day in Houston, the temperature is 35oC and the relative humidity is 77 percent.(a) What is the humidity?(b) To what temperature could the air be cooled before condensation would start to
A coin and a piece of glass are both heated to 60οC. Which will feel warmer when you touch it?
A submerged heater is used in an aquarium to keep the water above room temperature. Should it be placed near the surface of the water or near the bottom to be most effective? Explain.
On a hot summer day in Washington, D.C., the temperature is 868F, and the relative humidity is 70 percent. How much water vapor does each cubic meter of air contain?
On a cool night with no wind, people facing a campfire feel a breeze on their backs. Why?
Suppose you hang a bag of ice inside a room in which the air is at normal room temperature. If you position the palm of your hand a few inches to the side of the ice, what would you feel? Why? Would
The total volume of a new house is 800 m3. Before the heat is turned on, the air temperature inside is 10oC, and the relative humidity is 50 percent. After the air is warmed to 20oC, how much water
When heating water on a stove, a full pan of water takes longer to reach the boiling point than a pan that is half full. Why?
A 1-kg piece of iron is heated to 100οC, and then submerged in 1 kg of water initially at 0οC. The iron cools and the water warms until they are at the same temperature (in thermal equilibrium).
In cold weather, you can sometimes “see” your breath. What you are seeing is a mist of small water droplets, the same as in clouds and fog. Suppose air leaves your mouth with temperature 35oC and
What is the maximum efficiency that a heat engine could have when operating between the normal boiling and freezing temperatures of water?
A piece of aluminum and a piece of iron fall without air resistance from the top of a building and stick into the ground on impact. Will their temperatures change by the same amount? Explain.
The specific heat capacity of water is extremely high. If it were much lower, say, one-fifth as large, what effect would this have on processes such as fighting fires and cooling automobile engines?
Why does the temperature of water not change while it is boiling?
A proposed ocean thermal-energy conversion (OTEC) system is a heat engine that would operate between warm water (25οC) at the ocean’s surface and cooler water (5οC) 1,000 m below the surface.
Describe how changing the air pressure affects the temperature at which water boils.
The temperature in the deep interiors of some giant molecular clouds in the Milky Way galaxy is 50 K. Compare the amount of energy that would have to be transferred to this environment to the amount
One way to desalinate seawater—remove the dissolved salts so that the water is drinkable—is to distill it: boil the seawater and condense the steam. The salts stay behind. This technique has one
What is saturation density? How does it change when the temperature increases?
What effect does heating the air in a room have on the relative humidity?
Wood’s metal is an alloy of the elements bismuth, lead, tin, and cadmium that has a melting point of 70οC. Describe how it might be used in an automatic sprinkler system for fire suppression.
When trying to predict the lowest temperature that will be reached overnight, forecasters pay close attention to the dew-point temperature. Why is the air temperature unlikely to drop much below the
Explain what a heat engine does and what a heat mover does.
What is the difference between a mixture of two elements and a compound formed from the two elements?
Earth’s mass is 6 x 1024 kg, and its radius is 6.4 x 106 m. What is the average mass density of Earth? The density of the rocks comprising Earth’s outermost layer (its “crust”) ranges from
If you classify everything around you as an element, a compound, or a mixture, which category do you think would have the largest number of entries? Why?
The water in the plumbing in a house is at a gauge pressure of 300,000 Pa. What force does this cause on the top of the tank inside a water heater if the area of the top is 0.2 m2?
In 1993, a football coach in the United States accused an opposing team’s punter of using a football inflated with helium instead of air. Estimate how much lighter a football would be if inflated
Why can gases be compressed so much more readily than solids or liquids?
A viewing window on the side of a large tank at a public aquarium measures 50 in. by 60 in. The average gauge pressure from the water is 8 psi. What is the total outward force on the window?
Scuba divers take their own supply of air with them when they go underwater. Why couldn’t they just take a long hose with them from the surface and breathe through it
Two swimming pools are 8 ft deep, but one measures 20 ft by 30 ft, and the other measures 40 ft by 60 ft. Identical drain valves at the bottom of each pool are 10 in.2 in area. Compare the force on
Use the concept of pressure to explain why snowshoes are better than regular shoes for walking in deep snow.
A small statue is recovered in an archaeological dig. Its weight is measured to be 96 lb, and its volume 0.08 ft3.(a) What is the statue’s weight density?(b) What substance is it?
Suppose you are in the International Space Station in orbit around Earth and a fellow astronaut gives you what appears to be an inflated balloon. Describe how you could determine whether the balloon
A motorist driving through Colorado checks the tire pressure in Denver (elevation 5,000 ft) and then again at the Eisenhower Tunnel (elevation 11,000 ft). Would the pressures be the same? What two
Why is it that a person can lie still on a “bed” of nails (Figure 4.53) without suffering any serious injuries but would incur severe puncture wounds to his feet if he tried to stand barefoot on
A glass contains pure water with ice floating in it. After the ice melts, will the water level be higher, lower, or the same? (Ignore evaporation.)
Bicycle tires are often inflated to pressures as high as 75 psi, whereas automobile tires, which must support much heavier loads, are pumped to only 32 psi. Why is that? Explain.
The total mass of the hydrogen gas in the Hindenburg zeppelin was 18,000 kg. What volume did the hydrogen occupy?
At one point in the novel Slapstick by Kurt Vonnegut, the force of gravity on Earth suddenly “increased tremendously.” The result:. . . elevator cables were snapping, airplanes were
The same bicycle tire pump is used to inflate a mountain bike tire to 40 psi and then a road bike tire to 100 psi. What difference would the user notice when using the pump on the two tires?
A brick rests on a large piece of wood floating in a bucket of water. The brick slides off and sinks. Does the water level in the bucket go up, go down, or stay the same?
Explain the difference between gauge pressure andabsolute pressure.
A certain part of an aircraft engine has a volume of 1.3 ft3.(a) Find the weight of the piece when it is made of iron.(b) If the same piece is made of aluminum, what is its weight? Determine how much
As a helium balloon rises up in the air, work is done on it against the force of gravity. What is doing the work? What energy transfer or transformation is taking place?
How can you use the volume of some quantity of a pure substance to calculate its mass?
Prove Archimedes’ principle. That is, show that the buoyant force is equal to the weight of the displaced fluid. Assume the object submerged in the fluid is a rigid rectangular box with dimensions
Use conservation of energy to show that the speed with which water flows out of a tap near the bottom of an open container equals √2gh where h is the height of the freestanding surface of the water
Believe it or not, canoes have been made out of concrete (and they actually float). But even though concrete has a lower density than aluminum, a concrete canoe weighs a lot more than an aluminum one
Would the weight density of water be different on the Moon than it is on Earth? What about the mass density? Explain.
The depth of the Pacific Ocean in the Mariana Trench is 36,198 ft. What is the gauge pressure at this depth?
The mass density of a mixture of ethyl alcohol and water is 950 kg/m3. Is the mixture mostly water, mostly alcohol, or about half and half? What is your reasoning?
The way pressure increases with depth in a gas is different from the way it does in a liquid. Why?
Workers are to install a hatch (door) near the bottom of an empty storage tank. In choosing how strong to make the hatch, does it matter how tall the tank is? How wide it is? Whether it is going to
A storage tank 30 m high is filled with gasoline. (a) Find the gauge pressure at the bottom of the tank.(b) Calculate the force that acts on a square access hatch at the bottom of the tank that
If the acceleration due to gravity on Earth suddenly increased, would this affect the atmospheric pressure? Would it affect the pressure at the bottom of a swimming pool? Explain.
If Earth’s atmosphere warmed up and expanded to a larger total volume but its total mass did not change, would this affect the atmospheric pressure at sea level? Would this affect the pressure at
The highest altitude ever reached by a glider (as of this writing) is 15,460 m. What is the approximate air pressure at that altitude?
Explain how a barometer can be used to measure altitude.
Is there a pressure variation (increase with depth) in a fuel tank on a spacecraft in orbit? Why or why not?
An oak barrel is filled with water and then tightly sealed. A hole is drilled in the barrel’s top, and a narrow, open tube is fitted securely into the hole. Water is then slowly added to the tube.
If you hold a rubber ball at eye level and drop it, it will bounce back, but not to its original height. Identify the energy conversions that take place during the process, and explain why the ball
A woman is riding on a train while watching the display on her GPS unit. She notices that both the “speed” and the “direction” readings are not changing. What can the she conclude about the
Identify as many different ways as you can for giving energy to a basketball.

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