Does a car speedometer measure speed, velocity,1 /pks7qxne8+p7pt/qs h0,rm jdg(3at z* aud or both?

Can an object have a varying speed if its velocity is constant? If yes, give exg,p8y5slv*ex 1;ae l:ql(/q at fgdn7 aq *x:aepygq;desv5nlf 18,la(t/l g7mples.

When an object moves with cono:)ff 1h9 (zz:jml hsdec7 /rnstant velocity, does its average velocity during any time interval differ from its instare9fc z f7ozm)l(::1jnds hh/ ntaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossingh228l0ua wvrp mu4eo6b:zl; h the finish line to lose the race? Explaipr 2zh:ohal u4b 8v6 l;0em2uwn.

If one object has a greater speed than a sek)k1pvr fwy )5cond object, does the first necessarily have a greater acceleration? Exp)kpyrwf 5 k1v)lain, using examples.

Compare the acceleration of a mol0-2i 6yds lqttorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 16l dtsi02 l-yq0km/h in the same time.

Can an object have a nort0pz eiog s6+d0hward velocity and a southward acceleration? Explain.

Can the velocity of an object be negbt45;o 9-dq q* 4apam pphpw9vative when its acceleration is positive? What about vicehva9;wo-d*qmpb 4atp4 pq5 p9 versa?

Give an example where both the velocity ve q5v:+kj a.aand acceleration are negative.

Two cars emerge side by side from a tunnel. Car Auh,ep/s (zrq0 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 the other as they come out of the tunnel?qp0u,r sez h/( Explain your reasoning.

Can an object be increasing in speed as its acceleratio3(jt9 m4o6s vfrkaq np-0/m qpn decreases? If so, give an example. If -3nj m( ptkf9q6 r/aopv4qms0 not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the/- xz8p(q z qvq2kxoz8e5m s+i bat with a speed of 120km/h . In the absence of air resistance, how fast will the b i-2 koq 8mex5pqz+z(q8zsxv/all be traveling when the catcher catches it?

As a freely falling object speeds up, what is happenixuts+d 5goqs9.m 5c3ing to its acceleration due to gravity — does it increase,os 5dg .xst39+qcu5mi decrease, or stay the same?

How would you estimate the maximum height you could throw a bal ot k*nij)uf-qlg- b4z2*tmx1l vertically upward? How would you estimate the maxim2gmz 1nxj*qitl kut-f4*b) - oum speed you could give it?

You travel from point A to point -boe lbu:gm.v1h1q cu- 3q+ s 7rkc0plB in a car moving at a constant speed of Then you travel the same distance from point B to another poicrpb71km cs-0-1eol3 v ugq b:q+h.ul nt 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 demonstraep;xw3vm b)(y 4di 6ul69tkwe tion, a 3.0-m-long vertical string with ten bolts tied to it at e p v6d;uwtb9l i4k6weey 3xm()qual 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 equal intervals?

Which one of these motiost r l9 snix,)2-wqy;qns is 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 dish restingnrq)ylsx ;-w9sq,2i t on a table?

An object that is thrown vertically upward will return *z5t cle :gd qz*mau82to its original position 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 accel5ale*qt mz* dg8czu 2:eration 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? Giv8tq bi,bkp)49l ww 7fbe examb9q7 w 4bb kt)lpi8f,wples.

Can an object have zero acceleration and nonzero velocity at the samew2w2wz3;w:tb jnr 8ma time? Give 8w23n zb; mw: 2rtwajwexamples.

Describe in words the motion plottefi1qifyv ;;v-d in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving yyf1i fvv;qi- ;our hand.]

Describe in words the motion of the objp()r lwmedv , +ne(fr4ect graphed in Fig. 2–29.

  What must be your car’s average speed in order to t jk((,f)yteejravel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? za4lp,cb. a-h    h

  If you are driving along a straight road and y- -c /ozo j+l6z5trjksou look to the side for 2.0 s, how far do you travel during /kl j6j+5rz-cto oz-sthis inattentive period?    m

  Convert 35 mi/h to /(+, upvr/dc wbe/-o+z bc*gi etljs2
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from egxs 1.x ::mi8gwvli5 :( lhq8flr,ic $x_1$ = 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 km. It then beginr+cieh*5bqerh 7 omf9)0tf 6ys to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 m9 yhieqrr5fe fo*0m+b 76 )cthinutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning fla ns2- hbc:wnv)sh 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, estis: -hcwvn2n) bmate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a qu izw q fe,4z a*g5cyxm/(rb3*iarter-mile track in a total time of 12.5 min. Calculate ,b 5 z y*wga/mx3rq*ez4 c(iif
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straigb8+m 1x,id gbmht line, moving 116 m away in 14.0 s. It then turns abruptly8idm1g,bmxb + 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 parallel tracks,wydyz48s0/ x,ri bi b0/qje q. Each has a speed of 95 km/h with respect to the ground. If trw4,e/y qs,qy ix 0jd0 bibz/8hey are initially 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) xyrj0 /fezx6 How long will it take the cx/rjz6e)yf 0 xar to reach the truck?    s

  An airplane travels 3100 km at a speed of coeyj,3 l z es i7/kh1mta.4,/c9mpnk790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for thepk1 4e ak3j,t.e ,/mcoms9n hzlc 7i/y 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 ,yznl vlr++gp / j7ym.of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed bylzv/ .mlynpyj+ ,r g7+ a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball travelinggm tja9d (18bp with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound 1b dajgp(8t m9of the 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 remoh z,m-wn: 5qom-jy* oen,:vst to 95 km/h in 6.2 s. What is its average acceh-m,o,j o - emzv5nny*:wq m:oleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hzo -pcn7pv/( zer acceleration p/-7p nzo (vzc
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable o6dj7i:gt a v)5sq5u(g9 jdznaf an acceleration of about dgsnjijdzaq9a5t 5ug6 v7 : ()$1.6 m/s^2$ 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 travel * 1xricm;ptlp4lv -0 g6o9prrs 110 m in 5.0 s. If it then brakes and coc6pmv*p149tp0o-lgxr rlir ; mes 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 racing car, which starts from rr;p hhrodi , pxxa;/(5est 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 tx/ , 5irr pda;(;hophxime. Display each in a Table and on a graph.

  A car accelerates from 13 gnekuy) l7q*0f(:r djm/s to 25 m/s in 6.0 s. What was its acceleration? How far didq7urfj l0:kg*ed n(y) it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Wh33yg 5 ,fjbp8v 2i nod9r,cstiat was its acceleration, assumed 9t3 c3fdi 5 ypgoibs2,,j v8rnconstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s fo8p+8aiw cdldhp:3 5rnr takeoff. How long a runway is needed if the (constant) accelerah 3p+niladc858 pw:dr tion is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentiail3c qvy9 .buy2fn/4i lly 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, lyyv.9 cf32/ bn4qiiu and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniforpg sj0es/p n wg: ih52v5f*nr2mly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that e2i0fgs*nwngp5 rj2h vs5p/:time?    m

  In coming to a stop, a car leaves skid marks 92 m long o 9qf a9 ag/-f(krig/o.6juc ehn the highway. Assuming a 9 9 fu(/crhfagqg6ji .kea-o/ 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 froneu0r (tn) *rbfhcm7j jb x58j/t 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 /5jrbx * )mn0rj8jhe7uf(cb t 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 with an aj p6gdaqb/9 97wv6yuinitial speed of 95 km/h and human reactiqa796y /jb6pa 9d uwgvon time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation dv zlyd41q damr4,32vfor the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck gc , xq96 vct9ov7l)wycoing 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate at67wlc,c9x )ty ovv9cq 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 l 3*cw(te5aapobw6ga*ess than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must th*pae6oaw w(a3 * g5ctben 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 inters7apd 0ha r p6)nsrk*1uection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 knr170 dua p6 p)ar*shm 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 hits the ground below after, :5cbsu0 j+vprzo3wf *k1t le 3.25 s. How z0+:s5fwe3o brvtck l* 1 ujp,high is the cliff?    m

  If a car rolls gently (8jon )tb, zdk8$v_0\,=\,0$) 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 awz* yl3 20uyji 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 upward. With 7i7;- ,wuf1 jijewyqzl0 f5 ed,v5mjxwhat s;f jw ei-e7d 51,f5wv7xqlumz j0 y,jipeed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Drawjh r;7qgq o3:a graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistano7r3agqh; jq: ce.

A helicopter is ascending vertically with a speed of 5.20on;mg 15x : s*vgaq8gn m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much tgn5sx : ag*81m ;nvqogime does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the d*d g.wkxx 9,jxistance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figwxkx xd,.*9jgs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicalr( hyuo /gn876qg qg:qly) that a ball thrown vertically uyhn q7g goqg/uq(:r 68pward 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 vertically upward with a speed of 18.0 79rygu*ie j , 4j.swfvm/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 Fig. 2–18 (or n 756qpsz7roa0iczr ( aumber of photoflashes per second). Assume the appls apr7i5ar0qo zz(6 c7e 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 past a windw7xw6vhh 85bzj ;p.qxow 2.2 m tall (Fig. 2–32). Frohx7 ;bzw wqp65 vh8xj.m what height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking th2- ijs 4en*rxbe ocean is heard 3.2 s later. If the sps42r*- nbexi jeed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzllf vf wf91tn/ y2+yoo)mmy(n2e for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the mf lfvm+yn9wnf t2/2( y1)oyoground (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 spem z62wzb a8sn0ed of 12.0 m/s from the edge of a cliz6ns a 80bzw2mff 70.0 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)u6e1on 2knlxj * 4zwc by a window 28 m above the street with a vertical speed of 13 m/s If the ball was throjncz4*w26)1 nku le xown 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 ti +r/zszf nsxc7j;5i.e ; zwu1rain as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what pes5rf;;iw.+ zi/jn71xe s zz ucriods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbijk ehmh+r1(u5 o yyigyu8 e8+6t along a straight tunnel as a function of time is plotted in Fig. 2–28. What is its inst5+yh8gor h8 1uju+ey iyk6em(antaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in the velock( .gy: ds 0 5a-exh8lgh6jmlpity–time graph of Fig. 2–35. (The short fm hdhs8l (- a xl:0y6ggpkj.5elat 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 accelerationar.u,si g wjq xlqzqr0ef4ip- .nd+ *ybc-41* of the car in the previous Problem (Fig. 2–35) when ialpcb iqje-n *.4qw,s xid qy*1f0. u4+gr-zrt 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 objec r/iodxp 8e1v4ql1qg gt9-vf)x ) xj8zt traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functi cgk9w-7)ni kuon of time is given by Fic wk)ig7u -9nkg. 2–28.

Figure 2–36 is a position ve h s;ttl,v-h/xrsus time 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) F;s ,-v/lhthtxinally, 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’s safetyg)b g;j*;a bhv net. The survivor streg;hj gbb*;a) vtches 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 9qdxo *o/y wz8about one-sixth what it is on Earth. If an object is thrown vertically upward 8qd9*woo/zxy on the Moon, how 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-shoulder seat belt has (.e/s, djyk uca good chance of surviving a car collision if th,.y(/jcud kese 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,s 5.*rdsmbn5 ki7b/ xt 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 is passing are 25 m apart in this country. The bed of the.7mr/5 s*n b dtxsk5bi 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 t) kk ifj:sr105rp/ds)obqbw :bu8 0-pgwyd g(ested its cars for front-end collisions by hauling thek( r s:/s5rydk1b0f bod)gbup iw -pj0w): qg8m up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 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 trwu08a/wds, w80 y kfkqavels 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 amre l 2nu*b):dcceleration from rest. The front of the train has a speed of 25 m/s when it passes a railwn emrb 2:l)u*day 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 above tg mb0 wrx1r2k8+lg8dy he water’s surface into a deep pool. The persogr yl2grb0 81+md8kwxn’s downward motion stops 2.0 m 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 system, it is necessard1sppn rmh( b2dxw/.n1d14wt y to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make adxp.1db hwp4wm 1(n12tdsn/r 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 whenm9gy5 lv d:z9n diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committ 9dm zv9y5l:nged. 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 golfer strikes a ball is planned so that the yte(vko7: l9.t glto;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 downhil.l( ttle9ovoy tg7 k:;l 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 aoi24m/k/gq(8ogv cj )l)djmh-pi9kc freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes hi cjlkk9)/ (gc4i-/ o)odmijhpm2 v8gqm, 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 is drop(u 1bl91+p z4z )y46io.z (v c zikg8frdosbxsped 1.50 s later. How far apart are the stones when the second one ho) z xlfkbdrzz6goz 8p .b4+ iy1vsi4c19((s uas reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over t y lf jt93by0aj.*t vl2. g6jwa0m:ufwhe course of a time trial lasting ten laps. If jb .j f .vt lm63aa0w 0y:yfju9w*g2tlthe 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 Fran7 d89curbh2z ice crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed i buch7d 89rz2is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two tramp.u5z-mcbgc:a (tf s 2colines. The first child can bounce up one-and-a-half times higher than the second chi(ufcc5s zac2:m .-b tgld. 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 traveliotj4/vtae 45gng 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 havt av4jo54gte/ e 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 +ref2 3mah3pvo.i n9fp2hn1 wthe baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the t2 hrf 3mv9a2on1n3 p+ip ewhf.hrowing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerdm(5n- ,i qrdpation of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each inte:b*mw :qs z 44w3l4v m e;drnolu+y6iprsection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first interslebrd lyp+4s*u:m4 4:n wzo6i3q ;vwmection, 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 af j.hy) nj(n;bt a constant 120 km/h takes off in hot pursuit. The jn()jby hf.n; police officer catches 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 aftd epa6u(pcp5rb7t0a/ ouui* -er that, a second stone is thrown straight down with an initialap(p i d6-*0to /crep u5b7auu speed 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 the same time. The firstw:bc+yhirasyiu p; ,+,wh x,7 stone is thrown with an initial velocity of 11.0 m/,+wy,wip iah :y;r,7cbsuxh +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 long woul x vpfoje02n jey*wf+w7-1vg) sn+*dyd it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would hsyj0-df*n+*f v7e2wg1y +)xv pnjoew er 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 be9oiyjugypfol*0 4 ;yo. 5) e/j0ybmillt 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 trp5 jol 0l yogi)49ujf/ y.m 0biyo*y;eavel? 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 spl*efr nso 2r7r; sbk(v9h p.e-eed 1.5 times faster than Joe can. How many times higher will Bilrelb.s;*9 e 2 -rnofhp7r s(kvl’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 beltr gt4t:s(u y*ow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground:gttst 4y(r*u below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building using a)xi;t7 rn/qz9 wsf,qg barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports n,qz t x/rq7wg i9s;)fa 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 bicyc pn/:()ju2 gnmn+ 2 zqth3xkv-wvzjw6ph92ut les, 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 bicyh2w hz xw(n guk:znjpv ut/9t6p2m -)vq3j2n +cle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?