Does a car speedometer measure x3yef 7 6hv:ksof,,9jkh wm7lspeed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, giverk0xd,b 8-u:8ubsy l r exampley8ks-,uudl8x brbr:0 s.

When an object moves with constant velocity, does its aqb81hhka 1+ywc8 oy 2fverage velocity during any time interv 1yayb8h1c+k8ohqf 2wal differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing the a8b*lfoa:ab4, dd73yl p d es-qb1mf* finish line to lo1bldfaym7ap *d s*8 4q efb-3:daol,bse the race? Explain.

If one object has a greater speed than a second object, does odao27:qo91cnokl+d the first necessarily have a greater acceleration? Explainon:+dk21 9l7o cdqoa o, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90/ d1o0,70y yk vdrewhfkx;ig9j,der) km/h with the acceleration o)eijv0 e yxy7foh9,kr r1wk/dd0;gd, f a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward ve l-rb4vymvnlr 3vn.p87 1o2ozk;y7i rlocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Whaoq1rsl;,m: 5io1 mfq79phkuzt about vice1pm 1 k9:; 5,i lsqzfhqoroum7 versa?

Give an example where boklcjvo;p ,;c *th the velocity and acceleration are negative.

Two cars emerge side by side from a tunneq l/+(qxh)1/3 m ;im rplb9mneax9raal. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Carb rql 9 m39hl qm+(x/)inra1mp /aae;x B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acce*r4.:sji xiu ) orvyzvi (g(v-8ccacbi,0m(uleration decreases? If so, give an example. (u8coa(v.ub i *jx)zy0 s:,c rm c4iii(g vrv-If not, explain.

A baseball player hits a foul ball straightt uw9 ,fzikr,5 up 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 thutk 9fz,ri,5we catcher catches it?

As a freely falling object speej/2tjbzg6-. n v7hex qds up, what is happening to its acceleration due to gravity — does 2q bnvegz. j/6htxj7 -it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically upwago6b 7uw./nx zrd? How would you estimate the mno6bg/7 u zw.xaximum speed you could give it?

You travel from point A to point B in a car moving at a constant * ;rbl;efo )- bri-hfmey.c /aspeed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average sp-*;;b o rmifrlf.eba)e-/hcyeed 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 bolts tied to smr )eeg5em:: it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal inters:ge5)e :merm vals?

Which one of these motions is not at constanm aqk5jadq e(,cf50qhc,87q (whz k 4ft acceleration: a rock falling from a cliff, an elevator moving from thec8fq(,7 j fdh(qh 4q 0a, k5q5cawezmk second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertiw jfa ,k8g81sk, 3wyvecally upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is apswv318 key,wfgka,j 8preciable, 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 nonzer7 4ti6xmwds .utuua/1o acceleration at the same time? Give exaax7s46iwt/ u.uu1tmd mples.

Can an object have zero acceleratio nkd6.qi; 2zoq12zts gn and nonzero velocity at the same time? Give ex td2.6ikzq s2q 1ngoz;amples.

Describe in words the motion plotted in Fig. 2–28 in termsg+dapjm u6q3vn d zm7:x/,/ su of v, a, etc. [Hint: First try to duplicate the motion plotted by walkz:s/dgujxvq6,/3uma mdn + p 7ing or moving your hand.]

Describe in words the motion d g*8x(amfqu4of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to t*2+yqt7hiz eu ravel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long ;ah ybrjb/gvn5 ).m3bdoes it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 sho5aox83i)bo*f flgf.-s t3fc8 4wbc , how far do wlf.-)f5t*3o3 cag f4hsoob88 ibf xcyou travel during this inattentive period?    m

  Convert 35 mi/h to ;hy9 f am6gev.s+:xrd
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from g4r9lvvo0 hhumv1/++qnf* -bo:hrol$x_1$ = 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 1*/guj8u gp9p ,hdky/ wleb-v,30 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hoursp,ghyv w8,9 kg-pu* /jbdelu/ 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-thu9ekey/3y 5zq1rp8k k umb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming th/8zuykrekp5k 9qy 31eat 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 laht*ul ppvt4g35v bjt)3u8 8yrps around a quarter-mile track in a total time of 12.5 m 8jgr4vhtt up*u35 vyp3l8)bt in. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in shs( 1lf4d p(la straight line, moving 116 m away in 14.0 s. It then turns abruptly and ghs(1p lld 4sf(allops 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 n(4) c 6+ov6 zun(/pdddt jlzpon parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig/)(o+d(z4 j6pncludt d v6pn z. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck tlgrx r .vpg).1 3pd/juraveling How long will it take the car to reach td . )lgp rug/3v1jpxr.he truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounte 3lqmran y8,b,moretpbl v16 :5lh15qrs a tailwind that boosts its speebmnlr1q3m5p,b l 8ye:1,oh6 vt5lqrad to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-trip in wp i0:u .5 u3ar i1t5elxmd6bqlhich the outgoing 250 km is covered at 95 km/h followed by a 11i.5t50u:3im qad6 peu x bllr.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hi htu/ci2-s:u;ytt3oo ts the pins at the end of a bowling lane 16.5 m long. The bowler hears the sou3uhtsy-2 :/iocto ;tu nd 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 accelernr84+n z5 efhr*0iq mdates from rest to 95 km/h in 6.2 s. What is its average acceleration ir0e*n +dz4h if5nqmr8 n $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelxytp9hp xb7 4 )*x- rza7aryh2eration xhya 4 hbrx)z7p x9tpay-27r*
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is ca3bb 8mzw7+ vj4p uyrn9pable of an acceleration of about prz7w 9y+v3bbj u4m8n $1.6 m/s^2$ 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 then0a0xt 6wye :nwwy.zh8 brakes and comes to a stop in 4.0 s, what is its acceleyew6hw. nx0t way :0z8ration 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 j-atp offm:l+bj3cn so( 02c5r xtac)y7)q7q from rest at t = 0 and moves in a straight line, is given as - )pnj3a:s2 yfc0qjx7fm 5l+rqaoctt o7(bc) a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? abea w-,dnbr ctpwze,1v +c3f7e-; ;jHow far did it travel in this time? Assume cod;jbfzt,weae ; rv-pn ,3 -b+wcc1a7enstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/bq,yihis1:d0lzn b (e lwt80gr 8+ f;ms to rest in a distance of 85 m. What was its accelerationi t1w+flm0l:;i0 g8b,(rsn hby8deqz, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How l30petpzhknky6q8 5 +tong a runway is needed if the (constant) acqk t0+pkehpz 6y8t35n celeration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of rj07ejpa /5ezd;;-godx2j xma / kmy( the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of d7;x/agaz-/2 j;ermo(jejpmd xyk50 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 (:tqsj.;;z n vvqun )aspeed of 12.0 m/s to rest in 6.00 s. How far did it travel in thatvn)z:ajv .;s(;q u tnq time?    m

  In coming to a stop, a car h4huj6 ae4+4o )wt:8yi eqwwsleaves skid marks 92 m long on the highway. Assuming a he4aw 8:4w 4 6+tswqhjyi)eoudeceleration 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.g7r:.mr:w i. 0uvxdo n The front end of the car compresses and the driver comes to rest after traveling 0.80.0 7nriorw: xmd:gvu. 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 = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distancewv*re naj6v.- s for a car with an initial speed of 95 km/h and human re. 6njr-v vewa*action 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 for rs9 c1ul ng)k, 40qgnhpada m1)9/gi ethe 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 going 25 m/s on the highway. The car’s driver looks uh/:l/vqq6,nb/ aihf for an op/i/f6qqlbv nhh,:u /a portunity to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min.w zi4+-dkdpt 9 a;m2im8c zjn- After exactly 2+z4cz i9i8w; 2m tndampd-j- k7.0 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 4 n .tpwh,c5yllis obif:*((2u5 km/h approaches an intersection 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 ,:tnb. ou 2iih5l(sf y cwlp(*(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 fr+(u+v*kh 5ipa xyy 1*zvlwa)sx i b:1jom the top of a cliff. It hits the ground below after 3.25 yypa*1vazu)xli1k:j+s+ *i5 b x (hvws. How high is the cliff?    m

  If a car rolls gentlym3ev- 7,lsu9 mm xgydl1s 3m,wjxwdz;y6cz.4 ($v_0\,=\,0$) 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 thdycy;2p- j r2r7o gz,xe 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 afwk4s o)b +wa:-7kctc fter throwing it vertically upward. With what speed did he throtca wf7o cw4)b :+-kksw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls ui;3lqvr-+epfzrjp7yl 3mb8( nder the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 8 qj( ;-ri vreylm 33pb7+lzfp0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speedi dmf.p3cs7 xo 6*jmj( of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: T. i(3f7o6 m*s jxmjdpche package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that t6uvmzeo4 aq9 4he distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, et9z446o vmauq ec.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show+v6y.aj )bm fo 0fvdw- (algebraically) that a ball thrown vertically upward with a sa+) fvb0-m.dow6yv jf peed $v_0$ 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 mlm/(tye) /og*e n ca.u/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 inerxd- r6iv*8 s2f8p 77 pvqjww Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the- wr78e7pj6vsd8*qf xrv2 w pi top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a wf ,d +m1gh-kpsindow 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fas,g1d -fkhm+pll?    m

  A rock is dropped from a sea cliff, and the sound of it striking r+mdl7eq5 cd6the ocean is heard 3.2 s later. If t7m+ld5qe rc 6dhe speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water.+1 cej3gu *qrnwdt c/83sy+nz You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. yc8s+ /t3 edqucn3*wrn+z1 jg2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge ofu :3r; wxtn+ qsnm/n(y a cliff 70.0 m high (Fig. 2–34)+ nwsqux tn/n;3 r(y:m.
(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 2 2ydm6,j z:syq8 m above the street with a vertical speed of 13 m/s If the ball was thrown fro6m ,qsdy2:jy zm the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) r*xxz /*e28-ycmkfdh At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During whatf 8*2 x*dzmy/krhc-xe 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 ashza:ep:h)orc1fj;) a a function of time is plotted in Fig. 2–28. What is its instantaneous veej)pho1r : ahfzc ;a:)locity
(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 autom*uyx 7lrxj yu*:4at;kobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the x yxk*:u*;r4jya7l ut curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Probo7z,b ,quy2g jlem (Fig. 2–35) wbz, juoqg,72yhen 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 td 8o 9hg2(-u)vn8 zp ptga-qblhe distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function owy:.54 7ux tkszvrqn4f time is given by Fig. 2v:nu45s4wz7 rt.qk xy–28.

Figure 2–36 is a position versus time graph for the motionexhw0pu,9if 6. w.a ajaei0) n 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 ,.i n fhwa0xai.69awe) ju 0peobject 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-story window 15.0 m above a firefighte g.(5mh 1gc4 oo9xgbnljgi2+kr’s safety net. The survivor stretches the net 1.0 m before cog.9cjg1 b( +5ng oihm4k2lgxoming 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 l; v15-e3ppb6nshp xzon the Moon is about one-sixth what it is on Earth. If an object is thlb p;x1-n sve5ppz36hrown vertically upward 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 by7hdee l. s8crqms k3n 6/jn+e. an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g’shnc8m6enj 3/s7 ek de+.sr.ql” $(1.0 g\,=\,9.8\,m/s^2)$. 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, and his nkp1 s b*9.eyqpj;ju 5pursuers are getting too close for comfort. He spots a flatbed j1q9*e 5b ;k npsyj.putruck 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 manufact4 fkrguvdfbp-bqe8v 2j pp +4/765bkxurer tested its cars for front-end collisions by hauling them up on a crane apg- bk2bpfpj 4/bd8e6vx 5r u4 kqf7v+nd 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 travels am07mh 6gcgm5z bout $10^9\,km$ 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 fromor /b c f4wqcm4e ,m32ecuzqk9as.-9c rest. The front 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 cqbqafm,cwcmko 2 e /-9rue 44c9. s3zlast car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surfa3b;c:j*gks fawpqs+ y27 z*s mce into a deep pool. The person’s downward motion stops f:py2gc* sk*wam q;jsz s7b+3 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 tre 2b /xrpyfib -om-+emr /b1c8 mjo*z)ansit system, it is necessary to balance the average speed of a train against the distance between stops. The mom1 mbo -yczbe-2x8 f+r* /rb) m/peojire stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fid-( x uzl94m 62uytpp1 9zfkmish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a 9z-6( pkzp 9x1d myt4imfu2lufish 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 pla0 i0;e.srf 0 6qffxhw,wdvw 2wnned so that the ball will stop within some small distance of the cup, say, 1.0fv f fxehrww2 ww0 iqd,6;.0s0 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 constac7 q7:: iskr) cvqtx/88ovep bmnhg51nt speed of 6.0 m/s Just as an empty ck qbis7negv:/ 8 qvx15c 7oh8rm ):tpbox car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped fr3 ij-hcgwt +;b /5omfmom the roof of a high building. A second stone is dropped 1.50 s later. How far apart;i5moft m3 +j/bch- wg are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cour9 stsn vt/:to-se of a time trial lasting ten laps. If the first nine laps were done asv/ s9 n:-tottt 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 pass as hed(kpln5 rm0g ,cp*ihfhile; 3n,f emt m5)-* u moves at 18 km/h . At the bot 0;,f,5hnm(*-3mgnruiet)*ih lp dfke mc5 pltom, 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 bounce f (a(oz:57iybpq,t ow up one-and-a-half times higher than the second child. The initial speed up of the secap,:7byf owz5to(iq ( ond 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 tras+0 j+ frx(oq r+-:kzutx/ bzyin traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/t+qxz0+-jf(y k r oru:s/x+zbh . 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 kiad y1)bzr5-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 1dkiay 5r-z)b 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 acceleratio+hgc258 pe8q e 6oqgwm5 l0aign 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 patterj9 ygzv:8+py ,huhfim b/bp76n shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn greej/pz+ mu 9i :7bp,byg6h y8hfvn. 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 atan qw v:p25q-vl:0de v a constant 120 km/h takes off in hot pursuit. Th vqewn::dvl 0p2av -q5e 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; 2l )m(lz0cj i -v4it.wp.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time. l4t0pi j-m(c.wz v )il
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone+qknot3z l-63rg:c cs -nkp b, is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony ofcco-g l6+3bzs- kn3t,:r pnq k a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling para *f0.kv ;y7lg*cxd jqc+4hrph chutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to jl*dhpkf. +xgr;y7hcv0 4cq* perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to dvn 59 cvf zyw7*m;*5i0omgrksend the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers arn0m75cg*vkr9w mvi*zyo d5 ;fe 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 -o : vn3eu5zriw0z :b6refk2ythan Joe can. How many times higher will Bill’s ball go than Joe’ r:feikb-ryv0:o zwe2z5n3 u6s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below you6i;xh ,t 6kediqdi+t khj-;.q. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend tdk6ei6i.ihk-ttx+ , jd;q;h qhen 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 7pzwtat-s:4iq( eu ,b4yu t:nbarometer. Instead of using the barometer as an altitude-measuring device, they take it ttp-y:ett:z7 4sw, u nqa(bui 4o the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and/p0 q2u0qwrh d B. (a) Is there h q0/2q0dprwuany 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) Which bicycle has the higher average velocity?