Questions and Answers of College Physics A Strategic Approach 2nd

Brewed coffee is often too hot to drink right away. You can cool it with an ice cube, but this dilutes it. Or you can buy a device that will cool your coffee without dilution-a 200 g aluminum
Marianne really likes coffee, but on summer days she doesn't want to drink a hot beverage. If she is served 200 mL of coffee at 80°C in a well-insulated container, how much ice at 0°C should she
If a person has a dangerously high fever, submerging her in ice water is a bad idea, but an ice pack can help to quickly bring her body temperature down. How many grams of ice at 0°C will be melted
What is the temperature change of 1.0 mol of a monatomic gas if its thermal energy is increased by 1.0 J?
The temperature of 2.0 g of helium is increased at constant volume by ΔT. What mass of oxygen can have its temperature increased by the same amount at constant volume using the same amount of heat?
A 1.8-cm-thick wood floor covers a 4.0 m X 5.5 m room. The subfloor on which the flooring sits is at a temperature of 16.2°C, while the air in the room is at 19.6°C. What is the rate of heat
A copper-bottomed kettle, its bottom 24 cm in diameter and 3.0 mm thick, sits on a burner. The kettle holds boiling water, and energy flows into the water from the kettle bottom at 800 W. What is the
What is the greatest possible rate of energy transfer by radiation from a metal cube 2.0 cm on a side that is at 700°C? Its emissivity is 0.20.
Seals may cool themselves by using thermal windows, patches on their bodies with much higher than average surface temperature. Suppose a seal has a 0.030 m2 thermal window at a temperature of 30°C.
What is the greatest possible rate of energy transfer by radiation for a 5.0-cm-diameter sphere that is at 100°C?
Electronics and inhabitants of the International Space Station generate a significant amount of thermal energy that the station must get rid of. The only way that the station can exhaust thermal
If you lie on the ground at night with no cover, you get cold rather quickly. Much of this is due to energy loss by radiation. At night in a dry climate, the temperature of the sky can drop to
A 15-cm-diameter compressed-air tank is 50 cm tall. The pressure at 20°C is 150 atm.a. How many moles of air are in the tank? b. What volume would this air occupy at STP?
A 10-cm-diameter cylinder of helium gas is 30 cm long and at 20°C. The pressure gauge reads 120 psi. a. How many helium atoms are in the cylinder? b. What is the mass of the helium?
Party stores sell small tanks containing 30 g of helium gas. If you use such a tank to fill 0.010 m3 foil balloons (which don't stretch, and so have an internal pressure that is very close to
0.030 mol of an ideal monatomic gas undergoes an adiabatic compression that raises its temperature from 10°C to 50°C. How much work is done on the gas to compress it?
0.15 mol of an ideal monatomic gas undergoes an adiabatic expansion, cooling from 20°C to -10°C. How much work is done by the gas during the expansion?
Susan, whose mass is 68 kg, climbs 59 m to the top of the Cape Hatteras lighthouse. a. During the climb, by how much does her potential energy increase? b. For a typical efficiency of 25%, what
A 68 kg woman cycles at a constant 15 km/h. All of the metabolic energy that does not go to forward propulsion is converted to thermal energy in her body. If the only way her body has to keep cool is
The top layer of your goose down sleeping bag has a thickness of 5.0 cm and a surface area of 1.0 m2. When the outside temperature is -20°C, you lose 25 Cal/h by heat conduction through the bag
Suppose you go outside in your fiber-filled jacket on a windless but very cold day. The thickness of the jacket is 2.5 cm, and it covers 1.1 m2 of your body. The purpose of fiber- or down-filled
Two thin, square copper plates are radiating energy at the same rate. The edge length of plate 2 is four times that of plate 1. What is the ratio of absolute temperatures T1/T2 of the plates?
A drop of green ink falls into a beaker of clear water. First describe what happens. Then explain the outcome in terms of entropy.
If you hold a rubber band loosely between two fingers and then stretch it, you can tell by touching it to the sensitive skin of your forehead that stretching the rubber band has increased its
In areas in which the air temperature drops very low in the winter, the exterior unit of a heat pump designed for heating is sometimes buried underground in order to use the earth as a thermal
A heat engine does 20 J of work while exhausting 30 J of waste heat. What is the engine's efficiency?
When the sun's light hits the earth, the temperature rises. Is there an entropy change to accompany this transformation? Explain.
When you put an ice cube tray filled with liquid water in your freezer, the water eventually becomes solid ice. The solid is more ordered than the liquid-it has less entropy. Explain how this
A company markets an electric heater that is described as 100% efficient at converting electric energy to thermal energy. Does this violate the second law of thermodynamics?
A person is walking on level ground at constant speed. What energy transformation is taking place? A. Chemical energy is being transformed to thermal energy. B. Chemical energy is being transformed
Converting sunlight to electricity with solar cells has an efficiency of ≈15%. It's possible to achieve a higher efficiency. (though currently at higher cost) by using concentrated sunlight as the
A newly proposed device for generating electricity from the sun is a heat engine in which the hot reservoir is created by focusing sunlight on a small spot on one side of the engine. The cold
A refrigerator takes in 20 J of work and exhausts 50 J of heat. What is the refrigerator's coefficient of performance?
The thermal energy of a container of helium gas is halved. What happens to the temperature, in kelvin? A. It decreases to one-fourth its initial value. B. It decreases to one-half its initial
Air conditioners are rated by their coefficient of performance at 80F inside temperature and 95°F outside temperature. An efficient but realistic air conditioner has a coefficient of performance of
An inventor approaches you with a device that he claims will take 100 J of thermal energy input and produce 200 J of electricity. You decide not to invest your money because this device would
Find the maximum possible coefficient of performance for a heat pump used to heat a house in a northerly climate in winter. The inside is kept at 20°C while the outside is -20°C.
For how long would a 68 kg athlete have to swim at a fast crawl to use all the energy available in a typical fast-food meal of burger, fries, and a drink?
To a good approximation, the only external force that does work on a cyclist moving on level ground is the force of air resistance. Suppose a cyclist is traveling at 15 km/h on level ground. Assume
The winning time for the 2005 annual race up 86 floors of the Empire State Building was 10 min and 49 s. The winner's mass was 60 kg. a. If each floor was 3.7 m high, what was the winner's change in
A 68 kg hiker walks at 5.0 km/h up a 7% slope. What is the necessary metabolic power?
A 70 kg student consumes 2500 Cal each day and stays the same weight. One day, he eats 3500 Cal and, wanting to keep from gaining weight, decides to "work off" the excess by jumping up and down. With
To make your workouts more productive, you can get a generator that you drive with the rear wheel of your bicycle when it is mounted in a stand. a. Your laptop charger uses 75 W. What is your body's
The resistance of an exercise bike is often provided by a generator; that is, the energy that you expend is used to generate electric energy, which is then dissipated. Rather than dissipate the
Larger animals use proportionately less energy than smaller animals; that is, it takes less energy per kg to power an elephant than to power a human. A 5000 kg African elephant requires about 70,000
Smaller mammals use proportionately more energy than larger mammals; that is, it takes more energy per gram to power a mouse than a human. A typical mouse has a mass of 20 g and, at rest, needs to
A large horse can perform work at a steady rate of about 1 horsepower, as you might expect. a. Assuming a 25% efficiency, how many Calories would a horse need to consume to work at 1.0 hp for 1.0
A college student is working on her physics homework in her dorm room. Her room contains a total of 6.0 × 1026 gas molecules. As she works, her body is converting chemical energy into thermal energy
Describe the energy transfers and transformations that occur from the time you sit down to breakfast until you've completed a fast bicycle ride.
A 60% efficient device uses chemical energy to generate 600 J of electric energy.a. How much chemical energy is used? b. A second device uses twice as much chemical energy to generate half as much
A 10% efficient engine accelerates a 1500 kg car from rest to 15 m/s. How much energy is transferred to the engine by burning gasoline?
Rub your hands together vigorously. What happens? Discuss the energy transfers and transformations that take place.
Figure Q9.21 shows two blocks sliding on a frictionless surface. Eventually the smaller block overtakes the larger one, collides with it, and sticks. What is the speed of the two blocks after the
Density is the ratio of an object's mass to its volume. Would you expect density to be a vector or a scalar quantity? Explain.
Which of the following motions is described by the motion diagram of Figure Q 1.21?A. An ice skater gliding across the ice. B. An airplane braking to a stop after landing. C. A car pulling away
A bird flies 3.0 km due west and then 2.0 km due north. What is the magnitude of the bird's displacement? A. 2.0 km C. 3.6 km B. 3.0 km D. 5.0 km
The Empire State Building has a height of 1250 ft. Express this height in meters, giving your result in scientific notation with three significant figures.
A bird flies 3.0 km due west and then 2.0 km due north. Another bird flies 2.0 km due west and 3.0 km due north. What is the angle between the net displacement vectors for the two birds?A. 23° B.
A woman walks briskly at 2.00 m/s. How much time will it take her to walk one mile?A. 8.30 min B. 13.4 min C. 21.7 min D. 30.0 min
Compute 3.24 m + 0.532 m to the correct number of significant figures. A. 3.7 m B. 3.77 m C. 3.772 m D. 3.7720 m
A rectangle has length 3.24 m and height 0.532 m. To the correct number of significant figures, what is its area?A. 1.72 m2 B. 1.723 m2 C. 1.7236 m2D. 1.72368 m2
Carol and Robin share a house. To get to work, Carol walks north 2.0 km while Robin drives west 7.5 km. How far apart are their workplaces?
Joe and Max shake hands and say goodbye. Joe walks east 0.55 km to a coffee shop, and Max flags a cab and rides north 3.25 km to a bookstore. How far apart are their destinations?
A city has streets laid out in a square grid, with each block 135 m long. If you drive north for three blocks, then west for two blocks, how far are you from your starting point?
A butterfly flies from the top of a tree in the center of a garden to rest on top of a red flower at the garden's edge. The tree is 8.0 m taller than the flower, and the garden is 12 m wide.
A garden has a circular path of radius 50 m. John starts at the easternmost point on this path, then walks counterclockwise around the path until he is at its southernmost point. What is John's
Migrating geese tend to travel in straight-line paths at approximately constant speed. A goose flies 32 km south, then turns to fly 20 km west. How far is the goose from its original position?
A ball on a porch rolls 60 cm to the porch's edge, drops 40 cm, continues rolling on the grass, and eventually stops 80 cm from the porch's edge. What is the magnitude of the ball's net dis-
A kicker punts a football from the very center of the field to the sideline 43 yards downfield. What is the net displacement of the ball? (A football field is 53 yards wide.)
Joseph watches the roadside mile markers during a long car trip on an interstate highway. He notices that at 10:45 A.M. they are passing a marker labeled 101, and at 11:00 A.M. the car reaches marker
Alberta is going to have dinner at her grandmother's house, but she is running a bit behind schedule. As she gets onto the highway, she knows that she must exit the highway within 45 min if she is
The end of Hubbard Glacier in Alaska advances by an average of 105 feet per year. What is the speed of advance of the glacier in m/s?
The earth completes a circular orbit around the sun in one year. The orbit has a radius of 93,000,000 miles. What is the speed of the earth around the sun in m/s? Report your result using scientific
Shannon decides to check the accuracy of her speedometer. She adjusts her speed to read exactly 70 mph on her speedometer and holds this steady, measuring the time between successive mile markers
Your brain communicates with your body using nerve impulses, electrical signals propagated along axons. Axons come in two varieties: insulated axons with a sheath made of myelin, and uninsulated
Satellite data taken several times per hour on a particular albatross showed travel of 1200 km over a time of 1.4 days. a. Given these data, what was the bird's average speed in mph? b. Data on the
In 2003, the population of the United States was 291 million people. The per-capita income was $31,459. What was the total income of everyone in the United States? Express your answer in scientific
The sun is 30° above the horizon. It makes a 52-m-long shadow of a tall tree. How high is the tree?
A large passenger aircraft accelerates down the runway for a distance of 3000 m before leaving the ground. It then climbs at a steady 3.0 angle. After the plane has traveled 3000 m along this new
Starting from its nest, an eagle flies at constant speed for 3.0 min due east, then 4.0 min due north. From there the eagle flies directly to its nest at the same speed. How long is the eagle in the
John walks 1.00 km north, then turns right and walks 1.00 km east. His speed is 1.50 m/s during the entire stroll. a. What is the magnitude of his displacement, from beginning to end? b. If Jane
For each motion diagram in Figure P2.2, determine the sign (positive or negative) of the position and the velocity.Data in Figure P2.2 (a) 0 X (b) (c)
A person gets in an elevator on the ground floor and rides it to the top floor of a building. Sketch a velocity-versus-time graph for this motion.
Write a short description of the motion of a real object for which Figure P2.3 would be a realistic position-versus-time graph. x (m) 300 200- 100 0 200 FIGURE P2.3 400 -t (s) 600
Write a short description of the motion of a real object for which Figure P2.4 would be a realistic position-versus-time graph. x (mi) 40 20 0 -20- 2 3 درا FIGURE P2.4 5 1 (h)
You are driving down the road at a constant speed. Another car going a bit faster catches up with you and passes you. Draw a position graph for both vehicles on the same set of axes, and note the
The position graph of Figure P2.5 shows a dog slowly. sneaking up on a squirrel, then putting on a burst of speed. a. For how many seconds does the dog move at the slower speed? b. Draw the dog's
A car is traveling north. Can its acceleration vector ever point south? Explain.
The position graph of Figure P2.6 represents the motion of a ball being rolled back and forth by two children. a. At what positions are the two children sitting? b. Draw the ball's
Certain animals are capable of running at great speeds; other animals are capable of tremendous accelerations. Speculate on which would be more beneficial to a predator-large maximum speed or large
Figure Q2.9 shows an object's position-versus-time graph. The letters A to E correspond to various segments of the motion in which the graph has constant slope.a. Write a realistic motion short story
A bicyclist has the position-versus-time graph shown in Figure P2.9. What is the bicyclist's velocity at t = 10 s, at t = 25 s, and at t = 35 s? FIGURE P2.9 x (m) 100 50 0 10 20 30 40 -1 (s)
Figure Q2.10 shows the position graph for an object moving along the horizontal axis.Data in Figure Q2.10a. Write a realistic motion short story for an object that would have this position graph. b.
Figure Q2.11 shows the position- versus-time graphs for two objects, A and B, that are moving along the same axis. FIGURE Q2.11a. At the instant t = 1 s, is the speed of A greater than, less than,
In college softball, the distance from the pitcher's mound to the batter is 43 feet. If the ball leaves the bat at 100 mph, how much time elapses between the hit and the ball reaching the pitcher?
Figure Q2.12 shows a position- versus-time graph. At which lettered point or points is the object.Figure Q2.12a. Moving the fastest? b. Moving to the left? c. Speeding up? d. Slowing down? e.
Figure Q2.13 is the velocity-versus-time graph for an object moving along the x-axis.a. During which segment(s) is the velocity constant? b. During which segment(s) is the object speeding up? c.
A car traveling at velocity v takes distance d to stop after the brakes are applied. What is the stopping distance if the car is initially traveling at velocity 2v? Assume that the acceleration due
Figure Q2.17 shows an object's position-versus-time graph. What is the velocity of the object at t = 6 s?A. 0.67 m/s B. 0.83 m/s C. 3.3 m/s D. 4.2 m/s E. 25 m/s x (m) 40 30- 20 10- 0- 5 FIGURE
While running a marathon, a long-distance runner uses a stopwatch to time herself over a distance of 100 m. She finds that she runs this distance in 18 s. Answer the following by considering ratios,

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