Does a car speedometer measure sjzfgg 7t9yk r8ftx1;r ) r6pr.peed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, givefdm sydg0y( jp)y8a *,yj/ uk/g 4dl.l k((jtb exampletdk,slku 4b (.y g0j)daj p(dyj*/y(m/ 8lygfs.

When an object moves with constant velocity, does its averag:i1ch)h ))( j(p z omxytly)tke velocity during an)cxmit1k y(p :y)hltjo ())zh y time interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the grg5t*z-d3 pd zgeatest speed crossing the finish line to lose the race? *z 5 3dgzt-dpgExplain.

If one object has a grlg *j,8hdif8 qeater speed than a second object, does the first necessari i88j*d,qflg hly have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80k3b-x mbjooow4woqh+;px 1,9wm/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/hm41px+w,3wojh -;ob ooq 9 xwb in the same time.

Can an object have a nortw/do/n,- j hyphward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative whengv8u+0hd ,zxhi;4kdt its acceleration is positive? What about ikth uz4h+,x;8vd0d gvice versa?

Give an example where both the velocity ao*y4 lg z8gabebn-e vlf 6ov2wn0l16/nd acceleration are negative.

Two cars emerge side by7*k)qu+urs3w q ;c ipw side from a tunnel. Car 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/mi*u7w3k)uq + i p;csrwqn . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases?-xjl hx6 yegth*3 b(r5 If so, give an rt-h5(g6ex xb l3*hyj example. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the )h6fh2chz0jmmy k *(ebat with a speed of 120km/h . In the absence of air resis6hjc)2hf * mh zm(e0yktance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what ivrqzo27be0uuua, uh91 : :dwes happening to its acceleration due to gravity — does it increase, decrease, or stay th7 2,9uv1bq: h 0u :ueordawueze same?

How would you estimate the maximum height you couu- jbk.wg7q:h/oo+gp ld throw a ball vertically upward? How would you estimate the maximum speed you coguhpb-7g.w k/ jo+o:quld give it?

You travel from point A to point B in a car bmi)(ibz)v 9)spk8urufy y -,moving at a constant speed of Then you travel the same distance from point B to another point C, moving at v )sr,9)fb8- iu)m(zu ykpbiya 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 vertical string with ten c;ov:p7 gstj k;im o80bolts 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 voo0;;sp km :j78gict tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceler6dgz1gnd01il4- rhf iation: a rock falling from a cliff, an elevator moving fzgd1i1di4lhf 6 nr0g- rom the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticalt z5* xw;5.dwbxvx-un1 b;olyly upward will return to 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 altet-wx1oxzv * wb;;l.5u 5yndbx red, 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 acceleratio;xjijd* e p0eua- ph,3n at the same time? Give eu0 pijp;, -xe3*ade hjxamples.

Can an object have zero accelerajpewvz .+c1lhm,wf/ 2f tv9)p tion and nonzero velocity at the same time? Give exam)t lvzmp+h/ecf, 1 29fj w.wpvples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. qmeu 4wk )o8q2r5(tll[Hint: First try to duplicate the mo 82qukq o(w4)5mellt rtion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. k b2v8 hdj7tx57u4,0yu umgwf2–29.

  What must be your car’gw0fl 7 7lbj.xmnu.1vs average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long v 0(:fs mjh9 yz;-ksazdoes it take to fly 15 km?    h

  If you are driving along a straight road and yo/hh1gx /x;zs,lus ) hd;zi2 ofu look to the side for 2.0 s, how far do you travel during this inattentive period,shu2;/; zxs1hfo /z) ihdg xl?    m

  Convert 35 mi/h to bj bm)3f1 y9,tsf 7slu
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from( upouaq (;3covy* 0kh $x_1$ = 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 4v.s5c-rzq0 egx2 y4w pj2 qubat 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive eqjc5g v qrp z-bxy4022sw4.u 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, every51(;z.ksihn czl1tbeob(pl 8 five seconds between a lightning flash and the following thunder gives the distance to the flash in milesk1nl(ohz (.cztbl5is ;8 pe1b. 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 completm*vrc2*s y7c * h*ogqqe laps around a quarter-mile track in a total time of 12.5 min. Calcucsq c*oy* 7 mvhr2*qg*late
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from itsdm.3p +)y6 e7dd wfouy trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly a3p+ yyodudm e)6fd.7wnd 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 trackz i)+fp,x-rb qs. Each has a speed of 95 km/h with respect to the ground. If they,q b +i)rx-zfp 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 td (e6 xf7(r*wasj p,bis 110 m behind a truck traveling How long will it take thb(js, dw*6rp7a xe (tfe car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , -(8j e t/oi w n;og33txerav4u)g0yr wand then encounters a tailwind that boosts its speed to 990 km/h f-n;o3g0xt(j8 rtyvrwa 4 3o/ee)ui wg or 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 c 9bvwfq9l12ywomplete round-trip in which the outgoing 250 km is cov29l 91wqfybvw ered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball travemu ha;;i1 4yosling with constant speed hits the pins at the end of a bowlinsih ;;um1a yo4g lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 *lh0g h,x12w(l zcyhm- p o+owkm/h in 6.2 s. What is its average accelerh wl 1,cg-x(po0hh w+yz*l 2omation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelvrm( 6i,jeg +feration +mf,6r(giejv
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleration of 5e,-cyq 9m rd9fbnc+eaboute ce- cf9,m5d9yr +nqb $1.6 m/s^2$ 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. If it thd/vi42kbd7 y x6k *aiwen brakes and comes to a stop in 4.0 syv i4ikb a7k/w2d6dx *, 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 rest at t = 0i (0m7pktnr zll4 -wz6 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 lp6zzwtlm7 0i4r(nk- 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 was :4 /ixlr+pper s7e kw*ca93siits acceleration? How far did it travel in this time? Assume constant accell 34 ii7 rsrce9pkx+pea s/*w:eration.    $m/s^2$    m

  A car slows down from,kg h7krj 4ov* 23 m/s to rest in a distance of 85 m. What was its acceleration k* 7v4,rgjokh, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a rusc4g;oazw.5;i6 awc z nway is needed if the (constantza .5cg s w;4;6wazioc) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of mkro50k lbz: 9the 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 itl b: 509ozmkrk take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed+0k/h 8fkcq 5plg7nlo of 12.0 m/s to rest in 6.00 s. How far did8gcf lnq5h/l7 o0kpk+ it travel in that time?    m

  In coming to a stop, a car p :lc-ayvns c6g8+vu 3leaves skid marks 92 m long on the highway. Assuming a dece v:cl+a s8gnp-y3c 6vuleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/hb*8,pe+m ag3od trgl5zn2 -qaba54q x strikes 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 answer in terms of “g’s,” where 1.00 g = 9.8d gm t ngbqaa,5-pb r+28o3a4e*5x qzl $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 km/h andwp-/p.jl, 7,s zhy -z:pioc fy human reaction time of 1.7f zilsc h:z,pjy/ ow,-. y-pp0 s, for 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 distance o2d syvb2( c:qyf 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 driv + drrx4h8efa/er looks for an o/4x8f ar+r ehdpportunity 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 1fqk gx )0o3grone fdz36 4a.8z8sq n1t0,000-m run in less than 30.0 min. After exactly 27.0 min, fzgak txgqnoo3 n)4s 6.qfr8e081d3z there are still 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 intetu: mnt*p g./ersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she /gpt*.:tn ume 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 tqt9.azgipsfr df14r a1aoky 0- 0 3r0kop of a cliff. It hits the ground below after 3.25 s. How high is th4-s30.901qrf ryz io1 ka tprkfada 0ge cliff?    m

  If a car rolls gentlyoyvjh8qm+3ez0 1l l5a ($v_0\,=\,0$) 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 e dq4guj/ l:zw9+8ug twith a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a bpt-vz- 8 q4qzeall 3.0 s after throwing it vertically upward. With what speed did eq-p-zvtq84z 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 influ arfeut2iua y63vp1 )e1jw3g 6ence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistan 6f ej6tg3yu2wra)1 ipu a3v1ece.

A helicopter is ascendi10b9n ( pzeytpi;d016ggcmcqng vertically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time doe10y;gptqzg 06pi ecdn91( mb cs 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 ra.ig1 igrovc)2d9 q99lo n6ncest, show that the distance traveled during each successive second increaso9n2iocngvrc9q 91 gil.a6 )des in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that */a1phq1b7m g:rm *6wdyedi sa ball thrown verticallywmm gi *ey/a1hd:r7ps6 *dqb 1 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 vertically upward wj* eb8pgii9ov0z , yg9ith 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 each photoflash of the apple in Fig. 2–7wm5 h dnp8k f5v( woeu28u(ok18 (or number of photoflashes per secondo5u fvwke2npd 85(uk8 ( mo7hw). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall j-qe4:tylnd n ) bi(7b(Fig. 2–32). From what height above the top of the window did i-:7entbn byd4)(ljq the stone fall?    m

  A rock is dropped frob dnx o u ;tmv(8d,fhq91e*m8vm a sea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H = o,m*vdmx8euvb; 9 h (ndtqf18    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. eu :jbe kk mmowudf,g:;51-1zYou 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 2.0beod15z1wgku ef:-j: m;ku ,m 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 frov 7w6gj2o6rtc m the edge of a cliff 70.0 m high (Fiw tg co27v6r6jg. 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 5f busrz5.i i/43lj0 p9viqh)gv9h rx28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the street,9qjb.r4xrzhvfv)g 0/9ph ui3i 5si 5l
(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 velocityos(wl m - c3-.k*zbvqy of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the accelero - vyw-.skmc(l *zqb3ation greatest?

  The position of a rabbit along a straight tunnel as a fu3 +l -a +dns50coqie1zpub ye8nction of time is plotted in Fi8-0 bz dyncpe +31+eiao5ulsqg. 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 shown in the vbff wa4 mdtpgl6m2+9; elocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiftag9tm 42 l;bf+ pdf6wming of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Probtd jhr 0kpch8gf 4)pfd)53 or0lem (Fig. 2–35) d)k r8gp0f4)5 f tdr3hco h0jpwhen it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate thu xof/)+lr6zwgl(,uw e distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objed-b , yw6cll.ict whose displacement as a function of time is givelw y.bi -cl,6dn by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object :stzr f/+n4s jalong 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 objec4j :+n zrstf/st speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-s54u kvhz46l7 c 2cz)ci8y qdiutory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before comin 62vz4 5i7uc ziq hk8dclyc4u)g 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 ez 2m1hzuok 4a-mtg5dnw.;7 v 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, assuminh41m z avzkg7n5to me uwd.2;-g the same initial velocity?

  A person who is properly constrained by an over-the-shoulder ai)nf8+uj ou 6oe;+ xxseat belt has a good chance of surviving a car collision if the d6ea ;ux+u njo8if+)oxeceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m abovf3c uuoa 8-cg1qpf0 s1e the road below, and his pursuers are getting too close for comfort. He spots a flatbed truq1uac81 os3g c0 pu-ffck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for bqth v gjy12ad9477k0 tme0m efront-end collisions by hauling them up on a crane and dropping them from a certain heightgm42ae v 7q07mtdk ey01j9thb.
(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 about f zi ut2z177-tki*bj r$10^9\,km$ 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 frosos dj6r d rd8kk5j0(8nt of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Firs5d( k 6j8kds8 0ordjg. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’0 l63kpnaat)k s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the a0 a knl3p)kta6verage 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 to balance the averagvkzv7 2xq3a b)v: ;jr;zbbkf4 e speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To7b xf3; vva2qjzk4 :vb); rbzk 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 s/b:mv we3vw-a0r eko1c ub 2p(8cr9u mtraight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at thew cp1(wv3cr2m be ou9eu 8:/0vrba-km surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so thhq533 pbbe*k8s 51eji h3 eh i5ts2s,4wtkkd vat 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, d4e32qht k5we b3tipkh 18k*ss5ije5, vh3sb see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at p(w-hb:4mao k a constant speed of 6.0 m/s Just as an empty box car passes h wk:mao(-4h bpim, 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 higfsi;n+t; n g,yt)7q wph building. A second stone is dropped 1.50 s later. How far apart are the stones whe ftgsi 7;tw,npq+;) ynn the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time triaukvnjy crf3b 0cpm1c;(4m1(vl lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed vcmuk4pb31v cj r(y1c (n;fm0must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crest.ciras k2 tj07s a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther,tk20icj.7as r his speed is 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 trampolines. The first child c ;ah9mce +q ,tf9;zsblan bounce up one-and-a-half times higher than the second es;bz,lhqt fm ;9+c a9child. 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 overte)pe 4abw, nr:akes a 1.10-km-long train traveling in the same direction on a track parallel to 4,ebra)wpn e: the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In;623rqar cvu 06a ybgl throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind thaq g26lv3cur6ar;0b y e body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration o hb3z7(obc,n+ wmenj5f $3.2 m/s^2$ 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 patter0e/ db/ 9tbmcpn 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 a// pmbc9bde0t t the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/h t1 v7rr+e /fzeoakes off in hot pursuit. The police officer catchez e7fv1r+o re/s 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; 2.00xz8)b e:tyc,vhvcy2k 1 mdpg) f i33;f s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two fvcg8ezbyi )d1k2vt hf3c ,p)x3m:;ystones 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 vertical:8p myxgy*efg k 81ri,ly up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial veloiyr8xg8pem1fy:,k * gcity 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, h1cuf ybgr7 l)9:d+ (eugyfv-how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altituluf7g :-)b d ru 1gvcy9h+(yefde 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 belt to send the burgers t mj598gwrn jj-h,(+ zfvanj5qcbyr /,hrough 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 buj5aj w,c8yzn9 -rvf, j/ bn5rh+j(qmgrgers 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 faster than Joew * ehr9i(musvc6;qvky o;3(z can. How many times higher will Bill’s ball go tha e ;v; sw(uro kicq*9h3z6(vmyn Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff ( .be2. u./s-*pwscfwhntg flwhile your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is .u2w . fn-ss* wt peg/lh(bfc.the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a.ui, nmq 3 x0bub ncrj7enw*::k;xnz6 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 unmwrx6z,ne:c 7ni n ;.jx3 *0bqbku: 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 grap f msa8d3x jn6mr3r;(x5sdu(hh for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At whichxnsa8( 3fjrmr5h(;x3ddm u6 s 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?