Does a car speedometer measure speed,j j9pm4m:u q4v velocity, or both?

Can an object have a varying speed if its velocity is constan 3b d pamasb)an 1:ljbz/2xv1.t? If yes, give examplvmb x/ 2sa bj1b 1.dn)palz:a3es.

When an object moves with constant velocity, does itb3(adz : o:lnas average velocity during any time interval differ from its instd ( aa3no:z:blantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed cro.qyoqz 5opgs31:p3z kssing the 1po:gkq.pz3 yos q3 5zfinish line to lose the race? Explain.

If one object has a greater speed than a second obje9pl(4zkz-lk * kkxp+gct, does the first necessarily have a xlplzk+kz4 g k(p- 9k*greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km/h8df b(5( m-qxj (h+x2c iwe0cfe ujdx8 with the acceleration of a bicycle that accel mx f w+-jf2ieddchx8qj(50( ue(cb8x erates from rest to 10km/h in the same time.

Can an object have a northward velocity and a sot,qc vw) 5(qntuthward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? p zn0 *pmvk 4clyx32 k2l5u)zcWhat about vice verskpk vu 2zcpcyx*20)5 l m3nlz4a?

Give an example where both the velocity and accelerpk)/ xu6gh5sp. yh6kh. .c4n/sex3 tz do mvz0ation are negative.

Two cars emerge side by side from a tunner+ 4lhv1a+4g ojwepnw9 hxc68l. Car A is traveling with a speed of 60km/h and has an acceleration cw 1xhg+npw6r8+e9 4jloav h4of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as izs kg+xh;6-qzdii 6(nts acceleration decreases? If so, give ai6h6x qsz ;+k( zi-ngdn example. If not, explain.

A baseball player hits a foul ball straight up into taiga:(sm2r gx c5f,g3nw +wp3he air. It leaves the bat wngxg2amr, ic3p3w w fg(s5+:a ith a speed of 120km/h . In 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 hapkr(k dx .0v,v ac7 b3 jcxg.fmnn(5w)v*wy.vjpening to its acceleration due to gravity — does it increase, decrease, or stay thwmkr jcxv0k*,fj .n7v(bg (3).v v.a xdn5wcye same?

How would you estimate the maximum height you could throw a oj a3ud(-un 3pball vertically upward? How would you estimate the maximum speed you cjpun(3ad u3- oould give it?

You travel from point A to point B in a car movime. gkf t2(vx5ng at a constant speed of Then x 52vg.e(ftmkyou 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 not.

In a lecture demonstration, a 3.0-m-long verticd)26nylk v dyc- ,cu,sal string with ten bolts 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 clinuyydlvd,k -2c)s,n6 cks occur at equal intervals?

Which one of these motions ngd5r+86qrp v( /oa +t syw-tsis not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dg tvsrw6rda-nps+q5o +t /y8(ish resting on a table?

An object that is thrown veqirxt1j i4 s(x -t-q0artically upward will return to its original position with the same speed as it had initially if air rjttx ( q i-10r4q-saxiesistance 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 opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time? Givl 8i3 s*h*xm8igbb.dre exampllb**g8i x hdb.msr83i es.

Can an object have zero acceleration and nonzero velocity at the same time? wio mp,u6ykhu v7.e 3(Give exampleeui .wyo3u,h 6(7 mpvks.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, e /o5-s v1tycwhtc. [Hint: First try to duplicate the motion plotted by w ycso1t/ vw5h-alking or moving your hand.]

Describe in words the motion of the object graphed in Fiz6oykaq.6g )u(kh3 jlg. 2–29.

  What must be your car’s average speed in order tt e6lmds)0l z;wkr7 p6o travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long gk+*r h2kc .hvdoes it take to fly 15 km?    h

  If you are driving along a straight road and you loor 06 mz hrk:)/ps8mavgk to the side for 2.0 s, how far do you travel during this inat: )6a/shgzmmpr 8 k0vrtentive period?    m

  Convert 35 mi/h to bd z6no8 ,lii-2i.w gg
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro(rxd,xx21q; gx/qawese l x0hz.2g( r m $x_1$ = 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 sc pzfrok ).d6x(hool steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home aft ok6.r(pdf)xzer 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 lighfu/k tf72e(;v i0lg cys9y*raxa)j h5tning flash and the following thunder gives the distance to the/e yc*2av 5fhf)a( xg; yu70 ril9ktsj flash in miles. Assuming 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 complete laps around a quarter-mile track in3ysklmm; 5y 57h fvi5g a total time of 12.5 min. Ch5fi553 kmlg;yvym 7salculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in1yzn iw460yxdq d m5s3/ljfu0 a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfqy3 0yiuds/16z5d4 mf lw0xnjway 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 parallel tracks. Each j w+oqu 2 20ezmi:sbb8has a speed of 95 km/h with respect to the ground. If they are initsj oi2m:8ubq +w20ez bially 8.5 km apart, how long will it 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 it tf4rny g; s1+fuake the car to gyf1s4 nfu; r+reach the truck?    s

  An airplane travels 31,z zr83j:mmbr 00 km at a speed of 790 km/h , and then encounters a tailwind thatrb,mr 3m jzz8: boosts its speed to 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-trip in ak6g:)ke u :vnwhich the outgoing 250 km is covered at 95 km/h followed by a ak6):ukegn v: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 pins at thetmmu 0d-rn 4t( end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pmt0um(rn d t-4ins 2.50 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. What is its average(cny l0la z3yf1ig/ 8c acceleray3c /lfliyz(g1 ca 0n8tion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to6h n;soa3 d.fi+ba1j56kflpi 10.0 m/s in 1.35 s. What is her acceleration ip3 kj+5a6bl 6s d n.fihaof1;
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capableyr-0b1+eg5 +z aie-giyro 9yc;wwqp a:w .aj6 of an acceleration of abou wc pa aijy9wrgr- w+e:a6i-oe.qy0b;gy5+ 1zt $1.6 m/s^2$ 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 in 5.z02r3voax ;jk 0 s. If it then brakes and comes to a stop in 4.0 s, what is its acr2k0voj z ;3axceleration 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,m59 an ludbi6k7 s,j9a which starts from rest at t = 0 and moves in a strai79m u lakb,ias6jn9 d5ght 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 pyg ddi,h3:d8g p* v+ ep/qk0bx(m 3pfs. What was its acceleration? How far did it travelpg8xyfb/g(+d:k,dh q mvp0d 3i* ppe3 in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s tor3lm9t +;llsjo0nasn e+ q3h5 rest in a distance of 85 m. What was its acceleration,3r a l+nl90 hqts+3smle oj;n5 assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway i41)irrvv b 5wa89ia 8cvuo:rt s needed if the (cons5vbi4iavr1 )8c: r tw 98uovratant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks(4 m fkvl ngh4q)pj6pe *lj:g1 to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long doesll6g pq hv4j* :j p)ngf14ke(m 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 resaoq;7b lrq3g.l4m5 be t in 6.00 s. How far did it trbb7 gm laeq5l4r.o 3q;avel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long sdpzaj7t( rd k* s+.-/ncmqy:p(c+y hon the highway. Assuming +hqpak-sj*my:+7pds/ntdy zc .(cr( a deceleration 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 compressef7 uc5w*+ 2ny m0pyfvms 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 answeffpmyw+n0 uvcy7 m*52 r 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 with amd6a:ouqd /y yu6wztr /t;9 z/n initial speed of 95 km/h and human reaction time of 1.0 s, fqztzot6ur; y y dm/:9u/6d/awor an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping di+jb p ep0tn2/b nci:q:stance 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/s on the highway. Thhip707y x/jshe car’s driver looks for an opportunity to pass, pi7x07yhj/hs 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 1 k0b8f wsq4h,oso mgly.j 0t/br,:lr(0,000-m run in less than 30.0 min. After exactly 27.0 min, there are s,:s. bkgolm8,b 4 hor(0 w0trfjly/qstill 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 approaches an intersection jaf.gpsj5gw7 hlr.n, .ust as the traffic lighwga7 ..,gr5j .sp hfnlt 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 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 t,7 8uva w k;hr*d)uhxn*xw x6kop of a cliff. It hits the ground below after 3.25 s. How higkh)d k nwx*;xrx7*v ,h6 wua8uh is the cliff?    m

  If a car rolls gently skz 7x*mrx+ l6j0d0aef2y9 vga;sm6s ($v_0\,=\,0$) 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 sze30gx r)9 8dqb/xnfgpeed of 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 throwing it vertically upward. With w 3ocl(c(( 66v efnic-uzoq 9cmhat speed did he throw it, andc ezif9cclqo (3cu 6-6vo(n(m what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls undxxc-t7 x9mq 8her the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a futxxq m897 -xchnction of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height of2 +op13z dacd0ck(u --z mznjj 125 m above the Earth, a package is dropped from a window. How much time does it take for the pa1n2dd- 0jzc-juk+cmp oza(z3 ckage to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling18bp qr4wlxtsx;h *gj)l ;i,p freely from rest, show that the distance traveled during each successive second increases in the ratio of succes bw ijrg*x;1px8h t,l4;s)q plsive 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 (algebraically) that a ball thrown vertpw,p)d :jz 3ym dcgfan(qy6(7ical:dc63 g yzj),ap(w7dqn y( mpfly upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertica/ kw s6,zh4oahlly upward with a speed of 18.0 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 be0ia3y m 8yg5nytween each photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hingy 05m8i3nayy t: 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 past a wb3 3a ) )2ft8mcnbllfdindow 2.2 m tall (Fig. 2–32). From what height above the top offn2d)t fll8 3cmbb)3 a the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikingv6d7 -y1:svl2 etx ;i/m xrnlk the ocean is heard n/v xye-rxdlvts:6 1 i;lm72 k3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nihu6tci2 4x b6ozzle 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 vertical, you hear the water striking the ground next to you for another 2.0 s. What is the watxit642u c ibh6er speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edgo vomf:.54bjj bj54ege of a cliff 7ojb:ev.j4f 5mo g5j4b 0.0 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 abovidmjy ;l2(w7 v 0k2)r e(cofxge the street with a vertical speed of 13 m/s If the ball was the (2d xijkly;cmvgf7or(2 w )0rown 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. (a) At o fw:m.j p)7wuwhat 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 gf.jmo:u wp)w7 reatest?

  The position of a rabbit along a straight pns4i q;et )0b+2umds tunnel as a function of time is plotted in Fig.)s0eq +mbdup;tsin2 4 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 accelerate approximately as 9p tpd 6-asv,os+*sgi shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gear 6a sdvsitg +9opps,-*s.)
(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 Problem (Fig. z 79cg nwq8)x+o ghj-h2–35) when it isc7qogxwh8h)jng+ - z9 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 object travel8ci) vn;nk3g+gk qm+ bed during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object wh9obp/lr;pu, -( sk tdoose displacement as a function of timeoprkd9;(t, sl-puob / is given by Fig. 2–28.

Figure 2–36 is a position versus time graph bcq,q9+boh(z :q8 vwp for the motion of an object along 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 slowi89wb(ph:,ozqv+ qcb q ng 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-story window 15.0 m above a firefighter’sdf ,h uub;ej0scoz :3( safety net. Tshu 0;o ,u c(ebj3fzd:he 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 about one-sixth what4la i* .aiy2km it is on Earth. If an object is thrown vertically upward on the Moon, how .ly*m 24aiaik many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-soub 7wzgw8wl swd83.-houlder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 zl8o.wg sww3w7bd8u-“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 standinedls8kp*d ) *-8b.hv ry t2xczg on a bridge, 12 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 ix*e.dc zy*s)bp tl8h 2vr k-d8s 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 to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cvfp*ota,pr 1,* 94w wpub ..mmg:pdflars for front-end collisions by hauling them up on a crane and dmp.a.*4wbfld w,m p rv9:p,t p ugof1*ropping 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 z7d*o) 9b*yigdqx/jnhe(545zxl xv yabout $10^9\,km$ 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 acceleration from rest. The front of the trai7px7.vkao a+in 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 will be the speed of the last akv+ 7o7a.ip xcar 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 deep ppq. o r qs,tjza;299okool. The person’s downward motion stops 2.0 mzk;qt9jo9o2qrs p a., below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit syste5/ pxhf(owb y3m, it is necessary to balance the average speed of a trawbx5fyhp( /o3in 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 9.0-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 whezh :dx746ny51hch eh wn diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. Ifc4wzdh heh:51n hx7y6 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 with8s) y ;xgi2k;avzom*h 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 downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume gaxk8y* z os; h;ivm)2that 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 freongn t/ +2tohey+3c( xight train traveling at a constant speed of 6.0 m/s Just as an empty box car passest 2nt en3g(xyco+h+/ o him, the fugitive 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 saz9cu k2 9-l:mea b-dstone is dropped 1.50 s later. How far apart are the stones when the second one has reached a sklac92a--b:zed mu9 speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial / c 9zo;-bbqmilasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be;-mb z/ obc9qi maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he movesdw w-oh9vxfmfa*q.nmd;1- )s-ap8 n u at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was hisqx usw9f np8nmm;oa-f dh. vad-- 1w)* average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child1z3pya n0 tum y*9yni0 can bounce up one-and-a-half00znym9pn y 13i *tyua times higher than 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 a1 vvg 0ndo-c9 ,+nbl qjw3ai:95 km/h overtakes a 1.10-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. 2–40. What are tha-3ld:,+j0nnw icv ba9g1 q voe 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/se-1) arx1ofbl q/2b ks In throwing the baseball, the pitcher accelerates b lkafbx1 oq)rs/2-e1the 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, fr 0acrcfx,uf.ydbh9( 8om rest, 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 sh 2z00wpeo3npdnh b0 z*/ny3vjown 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 speed limit. p0n3w 0 ezzo/h3*p2 n vyjdb0nWhen 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 m rw).m2)j.twxk g;glg/b k 6cat a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, main)m k/gjbkwcg;m)rl6t wxg ..2taining a constant 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;bt.s q./9-y ,9acec tq7b orhz 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two sto-b hs.bz a9occ,.97 qt/rtq eynes 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 the same time. The first stone is tau+1fnh9 (6)dau.kv o60p nm nxclr :shrown with an initial velocity of 11.0 m/s from a 12th-floor balcons6m1kr)a :uvhdc +(n06xanuon9l . pfy 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 long would it take a free-..m rebgphl- 75ai 1jk 1wh5gcfalling 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 whb l j1i5ge5.7cmkrg. p -1ham? (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 throup s,1itd.:9 l2c tspsegh a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast m d s.e1pt2,s:ps i9lctust the conveyor belt travel? If the burgers 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 times fa+a2y c*igec8aster than Joe can. How many timei*agyc+c28e a s 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 grq o4n,se :yde(ound below you. You drop a(qye:nd os ,4e 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, 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 m d*:qjsgt(k; height of a particular building using a barometer. Instead of using the barometer as an altitude-mea: j(; tdqskmg*suring 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 for two bicy eyl358 /,c w6lndiintl9i-q ocles, 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 velqnnilw3 65e ciyo9,-dl l/ti8ocity? (e) Which bicycle has the higher average velocity?