Does a car speedometer measure speed,2rx 0g; xexyur w1ht6, velocity, or both?

Can an object have a varying speed if its velocity is constant? 8t +.i;ermuxiIf yes, give examples. 8rt;iumie+ .x

When an object moves with constant velocity, does its average velocity during mw -pa: 8ej(o 2u ykfub,s8+kuany time interval differ from its instantaneous velocity at akekyp( mbjf osuu+88-w:2,a uny instant?

In drag racing, is it poswh5qgj x21wt:,gd 1xgsible for the car with the greatest speed crossing the finish line to lose the race?wdhj t2 ,q1gx:g 15gxw Explain.

If one object has a greater speed than a second object, does th sgitnn6q-((rs (d9cy/ exa -me first necessarily have a greater acceleration? Exsiyc-(ens a gmtdqn6 (9-(r/xplain, using examples.

Compare the acceleration of a motorcycle that acce2qgd16;hs cj drp 4*felerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the sam2 s e6rc;4 hfpgddq*j1e time.

Can an object have a northward velocity5, iq(iulsn4 b and a southward acceleration? Explain.

Can the velocity of an objectx n(e,jb:2;,s2 n tevycj im4d be negative when its acceleration is positive? What about viebj 4sm2t:,vd(nx ije,yc;n 2ce versa?

Give an example where both the velocity and g y.djbzy du) eb4t3r f)xh1(- *qsmt:acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling withsewuh lu*))yc(kc, )d 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 . Whilhkw y) ,uu)cdsc *e)(ch car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelera -*7tvzdel(j tys2we/tion decreases? If so, give an example. If not,l/*2zsv7 e y-we(tdjt explain.

A baseball player hits a foulu a mnow,n0s-ge *m,d2rn7o/e ball straight up into the air. It leaves the bat with a speed of 120km/h . I age2nw 7,*m- do/somn,0urnen the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration dx0no9v,*, nygc zhhb6ue to gravznhh09g, *b6 o,v nyxcity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a bsaj2 5y qd88 tnf;n(ajall vertically upward? How would you estimate the maximum speed you coult2an(j8 ;5af s8ynjqdd give it?

You travel from point A to point B in a car moving at a constant speed of Theng zmu68*f rak)v0: bhd you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why nodur*bhv:z )86mgf0 akt.

In a lecture demonstration, a 3.0-m-long vertical string with ten vuth;sj m0;rrr 4k 9/csd(t5wbolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, 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 equalkmr r5;( rtw4v;j c9/s0htsud intervals?

Which one of these motions is not m. zfw..*ft5keui5gx at constant acceleration: a rock falling from a cliff, an elevator moving fromx.5g.wkf *5.eitfz mu the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original .s pz be9,e)ly yyd45 w7h+nyaposition 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, how? [Hint: The acceleration due to air resistance is always in a direction opposityy9n.+)57szhl yye ad4b pwe, e to the motion.]

Can an object have zero ven+ -xeoxj-n4- 7yftarlocity and nonzero acceleration at the same time? Give exfyo+47nn --jreat -xxamples.

Can an object have zero accelerati;z711mmz2.ew:lxe nh jvc :zron and nonzero velocity at the same time? Give ee::.m7;m lzexrvnj1 2 zc1 hwzxamples.

Describe in words the motion plotted i44dr+m v t+b:dk;lnetn Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by4d+ tlk; td:4bmer+ vn walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. 8iim( .spf 4z8wtddt)- evyb5

  What must be your cares5.w9jlac v *’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 1. v,hu9re nhd-o2vy s(5 km?    h

  If you are driving along a straight road and you look to the l0 s*y ij .xny/ln1:jmside for 2.0 s, how far do you travel during this inattentinjji*/ly10s :m.y nl xve period?    m

  Convert 35 mi/h to /*ah-sja tspx29m k( y
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from d-d5vb +6oqbx4lebj * $x_1$ = 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 from school steadily at 95 km/h fot m 4fryq d+d kzxa.1lc8a5s+8r 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and++ma8.a4 d5z8cq tsrxkdf l y1 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumte6bfs y lcv* ad08o(9b, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essenlay9d6fb*8 (to esc 0vtially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quartery obkho+t- 1;fym)q 8b-mile track in a total time of 12.obb-fkhy1mto)yq;8 +5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight l;s jjz-*f4 mbgz1siz 4ine, moving 116 m away in 14.0 s. It then turns abrup js1zm-4 gz;ifjz*4 bstly 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 approach each other on parallelxe ;dg(7 ojyq, tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart,q e;(xog7d,jy how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 1g 1qh8gzlg 8mh4t)j2k10 m behind a truck traveling How long will it take the car to reac4gghlk81 q2h8tj gz)mh the truck?    s

  An airplane travels 3100 km at + ckpw;pez4 aq;v69yga speed of 790 km/h , and then encounters a tailwind that boosts its speed to ak+6zg9;4eqp c v;wyp 990 km/h for the 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 average velocity of a complete round-ti :/ lyq1udj6 b7erd0vrip in which the outgoing 250 km is covered at 95 k/eirq1 jdb6dv7 u0:ly m/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pi9i *,eao1) q8iv /* xaqypenauns at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The yii8opqa1 *e9n*auve x,/)qaspeed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h x -ikpd gz017ein 6.2 s. What is its average accelerxd0epz i1- k7gation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. Wha4ud9olls-o6 ct is her acceleration 4o lc 6o-9dlus
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is ca mwk ,khud:i3 kn8 gh33/pqw:upable of an acceleration of about /i pwm hd3 h nuqkg,u:kw383:k$1.6 m/s^2$ 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 izz-3 sue;* wohn 5.0 s. If it then brakes anz hw-s ;e3ouz*d comes to a stop in 4.0 s, what 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 racin(ur-odn unyr1oc wsd4;4i47o g car, which starts from rest at t = 0 and moves in a straight 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. yrrw44s71du(d in 4-o nouco;Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceler)p9joq. 0fsx iation? How far did it travel in this op 0q sxi9.)fjtime? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its )6*czl 6mkoh-.ij l0lsyoum2 acceleratiokym uomz2j* i606)l. csho-lln, assumed constant?    $m/s^2$

  A light plane must rs)4t(k fakpn2i 3gzf6each a speed of 33 m/s for takeoff. How long a runway is needed if the (constant)tsgna)i32k6z f(4pfk acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blomon sg -7fy7n7cks to essentially top speed (of about 11.5 m/s) in the first 15.0 m n-m7nso 7 y7gfof the race. What is the average acceleration of 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 uniformly from a speed of 12.0 m/s to 4; 3e/isu5dlsvde/-nlf l sa:rest in 6.00 s. How far did it tfdel e:-ssd5l lu/;4 n a3iv/sravel in that time?    m

  In coming to a stop, a car e t6 ttd;5o jjk1y)/thleaves skid marks 92 m long on the highway. Assuming a decyh/6ottdkte 1j ;t 5)jeleration 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 eb4r*h *a; rm-zm2gpyhhtx2grc)f5 q(nd of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the colg22r bm4 r xqrc;g-(h z)hfh *ym*5ptalisi on? Express the answer in terms of “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 wig/,3wdbam 0v2d /tt7qax) hy qth an initial speed of 95 km/h and human reaction time of 1.0 s, for an acc,d tgmtwhqq)3 2a/a7y vbdx0/eleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stof/zcg2k:n u)tvn h..bpping 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 trujm4,a ea,.h6 z dqyja)ck going 25 m/s on the highway. The car’s driver looks for an opportunity to pase.m )ja46 yqa,,azd jhs, guessing that his car can 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,mje2curj.fd3 +g 04sigzs-r- 000-m run in less than 30.0 min. After exactly 27.0 min, there are stilsr43c .r-diszemuj-gf2jg +0l 1100 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?

A person driving her car at 45 km/h approac 4fn bf/b.a2lrhes 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 fa2n/.l rbfb4intersection 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.

  A stone is dropped from the top of a cliff. It hi ne m(;xr. cye*7xk/xits the ground below after 3.25 s. How high is the c* ikxye/(n7exr m.;cxliff?    m

  If a car rolls gently (w uqx ii90nydl)k2b b*0(k+ nr$v_0\,=\,0$) 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 air with a speed j j,-c26ptcy*fdy;h+dtctd jpg; 8+ j87zi etof 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after /1t0 bt ofbnbnm6g5vg i2q,t0 throwing it vertically upward. With what speed did he throw it, and what height did it nt 1o /b25q00, vmbtig t6bgfnreach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of .01 l/;zkn sgk1dcigmgravity. 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 k1c;sl0m idzkg1/n g .air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. l+qb0+ x)x4uw8h yxep6z)mmh At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals u xm+w+4 h)ylbhzxmq)x 680epthe helicopter’s.] t =__ s

For an object falling freeocg2. 2+-bg4xb+l gkn6(acluk l5c zxly from rest, show that the distance traveled during each slc+kb(. l gob4ung5 acxzgxl+62ck-2uccessive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (ae) j/s xve2 0acu4l(xyes(y (2fyowa* 8wkey/lgebraically) that a ball thrown vertically upward with a spee0kv(xoy4fl e 8 ay/x/c(y2weauyj e(2w*se )sd $v_0$ 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 18.0c mz/c b7mso4wiojme8;, a0*u m/s
(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 Fixg 5um;3wj u(osha(rdi - ,vl7g. 2–18 (or number of photofla,73gmjsu5o(iw ( dul; rhx-a vshes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel pas0 ki fmo9zvw:lei846 mt a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did f 0l4zem:mi8kv wo96ithe stone fall?    m

  A rock is dropped from a sea cliff 0 vr (r8l25he+mqqeog, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is th qvrm2 g(he8 e+lr50oqe cliff? H =    m

  Suppose you adjust your garden hoseeqlj(3 mir91 f nozzle for 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 vertie9j (fi1qlr 3mcal, you 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 wit v1*v9q3g 3bqn dn 9m*y9hkpgxh a speed of 12.0 m/s from the edge of a cliff 70bn qmqgnxd 1yh*v*9 v3k9pg3 9.0 m high (Fig. 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 by a window 28 m above the sto*0)a9uadp 0qt5.ra b.z nautreet with a vertical speed of 13 m/s If the ball wzd*t0ur o5. ) p0auqbaa9nt a.as 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 train as a function of time. (au(6pcfr*1sz05b osrg ) 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 0 grsr ubo*z1fsc5p( 6acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a ra/z d a8nwywxfrc8r4 7)n0rqz /bbit along a straight tunnel as a function of time is plotted in yzc8 04 n)8 rd/qw/wf7rarznx Fig. 2–28. What 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 acyehmm0b wmskk:3b /ue6w3 y*4c + ,szvcelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short fls4y e3 b,cm6mzksw be0*yu:h/ 3k+mwv at spots in the 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 previous Proble9a +44-/dm.fuhchxvjz * 0yvshde:w a5cw 7scm (Fig. 2–35) when it is in/ja-u0shwcy*h9h4dev.z:7 +f wdvmxc 5sc4a
(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 objectpu0 ,j;bp: +bol mb2nl traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a furmz kqch,yg9b nk; 39-nction of time is given by Fig. 2–2q9bm, g3- kh kr;9nycz8.

Figure 2–36 is a position versus time graph for the motion of an object alonal 9zw(:svmyk*9g/ w wg the x axis. Consider 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(ww /awsm9 kz*vlgy9: the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a +kfy 7j7nj-ic ..mn59hgkfa9js;ju kfjt. /gfirefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, j u9.kg f+jmn/nj;sfjakk-7cy f9gi j.7 5t.h 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 i hqbcu0g ru.o:b 17spfwa6o)(s about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many timewo0osrf1u)b6( 7au. :cbg phqs higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is propkmodq .10y* s;au0ge/h d5 excerly constrained by an over-the-shoulder seat belt has a good chance of surviy5h*d ;0a/ xomeds0q u1eck.gving a 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 the road below, xm/kd-2a4 ne hand 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 25nkxh2a/-em4 d 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 to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by haukw r9kn bb0czd 67v*9gling them up on a crane akk7gb b rd9vwz90c6 *nnd 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 travels t4qk9ny xy ,gaq:1zn0xesy57 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 uniform acceleratia/i: dp/bvx;n on 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 wherb;n/i :/d pvaxe the front of the train started. What will 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 h+xj0h- n,a z(kvoksvqck/81the 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 wah -k,q cn+vs/x 0o k(8ja1vzkhter. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the averagj2z-1 n mzy 7thfe82dze speed of a train against the distance between stops. The more stops there are, the slower the traizn2 2zed8-jmzythf7 1 n’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-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 when diving for fish u6rvqa(kjp7 ;2ly )qh. Suppose a pelican starts its dive from a height of 16.0 m j;q py6vh 7(qa)lu2rk 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.    m

  In putting, the force with which a golf:tttbue ty 1x by(nj(67,ru 7ter strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or ue :7(16 uytjtyrb, xn tttb7(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 ewbi ,9(1dav+qylyj;6p )s od traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest a6qwejsv )y( a1i 9pd o,ydl+;bnd 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 stoney8bo,zfwj166lgey w 1 is dropped 1.50 s later. How far apart are the stones when thl6o je6,1wfgyb8y 1zwe second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 kmifhs-/9un gmsi0f*t6 rh*:w r/h over the course of a time trial lasting ten lapsw*g shr:hti90nfm r 6/sfiu*- . If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he movesv+,w inbnw+tc+s -fs0 at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his averav n+sw , wf+-ctib0ns+ge acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The fir5 17 ) )lg8dymbzcrovgst child can bounce up one-and-a-half times higher than lv7dbgc ryoz gm)185 )the second child. The initial 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 traiq w xin6x2qdl:m3:k *0dw.nol3 k4 rfun traveling in the sq n3i3*ux2f wdd0:qmlk 6x:ok. rln4wame 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. 2–40. 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 throwing the basch 1l e8u81ixxeball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the bl8x8 uxc e1ih1ody 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, witw-ec vrp4, v:th 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 patfi9v,n tk e e2g9lwj(o*80ey .i4bfgilqeu)*tern shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the spee9l eeotffe (e,kl*08)vjg94yqwgn* .u i2iibd 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 l5eih,tc48ev at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a con 8i,clh4tv e5estant 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 from the roof of a building; 2.00 s af6afas 6aj*xbu a/ss1 (ter that, a second stone is thrown straight down with an initial sp6asjfa 1 (xs6/saaub* eed of 25.0 m/s 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 thgt a) fvb+rtapt4d w*znbe82kx452g :e same time. The first stone is thrown with an initial velocity ota4nfpdk)8z4gt *b2t5a2 wb:+g vrxe f 11.0 m/s from a 12th-floor balcony 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 resistance, how lonh6; q)xzh9nhgg 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? Wh9xzq hg6); hhnat would her speed be at 350 m? (In 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 send the burgers through aumxr:4vvri b m7arsq0 722oo + 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 b:msv722ooa rb+r0 x4v7im r quurgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 )3 c8asuzcj w, (4tgcbx u*p,ytimes faster than Joe can. How many j8w,tpg)xbcuzu c4* y(ca3s, times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below h-d(7zp y +txo7 hn3b/3wnbwnyou. You drop a ball from rest 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, suc7 ny7bz 3o h/ x-tbdw(h+wn3nph 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 buildw3s3 oy+4f 3ny-n)mkfy +td aving using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building a4my- vtfk3yd o+y) n+faw3ns3 nd 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 for two bicycles, A and B. (a) g- gao*-kt rlljw r)v 2idk*(/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 pas*irk *rd glltw )-gj 2k(ov-a/sing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?