Does a car speedometer measure vz m(i i-;wbp+c 2aeta(u f6y96ft:ejspeed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, g iorx)* khn()m com36k1ocuvl20be d* ive exam 1e6x*l omcuk2 brcoomdivh03* )n()kples.

When an object moves - xjiu7pqbc)z+t5;o ywith constant velocity, does its average velocity during any ;x5b)qoup+-c t jizy 7time interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for4supj .0vd k9cm(c fx) the car with the greatest speed crossing the finish line t9k uf.p0mc(x4 )sjvdco lose the race? Explain.

If one object has a greater o2fr u5 6e s3yumc0zl(speed than a second object, does the first necessarily have a greatermes560u( ocu l3rfz2y acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that acceleratesp .u i9)/mvutdqe hb31v7ei2k from 80km/h to 90km/h with the acceleration of a mv.t)v e/7kbhi2eudp1iq3 u9 bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acce zu0t;1l./ciwk*4x1i gk.j uxud:jkr leration? Explain.

Can the velocity of an object be negative when its accel 0+xoumzfzu m4t8 c97rie18d ceration is positive? Whate1 c fu7+irz 0zd9c8uxm m48ot about vice versa?

Give an example where bothxxbu,)a 3m 52x3fv,bw q mwx-tfw;8p0lnz2xr the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. /z noxv.ey(1i) o6m jrCar A is 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 is passing ve1jm i y(x6/ z)ono.rthe other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, p +lz .x zn85jme8-kisgive an examizk x58e-+j8lzp .nmsple. If not, explain.

A baseball player hits a foul bal-ekzgh2vkgs07g 1 o 2ll straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fasez0hk- 7gl 1g2 sokg2vt will the ball be traveling when the catcher catches it?

As a freely falling object speeds upw(bq .pbq1ou rm62(ru , what is happening to its acceleration due to gravity — does iq( rbpoub(mw6u qr.1 2t increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vl9u03h/ namzbjjt )umw, b2 q6ertically upward? How wo 2z,m)ujtna m3blh b69u0wj/ quld you estimate the maximum speed you could give it?

You travel from point A to point B in a c 6pd6vyz6*v m nsh-)v*oy2ru tar 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 average speed for the entire trip from A6z tn6vo -mvp)*v*6y2hydurs to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long ve *;;uw1hv lfzqrtical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lec; vh1 flzuw;*qture 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 equal intervals?

Which one of these motions is not p 6md4gfb1in8v*m1ph tl 3c5k at constant acceleration: a rock falling from a cliff, an elevator moving from the second flopb1t *34d v5pcl8 gfkmnh1i 6mor 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 pos*xf6mq,ko s;3 p6qwmev 8gw rudl/+)cition with the same qml36sg,wkpcd+u/e v;xf8 q*o)wm r6 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 opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same tqksz1 2+cpc7/dj *xjsime? Give ex27 qjckpj ds /+1*sczxamples.

Can an object have zero acceleration and nonzero velocity atstw a:z)c)e9)j,zg*qs tk mav,iz 6 u( the same time? Givettq*a a)s9 msi ()g6:zz cv,,zuwe)jk examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: a7plun(j*k e 94i) yriq 5txq/First try to duplicate q7a)lyq/j5 xpn(t*euk4iir 9 the motion plotted by walking or moving your hand.]

Describe in words the motion(rzv74urgna jrk*j +z vbzcvd+5 yx0hf6 7c,1 of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 huaa.qz 4i,lgz3aiirc16:ws ;?    km/h

  A bird can fly 25 km/h How f7f gh8 )qkyzm+qa3 itsk+p4h h;8t9ylong does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 s,8p8m9mc(n r kx how far do you travel during this inattentive per(p 9rx m8nmk8ciod?    m

  Convert 35 mi/h to 750.;qyfku ip,ops md
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from6d0gqltctmn :a4nv*rn p(ri,8 rrk499inwc / $x_1$ = 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 for 130 kur6boh*-8+wuwl/- i y *h45dli lkxpsm. It then begins to rain and you slow to/byld5uk* +l4h*o iw6r--p x iul8 shw 65 km/h You arrive home after 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, evyimd,db;*vta5lz/1 90jb3 nw v wn k) k8vgb9nery 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 essentially no time at all, estimate the speed of sound in m/s from this rbn58gbk/zv nlw9tmv d0,*ki)b3ja9n;w yv 1d ule.    m/s

  A person jogs eight complebx1pql kpu*-w+jwa (9te laps around a quarter-mile track in a total time of 12.5 min. Cal- +p9xw(1ka qbj pw*ulculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, movin o(hol5ini6x (g 116 m away in 14.0 s. It then turns abruptly and gallops halfway back n o 6xilh(io(5in 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 p6-y-nuok7trrr0 yt3each 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 be before they reach each other? (See Fig.p -o3rnktuyy0 t6-r 7r 2–30).    min

  A car traveling 88 km/h is 110 m behin c uu;s6fbzu3x5 xmkn0: )cj7dd a truck traveling How long will it take the car to reacs)cczxx: 36 jnu7fb muud0 ;k5h the truck?    s

  An airplane travels 3100 km a,k axpf58/.ieh(ryid gga5-a t a speed of 790 km/h , and then encounters a tailwind that boosts its speed toagr(di p-fea 5/ ykah.8igx5, 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 ivc n(8 o)s.du;www*i which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km ;wsw*.uc ivio wd8()nis covered at 55 km/h.    km/h

  A bowling ball traveling withzs *by.w(i5ypfo;)98psnt ad constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of t p(nz* ;8ysb.siw 9dpot)5ya fhe ball hitting the pins 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 lm+olk)t,ui r s;y k3z 0*ml4s6.2 s. What is its average acceleration usm;s kly 0,43ok +mzl i)tlr*in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to- ch2 /p;swkuq 10.0 m/s in 1.35 s. What is her acceleration c /us- h2qpk;w
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablewib q9p12v. h:s 2galyao59ft of an acceleration of aboutvo2s1 5i92qp.ay9bgltf aw:h $1.6 m/s^2$ 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 5.0 s. x,(bbd 1i +hsxfp n3 j/ xxe,8nsuz:1vIf it then brakes and comes to a stop in 4.0 s, what is its acc1i/zp d1(,xs8xn,3 hf ub+xev b:ns xjeleration 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 tq nu91y7h6 /k.ksnkfpbd 2( nd = 0 and moves in a straight line, is given as a function of time in the following 1u92b/dnhnn .qf7 kdsk(p y 6kTable. 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. What +5 qmcbg: .wj(gi7efywas its acceleration? How far did it travel in this time? Assume constant ac(ymge5:gb cwfiq.+ 7jceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a didxa8x:ac eq big,z1 /g1) o-gbstance of 85 m. What was its acceleration, assumed b8-gcxaagg:zxb/i ,) q11de oconstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runvv,ods dni h) ,iji+y1s46 kw8way is needed if the (constant) acceleration isv4is)iv +jdyo68k,i d1wsnh , $3.0 m/s^2$ ?    m

  A world-class sprinter can bu39 zlag9mbgdj9 y4uh9 rst out of the blocks 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 does zay9uh9 lgjm94bg d 39it 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 rest in 6. ge yh4*xh(nm 1u8f*,mhyo;et00 s. How far did it travel myy ghone*e*1(; xuthm,8 h4f in that time?    m

  In coming to a stop, a car leaves skid mlt) ,a /lieva5arks 92 m long on the highway. Assuming a deceletl/a)il5, ea vration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h striosmlk 93:1c cwkes a tree. The front end 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 collisi on? Express the answc:s l1m9woc k3er 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 an initiw701n63 ebjbk1x np skal speed of 95 km/h and human reaction time of 1.0 s, fnw sk1x0e b1kn37j p6bor an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the s b,ot 5tfg/;bx3 r6jxttopping 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/s on the highway. The car’s c6-:1o56 k o:le sfc folafsl8driver looks for an oppk:o6cl-c a ff:sl8les5o6o1 fortunity to pass, 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 10,000-m run in less than 300 z6scox1ee-iv 0wh(j .0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then ac-xhic ev0 o10(ewzs 6jcelerate 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 just as the traf-/bql.vr:4mvek pd)g( g0 aqzfic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away fv 4)gq leg/. -:q(mkar z0vdpbrom 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 top of 9-(v8p-h90k0hgox:q tq yif haset2pa cliff. It hits the ground below after 3.25 s. How high is the of t- sh q82yh(epp h:90i0vktgx-q9a cliff?    m

  If a car rolls gentljc:cwl82v-+;-,0muz vy2sw j, rbpgfv 0alr cy ($v_0\,=\,0$) 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 w i5*gljgx/xzjy/2u- speed 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 upwarf,kx3 tskax/a7wm6s )d. With what speed did he throw it, and what height did ita,x/3skx wf7 tk sma)6 reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravy 5oluq e 0e)v-mpjg2 ur1/2st cov6wqhc8q94ity. Draw graphs of (a) its s r )h28 uuq1qw45s vc6m-gvpt/ 2cleyoqje0o9 peed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with6acsd0 2l 1jut 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 time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =_ltd 0a1su6cj2_ s

For an object falling freely fro t :*6nq( il hnkvb44xzju.;wom rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). Thi jhqu4n l(bo;:wtnvx. ik 6*4zs was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected,*rs:7y6oqx j :o1)a7htggwp q show (algebraically) that a ball thrown vertically upward p*wt:1s aqjxg6hoqy g7:ro) 7with 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 n 5wfs6r bl,0pje25iylly 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 between eachy v;g a6d,vyj l9;ct oc+f(rgi)(lg5y photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume cv(;g()ra;ilyy,6glf o dt9 cgv+5 jythe 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 trav8.-a b;:spi;h ahc uzuel past a window 2.2 m tall (Fig. 2–32). From what height above the top czup.;s:ha a bh8i;u- of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikingcffox. mee c57v/5 q9tbk)8hi/ 5daxg the ocean is heard 3.2 s later. If the speo5 f.hxgatxqbv ic5) 5dc7/m8efk/9 eed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your g)n 8 uw9imo*bbarden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m 8 iunmw9b*ob)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 water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge of a ,acuvhn a 0cqu0oz)/1ct ph /9cliff 70.0 m high (Fig. 2–34). u,p 9vahntzohc/0 1 )cc q/au0
(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 28hx;nxx)haqjl-2y. t 9 m above the street with a vertical speed of 13 m/s If the bh -;. 2q)9xt jxnylhxaall 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 train asvbc8*a5 a;o ho a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude a 5vhc8a* ob;oof the acceleration greatest?

  The position of a rabbit alon :rsy)yc 88lwk8uy ;jhg a straight tunnel as a function of time is plotted in Fig. 2–28. What isuh8 y jl:8yrykcw)8;s 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 automobilenftm l( -+m-1t xfz0cg can accelerate approximately as shown in the velocity–time graph of +z0 tn(g1ffxcm --l tmFig. 2–35. (The short flat 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 thp 92sbodx*v1ye previous Problem (Fig. 2–35) when ib *d92vs oyxp1t 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 object m zp(f9m( 1w1whjxpt( traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t grapgymqmp1i 7 9t01zb3ejh for the object whose displacement as a function of tt1 zji1gmq0 mep79yb3 ime is given by Fig. 2–28.

Figure 2–36 is a position versus tipc6psav)-otuouv7d.9* 4yf mme graph 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 slowing down? (f) Is the acceleration of the object positive or negative? (g) Fou v)fy6pt97o-up m.d cv4a*s inally, 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 fiayi-sc2y 4npixsk ./1 refighter’s safety net. The survivor stretches the net 1.0 m before .yia2s xc/ kn-4psy i1coming 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 toehpfe4m 2z 5b :3)b1i,yoo fhr gravity on the Moon is about 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 Earth, as4o3h:zhp ybb i,e52em)1rffo suming the same initial velocity?

  A person who is properly constrained by ae u0t1kafq 3/myglff7q6 olrxb+v 8+.n over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does n xqf8akf/ 1or.u7+ 3 fmllq t0+b6vygeot 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 standim1* rwxm s/d7 :b0cuohy;u,wdng 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 tsoc7*w/yh, 1muux b;dd wrm:0he 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 to make his getaway. How many poles is it?    poles

  Suppose a car manufact evppcc xm7/zhue*;,.urer tested its cars for front-end collisions by hauling them up on a crane and dropping them from a certain height.zhcp;.7ec p,x*e m /vu
(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 tu fl-5fqc5e4s.ttv( 5pi7+ +lb z5ij1ks uxveravels 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 acceleration from rest. The front of the traib1vp7q p ;yu6ln has a spe7uvyp6;1q p bled 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 car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above7-63x; iq *eqyui lquw the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the aii7wyqlux q-3; *qe6u verage deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary toena1ii j aqt)pi3/0j . 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 a0jpiaij3i. t 1nq e)/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 fp+wln0,c8fi n/y9k lmall straight down when diving for fish. Suppo,n n8plc9liym+0/k f wse 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 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 golfwif 5 f 1kur0yii-v1v9er 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 morerv 91i5f 0ui wy1ifv-k 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 traveling at a cony-ibg2wre -w+:2mzc mstant speed of 6.0 m/s Just as ecyb i:r2+ 2gmzwm --wan empty box car passes 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 stone i2cw3 so0xk*fu s dropped 1.50 s later. How far apart a2sku3c xfo0w*re the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over3g:bdkb l;s/;f 8hrbk( ay rp1 the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what averaksfd/g3k 1bb:; 8rhb;y( rlp age speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves)- nf1x80 zdejlco r-n at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . Whatn 8dero-cj -0 n1z)lfx was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The fir ,v0yt kvo6p toxnejh5o,70, dwv;c2jst child can bounce up one-and-a-half times higher than the second chil05j7o0othx2 t,vp;eo kjwy6, ,v cvn dd. 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 train traveling in t zwb+i k)jp1pud.6 vx4he 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 tr4iwzp)kupjbv .6d+1 xaveled 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 rlw*1 r a o:tsi1m2k5mwith a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the bom1krw a: to 2rl*1s5imdy 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, with an ftcoum2 +wecx8 :kd fc75s+8+mx*j rkacceleration 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 patoomsqi7w.c m*+-d y).asyp(t 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 speed lim.s-+po(c sy ayoimw 7)d*tq.mit. 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 a constant 120 k:)k-uvu t b40bmwe , kjzu):ndm/h takes off in hot pursuit. The police officer catchesuudvk) jm)4b z -kewbn:u,0 :t up to the speeder in 750 m, maintaining 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; 2.00 s a+n6c / bhc4+jvndtxe+s1w by5fter that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stbsyn ct5 bh /+nx4+e1vcwd+j6ones 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 throwcn)v k ej:l:7nn vertically up at the same time. The first stone is thrown with an initial velocity of n7ljk:vc )n:e 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 reu *o 5cm64wobjsistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an owc mo5*46 bujaltitude of 350 m, where she will pull her ripcord? What 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 belt18i;fun 6wj y2ln(6ye m4gbx :zvk)zh to send 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 pr 8w;4 kefhgz6) 6:( zilyuvjy2nnbmx 1oduction (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe caugvfqm vp661 g bab7y,;z-e(vhw0fk- n. How many times higher will Bill’s ball go than Joe’s? ,fgy0k 7b a;6p-vf(6vgvw1zhu-b q m e$\approx$ =    (retain one decimal places)

  You stand at the top of a /5vy:l yal9b21h jrxq cliff while your friend stands on the ground below you. You drop a ball from rest and see thatrylh vq2aj5:91y /xbl 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 ,hr dh*l,qjj5 8e9mop particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reppoqd lrmj * heh,98j,5orts 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. timeq +,lrb 8bks7f graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has th,r8 qbk7b+fs le 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 average velocity?