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All Textbook Solutions for An Introduction to Physical Science

1SA 2SA Consider a child holding a helium balloon in a closed car at rest. What would the child observe the balloon to do when the car (a) accelerates from rest and (b) brakes to a stop? (The balloon does not touch the roof of the car.)An old party trick is to pull a tablecloth out from under dishes and glasses on a table. Explain how this trick is done without pulling the dishes and glasses with the cloth.5SA When a paper towel is torn from a roll on a rack, a jerking motion tears the towel better than a slow pull. Why? Does this method work better when the roll is large or when it is small and near the end? Explain.It is said that Newtons first law can be derived from his second law. Explain this statement.Can an object be at rest if forces are being applied to it? Explain.9SA What is the unbalanced force acting on a moving car with a constant velocity of 25 m/s (56 mi/h)?The coefficient of kinetic friction is generally less than the coefficient of static friction. Why?A 10-lb rock and a 1-lb rock are dropped simultaneously from the same height. (a) Some say that because the 10-lb rock has 10 times as much force acting on it as the 1-lb rock, it should reach the ground first. Do you agree? (b) Describe the situation if the rocks were dropped by an astronaut on the Moon.When a rocket blasts off, is it the fiery exhaust gases pushing against the launch pad that cause the rocket to lift off? Explain.There is an equal and opposite reaction for every force. Explain how an object can be accelerated when the vector sum of these forces is zero.When a person pushes on a wall, the wall pushes on the person (Newtons third law). Suppose the person puts a block of wood between his or her hand and the wall. Analyze the forces on the block of wood. Why doesnt it move?Two masses are attached to a spring scale as shown in Fig. 3.25. If both masses are 1 kg, which force, in newtons, would the scale read? (Hint: Think of holding a free end of the rope on one side of the scale with only the weight on the other.) Figure 3.25 What Does the Scale Read? See Short Answer 16.17SA The gravitational force is said to have an infinite range. What does that mean?Explain why the acceleration due to gravity on the surface of the Moon is one-sixth that of the acceleration due to gravity on the Earths surface.An astronaut has a mass of 70 kg when measured on the Earth. What is her weight in deep space far from any celestial object? What is her mass there?21SA In Chapter 1.6 in the discussion of the hydrometer, it is stated: The higher the bulb floats, the greater the density of the liquid. Why is this? (See Fig. 1.14.)What is a major consideration in constructing a life jacket that will keep a person afloat?24SA 25SA Is it easier for a large person to float in a lake than a small person? Explain.27SA 28SA Explain how the conservation of linear momentum follows directly from Newtons first law of motion.30SA When a high diver in a swimming event springs from the diving board and tucks in, a rapid spin results. Why?Visualize the connections for the descriptions of the laws in the sections and give answers in the blanks. Compare your answers with those at the back of the book. First Law Second Law Third Law also called law of cause for every a. _________ d. _________ g. _________ a measure of inertia effect there is an b. _________ e. _________ h. _________ type of motion units of effect acting on c. _________ f. _________ i. _________Astronauts walking on the Moon are seen bounding rather than walking normally. Why?A person places a bathroom scale in the center of the floor and stands on the scale with his arms at his sides ( Fig. 3.26a). If he keeps his arms rigid and quickly raises them over his head (Fig. 3.26b), he notices the scale reading increases as he brings his arms upward. Why? Then, with his arms over his head (Fig. 3.26c), he quickly lowers his arms to his side. How does the scale reading change and why? (Try it yourself.)3AYK 4AYK In a washing machine, water is extracted from clothes by a rapidly spinning drum ( Fig. 3.27). Explain the physics behind this process. Figure 3.37 Get the Water Out See Applying Your Knowledge Question 5.When you push on a heavy swinging door to go into a store, why is it harder to push the door open if you mistakenly push on the side closer to the hinges?When unable to loosen the lug nut on an automobile tire, a mechanic may put a piece of pipe on the handle of the tire wrench so as to extend its length. How does that help?What is the net force of a 5.0-N force and an 8.0-N force acting on an object for each of the following conditions? (a) The forces act in opposite directions. (b) The forces act in the same direction.A horizontal force of 250 N is applied to a stationary wooden box in one direction, and a 600-N horizontal force is applied in the opposite direction. What additional force is needed for the box to remain stationary?Determine the net force necessary to give an object with a mass of 3.0 kg an acceleration of 5.0 m/s2.A force of 2.1 N is exerted on a 7.0-g rifle bullet. What is the bullets acceleration?A 1000-kg automobile is pulled by a horizontal tow line with a net force of 950 N. What is the acceleration of the auto?A 6.0-N net force is applied to a 15-kg object. What is the objects acceleration?What is the weight in newtons of a 6.0-kg package of nails?What is the force in newtons acting on a 4.0-kg package of nails that falls off a roof and is on its way to the ground?(a) What is the weight in newtons of a 120-lb person? (b) What is your weight in newtons?A 75-kg person is standing on a scale in an elevator. What is the reading of the scale in newtons if the elevator is (a) at rest, and (b) moving up with a constant velocity of 2.0 m/s?Two 3.0-kg physical science textbooks on a bookshelf are 0.15 m apart. What is the magnitude of the gravitational attraction between the books?(a) What is the force of gravity between two 1000-kg cars separated by a distance of 25 m on an interstate highway? (b) How does this force compare with the weight of a car?How would the force of gravity between two masses be affected if the separation distance between them were (a) doubled? (b) decreased by one-half?The separation distance between two 1.0-kg masses is (a) decreased by two-thirds and (b) increased by a factor of 3. How is the mutual gravitational force affected in each case?(a) Determine the weight on the Moon of a person whose weight on the Earth is 180 lb. (b) What would be your weight on the Moon?Suppose an astronaut has landed on Mars. Fully equipped, the astronaut has a mass of 125 kg, and when the astronaut gets on a scale, the reading is 49 N. What is the acceleration due to gravity on Mars?A childs cubic play block has a mass of 120 g and sides of 5.00 cm. When placed in a bathtub full of water, will the cube sink or float? (Hint: See Chapter 1.6.)A ball with a radius of 8.00 cm and a mass of 600 g is thrown into a lake. Will the ball sink or float?Calculate the linear momentum of a pickup truck that has a mass of 1000 kg and is traveling eastward at 20 m/s.A small car with a mass of 900 kg travels northward at 30 m/s. Does the car have more or less momentum than the truck in Exercise 19, and how much more or less? (Is direction a factor in this exercise?)Two ice skaters stand together as illustrated in Fig. 3.28. They push off and travel directly away from each other, the boy with a velocity of 0.50 m/s to the left. If the boy weighs 735 N and the girl weighs 490 N, what is the girls velocity after they push off? (Consider the ice to be frictionless.)For the couple in Fig. 3.28, suppose you were told that the girls mass was three-fourths that of the boys mass. What would be the girls velocity in this case?A comet goes around the Sun in an elliptical orbit. At its farthest point, 600 million miles from the Sun, it is traveling with a speed of 15,000 mi/h. How fast is it traveling at its closest approach to the Sun, at a distance of 100 million miles?Taking the density of air to be 1.29 kg/m3, what is the magnitude of the linear momentum of a cubic meter of air moving with a wind speed of (a) 36 km/h, and (b) 74 mi/hthe wind speed at which a tropical storm becomes a hurricane?Is work a vector quantity? In other words, does it need a direction associated with it?What are the units of work?By what process is energy transferred from one object to another?To find the difference in gravitational potential energies, the difference in heights is used. What is used to find the difference in kinetic energies?4.1CE Overall, can energy be created or destroyed?What is the difference between total energy and mechanical energy?Find the kinetic energy of the stone in the preceding example when it has fallen 5.0 m.What is the difference in the operations of a 2-hp motor and a 1-hp motor?Electric bills from power companies charge for so many kilowatt-hours (kWh). What are we paying for?A student expends 7.5 W of power in lifting a textbook 0.50 m in 1.0 s with a constant velocity. (a) How much work is done, and (b) how much does the book weigh (in newtons)? The answers to Confidence Exercises may be found at the back of the book.4.4CE 1PQ 2PQ What is the difference between alternative and renewable energy sources?2PQ KEY TERMS 1. work (4.1) 2. joule 3. foot-pound 4. energy (4.2) 5. kinetic energy 6. potential energy 7. gravitational potential energy 8. conservation of total energy (4.3) 9. conservation of mechanical energy 10. power (4.4) 11. watt 12. horsepower 13. kilowatt-hour 14. alternative energy sources (4.6) 15. renewable energy sources For each of the following items, fill in the number of the appropriate Key Term from the preceding list. a. _____ Energy sources other than fossil fuels and nuclear reactions BM CM DM EM FM GM HM IM JM KM LM MM KEY TERMS 1. work (4.1) 2. joule 3. foot-pound 4. energy (4.2) 5. kinetic energy 6. potential energy 7. gravitational potential energy 8. conservation of total energy (4.3) 9. conservation of mechanical energy 10. power (4.4) 11. watt 12. horsepower 13. kilowatt-hour 14. alternative energy sources (4.6) 15. renewable energy sources For each of the following items, fill in the number of the appropriate Key Term from the preceding list. n. _____ Time rate of doing work KEY TERMS 1. work (4.1) 2. joule 3. foot-pound 4. energy (4.2) 5. kinetic energy 6. potential energy 7. gravitational potential energy 8. conservation of total energy (4.3) 9. conservation of mechanical energy 10. power (4.4) 11. watt 12. horsepower 13. kilowatt-hour 14. alternative energy sources (4.6) 15. renewable energy sources For each of the following items, fill in the number of the appropriate Key Term from the preceding list. o. _____ The ability to do work Work is done on an object when it is ___. (4.1) (a) moved (b) stationary (c) acted on by a balanced force (d) none of the preceding Which of the following is a unit of work? (4.1) (a) W (b) J s (c) N/s (d) N m 3MC Which of the following objects has the greatest kinetic energy? (4.2) (a) an object with a mass of 4m and a velocity of v (b) an object with a mass of 3m and a velocity of 2v (c) an object with a mass of 2m and a velocity of 3v (d) an object with a mass of m and a velocity of 4v A pitcher throws a fastball. When the catcher catches it, ___. (4.2) (a) positive work is done (b) negative work is done (c) the net work is zero The reference point for gravitational potential energy may be which of the following? (4.2) (a) zero (b) negative (c) positive (d) all of the preceding When the height of an object is changed, the gravitational potential energy ___. (4.2) (a) increases (b) decreases (c) depends on the reference point (d) remains constant Mechanical energy is ___. (4.2) (a) the sum of kinetic and potential energies (b) always conserved (c) the same as total energy in all cases (d) all of the preceding On which of the following does the speed of a falling object depend? (4.3) (a) mass (b) h (c) 12mv2 (d) parallel distance Power is expressed by which of the following units? (4.4) (a) J/s (b) N m (c) W s (d) W/m If motor A has twice as much horsepower as motor B, then motor A has the power capability to do ___. (4.4) (a) half the work in twice the time (b) the same work in half the time (c) twice the work in half the time (d) none of the preceding 12MC Which one of the following would not be classified as a total alternative fuel source? (4.6) (a) photocells (b) gasohol (c) windmills (d) wood 14MC Work is equal to the force times the ___ distance through which the force acts. (4.1)2FIB The unit N m is given the special name of ___ . (4.1)4FIB 5FIB The stopping distance of an automobile on a level road depends on the ___ of the speed. (4.2)Kinetic energy is commonly referred to as the energy of ___, and potential energy as the energy of ___. (4.2)8FIB 9FIB 10FIB 11FIB 12FIB Renewable energy sources cannot be ___ . (4.6)Gasohol is gasoline mixed with ___ . (4.6)1SA Do all forces do work? Explain.What does work on a shuffleboard puck as it slides to rest? Why is the board dusted, and how does this affect work?A weight lifter holds 900 N (about 200 lb) over his head. Is he doing work on the weights? Did he do any work on the weights? Explain.For the situation in Fig. 4.4a, if the applied force is removed, then the frictional force will continue to do work, so there is an energy transfer. Explain this transfer.Car B is traveling twice as fast as car A, but car A has three times the mass of car B. Which car has the greater kinetic energy?7SA If the speed of a moving object is doubled, how many times more work is required to bring it to rest?A book sits on a library shelf 1.5 m above the floor. One friend tells you the books total mechanical energy is zero, and another says it is not. Who is correct? Explain.(a) A car traveling at a constant speed on a level road rolls up an incline until it stops. Assuming no frictional losses, comment on how far up the hill the car will roll. (b) Suppose the car rolls back down the hill. Again, assuming no frictional losses, comment on the speed of the car at the bottom of the hill.An object is said to have a negative potential energy. Because it is preferable not to work with negative numbers, how can you change the value of the objects potential energy without moving the object?12SA A ball is dropped from a height at which it has 50 J of potential energy. How much kinetic energy does the ball have just before hitting the ground?14SA A simple pendulum as shown in Fig. 4.24 oscillates back and forth. Use the letter designations in the figure to identify the pendulums position(s) for the following conditions. (There may be more than one answer. Consider the pendulum to be ideal with no energy losses.) (a) Position(s) of instantaneous rest ___ (b) Position(s) of maximum velocity ___ (c) Position(s) of maximum Ek ___ (d) Position(s) of maximum Ep ___ (e) Position(s) of minimum Ek ___ (f) Position(s) of minimum Ep ___ (g) Position(s) after which Ek increases ___ (h) Position(s) after which Ep increases ___ (i) Position(s) after which Ek decreases ___ (j) Position(s) after which Ep decreases ___ Figure 4.24 The Simple Pendulum and Energy Two students throw identical snowballs from the same height; both snowballs having the same initial speed vo ( Fig. 4.25). Which snowball has the greater speed on striking the level ground at the bottom of the slope? Justify your answer using energy considerations. Figure 4.25 Away They Go! See Short Answer Question 16.17SA When you throw an object into the air, is its return speed just before hitting your hand the same as its initial speed?(Neglect air resistance.) Explain by applying the conservation of mechanical energy.19SA Persons A and B do the same job, but person B takes longer. Who does the greater amount of work? Who is more powerful?What does a greater power rating mean in terms of (a) the amount of work that can be done in a given time and (b) how fast a given amount of work can be done?What do we pay the electric company for, power or energy? In what units?23SA 24SA 25SA On average, how much energy do you radiate each second?27SA 28SA 29SA 30SA 1VC A fellow student tells you that she has both zero kinetic energy and zero potential energy. Is this possible? Explain.Two identical stones are thrown from the top of a tall building. Stone 1 is thrown vertically downward with an initial speed v, and stone 2 is thrown vertically upward with the same initial speed. Neglecting air resistance, how do their speeds compare on hitting the ground?A person on a trampoline can go higher with each bounce. How is this possible? Is there a maximum height to which the person can go?With which of our five senses can we detect energy?What are three common ways to save electricity to reduce electric bills?A worker pushes horizontally on a large crate with a force of 250 N, and the crate is moved 3.0 m. How much work was done?While rearranging a dorm room, a student does 400 J of work in moving a desk 2.0 m. What was the magnitude of the applied horizontal force?A 5.0-kilo bag of sugar is on a counter. How much work is required to put the bag on a shelf a distance of 0.45 m above the counter?How much work is required to lift a 6.0-kg backpack 1.5 m to put it on?A man pushes a lawn mower on a level lawn with a force of 200 N. If 40% of this force is directed downward, then how much work is done by the man in pushing the mower 6.0 m?If the man in Exercise 5 pushes the mower with 40% of the force directed horizontally, then how much work is done?How much work does gravity do on a 0.150-kg ball falling from a height of 10.0 m? (Neglect air resistance.)A student throws the same ball straight upward to a height of 7.50 m. How much work did the student do?(a) What is the kinetic energy in joules of a 1000-kg automobile traveling at 90 km/h? (b) How much work would have to be done to bring a 1000-kg automobile traveling at 90 km/h to a stop?A 60-kg student traveling in a car with a constant velocity has a kinetic energy of 1.2 104 J. What is the speedometer reading of the car in km/h?What is the kinetic energy of a 20-kg dog that is running at a speed of 9.0 m/s (about 20 mi/h)?Which has more kinetic energy, a 0.0020-kg bullet traveling at 400 m/s or a (6.4 107)-kg ocean liner traveling at 10 m/s (20 knots)? Justify your answer.13E How much farther would the force in Exercise 13 have to act for the block to have 42 J of kinetic energy?What is the potential energy of a 3.00-kg object at the bottom of a well 10.0 m deep as measured from ground level? Explain the sign of the answer.How much work is required to lift a 3.00-kg object from the bottom of a well 10.0 m deep?An object is dropped from a height of 12 m. At what height will its kinetic energy and its potential energy be equal?A 1.0-kg rock is dropped from a height of 6.0 m. At what height is the rocks kinetic energy twice its potential energy?A sled and rider with a combined weight of 60 kg are at rest on the top of a hill 12 m high. (a) What is their total energy at the top of the hill? (b) Assuming there is no friction, what would the total energy be on sliding halfway down the hill?A 30.0-kg child starting from rest slides down a water slide with a vertical height of 10.0 m. What is the childs speed (a) halfway down the slides vertical distance and (b) three-fourths of the way down? (Neglect friction.)If the man in Exercise 5 pushes the lawn mower 6.0 m in 10 s, how much power does he expend?If the man in Exercise 5 expended 60 W of power in pushing the mower 6.0 m, how much time is spent in pushing the mower this distance?A student who weighs 556 N climbs a stairway (vertical height of 4.0 m) in 25 s. (a) How much work is done? (b) What is the power output of the student?A 125-lb student races up stairs with a vertical height of 4.0 m in 5.0 s to get to a class on the second floor. How much power in watts does the student expend in doing work against gravity?On a particular day, the following appliances are used for the times indicated: a 1600-W coffee maker, 10 min, and a 1100-W microwave oven, 4.0 min. With these power requirements, find how much it costs to use these appliances at an electrical cost of 8 per kWh.26E We talk about temperature, but what does it physically represent?Are there any limits on the lowest and highest temperatures?Show that a temperature of 40 is the same on both the Fahrenheit and the Celsius scales.1PQ Most substances contract with decreasing temperature. Is this true for water?What is specific about specific heat?2PQ 5.2CE How much heat must be removed from 0.20 kg of water at 10C to form ice at 0C? (Show your calculations.)What are the three methods of heat transfer?2PQ 1PQ 2PQ In the ideal gas law, pressure is directly proportional to what temperature?2PQ 5.4CE 1PQ 2PQ AM BM CM DM EM FM GM HM IM JM KM LM MM NM OM PM QM RM SM TM UM VM WM XM YM 1MC Which unit of the following is smaller? (5.2) (a) a degree Fahrenheit (b) a kelvin (c) a degree Celsius 3MC 4MC 5MC 6MC 7MC Which of the following has a definite volume but no definite shape? (5.5) (a) solid (b) liquid (c) gas (d) plasma If the average kinetic energy of the molecules in an ideal gas initially at 20C doubles, what is the final temperature of the gas? (5.6) (a) 10C (b) 40C (c) 313C (d) 586C When we use the ideal gas law, the temperature must be in which of the following units? (5.6) (a) C (b) F (c) K 11MC 12MC When a bimetallic strip is heated, it bends away from the metal with the ___ thermal expansion. (5.1)2FIB 3FIB 4FIB 5FIB 6FIB 7FIB The ___ phase of matter has no definite shape, and no definite volume. (5.4)9FIB In the ideal gas law, pressure is ___ proportional to volume. (5.6)11FIB 12FIB When the temperature changes during the day, which scale, Fahrenheit or Celsius, will have the greater degree change?2SA The two common liquids used in liquid-in-glass thermometers are alcohol (ethanol) and mercury, which have melting points and boiling points of 114C, 79C and 39C, 357C, respectively. Would either one of these thermometers be better for low-temperature or high-temperature measurements?An older type of thermostat used in furnace and heat pump control is shown in Fig. 5.21. The glass vial tilts back and forth so that electrical contacts are made via the mercury (an electrically conducting liquid metal), and the furnace or heat pump is turned off and on. Explain why the vial tilts back and forth. (Newer thermostats are electronic.) Figure 5.21 An Exposed View of a Thermostat See Short Answer Question 4.Heat may be thought of as the middleman of energy. Why?When one drinking glass is stuck inside another, an old trick to unstick them is to put water in one of them and run water of a different temperature on the outside of the other. Which water should be hot, and which water should be cold?7SA What does the specific heat of a substance tell you when you compare it with the specific heat of another substance?When eating a piece of hot apple pie, you may find that the crust is only warm but the apple filling burns your mouth. Why?10SA When you exhale outdoors on a cold day, you can see your breath. Why?Compare the SI units of specific heat and latent heat and explain any differences.Give two examples each of good thermal conductors and good thermal insulators. In general, what makes a substance a conductor or an insulator?14SA 15SA Thermal underwear is made to fit loosely. ( Fig. 5.23). What is the purpose of this? Figure 5.23 Make Them Loose-Fitting See Short Answer Question 16.What determines the phase of a substance?Give descriptions of a solid, a liquid, and a gas in terms of shape and volume.19SA How does the kinetic theory describe a gas?21SA 22SA 23SA In terms of kinetic theory, explain why a basketball stays inflated.25SA 26SA 27SA 28SA What can be said about the total entropy of the universe? Why is it true?30SA 31SA 1VC 1AYK 2AYK 3AYK 4AYK 5AYK 6AYK When you freeze ice cubes in a tray, there is a decrease in entropy because there is more order in the crystalline lattice of the ice than in the water you started with. Are you violating the second law? Explain.8AYK 1E 2E 3E 4E Researchers in the Antarctic measure the temperature to be 40F. What is this temperature (a) on the Celsius scale? (b) on the Kelvin scale?6E A college student produces about 100 kcal of heat per hour on the average. What is the rate of energy production in joules?8E A pound of body fat stores an amount of chemical energy equivalent to 3500 Cal. When sleeping, the average adult burns or expends about 0.45 Cal/h for every pound of body weight. How many Calories would a 150-lb person burn during 8 hours of sleep?

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