Does a car speedometer measure speed, veww m7+upq)/n dbwc y 9fe*py./locity, or both?

Can an object have a 1ylm(06bv)v sfk9t 00vqdwg:quvpj3 varying speed if its velocity is constant? If yes, give examples. q10(jq0g6lk 3f) b9uw :vd0 stvpmvvy

When an object moves with constant velocity, does its averaqb0ln 7vxidsbwj3kr )p2*5 p.ge velocity during any time inte kq i.vjp75sd rb pbwn0l*)2x3rval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greates arp(d 2t/ev/kt speed crossing the finish line to lose the raa2e/ trpk v(/dce? Explain.

If one object has a greater speed than a swb6g, r0t1ipqecond object, does the first necessarily have a greateigqrp 1t ,6bw0r acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates fromw5 *u3eh1b:aszdmy rkj**y j9 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest *3a9s:1u kmyjhy z *re5*bwjdto 10km/h in the same time.

Can an object have a northward velocity and a south u *enyr6;zppyy/9uu ,ward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wha*zis)n fx llt89iyym)nk r8; :t about;sximni)rn lzf *8l8ty)k 9y : vice versa?

Give an example where both the velocity and acceleration aqu6 h-e(:e ucjre negative.

Two cars emerge side by side from a t84,vim p9pj so) h9tusunnel. 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 hh)9ssp4 p ou9vti,8mj as an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so,. am5*,j kidin-ntn7w give an example.i-7n5tkn.m*andjiw , If not, explain.

A baseball player hits a foul ball straight u6gnd(,g f*f)gg*5 k-e ontspbp into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catsk(* gtn dggf*, pe-b)g56n ofches it?

As a freely falling object speeds up, what is happeni 0s fazsv05ym 03xgwo3ng to its acceleration due to gravity — does itm xvs f053o3 w00szgya increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertica zaq0ec9a 4me9lly upward? How would you estimate the mac4qze9 aea09 mximum speed you could give it?

You travel from point A to point B in a c qd0zxl x8vt5+w7yll 8ar 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 90kml t8ywl xv l7xq50z8+d/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 verf0p(dg, k tyb;tical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the f;pb t, fykgd(0all? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accelerambok 5,1 tyk4qtion: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on q,t 41 ykok5bma table?

An object that is thrown vertically upward will return to itss, n(ssik.s ef 9b6m.b7.vugb original position with the same speed as it had initially if air resistance is negligible. If 6,kv. b.mbsn9isefs .b s (u7gair resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time? Giv))bnzqwca ia1 rb00( cp fe5+be ezc+) w0()fnib crapeabq 051bxamples.

Can an object have zero acceleration and nonzer-g* ,/69tlmone+wslbbfi2 r to velocity at the same time? Give exampn eb62o-lmfit bwsrgl/t9+*,les.

Describe in words the motion plotted in Ffiy* 79 .w xpgycyt-5lig. 2–28 in terms of v, a, etc. [Hint: First tryl7xyp 5c-yigw9ft.*y to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the u jjgotu fd /:q4vad2-/l y-a1object graphed in Fig. 2–29.

  What must be your car’s average speed in ordersd u82: q4jbs:bju 5zp9fyby8 to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h mykl-aze -*s )How long does it take to fly 15 km?    h

  If you are driving along a straight road and jcl,cr02dx2 fkp1w u4you look to the side for 2.0 s, how far do you travel duringrkwpc, j2cld0f2ux14 this inattentive period?    m

  Convert 35 mi/h to hj z,5 g7i*0ti. xxcma
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from6/i:jk g6sz c6yb (wcz $x_1$ = 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 t d-v77adb+8wvj 0f6uyt1csmpd2 1bh-b mi)c when begins to rain and you slow to 65 km/1i8 wbjf d2c-hu+1 bdcp-wtd 6m770)bvms vy ah 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-d3sq/t hu .jej/6 rk8aof-thumb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming /t.3h6e jksjd/uaqr 8that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track 5 v(yki7te/ wdin a total time of 12./divek5tw( 7 y5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in acjeb fkc4 8rb.*q5ht; straight line, moving 116 m away in 14.0 s. Itef8qk ;5tb.h*c4j r cb then turns abruptly 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 6t2:i8wkyzzxz rx s+t ,i3ff8parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initizwfk 88 r3tsz+2zx i:fxi y,6tally 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 kgb s)y ce+ :c/)hkf5i110 m behind a truck traveling How long will it take the+hk)ky5/sgbe:ci ) cf car to reach the truck?    s

  An airplane travels 3100 km amx;l va4.qy 2m-hv.ia t a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h foaxy m;- q.l 2v.avhim4r 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 ve* 2g)c6 yur m6zx8bbctlocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour 6z26r8g)xcbcbmt y *u lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits tj f0e f +1fwj+bjh;yn/he pins at the end of a bowling lane 16.5 m lo+nj+f0;yw f1bjhf je/ ng. 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 km/h in 6.2 s. What i /3uws0vp2fqz s its average acceleration is/2z30qw pvfu n $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hrooav+hn 1(s 8er acceleration1v(ho8osanr +
(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 accelerat7f94ptoqv82xvddg) o ion of aboutd2 t9oxp7d8)gf v ov4q $1.6 m/s^2$ 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 speq .z/w0dxafz,+ ipwdq(cula ;6 7x6bzed travels 110 m in 5.0 s. If it then brakes a +z ibz.,6wl6wxu d;c0px/fq(zaad7 qnd comes to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 cq/fve,/vp-u and moves in a straight line, is given as a function of time in the followf/q vepv/,c -uing Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? c n4-.fza3ob ,:ojsg cHow far did it travel in this time? Assume cc .j:z3soabcf,ogn-4onstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to reda4c )iwgto 82 :i8d..vb05i hsly imfst in a distance of 85 m. What was its accelerati 8sa2h5df ogltdvii4. y8bci0mi.): won, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How loncfdk3u;g*d )5o/ .y7 kk nocc dk7v+slg a runway is needed if the (constant) acceleration s75;*duk7d)ldovkyc+of k3nk gc c./is $3.0 m/s^2$ ?    m

  A world-class sprintero::egj-lw c: kgem 2,rs7fvx; can burst out of the blocks to essentially top speed (of about 11.5 m/s) in the firssr em2:kc7wg flxo-gev:,;: j t 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s z uv7tjd(kba ec+0wd a+*b,gu:e/;s fto rest in 6.00 s. How far did it travel i jbk7:t,deudbfc/+a*u w;(+s zegva 0n that time?    m

  In coming to a stop, a car leaves skid marks 92 hn/*j8sc(hb6eyz1y slnec6r(f- x4k m long on the highway. Assuming * 6crkelsnxs -z((/yyn6j4 fhce 1hb 8a deceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front *;y7ydv+ 5 fqs.xazzq9x .u (mdn ;gzf+lho)jend 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,” .f; v.n;x u7 fzsg+9yhx y)mq5ad+qzo( zj*dlwhere 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 initial spee:mri)zc r0qtme5o g:ees ).9dd of 95 km/h and human reaction time o )9erszd m)eo5:r 0:m.egicqtf 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 for the stopping distance of b)q70 1z)pm,bnfx8hzlcg 6; der ss/ra 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/jkao-:zy)i m2: p ..jwd2hvv ws on the highway. The car’s driver looks for an opportunity to pass, guessing tha-)v 2 o.z:jmakw.ypjvdhi2w:t 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 30.0 min. After exa 3 e9)ebztop6r z7p80hqosl8ectly 27.0 3rlzbe)6zep 8tpo7e0qsh 8 o9 min, 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 approakz7-wyqg3pqd( k:7 aom(2g hmches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.2mp(g7(o7wykk:qm hg 3- qad z0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped f vh0l)n rz y)t*(q9ig(hmo; ssrom the top of a cliff. It hits the ground below after 3.25 s. How high is the cliff? y(q()9;zrml0s*osh h itvg)n   m

  If a car rolls gentlyed9d +,kl r.zn ($v_0\,=\,0$) 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 ne* r/l)t;q m dw9lqnd5narly straight up into the air with 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 ball 3.0 s after throwing it vertically upward. Witx nop guay.c +d-e+l1*h what speed did he throw it, and what height didelgp* xoyn1-+cu +. da it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence omshdwo 3ji42 9oi wgq c*x(3u;f gravity. Draw graphs of (3 x24*do(jui whoi 3qsw; 9gcma) its speed 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 with a speed of 5.20 m/s. At n +g. qq;d/va7b(aw 8ytiet e9a height of 125 m a9t/niqw b; aq. vtge+a( d8y7ebove 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 =__ s

For an object falling freely from rest, shok1(lual nl f 1+kkj:gyjmj42+w that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galily+kl jn1(+ u4 :jlfg j1mk2lkaeo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown v/ ntwu d0 j 3a9j2v4r7,oxl oewpf+.ydertically upward with a speedy+9wox 2re v0 ld.t,d734oj ajf/wup n $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verticuh/)h l :71m/cwmwowh jj))mqally 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 each photoflash of the apple in Fig. 2–18 (orpec .x0yrml 77 number of photoflashes per second). Assume c.xpm 70el 7rythe 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 past2 nlw)tc+yh1b a window 2.2 m tall (Fig. 2–32). From what height above the top of+b wnht2lc1y) the window did the stone fall?    m

  A rock is dropped from a sea cliff, ayy 2 l2g1v4seend the sound of it striking the ocean is heard 3.2 s later. If the speed of sound1 ylyesg224ev is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You poin p8+vjxaqe8f+wgo 5;pt 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 ve8wpx5f++ vjpeg;qao 8rtical, 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 fr ;j0.not bt)cyprrm3(om the edge of a cliff 70.0 m h.or(3nr j mpt;tc0yb )igh (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 upwar)ea*srm4yk+ qd by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the street, k)ym*arq4s+ e
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. tvznt0r( .:e j2rkg,h (a) At what time was its velocity greatest? (b) During whj zeh(:2 0krt n,r.tvgat periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel 7 rflb 9g lpk22 5gpsgup:89o*,dj ofeas a function of time is plotted in Fig. 2–28. What is ig *9 lr8:5spfo,o k92 ubpjlg7d2gpfets 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 qh xe; 0kfx9.o16ugu;(v oeq xthe velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the qexqxu 9;.xogf1 (6uev;k0oh 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 Problem ys ,o8d6x9 ;x5rdinqz(Fig. 2–35) w9drz,x 85;o qnisdy6x hen 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, estimatepoc: ( w-9 fdxfy res wjmwe7id-21):r the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacemeltkd952b 7vzktme*m :nt as a function of time is given by Fig. 2–2kt9 t*lbm: 752kz vdem8.

Figure 2–36 is a position versus time graph for the motion of an o0ig;uewif4,+2vhtv z bject 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) Finally, answer these same threfehg v02 +zi;4ti wv,ue questions for the time interval from C to D.

  A person jumps from a fourth-story o2 w6e+rmiz hk.44mkxablmj+0u 9ii8window 15.0 m above a firefighter’s safety net. The survik ua0ji+86wi.4x4ie z+kmhbml9mo2r vor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gpzb:6q /ay3t sx +zjel-exa3 ;ravity 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 t-ejyz + q3eazsaxl6b 3:px;/will it go than it would on Earth, assuming the same initial velocity?

  A person who is properlh 5j8h,yhkb ty-5 m,rly constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleratbk,m85,yljy- hr5 h thion does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below,ye6qxao 94cp, 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 truck is 1.5 m above the road, and Bond quickly calculates how many poles awyxqao 96c4,ep ay the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end c1 .0xk0l-d2edvlo/g7 rnu lc qollisions by hauling them up on a crane and dropping them from a certain heige-r1.lo ddxng vu7k l/l0 q02cht.
(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 abouv+v: eprorc3ym, 1pd,;x2bxc t $10^9\,km$ 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 fm;m ,rkscex4z 6jp-6train has a speed of 25 m/s when it passes a railwafme-;crm,x6 4p zs6j ky 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 mrmw8v ;6 nrk2n above 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 av8;r kn6m2nvrwerage 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 averr 2u)/ul .qgv 1yzfe9ob +7u(wx hwsr/age 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, cayfq(r he /9vb.) +ou/xlwg1s7w 2 zurulculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fis02t;t n0e wruch. 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 perform0e2t n trw0u;c 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 +ci*k)a.-lmtyu t 5adball is planned so that the ball will stop within some small distance of the cup, say, 1.0yca+)i5tau* mlk .-d t m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume 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 constant /ycun py j7t* xodbz2q5t0 h1e+u0 m,ospeed of 6.0 m/s Just as an empty box car passes him,cjt 1 o2mz0h , qupyx7n+y*/tou05ebd 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-pr;u *gv e3v1p.suf p building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one h3s fg;ep p. vup1u-r*vas reached a speed of 12.0 m/s ?    m

  A race car driver must e d3zkmx+89gc average 200.0 km/h over the course of a time trial lasting ten laps. If z 9kcemxdg+ 38the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain p7.(u g ;izky3c or6qliass as he moves at 18 km/h . At(7zli i 6;3york cgqu. the bottom, 4.0 km farther, 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 can b3ar u-l8rou+ gounce up one-and-a-half tim uo- ga38rrul+es higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long t x)n/oh h uh4s/1er8sgrain traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling e)8ru/h1s /4h sghoxnin 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 thro 0kjoofev6 ;4bws a baseball with 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 body to the point where it is releas;4e0bv 6fkjooed (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 accekd xbxbx6, 5x,leration 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 inters/ p1tijime 6gd (tev/*ection has a traffic signal/gt*d1v6e t/ji mipe(, 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 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 10 u:g;.atyger-ilcdue,- ib*20 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration. a.*:;gu ,-dii0ceg -buyter l
(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 after that, 5r9e6-7qrc90 uvp fkos crj40q4pay ha second stone is thr 0cko57s9jhv4 y96rrcpq ua0qe4rpf-own straight down with an initial 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.k(w5) y+afe1mqb.7 yk7 b rpvw The first stone is thrown with an initial velo .r kq5m +7vabyy b7)fw(pew1kcity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how lo nqrs0 y6yq3fdbt,imr0 *b/)h ng would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull h rrqfm/h3,s yi*b qb ytnd)006er 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 uizg.-;wwl)z;r3cz vp ses a conveyor belt 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 tra)wc;l z prz. 3v;zg-wivel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe can. How meby- (3uvc es+ia*+ ssany times higher will Bill’s balls3(e s v+-su ibea+yc* go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while yourrwswwsng.5pn w, ;3vfu5+ +gk 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 the speed with which your friend ng wkf .vrsw+n3,55p +uww;gs threw the ball?    m/s

  Two students are askewtb3 dy6y( g7.knhsd4t rum c o/u)4i9d to find the height of a 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, tsygruy6b(4iucmwt3ho 74n9) d t/. dkiming 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 posit.m-cwbmj5/u gion vs. time 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 the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Wh bg5/mjuc wm.-ich bicycle has the higher average velocity?