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James T. Shipman, Jerry D. Wilson, An introduction to physical science, 11th edition, Brooks/Cole, 2012


Chapter 2

1. A gardener walks in a flower garden as illustrated in Fig. 2.21. What distance does the gardener travel?

2. What is the gardener’s displacement (Fig. 2.21)? Give a general direction, such as south or west.

3. At a track meet, a runner runs the 100-m dash in 12 s. What was the runner’s average speed?

4. A jogger jogs around a circular track with a diameter of 300 m in 10 minutes. What was the jogger’s average speed in m/s?

5. A space probe on the surface of Mars sends a radio signal back to the Earth, a distance of 7.86 × 107 km. Radio waves travel at the speed of light (3.00 × 108 m/s). How many seconds does it take the signal to reach the Earth?

6. A group of college students eager to get to Florida on a spring break drove the 750-mi trip with only minimum stops. They computed their average speed for the trip to be 55.0 mi/h. How many hours did the trip take?

7. A student drives the 100-mi trip back to campus after spring break and travels with an average speed of 52 mi/h for 1 hour and 30 minutes for the first part of the trip. (a) What distance was traveled during this time? (b) Traffic gets heavier, and the last part of the trip takes another half-hour. What was the average speed during this leg of the trip? (c) Find the average speed for the total trip.

8. Joe Cool drives to see his girlfriend who attends another college. (a) The 130-km trip takes 2.0 h. What was the average speed for the trip? (b) The return trip over the same route takes 3.0 h because of heavy traffic. What is the average speed for the return trip? (c) What is the average speed for the entire trip?

9. An airplane flying directly eastward at a constant speed travels 300 km in 2.0 h. (a) What is the average velocity of the plane? (b) What is its instantaneous velocity?

10. A race car traveling northward on a straight, level track at a constant speed travels 0.750 km in 20.0 s. The return trip over the same track is made in 25.0 s. (a) What is the average velocity of the car in m/s for the first leg of the run? (b) What is the average velocity for the total trip?

11. A sprinter starting from rest on a straight, level track is able to achieve a speed of 12 m/s in 6.0 s. What is the sprinter’s average acceleration?

12. Modern oil tankers weigh more than a half-million tons and have lengths of up to one-fourth mile. Such massive ships require a distance of 5.0 km (about 3.0 mi) and a time of 20 min to come to a stop from a top speed of 30 km/h. (a) What is the magnitude of such a ship’s average acceleration in m/s2 in coming to a stop? (b) What is the magnitude of the ship’s average velocity in m/s? Comment on the potential of a tanker running aground.

13. A motorboat starting from rest travels in a straight line on a lake. (a) If the boat achieves a speed of 8.0 m/s in 10 s, what is the boat’s average acceleration? (b) Then, in 5.0 more seconds, the boat’s speed is 12 m/s. What is the boat’s average acceleration for the total time?

14. A car travels on a straight, level road. (a) Starting from rest, the car is going 44 ft/s (30 mi/h) at the end of 5.0 s. What is the car’s average acceleration in ft/s2? (b) In 4.0 more seconds, the car is going 88 ft/s (60 mi/h). What is the car’s average acceleration for this time period? (c) The car then slows to 66 ft/s (45 mi/h) in 3.0 s. What is the average acceleration for this time period? (d) What is the overall average acceleration for the total time?

15. A ball is dropped from the top of an 80-m-high building. Does the ball reach the ground in 4.0 s?

16. What speed does the ball in Exercise 15 have in falling 3.5 s?

17. Figure 1.18 (Chapter 1) shows the Hoover Dam Bridge over the Colorado River at a height of 271 m. If a heavy object is dropped from the bridge, how much time passes before the object makes a splash?

18. A student drops an object out the window of the top floor of a high-rise dormitory. (a) Neglecting air resistance, how fast is the object traveling when it strikes the ground at the end of 3.0 s? Express the speed in mi/h for a familiar comparison. Can things dropped from high places be dangerous to people below? (b) How far, in meters, does the object fall during the 3.0 s? Comment on how many floors the dormitory probably has.

19. A person drives a car around a circular, level cloverleaf with a radius of 70 m at a uniform speed of 10 m/s. (a) What is the acceleration of the car? (b) Compare this answer with the acceleration due to gravity as a percentage. Would you be able to sense the car’s acceleration if you were riding in it?

20. A race car goes around a circular, level track with a diameter of 1.00 km at a constant speed of 90.0 km/h. What is the car’s centri petal acceleration in m/s2?

21. If you drop an object from a height of 1.5 m, it will hit the ground in 0.55 s. If you throw a baseball horizontally with an initial speed of 30 m/s from the same height, how long will it take the ball to hit the ground?

22. A golfer on a level fairway hits a ball at an angle of 42° to the horizontal that travels 100 yd before striking the ground. He then hits another ball from the same spot with the same speed, but at a different angle. This ball also travels 100 yd. At what angle was the second ball hit?

Chapter 3

1. 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.

2. 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?

3. Determine the net force necessary to give an object with a mass of 3.0 kg an acceleration of 5.0 m/s2

4. A force of 2.1 N is exerted on a 7.0-g rifle bullet. What is the bullet’s acceleration?

5. 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?

6. A constant net force of 1500 N gives a toy rocket an acceleration of 2.5 m/s2. What is the mass of the rocket?

7. What is the weight in newtons of a 6.0-kg package of nails?

8. 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?

9. (a) What is the weight in newtons of a 120-lb person? (b) What is your weight in newtons?

10. What is the weight in newtons of a 250-g package of breakfast cereal?

11. 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?

12. (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?

13. 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?

<p>14. 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?</p>

15. (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?

16. 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?

17. A child’s 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?

18. 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?

19. Calculate the linear momentum of a pickup truck that has a mass of 1000 kg and is traveling eastward at 20 m/s.

20. 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?

21. 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 girl’s velocity after they push off?

22. For the couple in Fig. 3.28, suppose you were told that the girl’s mass was three-fourths that of the boy’s mass. What would be the girl’s velocity in this case?

23. 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?

24. An asteroid in an elliptical orbit about the Sun travels at 1.2 × 106 m/s at perihelion (the point of closest approach) at a distance of 2.0 × 108 km from the Sun. How fast is it traveling at aphelion (the farthest point), which is 8.0 × 108 km from the Sun?

Chapter 4

1. 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?

2. 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?

3. 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?

4. How much work is required to lift a 4.0-kg concrete block to a height of 2.0 m?

5. 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?

6. If the man in Exercise 5 pushes the mower with 40% of the force directed horizontally, then how much work is done?

7. How much work does gravity do on a 0.150-kg ball falling from a height of 10.0 m?

8. A student throws the same ball straight upward to a height of 7.50 m. How much work did the student do?

9. (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?

10. 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?

11. 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)?

12. 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.

13. A 0.50-kg block initially at rest on a frictionless, horizontal surface is acted upon by a force of 8.0 N for a distance of 4.0 m. How much kinetic energy does the block gain?

14. If the force in Exercise 13 had acted for a distance of 8.0 m, then what would be the block’s velocity?

15. 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.

16. How much work is required to lift a 3.00-kg object from the bottom of a well 10.0 m deep?

17. An object is dropped from a height of 12 m. At what height will its kinetic energy and its potential energy be equal?

18. A 1.0-kg rock is dropped from a height of 6.0 m. At what height is the rock’s kinetic energy twice its potential energy?

19. 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?

20. A 30.0-kg child starting from rest slides down a water slide with a vertical height of 10.0 m. What is the child’s speed (a) halfway down the slide's vertical distance and (b) three-fourths of the way down? (Neglect friction.)

21. If the man in Exercise 5 pushes the lawn mower 6.0 m in 10 s, how much power does he expend?

22. 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?

23. 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?

24. 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?

25. 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.

26. A microwave oven has a power requirement of 1250 W. A frozen dinner requires 4.0 min to heat on full power. (a) How much electrical energy (in kWh) is used? (b) If the cost of electricity is 12¢ per kWh, then how much does it cost to heat the dinner?

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