Does a car speedometer measure speed, veuq3-i * uua6kmo4f2)ipm q.ei locity, or both?

Can an object have a zee9bhxeys( mvvt;;18d4o i* varying speed if its velocity is constant? If yes, give exambez *te8o;h9vmi(ye1s v;x4d ples.

When an object moves with constant velocity, dom17q.kgbrr) i es its average velocity during any time interval differ from its instantaneouri.7 g1b)q mkrs velocity at any instant?

In drag racing, is it possible for the car with the greate d jd6;xiri1g c9pk85wst speed crossing the finish line to lose the race? Erpidc9 jk8g w5ix61 ;dxplain.

If one object has a greater speed than a second object, does the firstdz tq; elx rpiq9xi9hh/2u:q4yo-75i necessarily have a greater accelerae4qqrq ohi;h/upi 2y7:-l xt99z dix5tion? Explain, using examples.

Compare the acceleration of a motorcycle that accelewet61lef fr 5j3l;a4qrates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the 3tqal5e1 lw6jr e4ff;same time.

Can an object have a noe6;peoxwu*l7b1p wyc 6c) l;frthward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wharqmav6 7-(xfh6gz; ekt6q (xr7v m; gzh6a-ekf about vice versa?

Give an example wherejnue0o4)kp1ue7/g ) 7tssog j both the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is:crzm:m zwju7o+jqgvm8e9 8 p ufz ;,1 traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car im1mr9 pq,: gj+jzc7;vzwz: u 8me8fu os passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be incu,ess+la xi)kezznad rjn732 o)u++,reasing in speed as its acceleration decreases? If so, give an esko3rj n+au )u,dz),+z+islne 2a 7xexample. If not, explain.

A baseball player hits a foul ball straight up into the+s dy*,h8aiw e(0g-dp;udb spx ;sr*i air. It leaves the bat with a speed of 120km/h . In dwd,s ; xhs(-*uer p0;ps y+ai*igb8 dthe absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling o wmp t5u5c-x)fbject speeds up, what is happening to its acceleration due to gravity — does it increa -u5p5 tmwcxf)se, decrease, or stay the same?

How would you estimate the maximum height yoin (z2o ktu0*g 0hh+qfu could throw a ball vertically upward? How would you estima*o+ u2ngft i(k 0qhh0zte the maximum speed you could give it?

You travel from point A to point B ryo3+ q66re wzin a car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your q6zy rr36o w+eaverage speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten boltsa8 y:wyz:z we/ tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plat/zw:8yzy wae:e, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motz5.qtj(aikw )ions is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops alki jz a.()5twqong the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original pof - b2, el h fx-7wfn32eou3u+; uybofs(x4uensition with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, hf xeu -x4 ; ,s fhe-ny2l2b7oub3uf3uw+efon(ow? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the sawm ; c*x-pddto.+hi(z me time? Give exampli*w+dc tzm;.odx(-p hes.

Can an object have zero acceleration and nonzero velocity at ia i 0/(ve/b y :5q3vfm-qchfmthe same time? Give example: 0-mhyvvc(qib 53f/qe fai/m s.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint38rosw)mp3sc fxn/9q o5f:t/tzt 2 hg : 2//ohwctr38 fzo9stg)t:5n 3q fmpsxFirst try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. svwhvna5djx4v;w .):

  What must be your car’s average speed in order to travgsa-( 1- wmjhfel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long 3 ewyivbmjk i9;-wc29does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0zw-c;z. lzg *w s, how far do you tr*wz ;-czzl. wgavel during this inattentive period?    m

  Convert 35 mi/h to 4w*jif vji:f; ,0bj0 amt k4xh
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves f *px.rfo8fl0td;u0af rom $x_1$ = 3.4 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?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home f e-hn9aw89ccz j5)n:,.zq; vqz tvs abrom school steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home n.9hz :9;w- znvzsc5),8jtqb aq a vceafter driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash dskoo:3hnc;f,2*; d 1smsf yr cpp-g9 and the following thunder gives the distance to the flash in miles. Assumingsyn-pp cs;*f orkcfd1;32d,s:og h9m that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight qd8qvz)(y pkjas f34 5complete laps around a quarter-mile track in a total time of 12.5 min. Calc)kaq85 fpsd vy 4(zjq3ulate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight lin/ink6cc3*jjc p h 4ej1e, moving 116 m away in 14.0 s. It theij*k3c4chenjjpc16 / n turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach4cgy1j:lu6t8k k h:vn ;so,rg each other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it;vj4c l:nt:k u8g rhs1yk 6o,g be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long will 9zpf.be0g b1 tit take the car to reacz1e0pt.9b gbf h the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters mv . hqt- -tn kurv4,e xv+3rm+wce1+na tailwind that boosts its speed to 990 km/h for th--vq3ewtc+1+m mrnv4 ,h .eu r txk+nve next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and averaga0vktx ..- r8s+rgou re velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunur0x t ksor8 g.+-arv.ch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at theu 4u ev8whoooue f2;lsh)*a ml8l:1y+ end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2o*mleul2 s :+ u;l1ofwh)y8a 8e4v ohu.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s m(f)5zpnn5cf . What is its average accelc(fpf5) n mz5neration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/:k bgjvco4b b,pg0:iav1 6xj,s in 1.35 s. What is her acceleration a xvb,cbj, p 4jgv6:g k:io1b0
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobil+;x+/wvn jjzna8kl0f e is capable of an acceleration of about n/ za0vjn8x kfl w+j;+$1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m iw i.w 0 .lhy/uqv5l2nun 5.0 s. If it then brakes and comes to a stop in 4.0 s, whnlyvw .0 u lwu52i/.qhat is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0sh8x h6q,az49n*augx and moves in a straighxaq6u zns8h,49xh*ag t line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. 8jv7.t chdpw*/jxqf1What was its acceleration? How far did it travel in this timhq7p w*c t. fjj1vxd8/e? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dista7m.e )cou.kpynce of 85 m. What was its acceleration, k .m7ep.c) uyoassumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway n2c2h cd52k ubv;:c qfk(s0wmis needed if the (constant) acce22 5dc hk;wqbn:( s02 ckvmucfleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (of wi/5)kng3ms cabout 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration cwng)5 3 mis/kof this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down unif4 :ad3hx8mihz a*qzq ,r yim,6ormly from a speed of 12.0 m/s to rest in 6.00 s. How far di hzax d:q3 i6q8* rmz4ahm,,yid it travel in that time?    m

  In coming to a stop, a car.rov0 bm6t, gr leaves skid marks 92 m long on the highway. Assuming a decelem0g brotv 6r.,ration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compres++/w5h y c7asz ziae3ises and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms o+zi+as /5hc3ea7iwy zf “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 k+ wvt+d fz /e5wen)ty2m/h and human reatd v)e++newywt/5 f2zction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation ,f ;2(up 6)teh9k b(sbt mlviga3*j9j /zpawffor the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/stu;v 7,q hth)n on the highway. The car’s driver looks for an opportunity to pass, guessing that his car cantvh;,uh) 7 qnt accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room 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 also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0pcqr92u xnar4bl6*v 1 min. After exactly 27.0 min, there are still 1100 m to g q*bv2xu 6rpr 14lna9co. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approac36z lvym6;ik;e7f)el8 nqj60 a tig uehes an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). 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 ejii6 f);glek e87t ;l6 0nuzayvq6m3car’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.

  A stone is dropped from the top of a cliff. It h9uza-*u l n4woits the ground below after 3.25 s. How high is the clin*uz4 w-ou 9laff?    m

  If a car rolls gently q2 nuj*s ;3pcr($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air4vg oi 7sqci9 8gl1r3w with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches xsde d9 p/j rmq1f2c/;x 2se:ma ball 3.0 s after throwing it vertically upward. With what speed did he throw it, an91ecr xj2:dxms q/2 pfs;/ed md what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls )+jx /jni.y ct8x cyh t,on.2zunder 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 resistancxj c.zhjt yncy ix)8+,/2.no te.

A helicopter is ascending verticalu7v-28h; uij lxpkn 53s gn*fkly with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much timekg kv s2xlphi3nj85f*n ;u7-u does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance travea3b+2aym sx:n sv. v*tled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and a vnabvs3:tx*sym.+2 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown verticalql 0dws0;bx l8ly upward withlws bql d80;x0 a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 m/s 5td/)nlglh4o jr pg - *v0nu-f
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–18 (or number mfx4m z8.7a juof photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use twjzf .8m mu4x7ao apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 msotchtfe )-9v/ y-zlqd) /9 n0zffjl8 tall (Fig. 2–32). From what height above the top of the window did th-8 llecsfy)ohf jd//)tf v9nz-z0t q9e stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocej(s84qj)km za0-oi dwan is heard 3.2 s ljo k84qs wi0)-mzd(j aater. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle fou)rj ki c)e72gnf7d) 4orpt4jr a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, ynf2rtg4je)cok du )i p7j r)74ou hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from1;/ud6z0rsowf5q c xf the edge of a cliff 70.0 m high (Figr/f6w; 5zxoq 01sfudc. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward-3o wr+fbr mg /g19isv by a window 28 m above the street with a vertical speed of 13 m/s If the1grmw bv 9 3o+igf-r/s ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a tra-y vg fjh grur5l;2r)7osf:k0in 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 maf;lguo72shy0:f)v j -r krg5 rgnitude of the acceleration greatest?

  The position of a rabbit along a straight tunx1j;)w( 5we5)lko h upk f4qganel as a function of time is plotted in Fig. 2–28. Wha(q;5ko)x wa) ukj4w1e5flg hpt is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as shown in the vel0 w4iwrdnsu d;27f;gbuaz87gocity–time graph of Fig. 2–35. (The short flat spots in the4i 7 ;fbr2 d7z0 wuds8gga;wnu curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the p 6vm2vkg3;8dg *l f l0ivjn,ufb: bx-a0cr+vorevious Problem (Fig. 2–35) whenrl ndbjfvbx3c -;08:f *62ogg a ivv+u,lv0mk it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the objectl 5ir9(n*d hh 7kbxmd0 traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object eq4df4 ,rs .;xi afcipq8zt*:epx;h 7whose displacement as a function of time is given by Fig. 2–xf.prq4,;:pqad ; 87cfe*tes4 ihxzi28.

Figure 2–36 is a position versus time graph t-q3(yhe0m8g5 mcujvniw r )7 for the motion of an object along the x axis. Consih(0wvt 87yq-jmun )em3 ir 5gcder the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-sts.06v sb 1n-mj: nmqqrory window 15.0 m above a firefighter’s safety nens0v 1.mnj6smr q:q-b t. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is abou:of6 y/w6pszm65vf: kdoi *iu t one-sixth 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 miiop z/fkf 6w *5:yv6ud6so :Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-th nv,5o2h1xa j pk8w6hr- u0nbce-shoulder seat belt has a good chance of surviving anc rh-2kx6jp0b1wh58uo, na v car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, 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 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above j-xbjxju 92j96n gmj5c c:wt+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 country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck -6nj5wuj9:+ bxg tjxc jc29j mto make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by hauling mhn6 6aquaf 0+them up on am+qu6a0h6 nfa 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) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth trave lp1t1es8n2h els about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uhdj3f*.y0+t wr kc e-1btj, coniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will1*b.w,cjrfj+ ykeo0cd -t3h t be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a deetwsig97dpm d.5w,be .p pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person whil t5b9m ..wwg,edip7dse under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is nece0foij:v:wdn wyc9d /,ssary to balance the average speed of a train against the distance between 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 9:iwf d/nvwjc9o: d,y 0.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 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 90 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 20 s.    min

  Pelicans tuck their wings and free fall straight down wheiu9,dpr,6zj)s d 8xs rn diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at whp xr6 r s,9j,sz)did8uat minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball+n88be n1(yvmr;um4ds c cxh dg m)e). is planned so that the ball will stop within some small distance of the cup, say, 1.0 m lus88nmdmvenx g ;c.c4)1)b +m re(dh yong or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ 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.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train tro /bd5hs8w-kn6,lzpr aveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugi8lbpor,n6dw k s5z- /htive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone is droppko52 dvsp5,z3 .wwn zhp6u;z oed 1.50 s later. How far apart are the ston3hn,zo. ;6u52pw okz5dws pzv es when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of 2 nmriq,2c9e ua time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintainederm2c ,2nuq 9i for the last lap?    km/h

  A bicyclist in the Tour de Francs :- afeqkk*w-glu:o7 e crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (iw::ou-gske 7a- l*kqf n $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolinh /v70+ev:*ylxc7lk iqiyj /yes. The first child can bounce up one-and-a-half times higher than the second child. The initia77ljl0/e +yx:v *cy/yhq vii kl speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling ikk,u g kfvij k,qjx52r;))8qt ou42 scn 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 c,gko)rus 8x;qkqi2 ,4 jkcktvj)5fu2 ar have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In thrhm: jdt-0te;vejl44rowing the baseball, the pitcher acceler0ed m:tvet-r4hj4;jl ates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest,o wprek,05j4j with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 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? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Eacx2gheq9(esl e, 8:lejh intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving fx8hljeesq,92el e(g :rom the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at i(2 m cw0z a*f-u5vsa)e oudp(a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a m*(aew (so)p v-5a0 u2ucfidzconstant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped fr z -k)5;7e hrnh;ki8jpco()n* sh 4mbe:esefzom the roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s:o r chj8()z h;eiemnn* pkbse7;4hksf ze5 -) and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at thrnw2t thlopox/lev7l +87 x :0e same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcpovw /h+r t7 8xne7l l0t2lo:xony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air rf 99 zhi9r) ef fd,cn2a1m;fijesistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (9c9di ;iazfme h19fr2,n fj )fIn reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to sendpfslr, f 7aen87j5bi3 the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger producti3f8 jefls n,rba7p75ion (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically atk18- uqjnwa*m yj0 u;c a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go u80-;mu qc *jywka1jn than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a qjv z,8t cpu3uf.ogz.81-owq cliff while your friend stands on the ground below you. You drop a ball from rest fu cpq .8w-zgtu.1 8v,o3jzqo and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular 3i9qct-piya7 kyt36uqy8i) es5yk)x building using a barometer. Iqt)c3axey7yky6q)5s3-p iut y98iik nstead 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. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph fof 7xi;pux:+ru v(b.cir two bicycles, A and B. (a) Is there 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 highest instantaneous velocity? (e) Which bicycle has the higher a7c:u+ xipvr xu; b(if.verage velocity?