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Physics: Principles with Applications

Douglas C. Giancoli

Chapter 2

DESCRIBING MOTION: KINEMATICS IN ONE DIMENSION - all with Video Answers

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Chapter Questions

01:16

Problem 1

(I) If you are driving 95 km/h along a straight road and you look to the side for 2.0 s, how far do you travel during this inattentive period?

Prabhu Ramji
Prabhu Ramji
Numerade Educator
01:12

Problem 2

(I) What must your car's average speed be in order to travel 235 km in 2.75 h?

Vishal Gupta
Vishal Gupta
Numerade Educator
01:39

Problem 3

(I) A particle at $t_1 = -$2.0 s is at $x_1 =$ 4.8 cm and at $t_2 =$ 4.5 s is at $x_2 =$ 8.5 cm. What is its average velocity over this time interval? Can you calculate its average speed from these data?Why or why not?

Averell Hause
Averell Hause
Carnegie Mellon University
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Problem 4

(I) A rolling ball moves from $x_1 =$ 8.4 cm to $x_2 = -$4.2 cm during the time from $t_1 =$ 3.0 s to $t_2 =$ 6.1 s. What is its average velocity over this time interval?

Charles Maxwell
Charles Maxwell
Numerade Educator
02:10

Problem 5

(I) A bird can fly 25 km/h. How long does it take to fly 3.5 km?

Guilherme Barros
Guilherme Barros
Numerade Educator
03:10

Problem 6

(II) According to a rule-of-thumb, each five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. ($a$) Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule. ($b$) What would be the rule for kilometers?

Raiya Ebini
Raiya Ebini
Kansas State University
02:13

Problem 7

(II) You are driving home from school steadily at 95 km/h for 180 km. It then begins to rain and you slow to 65 km/h. You arrive home after driving 4.5 h. ($a$) How far is your hometown from school? ($b$) What was your average speed?

Averell Hause
Averell Hause
Carnegie Mellon University
03:20

Problem 8

(II) A horse trots away from its trainer in a straight line, moving 38 m away in 9.0 s. It then turns abruptly and gallops halfway back in 1.8 s. Calculate ($a$) its average speed and ($b$) its average velocity for the entire trip, using "away from the trainer" as the positive direction.

Raiya Ebini
Raiya Ebini
Kansas State University
02:20

Problem 9

(II) A person jogs eight complete laps around a 400-m track in a total time of 14.5 min. Calculate ($a$) the average speed and ($b$) the average velocity, in m/s.

Krystal K
Krystal K
Numerade Educator
01:24

Problem 10

(II) Every year the Earth travels about 10$^{9}$ km as it orbits the Sun. What is Earth's average speed in km/h?

Keshav Singh
Keshav Singh
Numerade Educator
01:26

Problem 11

(II) A car traveling 95 km/h is 210 m behind a truck traveling 75 km/h. How long will it take the car to reach the truck?

Averell Hause
Averell Hause
Carnegie Mellon University
06:30

Problem 12

(II) Calculate the average speed and average velocity of a complete round trip in which the outgoing 250 km is covered at 95 km/h, followed by a 1.0-h lunch break, and the return 250 km is covered at 55 km/h.

Raiya Ebini
Raiya Ebini
Kansas State University
00:46

Problem 13

(II) Two locomotives approach each other on parallel tracks. Each has a speed of 155 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2-35.) (Figure can't copy)

Averell Hause
Averell Hause
Carnegie Mellon University
01:25

Problem 14

(II) Digital bits on a 12.0-cm diameter audio CD are encoded along an outward spiraling path that starts at radius $R_1 =$ 2.5 cm and finishes at radius $R_2 =$ 5.8 cm. The distance between the centers of neighboring spiralwindings is 1.6 $\mu$m (= 1.6 $\times$ 10$^{-6}$ m). ($a$) Determine the total length of the spiraling path. [$Hint$: Imagine "unwinding" the spiral into a straight path of width 1.6$\mu$m and note that the original spiral and the straight path both occupy the same area.] ($b$) To read information, a CD player adjusts the rotation of the CD so that the player's readout
laser moves along the spiral path at a constant speed of about 1.2 m/s. Estimate the maximum playing time of such a CD.

Penny Riley
Penny Riley
Numerade Educator
02:14

Problem 15

(III) A bowling ball traveling with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.80 s after the ball is released from his hands. What is the speed of the ball, assuming the speed of sound is 340 m/s?

Suzanne W.
Suzanne W.
Numerade Educator
06:04

Problem 16

(III) An automobile traveling 95 km/h overtakes a 1.30-km-long train traveling in the same direction on a track parallel to the road. If the train's speed is 75 km/h, how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2-36. What are the results if the car and train are traveling in opposite directions?
Fig. 2-36 (Figure can't copy)

Raiya Ebini
Raiya Ebini
Kansas State University
01:35

Problem 17

(I) A sports car accelerates from rest to 95 km/h in 4.3 s. What is its average acceleration in m/s$^2$?

Averell Hause
Averell Hause
Carnegie Mellon University
03:11

Problem 18

(I) A sprinter accelerates from rest to 9.00 m/s in 1.38 s. What is her acceleration in ($a$) m/s$^2$; ($b$) km/h$^2$?

Raiya Ebini
Raiya Ebini
Kansas State University
01:42

Problem 19

(II) A sports car moving at constant velocity travels 120 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is the magnitude of its acceleration (assumed constant) in m/s$^2$, and in $g's$ ($g =$ 9.80 m/s$^2$)?

Averell Hause
Averell Hause
Carnegie Mellon University
03:34

Problem 20

(II) At highway speeds, a particular automobile is capable of an acceleration of about 1.8 m/s$^2$. At this rate, how long does it take to accelerate from 65 km/h to 120 km/h?

Raiya Ebini
Raiya Ebini
Kansas State University
01:44

Problem 21

(II) A car moving in a straight line starts at $x =$ 0 at $t =$ 0. It passes the point $x =$ 25.0 m with a speed of 11.0 m/s at $t =$ 3.00 s. It passes the point $x =$ 385 m with a speed of 45.0 m/s at $t =$ 20.0 s. Find ($a$) the average velocity, and ($b$) the average acceleration, between $t =$ 3.00 s and $t =$ 20.0 s.

Averell Hause
Averell Hause
Carnegie Mellon University
02:11

Problem 22

(I) A car slows down from 28 m/s to rest in a distance of 88 m. What was its acceleration, assumed constant?

Raiya Ebini
Raiya Ebini
Kansas State University
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Problem 23

(I) A car accelerates from 14 m/s to 21 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceleration.

SY
Sandeep Yadav
Numerade Educator
01:39

Problem 24

(I) A light plane must reach a speed of 35 m/s for takeoff. How long a runway is needed if the (constant) acceleration is 3.0 m/s$^2$?

Raiya Ebini
Raiya Ebini
Kansas State University
01:11

Problem 25

(II) A baseball pitcher throws a baseball with a speed of 43 m/s. Estimate the average acceleration of the ball during the throwing motion. In throwing the baseball, the pitcher accelerates it through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2-37). (Figure can't copy)

Averell Hause
Averell Hause
Carnegie Mellon University
03:21

Problem 26

(II) A world-class sprinter can reach a top speed (of about 11.5 m/s) in the first 18.0 m of a race. What is the average acceleration of this sprinter and how long does it take her to reach that speed?

Donald Albin
Donald Albin
Numerade Educator
01:33

Problem 27

(II) A car slows down uniformly from a speed of 28.0 m/s to rest in 8.00 s. How far did it travel in that time?

Averell Hause
Averell Hause
Carnegie Mellon University
01:45

Problem 28

(II) In coming to a stop, a car leaves skid marks 65 m long on the highway. Assuming a deceleration of 4.00 m/s$^2$, estimate the speed of the car just before braking.

Raiya Ebini
Raiya Ebini
Kansas State University
02:01

Problem 29

(II) A car traveling at 95 km/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the magnitude of the average acceleration of the driver during the collision? Express the answer in terms of "$g$'s," where 1.00 $g =$ 9.80 m/s$^2$.

Averell Hause
Averell Hause
Carnegie Mellon University
09:04

Problem 30

(II) A car traveling 75 km/h slows down at a constant 0.50 m/s$^2$ just by "letting up on the gas." Calculate ($a$) the distance the car coasts before it stops, ($b$) the time it takes to stop, and ($c$) the distance it travels during the first and fifth seconds.

Raiya Ebini
Raiya Ebini
Kansas State University
03:39

Problem 31

(II) Determine the stopping distances for an automobile going a constant initial speed of 95 km/h and human reaction time of 0.40 s: ($a$) for an acceleration $a = -$3.0 m/s$^2$; ($b$) for $a = -$6.0 m/s$^2$

Averell Hause
Averell Hause
Carnegie Mellon University
04:45

Problem 32

(II) A driver is traveling 18.0 m/s when she sees a red light ahead. Her car is capable of decelerating at a rate of 3.65 m/s$^2$. If it takes her 0.350 s to get the brakes on and she is 20.0 m from the intersection when she sees the light, will she be able to stop in time? How far from the beginning of the intersection will she be, and in what direction?

Raiya Ebini
Raiya Ebini
Kansas State University
02:54

Problem 33

(II) A 75-m-long train begins uniform acceleration from rest. The front of the train has a speed of 18 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2-38.)

Averell Hause
Averell Hause
Carnegie Mellon University
05:04

Problem 34

(II) A space vehicle accelerates uniformly from 85 m/s at $t =$ 0 to 162 m/s at $t =$ 10.0 s. How far did it move between $t =$ 2.0 s and $t =$ 6.0 s

Raiya Ebini
Raiya Ebini
Kansas State University
02:13

Problem 35

(II) A runner hopes to complete the 10,000-m run in less than 30.0 min. After running at constant speed for exactly 27.0 min, there are still 1200 m to go. The runner must then accelerate at 0.20 m/s$^2$ for how many seconds in order to achieve the desired time?

Averell Hause
Averell Hause
Carnegie Mellon University
03:15

Problem 36

(III) A fugitive tries to hop on a freight train traveling at a constant speed of 5.0 m/s. Just as an empty box car passes him, the fugitive starts from rest and accelerates at $a =$ 1.4 m/s$^2$ to his maximum speed of 6.0 m/s, which he then maintains. ($a$) How long does it take him to catch up to the empty box car? ($b$) What is the distance traveled to reach the box car?

Eric Mockensturm
Eric Mockensturm
Numerade Educator
03:11

Problem 37

(III) Mary and Sally are in a foot race (Fig. 2-39). When Mary is 22 m from the finish line, she has a speed of 4.0 m/s and is 5.0 m behind Sally, who has a speed of 5.0 m/s. Sally thinks she has an easy win and so, during the remaining portion of the race, decelerates at a constant rate of 0.40 m/s$^2$ to the finish line. What constant acceleration does Mary now need during the remaining portion of the race, if she wishes to cross the finish line side-by-side with Sally?

Averell Hause
Averell Hause
Carnegie Mellon University
09:27

Problem 38

(III) An unmarked police car traveling a constant 95 km/h is passed by a speeder traveling 135 km/h. Precisely 1.00 s after the speeder passes, the police officer steps on the accelerator; if the police car's acceleration is 2.60 m/s$^2$, how much time passes before the police car overtakes the speeder (assumed moving at constant speed)?

Dading Chen
Dading Chen
Numerade Educator
00:43

Problem 39

(I) A stone is dropped from the top of a cliff. It is seen to hit the ground below after 3.55 s. How high is the cliff?

Averell Hause
Averell Hause
Carnegie Mellon University
03:34

Problem 40

(I) Estimate ($a$) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), and ($b$) his velocity just before "landing."

Dading Chen
Dading Chen
Numerade Educator
01:50

Problem 41

(II) A ball player catches a ball 3.4 s after throwing it vertically upward. With what speed did he throw it, and what height did it reach?

Averell Hause
Averell Hause
Carnegie Mellon University
02:55

Problem 42

(II) A baseball is hit almost straight up into the air with a speed of 25 m/s. Estimate ($a$) how high it goes, ($b$) how long it is in the air. ($c$) What factors make this an estimate?

Shoukat Ali
Shoukat Ali
Other Schools
01:47

Problem 43

(II) A kangaroo jumps straight up to a vertical height of 1.45 m. How long was it in the air before returning to Earth?

Averell Hause
Averell Hause
Carnegie Mellon University
06:23

Problem 44

(II) The best rebounders in basketball have a vertical leap (that is, the vertical movement of a fixed point on their body) of about 120 cm. ($a$) What is their initial "launch" speed off the ground? ($b$) How long are they in the air?

Timothy Vitale
Timothy Vitale
Numerade Educator
04:43

Problem 45

(II) An object starts from rest and falls under the influence of gravity. Draw graphs of ($a$) its speed and ($b$) the distance it has fallen, as a function of time from $t =$ 0 to $t =$ 5.00 s. Ignore air resistance.

Averell Hause
Averell Hause
Carnegie Mellon University
02:48

Problem 46

(II) A stone is thrown vertically upward with a speed of 24.0 m/s. ($a$) How fast is it moving when it is at a height of 13.0 m? ($b$) How much time is required to reach this height? ($c$) Why are there two answers to ($b$)?

Suzanne W.
Suzanne W.
Numerade Educator
02:14

Problem 47

(II) For an object falling freely from rest, show that the distance traveled $during$ each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). (This was first shown by Galileo.) See Figs. 2-19 and 2-22.

Suzanne W.
Suzanne W.
Numerade Educator
10:38

Problem 48

(II) A rocket rises vertically, from rest, with an acceleration of 3.2 m/s$^2$ until it runs out of fuel at an altitude of 775 m. After this point, its acceleration is that of gravity, downward. ($a$) What is the velocity of the rocket when it runs out of fuel? ($b$) How long does it take to reach this point? ($c$) What maximum altitude does the rocket reach? ($d$) How much time (total) does it take to reach maximum altitude? ($e$) With what velocity does it strike the Earth? ($f$) How long (total) is it in the air?

Vysakh M
Vysakh M
Numerade Educator
01:43

Problem 49

(II) A helicopter is ascending vertically with a speed of 5.40 m/s. At a height of 105 m above the Earth, a package is dropped from the helicopter. How much time does it take for the package to reach the ground? [$Hint$: What is $\upsilon_0$ for the package?]

Averell Hause
Averell Hause
Carnegie Mellon University
05:42

Problem 50

(II) Roger sees water balloons fall past his window. He notices that each balloon strikes the sidewalk 0.83 s after passing his window. Roger's room is on the third floor, 15m above the sidewalk. ($a$) How fast are the balloons traveling when they pass Roger's window? ($b$) Assuming the balloons are being released from rest, from what floor are they being released? Each floor of the dorm is 5.0 m high.

Dading Chen
Dading Chen
Numerade Educator
01:45

Problem 51

(II) Suppose you adjust your garden hose nozzle for a fast stream of water. You point the nozzle vertically upward at a height of 1.8 m above the ground (Fig. 2-40). When you quickly turn off the nozzle, you hear the water striking the ground next to you for another 2.5 s. What is the water speed
as it leaves the nozzle? (Fig. 2-40) (Figure can't copy)

Averell Hause
Averell Hause
Carnegie Mellon University
16:33

Problem 52

(III) A baseball is seen to pass upward by a window with a vertical speed of 14 m/s. If the ball was thrown by a person 18 m below on the street, ($a$) what was its initial speed, ($b$) what altitude does it reach, ($c$) when was it thrown, and ($d$) when does it reach the street again?

Matthew Muscat
Matthew Muscat
Numerade Educator
03:30

Problem 53

(III) A falling stone takes 0.31 s to travel past a window 2.2 m tall (Fig. 2-41). From what height above the top of the window did the stone fall?

Averell Hause
Averell Hause
Carnegie Mellon University
05:09

Problem 54

(III) A rock is dropped from a sea cliff, and the sound of it striking the ocean is heard 3.4 s later. If the speed of sound is 340 m/s, how high is the cliff?

Keshav Singh
Keshav Singh
Numerade Educator
02:50

Problem 55

(II) Figure 2-42 shows the velocity of a train as a function of time. ($a$) At what time was its velocity greatest? ($b$) During what periods, if any, was the velocity constant? ($c$) During what periods, if any, was the acceleration constant? ($d$) When was the magnitude of the acceleration greatest?

Averell Hause
Averell Hause
Carnegie Mellon University
01:52

Problem 56

(II) A sports car accelerates approximately as shown in the velocity-time graph of Fig. 2-43. (The short flat spots in the curve represent manual shifting of the gears.) Estimate the car's average acceleration in ($a$) second gear and ($b$) fourth gear.

Shoukat Ali
Shoukat Ali
Other Schools
03:18

Problem 57

(II) The position of a rabbit along a straight tunnel as a function of time is plotted in Fig. 2-44. What is its instantaneous velocity ($a$) at $t =$ 10.0 s and ($b$) at $t =$ 30.0 s? What is its average velocity (c) between $t =$ 0 and $t =$ 5.0 s, (d) between $t =$ 25.0 s and $t =$ 30.0 s, and (e) between $t =$ 40.0 s and $t =$ 50.0 s?

Nicholas Mogoi
Nicholas Mogoi
Numerade Educator
01:38

Problem 58

(II) In Fig. 2-44, ($a$) during what time periods, if any, is the velocity constant? ($b$) At what time is the velocity greatest? ($c$) At what time, if any, is the velocity zero? ($d$) Does the object move in one direction or in both directions during the time shown?

Shoukat Ali
Shoukat Ali
Other Schools
02:31

Problem 59

(III) Sketch the $\upsilon$ vs. $t$ graph for the object whose displacement as a function of time is given by Fig. 2-44.

Averell Hause
Averell Hause
Carnegie Mellon University
02:25

Problem 60

The acceleration due to gravity on the Moon is about onesixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

Sachin Rao
Sachin Rao
Numerade Educator
03:08

Problem 61

A person who is properly restrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed 30 "$g$'s" (1.00 $g =$ 9.80 m/s$^2$). Assuming uniform deceleration at 30 $g$'s, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 95 km/h.

Averell Hause
Averell Hause
Carnegie Mellon University
06:25

Problem 62

A person jumps out a fourth-story window 18.0 m above a firefighter's safety net. The survivor stretches the net 1.0m before coming to rest, Fig. 2-45. ($a$) What was the average deceleration experienced by the survivor when she was slowed to rest by the net? ($b$) What would you do to make it "safer" (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain. (Figure can't copy)Fig. 2-45

Donald Albin
Donald Albin
Numerade Educator
03:02

Problem 63

Pelicans tuck their wings and free-fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 14.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.

Averell Hause
Averell Hause
Carnegie Mellon University
01:58

Problem 64

A bicyclist in the Tour de France crests a mountain pass as he moves at 15 km/h. At the bottom, 4.0 km farther, his speed is 65 km/h. Estimate his average acceleration (in m/s$^2$) while riding down the mountain.

Sachin Rao
Sachin Rao
Numerade Educator
05:56

Problem 65

Consider the street pattern shown in Fig. 2-46. Each intersection has a traffic signal, and the speed limit is 40 km/h. Suppose you are driving from the west at the speed limit. When you are 10.0 m from the first intersection, all the lights turn green. The lights are green for 13.0 s each. ($a$) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping? ($b$) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of 2.00 m/s$^2$ to the speed limit. Can the second car make it through all three lights without stopping? By how many seconds would it make it, or not make it? (Figure can't copy)Fig. 2-46.

Averell Hause
Averell Hause
Carnegie Mellon University
03:25

Problem 66

An airplane travels 2100 km at a speed of 720 km/h, and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km. What was the total time for the trip? What was the average speed of the plane for this trip? [$Hint$: Does Eq. 2-11d apply?]

Vishal Gupta
Vishal Gupta
Numerade Educator
02:39

Problem 67

Suppose a car manufacturer tested its cars for front-end collisions by hauling them up on a crane and dropping them from a certain height. ($a$) Show that the speed just before a car hits the ground, after falling from rest a vertical distance $H$, is given by $\sqrt{ 2gH }$ . What height corresponds to a collision at ($b$) 35 km/h? ($c$) 95 km/h?

Averell Hause
Averell Hause
Carnegie Mellon University
02:07

Problem 68

A stone is dropped from the roof of a high building. A second stone is dropped 1.30 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s?

Sachin Rao
Sachin Rao
Numerade Educator
02:35

Problem 69

A person jumps off a diving board 4.0 m above the water's surface into a deep pool. The person's downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water.

Anand Jangid
Anand Jangid
Numerade Educator
03:32

Problem 70

In putting, the force with which a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting the ball downhill, see Fig. 2-47) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at 1.8 m/s$^2$ going downhill, and constantly at 2.6 m/s$^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup. Do the same for a downhill lie 7.0 m from the cup. What in your results suggests that the downhill putt is more difficult? (Figure can't copy)Fig. 2-47

Averell Hause
Averell Hause
Carnegie Mellon University
06:28

Problem 71

A stone is thrown vertically upward with a speed of 15.5 m/s from the edge of a cliff 75.0 m high (Fig. 2-48). ($a$) How much later does it reach the bottom of the cliff? ($b$) What is its speed just before hitting? ($c$) What total distance did it travel?(Figure can't copy)

Averell Hause
Averell Hause
Carnegie Mellon University
14:00

Problem 72

In the design of a $\textbf{rapid transit system}$, it is necessary to balance the average speed of a train against the distance between station stops. The more stops there are, the slower the train's average speed. To get an idea of this problem, calculate the time it takes a train to make a 15.0-km trip in two situations: ($a$) the stations at which the trains must stop are 3.0 km apart (a total of 6 stations, including those at the ends); and ($b$) the stations are 5.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of 1.1 m/s$^2$ until it reaches 95 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-$2.0 m/s$^2$. Assume it stops at each intermediate station for 22 s.

Keshav Singh
Keshav Singh
Numerade Educator
03:50

Problem 73

A person driving her car at 35 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning to red, and she is 28 m away from the near side of the intersection (Fig. 2-49). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car's maximum deceleration is $-$5.8 m/s$^2$, whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.(Figure can't copy) (Fig. 2-49).

Suzanne W.
Suzanne W.
Numerade Educator
05:00

Problem 74

A car is behind a truck going 18 m/s on the highway. The car's driver looks for an opportunity to pass, guessing that his car can accelerate at 0.60 m/s$^2$ and that he has to cover the 20-m length of the truck, plus 10-m extra space at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably at the speed limit, 25 m/s (55 mph). He estimates that the car is about 500 m away. Should he attempt the pass? Give details.

David Cantin
David Cantin
Numerade Educator
03:26

Problem 75

Agent Bond is standing on a bridge, 15 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s, which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this region. The roof of the truck is 3.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he drops down from the bridge onto the truck, making his getaway. How many poles is it?

Averell Hause
Averell Hause
Carnegie Mellon University
01:13

Problem 76

A conveyor belt is used to send burgers through a grilling machine. If the grilling machine is 1.2 m long and the burgers require 2.8 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 25 cm apart, what is the rate of burger production (in burgers/min)?

Averell Hause
Averell Hause
Carnegie Mellon University
02:34

Problem 77

Two students are asked to find the height of a particular building using a barometer. Instead of using the barometer as an altitude measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. What % difference does the 0.3 s make for the estimates of the building's height?

Averell Hause
Averell Hause
Carnegie Mellon University
05:40

Problem 78

Figure 2-50 shows the position vs. time graph for two bicycles, A and B. ($a$) Identify any instant at which the two bicycles have the same velocity. ($b$) Which bicycle has the larger acceleration? ($c$) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? ($d$) Which bicycle has the larger instantaneous velocity? ($e$) Which bicycle has the larger average velocity?(Figure can't copy)Figure 2-50 (Fig. 2-48)

Vishal Gupta
Vishal Gupta
Numerade Educator
01:42

Problem 79

A race car driver must average 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at an average speed of 196.0 km/h, what average speed must be maintained for the last lap?

Averell Hause
Averell Hause
Carnegie Mellon University
04:43

Problem 80

Two children are playing on two trampolines. The first child bounces up one-and-a-half times higher than the second child. The initial speed up of the second child is 4.0 m/s. ($a$) Find the maximum height the second child reaches. ($b$) What is the initial speed of the first child? ($c$) How long was the first child in the air?

Evan Sullivan
Evan Sullivan
Numerade Educator
02:56

Problem 81

If there were no air resistance, how long would it take a free-falling skydiver to fall from a plane at 3200 m to an altitude of 450 m, where she will open her parachute? What would her speed be at 450 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h.)

Averell Hause
Averell Hause
Carnegie Mellon University
01:56

Problem 82

You stand at the top of a cliff while your friend stands on the ground below you. You drop a ball from rest and see that she catches it 1.4 s later. Your friend then throws the ball up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?

Sachin Rao
Sachin Rao
Numerade Educator
03:11

Problem 83

On an audio compact disc (CD), digital bits of information are encoded sequentially along a spiral path. Each bit occupies about 0.28 $\mu$m. A CD player's readout laser scans along the spiral's sequence of bits at a constant speed of about 1.2 m/s as the CD spins. ($a$) Determine the number N of digital bits that a CD player reads every second. ($b$) The audio information is sent to each of the two loudspeakers 44,100 times per second. Each of these samplings requires 16 bits, and so you might expect the required bit rate for a CD player to be $$N_0 = 2\bigg( 44,100\frac{samplings}{s}\bigg)\bigg(16\frac{bits}{sampling}\bigg) = 1.4 \times 10^6 \frac{bits}{s} , $$ where the 2 is for the 2 loudspeakers (the 2 stereo channels). Note that $N_0$ is less than the number $N$ of bits actually read per second by a CD player. The excess number of bits ($= N - N_0$) is needed for encoding and error-correction. What percentage of the bits on a CD are dedicated to encoding and error-correction?

Averell Hause
Averell Hause
Carnegie Mellon University