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physics
conceptual physical science
Conceptual Physical Science 6th Edition Paul G. Hewitt, John A. Suchocki, Leslie A. Hewitt - Solutions
The depth of water behind the Hoover Dam is 220 m. Show that the water pressure at the base of this dam is 2160 kPa.
Show that the water pressure at the bottom of the 50-m-high water tower in Figure 5.3 is 490,000 N/m2, which is approximately 500 kPa.
A 1-m-tall barrel is filled with water (with a weight density of 9800 N/m3). Show that the water pressure on the bottom of the barrel is 9800 N/m2, or, equivalently, 9.8 kPa.Pressure = weight density × depth
Make a small hole near the bottom of an open tin can. Fill the can with water, which then proceeds to spurt from the hole. If you cover the top of the can firmly with the palm of your hand, the flow stops. Explain.
Do as Professor Dan Johnson does and pour about a quarter cup of water into a gallon or 5-liter metal can with a screw top. Place the can open on a stove, and heat it until the water boils and steam comes out of the opening. Quickly remove the can and screw the cap on tightly. Allow the can to
Raise a filled glass of water above the waterline, but with its mouth beneath the surface. Why does the water not flow out? How tall would a glass have to be before water began to flow out? (You wont be able to do this indoors unless you have a ceiling that is at least 10.3 m higher
Try this in the bathtub or when youre washing dishes: Lower a drinking glass, mouth downward, over a small floating object such as a Ping-Pong ball. What do you observe? How deep must the glass be pushed in order to compress the enclosed air to half its volume? (You wont be
Place a wet Ping-Pong ball in a can of water held high above your head. Then drop the can on a rigid floor. Because of surface tension, the ball is pulled beneath the surface as the can falls. What happens when the can comes to an abrupt stop is worth watching!
Punch a couple of holes in the bottom of a water-filled container, and water spurts out because of water pressure. Now drop the container, and, as it freely falls, note that the water no longer spurts out. If your friends dont understand this, could you explain it to them?
What do peaked roofs, convertible tops, and airplane wings have in common when air moves faster across their top surfaces?
Does Pascal’s principle provide a way to get more energy from a machine than is put into it? Defend your answer.
What weight of water is displaced by a 100-ton floating ship? What is the buoyant force that acts on this ship?
Does the buoyant force on a floating object depend on the weight of the object or on the weight of the fluid displaced by the object? Or are these two weights the same for the special case of floating? Defend your answer.
What is the difference between being immersed and being submerged?
State Archimedes’ principle.
How does the pressure exerted by a liquid change with depth of the liquid? How does the pressure exerted by a liquid change as the density of the liquid changes?
Distinguish between force and pressure. Compare their units of measurement.
What happens to the volume of a loaf of bread that is squeezed? What happens to the mass of the squeezed bread? What happens to the density of the squeezed bread?
Give two examples of a fluid.
When the brakes are applied on a vehicle moving to the right, the horizontal net force on the vehicle is to the left. A friend says that the velocity and acceleration of the vehicle are in opposite directions. Do you agree or disagree? Defend your answer.
The first stage of each SpaceX rocket that services the ISS no longer is dumped into the sea, but is returned for recycling (when all goes well). As the empty first stage falls back to Earth, one of its main engines slows its descent velocity to zero at the moment of touchdown. Is it correct to say
Occupants inside future donut-shaped rotating habitats in space will be pressed to their floors by rotational effects. Their sensation of weight feels as real as that due to gravity. Does this indicate that weight need not be related to gravity?
A friend says that astronauts inside the International Space Station (ISS) are weightless because they’re beyond the pull of Earth’s gravity. Correct your friend’s reasoning.
Two facts: A freely falling object at Earth’s surface drops vertically 5 m in 1 s. Earth’s curvature “drops” 5 m for each 8-km tangent. Discuss how these two facts are related to the 8-km/s orbital speed necessary to orbit Earth.
Shruti Kumar projects a ball at an angle of 30° above the horizontal. Which component of initial velocity is larger: the vertical or the horizontal? Which of these components undergoes the least change while the ball is airborne? Defend your answer.
“Okay,” a friend says, “gravitational force is proportional to mass. Is gravitation then stronger on a crumpled piece of aluminum foil than on an identical piece of foil that has not been crumpled? Isn’t that why the crumpled one falls faster when they are dropped together?” Defend your
In the 2014 Rosetta mission, when a probe from Earth landed on the low-mass comet, the probe bounced. Why were scientists overseeing the mission concerned about the comet’s escape speed?
Earth is farthest away from the Sun in July and closest in January. In which of these two months is Earth moving faster around the Sun?
The force of gravity on an Earth satellite in circular orbit remains constant at all points along the orbit. Why is this not the case for a satellite in an elliptical orbit?
If you stopped an Earth satellite dead in its tracks—that is, if you reduced its tangential velocity to zero—it would simply crash into Earth. Why, then, don’t the communications satellites that “hover motionless” above the same spot on Earth crash into Earth?
How could an astronaut in a space vehicle “drop” an object vertically to Earth?
If a space vehicle circled Earth at a distance equal to the Earth–Moon distance, how long would it take for it to make a complete orbit? In other words, what would be its period?
Does the speed of a falling object depend on its mass? (Recall the answer to this question in earlier chapters.) Does the speed of a satellite in orbit depend on its mass? Defend your answers.
Hawaii presents the most efficient launching site in the United States for nonpolar satellites. Why is this so?
Chuck Stone releases a ball near the top of a track and measures the balls speed as it rolls horizontally off the end of the table. Students make measurements to predict where a can must be placed to catch the ball. How will the balls speed affect the time it takes to reach
Earth and the Moon are gravitationally attracted to the Sun, but they don’t crash into the Sun. A friend says that is because Earth and the Moon are beyond the Sun’s main gravitational influence. Other friends look to you for a response. What is your response?
Elements beyond the naturally occurring elements that have been discovered that are named Neptunium and Plutonium. How was the naming process related to discovery of new planets?
How does the size of Pluto compare with that of planets in the solar system?
In the 2014 Rosetta mission, a probe from Earth landed on a comet of very low mass. If the probe had been twice as massive, how would its weight on the comet surface have been affected?
To begin your wingsuit flight, you step off the edge of a high cliff. Why are you then momentarily weightless? At that point, is gravity acting on you?
Why do the passengers in high-altitude jet planes feel the sensation of weight, while passengers in the International Space Station do not?
The intensity of light from a central source varies inversely as the square of the distance. If you lived on a planet only half as far from the Sun as our Earth, how would the light intensity compare with that on Earth? How about a planet five times as far away as Earth?
Earth is not exactly a sphere but, rather, bulges outward at the equator. How does this bulge affect the relationship between a person’s weight in Singapore and his or her weight in Hong Kong?
In 2013, Curiosity landed on the surface of Mars. Does the weight of Curiosity vary if it makes its way from a valley floor to the top of a tall hill? Explain.
Phil works on the 15th floor of an office building, and his wife Jean works on the 30th floor, which is twice as high as Phil’s workplace. Is the force of gravity half as much in Jean’s workspace as in Phil’s? Explain why or why not.
How would the force between a planet and its moon change if its moon were boosted to twice its distance from the center of the planet? If it were instead brought to half its distance from the center of the planet?
Is the gravitational force greater on a 1-kg piece of iron or on a 1-kg piece of glass? Defend your answer.
Students in a lab measure the speed of a steel ball launched horizontally from a tabletop to be v. The tabletop is distance y above the floor. They place a tin coffee can of height 0.1y on the floor to catch the ball.(a) Show that the can should be placed a horizontal distance from the base of the
A baseball is tossed at a steep angle into the air and makes a smooth parabolic path. Its time in the air is t, and it reaches a maximum height h. Assume that air resistance is negligible.(a) Show that the height reached by the ball is gt2/8.(b) Show that if the ball is in the air for 4 s, it
A rock thrown horizontally from a bridge hits the water below. The rock travels a smooth parabolic path in time t.(a) Show that the height of the bridge is 1/2 gt2.(b) What is the height of the bridge if the time the rock is airborne is 2 s?(c) To solve this problem, what information is assumed
An airplane is flying horizontally with speed 1000 km/h (280 m/s) when an engine falls off. Neglecting air resistance, assume that it takes 30 s for the engine to hit the ground.(a) Show that the altitude of the airplane is 4.4 km. (Use g = 9.8 m/s2.)(b) Show that the horizontal distance that the
Consider a pair of planets in which the distance between them is decreased by a factor of 5. Show that the force between them becomes 25 times as strong.
A space vehicle can outrun Earth’s gravity, but can it get entirely beyond Earth’s gravity?
What happens to an object close to Earth’s surface if it is given a speed exceeding 11.2 km/s?
Discuss the physics that explains how the girl in Figure 3.29 can jack up a car while applying so little force.Figure 3.29 5000 N 25 cm Fd=Fd p- 50 N× 25 cm = 5000 N × 0.25 cm
What is the argument that the energy provided by a hydrogen fuel cell is actually solar energy?
If a satellite were beyond Earth’s gravity, what path would it follow?
When a satellite is above Earth’s atmosphere, is it also beyond the pull of Earth’s gravity? Defend your answer.
Why is it important that a satellite remain above Earth’s atmosphere?
A projectile is launched upward at an angle of 75° from the horizontal and strikes the ground a certain distance downrange. For what other angle of launch at the same speed would this projectile land just as far away?
Which is thought to be more prevalent in the universe, dark matter or dark energy?
What is the status of Pluto in the family of planets?
The perturbations of Uranus led to what greater discovery?
Under what conditions is your weight equal to mg?
Where do you weigh more—at sea level or atop one of the peaks of the Rocky Mountains? Defend your answer.
How does the force of gravity between two bodies change when the distance between them is tripled?
Consider a bob attached by a stringa simple pendulumthat swings to and fro.(a) Why does the tension force in the string not do work on the pendulum?(b) Explain, however, why the force due to gravity on the pendulum at nearly every point does do work on the pendulum.(c) Where
No work is done by gravity on a bowling ball resting or moving on a bowling alley, because the force of gravity on the ball acts perpendicular to the surface. But on an incline, the force of gravity has a vector component parallel to the alley, as sketch b shows. Discuss two ways in which this
A red ball of mass m and a blue ball of mass 2m have the same kinetic energy. Explain which of the two has the larger momentum, letting equations guide your discussion.
Does the electric power produced by wind-powered generators affect the speed of the wind? That is, would locations behind the wind blades be windier if the generators werent there?
Your friend says that one way to improve air quality in a city is to synchronize traffic lights so that motorists can travel long distances at constant speed. Discuss the physics that supports this claim.
Does a car burn more fuel when its lights are turned on? Does the overall consumption of fuel depend on whether the engine is running while the lights are on? Discuss and defend your answers.
What are the roles of water, energy, hydrogen, and oxygen in(a) Electrolysis,(b) Operation of a fuel cell?
Arrange the following four energy-transforming devices or processes in the correct order for converting solar energy to the kinetic energy of vehicles: (1) fuel cell, (2) electrolysis, (3) electric motor, (4) photovoltaic cell.What are the roles of water, energy, hydrogen, and oxygen in (a)
Imagine that you’re in a completely dark room with no windows except a 1-ft2 round hole in the roof. When the Sun is high in the sky, about 100 W of solar power enters the hole. On the floor where the light hits, you place a beach ball covered with aluminum foil, with the shiny side out. Discuss
What is the fuel that powers a fuel cell in forklifts, busses, and trains?
What is the argument that dry-rock geothermal power is a form of nuclear power?
In the pulley system shown, Block A has a mass of 10 kg and is suspended precariously at rest. Assume that the pulleys and string are massless and there is no friction. No friction means that the tension in one part of the supporting string is the same as in any other part. Discuss why the mass of
If your momentum is zero, is your kinetic energy necessarily zero also?
If an object’s kinetic energy is zero, what is its momentum?
Which, if either, has greater momentum: a 1-kg ball moving at 2 m/s or a 2-kg ball moving at 1 m/s? Which has greater kinetic energy?
When the velocity of an object is doubled, by what factor is its momentum changed? By what factor is its kinetic energy changed?
When the mass of a moving object is doubled, with no change in speed, by what factor is its momentum changed? By what factor is its kinetic energy changed?
When a driver applies the brakes to keep a car going downhill at constant speed and constant kinetic energy, the potential energy of the car decreases. Where does this energy go? Where does most of it appear in a hybrid vehicle?
You’re on a rooftop and you throw one snowball downward to the ground below and another upward. The second snowball, after rising, falls and also strikes the ground below. If air resistance can be neglected, and if downward and upward initial speeds are the same, how do the speeds of the
In the absence of air resistance, a snowball thrown vertically upward with a certain initial KE returns to its original level with the same KE. When air resistance is a factor affecting the snowball, does it return to its original level with the same, less, or more KE? Does your answer contradict
Consider the identical balls released from rest on tracks A and B, as shown. When they reach the right ends of the tracks, which will have the greater speed? Why is this question easier to answer than the similar one(Discussion Question 107)in Chapter 1? -B
On a playground slide, a child has potential energy that decreases by 1000 J while her kinetic energy increases by 900 J. What other form of energy is involved, and how much?
Compared with a pickup truck moving at a certain speed and braking to a stop, how much work must the brakes do to stop the truck when it is moving at twice that speed?
A friend says that when twice as much work is done on a wagon, it will gain twice as much kinetic energy. Another friend say it will gain four times as much kinetic energy. Which friend do you agree with?
Why do you run out of breath when running up the stairs but not when walking up the stairs?
Two people of the same weight climb a flight of stairs. The first person climbs the stairs in 30 s, and the second person climbs them in 40 s. Which person does more work? Which uses more power?
Which requires more work: stretching a strong spring a certain distance or stretching a weak spring the same distance? Defend your answer.
If your friend pushes a stroller four times as far as you do while exerting only half the force, which one of you does more work? How much more?
When vertically falling sand lands in a horizontally moving cart, the cart slows. Ignore any friction between the cart and the tracks. Give two reasons for the slowing of the cart, one in terms of a horizontal force acting on the cart, and one in terms of momentum conservation.
A pair of skaters who are initially at rest push against each other so that they move in opposite directions. What is the total momentum of the two skaters as they move apart? Is there a different answer if their masses are not the same?
In terms of impulse and momentum, when a boxer is being hit, why is it important that he or she move away from the punch? Why is it disadvantageous to move into an oncoming punch?
If you throw a raw egg against a wall, you’ll break it; but if you throw it with the same speed into a sagging sheet, the egg won’t break. Explain, using concepts from this chapter.
A lunar vehicle is tested on Earth at a speed of 12 km/h. When it travels at that same speed on the Moon, is its momentum more, less, or the same?
Rank the scale readings from greatest to least. (Ignore friction.) B -? IG-B
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