Inquiry into Physics 8th edition Vern J. Ostdiek, Donald J. Bord - Solutions

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 you feel anything different if you placed your palm the same distance away but below the ice?
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 vapor must be added to the air to make the relative humidity 50 percent?
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). Assuming there is no other transfer of heat involved, is the final temperature closer to 0οC, 50οC,
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 humidity 0.035 kg/m3 and mixes with an equal amount of air at 5oC and humidity 0.005 kg/m3. (a)
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. What is the maximum possible efficiency of the system?
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 that would have to transferred to a room temperature environment to bring about a 1.0 J/K increase
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 major disadvantage. It consumes a large amount of energy. Why is that?
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 dew point?
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 2,000 to 3,500 kg/m3. Based on your answer, what can you conclude about the material deep inside
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 to a gauge pressure of 1 atm with helium instead of air. The volume of a football is approximately
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 each valve.
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 contains a gas, a liquid, or a solid.
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 main factors affect the tire pressure as the car climbs?
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 the same “bed”?
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 crashing, ships were sinking, motor vehicles were breaking their axles, bridges were collapsing, and on and
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 weight is saved by using aluminum instead of iron.
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 l, w, and h with its top and bottom faces oriented horizontally.
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 above the tap. Assume that the water at the surface is moving with negligible velocity.
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 of the same size. Why is that?
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 hold water or mercury? Explain.
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 measures 0.5 m by 0.5 m.
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 top of Mount Everest? Explain.
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. When the height of the water column reaches a certain point, the barrel bursts apart. Explain this
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 does not reach its original release level.
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 net force acting on the train car?
Identify as many different ways as you can for giving energy to a basketball.
A running back with a mass of 80 kg and a speed of 8 m/s collides with, and is held by, a 120-kg defensive tackle going in the opposite direction. How fast must the tackle be going before the collision for their speed afterward to be zero?
Identify as many different forms of energy as you can that are around you at this moment.
When you throw a ball, the work you do to accelerate it equals the kinetic energy the ball gains. If you do twice as much work when throwing the ball, does it go twice as fast? Explain.
Describe the motion of an object that possesses kinetic energy yet undergoes no net displacement.
How can the gravitational potential energy of something be negative?
What is elastic potential energy? Identify some of the things that currently surround you that possess elastic potential energy.
If a spring is compressed to half its length, by how much does the amount of energy stored in the spring change?
As it orbits Earth, the 11,000-kg Hubble Space Telescope travels at a speed of 7,900 m/s and is 560,000 m above Earth’s surface.(a) What is its kinetic energy?(b) What is its potential energy?
Identify the energy conversions taking place in each of the following situations. Name all of the relevant forms of energy that are involved.(a) A camper rubbing two sticks together to start a fire.(b) An arrow shot straight upward, from the moment the bowstring is released by the archer to the
Solar-powered spotlights have batteries that are charged by solar cells during the day and then operate lights at night. Describe the energy conversions in this entire process, starting with the Sun’s nuclear energy and ending with the light from the spotlight being absorbed by the surroundings.
Truck drivers approaching a steep hill that they must climb often increase their speed. What good does this do, if any?
A worker at the top of a 629-m-tall television transmitting tower in North Dakota accidentally drops a heavy tool. If air resistance is negligible, how fast is the tool going just before it hits the ground?
A ball is thrown straight upward from the surface of the Moon. Is the maximum height it reaches less than, equal to, or greater than the maximum height reached by a ball thrown upward on Earth with the same initial speed? (Ignore air resistance in both cases.) Explain.
Describe the distinction between elastic and inelastic collisions. Give an example of each.
Many sports involve collisions between things—such as balls and rackets—and between people—as in football or hockey. Characterize the various sports collisions as elastic or inelastic.
Carts A and B stick together whenever they collide. The mass of A is twice the mass of B. How could you roll the carts toward each other in such a way that they would be stopped after the collision? (Assume there is no friction and that the carts move on level ground.)
The cliff divers at Acapulco, Mexico, jump off a cliff 26.7 m above the ocean. Ignoring air resistance, how fast are the divers going when they hit the water?
Is it possible for one object to gain mechanical energy from another without touching it? Explain.
How are the physical concepts power and speed similar?
The fastest that a human has run is about 12 m/s.(a) If a pole vaulter could run this fast and convert all of her kinetic energy into gravitational potential energy, how high would she go?(b) Compare this height with the world record in the pole vault.
Two cranes are lifting identical steel beams at the same time. One crane is putting out twice as much power as the other. Assuming friction is negligible, what can you conclude is happening to explain this difference?
A person runs up several flights of stairs and is exhausted at the top. Later, the same person walks up the same stairs and does not feel as tired. Why is this? Ignoring air resistance, does it take more work or energy to run up the stairs than to walk up?
In January 2003, an 18-year-old student gained a bit of fame for surviving—with only minor injuries—a remarkable traffic accident. The vehicle he was driving was “clipped” by another one, left the road, and rolled several times. He was thrown upward from the vehicle (he wasn’t wearing a
How can a satellite’s speed decrease without its angular momentum changing?
Why do divers executing midair somersaults pull their legs in against their bodies?
It is possible for a body to be both spinning and moving in a circle in such a way that its total angular momentum is zero. Describe how this can be.
Five identical boxes with the same speeds slide along a frictionless horizontal surface. The mass of each box is 10 kg. The same magnitude force, F, is applied to each box, but along different directions. Rank the five situations described here from greatest to smallest according to the work done
Eight cars move along smooth horizontal roadways in the same direction at specified speeds, v, toward identical barriers. All the cars have the same size and shape, but carry different loads and, hence, have different masses, m. The cars collide with the barriers and come to a stop after having
A 1,000-W motor powers a hoist used to lift cars at a service station.(a) How much time would it take to raise a 1,500-kg car 2 m?(b) If the original motor is replaced with one rated at 2,000 W, how long would it take to complete this task?
Six blocks with different masses, m, each start from rest at the top of smooth, frictionless inclines having length d and vertical height h and slide down. Rank the order, from greatest to smallest, of the final kinetic energies of the masses when they reach the bottom of the inclines after having
An elevator is able to raise 1,000 kg to a height of 40 m in 15 s.(a) How much work does the elevator do?(b) What is the elevator’s power output?
A compact car can climb a hill in 10 s. The top of the hill is 30 m higher than the bottom, and the car’s mass is 1,000 kg. What is the power output of the car?
It takes 100 minutes for a middle-aged physics professor to ride his bicycle up the road to Alpe d’Huez in France. The vertical height of the climb is 1,120 m, and the combined mass of the rider and bicycle is 85 kg. What is the bicyclist’s average power output?
When exactly 1 cup of sugar is dissolved in exactly 1 cup of water, less than 2 cups of solution result. Why?
The following terms were introduced: elements, atoms, electrons, protons, neutrons, nucleus, molecules, compounds, mixtures, and solutions.Create a concept map explaining the composition of matter by appropriately organizing and linking these concepts to form meaningful propositions. After
Describe the four phases of matter. Compare their external, observable properties. Compare the nature of the forces between atoms or molecules (or both) in the solid, liquid, and gas phases.
Identify some of the elements that exist in pure form (not in compounds) around you.

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Inquiry into Physics 8th edition Vern J. Ostdiek, Donald J. Bord - Solutions

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