Does a car speedometer measure speed, vrd;f9 x0rdmm)elocity, or both?

Can an object have a varyin eupz2jrhty 9f c+ d7zx**h5upa6d(*jg speed if its velocity is constant? If yes, give example r5px* eu t27u(a+f*pd6cj9jd*yhhz zs.

When an object moves with constant velocity, does its average velocity durk9+zk ltylw.r9 .qcz +ing any time interval differ frllwkc+ . z y9rkt+q9z.om its instantaneous velocity at any instant?

In drag racing, is it possible i7(es32/z m z*gnov rkfor the car with the greatest speed crossing the finish line to lose the ra3m2/7sn(z izerg o* vkce? Explain.

If one object has a grebpvfp ssx og9 vkg+2/793 (gpiater speed than a second object, does the first necessarily have a greater acceleration? Explaipsgkv9i (27g3bpxfg / ov+ s9pn, using examples.

Compare the acceleration of a motorcycle that accelerates from 80 s9ged*vbv8+y /9has skm/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the syg*vvsshb8da9/9 se + ame time.

Can an object have a northward velocity and a southward ac -+iv /z2qm+y7oa;dge pgfrv 0celeration? Explain.

Can the velocity of an object be neg8f;;f pvi -z 3izrbvx*ative when its acceleration is positive? What about vice ve bz f;ivf-;r3xvzp8i*rsa?

Give an example where both the velocity and acceleration are neh o-rtt*(+dgpc ) ; vs*k;inkmgative.

Two cars emerge side by side from a tunnel. Car A is traveling with a s wljb3 5-j7 xf+whd;p9cpojn zyv/u:1peed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . jpo+undb19j w / cvj7zx3pwf5-l;:y hWhich car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in spu0vy5c 7)0+drktrrcg eed as its acceleration decreases? If so, give acu+yctrrgv r0kd0 5)7 n example. If not, explain.

A baseball player hits a foul ball straigiar )r4g*t:fuht up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how faa: rr)i4fg* tust will the ball be traveling when the catcher catches it?

As a freely falling object zr ofuy1*o5 4mspeeds up, what is happening to its acceleration due to gravity — does oy uom51*4f zrit increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vert (,lgjyob rn/u e00n+aically upward? How r oj+0ab/(ny nl ,ueg0would you estimate the maximum speed you could give it?

You travel from point A to point B in a car movin ai:b ef3loy es,t/-4bg at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why -ob il4y:3sa/ebe , tfor why not.

In a lecture demonstration, a 3.0-m-long vertiv9q 3c k47cnmafj n-c+cal string with ten bolts tied to it at equal intervals is dropped from the cei vmfqa ck7+j9cn3 4n-cling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration:)6u 4qnekl ua8 a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along tn)8aeklu46q uhe way, a dish resting on a table?

An object that is thrown- ucz0xb z2kv8aarif7u 6 i*4g vertically upward will return to its original position with the same speed as it had initially if ai*0aub-ia uz 42rv 8iz gfxck67r resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same ti e- 81t6r:yfhyudr4(cojdgf(me? Givegjdr yo-1hfy:f84 uc6td((e r examples.

Can an object have zero acceleration and nonzero velocity at the sascm ):dlr jobc.9d7sc c+xh*.me time? Give examp9m)c:hx. cdb.* cl+7 s csjdroles.

Describe in words the motion plottedcwzc v3qcqs :) 9atz)id:i46 s in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplzi q:ssatz6w493 cv) cqdi):c icate the motion plotted by walking or moving your hand.]

Describe in words the motion of the objec :iv4yxgf7i+g t graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.2j 3 x-xj.i rqq)v/ pj5.mhl,jnz s2l(q5 h?    km/h

  A bird can fly 25 km/h How iam hs/5y3k o-e9) bo4towb8ylong does it take to fly 15 km?    h

  If you are driving along a straight road and you j/d4yousct 1 9look to the side for 2.0 s, how far do you travel during this indt41/ cuyo sj9attentive period?    m

  Convert 35 mi/h to 3y14 e(xfxv( nlsd;(c5dh6 6zfctrmb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro v:1rqi2*hg ehm $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km. It then begi0p* as(lb7 xlg7if om5ns to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minuteo(lsa*70pl f5bxgim 7 s.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds beti+r h3ky-sfs zl3*cx(n*emp 3ween a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all,ishs-* c 3z*3+rmx lkpy(e3fn estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quar;/q 36myk 4 :qrfzyvzzter-mile track in a total time of 12.5 min. Calculatrzyzq: v fkm4 z/6;3qye
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight lin0z ( vmz fnti/2tijk26e, moving 116 m away in 14.0 s. It then turns abruptly and gallops half kt2zzm6iij nt/v0 (2fway 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 trazsal pm4s zmw0; ka3-wlb42:pcks. 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 b wlk mmpzsp2-s0 al:3zb a4;w4e before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck trave.ad ;cn8*9 u fvt7)7swgsqqppling How long will it take the car to reav8pds s f7an.tg *9c pw;)uq7qch the truck?    s

  An airplane travels 3100i-w4dzk m7ps 3 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed w 7mp3d-kzsi4 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 averdu /fxu:)q6yxj38gaj age velocity of a complete round-trip in which the outgoing 250 km u/ u:6yfagqxdj 3)8xj is covered 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 traveling with constant speed hits tvjj -y.+ ( p/,wm4a aumdzfvj*he pins at the end of a bowling 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 ha+ pu v(j zfj.a,4mmw*d-/vaj ynds. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from ress)0b 03e1vvx*b6tmumg3crv oyf3(dm t to 95 km/h in 6.2 s. What is its average acceleration3r6sdmbb e *cv v0ux1 goy3)03(mmvft in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hergf1)3 g7 rylil acceleration i13 flly )grg7
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobill+z33:qsoa l-9mti2etg/2eut cwt/ae is capable of an acceleration of about ua3t / q-:lgee2i tomlzc+wtts /9a32$1.6 m/s^2$ 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 ap5d/s l fzf-u 2t4dq6qf k.edn-;auo.t constant speed travels 110 m in 5.0 s. If it then brakes and comes tn;zo5 pdfu.fq ddu/q 2at4klse.-- 6fo 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 and moves in a st u-tk-, 2mp ln3g nv0oc8 a(gjdnun)4mraight line, is given as a m (-)g84 nmldj 0 a,ucnnuko gp-tvn23function 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? Hoe2rj vuhvh)tkj -)6 o,s74dczw far did it travel in this time? Assume constant accelera-jrv 2s74uzjock e)tdh6),hv tion.    $m/s^2$    m

  A car slows down from 23 m /kz:*ek9u+lqbn r q;p/s to rest in a distance of 85 m. What was its acceleration, assumed con:;unp ek/+qqlrb *z9kstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How lonyc ue0 9f+n7nyk a1q;;llfac 9g a runway is neede9;7+nyfq k09lucnal ;c 1fyea d if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst ouxh/+val ng/n5 t of the blocks to essentially top speed (of about 11.5 m/s) in the fivg /+n5hlx na/rst 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.v; g 1w,ipc7 ;o/lzfbvkqr,0g0 m/s to rest in 6.00 s. How far did it travepvg; c0i,k v/, ogzqlbrf7;1w l in that time?    m

  In coming to a stop, a car leaves skid markay gzd8 i99p7p2z /b*zvo* zet cx7c7es 92 m long on the highway. Assuming a deceleration otecgozi8d7z79**b9px ezc v/2a z7 pyf $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car comprezosuj8 -lw*j 3sses and the driver comes to rest after traveling 0.80 m. What was the average accsu*owjlj83 -z eleration 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 distances for a gz 0kb9md;/hbj r5ie/car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an accelera/50 g ; rdhibj9/bkzemtion
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance ywep ujg c*,njz)z4 ()z 4f7fyof 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 od2mk+w1)7yucs e sio+n the highway. The car’s driver looks for an opportunity to pass, guessing that h1y+ wmiocsud)esk27+is 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 thmepuv ui3f)t:b2 .qb 3*c8cq)gytss.e 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are )ymqsutut3i *s8e)c2c.:pvb . q3 gbfstill 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 approac:- ci3yop(ebzhes an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turnoy-:zib3 p(ecing 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 from the top of d6n6m pc0(kid a cliff. It hits the ground below after 3.25 s. How high ism(i6dpc6d 0nk the cliff?    m

  If a car rolls gently (mc ,ft)ga/md e/m;j-w 3k wmt.$v_0\,=\,0$) 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 uii7 g j0du bvq8 f85)ef)a7egxp 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. With ze4r97:kltqqqh v v 1t,csu24what speed did he throw it, and what height did :h 4q,k1cs2l t9u4 7vq vqzertit reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw oj+ 6:rx 7fpxxq:h:urgraphs of (a) its speed and (b) the distance it has fallen, as a function ofo:6jpuq rrx:f7x:x +h 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 a height ox3 v5suwqe4y5 f 125 m above the Earth, a package is dropped from a window. How much time does it take for the package uq w5e4y s5vx3to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show ug*8w/x- e:lzkcnxb90 w3cod 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 Galileo. See Figs. 2–18bdl/x*098 c xzc:w3wguo kn e- and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown ver9;k b d-t xhb*9iygw; 8tw;emmtically upward with *t9w-exk my;gm9wb; dhb;i8ta 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 w xl;0nnge e35hith 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 o v.xa:ma5ixu)xz7 ,i hf the apple in Fig. 2–18 (or number of photoflashes7z) ,v.xax 5hx um:iai per second). 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 (Fig. 2–32). F()akdvxsh wh le)fjgvd9o/0( tm 01*vrom what height above the top of th()d()gt/0k0olvh9x sm v vhwde1a j*fe window did the stone fall?    m

  A rock is dropped from a 4: *h8jsltvkrodt -c.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 orsh k tld-vt4 :*.cj8the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You poi 8fw)mr,q/ep:.j kobhnt the nozzle vertically upward at a height of 1.5 m above the ground (F8)m .kfr e/ wo,jqhpb:ig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upwaxsvzs*xfio7:gx *(+i m9 o ox0rd with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34). zio:x7mxx+ osvo09*x*fi (g s
(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 upw0 (t+:2 a:cnc qdpm,mer,rbbg ddkc+1ard by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the stree ga(ed p0 c+1b :mtcdnd,+rcq:k2,mrbt,
(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 ll h zw)i5/d6vof 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) Wihld5lv/z6 )w hen was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is9e my3 rt y:dw90-s8aficu k8c plotted in Fig. 2–28. What is its instantaneous velocity r8c-y8c90tdmf:w9 ua i3keys
(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 aukfnv c wdcb,r8y3* 9x5tomobile can accelerate approximately as shown in the velocity–time g r53vkf9db cc8nw ,yx*raph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in 9w4g1yxbs4,az bwu8 o the previous Problem (Fig. 2–35) when it ya w, 8uo1bxg94z b4wsis in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveledh+krrcb0*l/ s3p b;(udq)u et during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function ofj(d;/(1 jjhpa.r 8txao hgxm8 time is gi mh;/xrj (x818t.aj(pghjo adven by Fig. 2–28.

Figure 2–36 is a posit6e5g) x hmzbt4ion versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up ob54)tg emhx 6zr 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 three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s safety h ac1qn8o5j/x) 0bf,eaml)t xnet. The survivor stretches the net 1.0 m before coming to resomeq xxtl8) cj5bn0 f/),ha 1at, 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 isl3ox nn r:ev62 about one-sixth what it is on Earth. If an object is thrown vertnr3ox6n: 2el vically 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 by an over-the-shoulder seat m6*p o+he*8 i r1kzympbelt has a good chance of surviving a car collision if the deceleration does okz1me*+p y hr 6*m8pinot 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 bqc, t u)ha,ar8elow, 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 )a 8tq,ur,hcais 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 it)4mx8vtd2kffehr b5 9s cars for front-end collisions by hauling them e)9t2fv48hbr5k mxfd up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels about(o*nj8hzs-t.5 - 4dlnrjgv pf $10^9\,km$ 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 frontn8 : 8/yd,xq-wfted pl of the train has a pt,w88yf-le :xnddq /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 Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a dee4qd t fmy)hv-q/h 2u,alll2 elf-.e8 cp pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the pervfl e l-dq.muhy/f-8e4t ah q)c2ll,2son 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 th5p,dj) rl1oe pe average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate trpo e,5l1j p)dhe 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 fish. Supp;3; fzzsseod2iem;1nose a pelicm1d2z3s; if;eozen; san starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is plannedx (*wk auq6weezu /8*f so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from aex*6 uw 8waq(euzf*/ kn 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 trail/87 :7r bdigicv uvf;n traveling at a constant speed of 6.0 m/s Just as an empty bc7:r; ii 7v/d8glvbfuox car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone is u,rq99m+ed)y g,6iua r+r shxll v;w1 dropped 1.50 s later. How far i,)+uu;rs6 lmw1+e,9d xa hrqrvyg 9lapart 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 course of a t(0riah 6io(zkime trial lasting ten laps.(r zoh06 ia(ki If the 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 cribhe 1:guq (e3ests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was h1(bieq :3euhg is 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 ntgdvbo+/(1al;l jx 33w8ddd up one-and-a-half times higher than the second child. The initial speed uv1lwa/+xd3ddbn(;d tjl og83p 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 kgrqf yp)su;)e2e-t(xq/ px -fqe0 yt;m/h overtakes a 1.10-km-long train 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 timef0r feeeux -qpx;t/-p g;y2q)s(qyt )? 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 throwinubr1,tw w6b 2lg 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 released (Fig. 2–41). Estimate the average , wru b1tw2lb6acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, fro+e 5w*0x,8yv was.byj)j jszmm rest, with an acceleration 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 show+1j omy ht00/: hbadtbi,87bsbr -)xgtjzpi-n in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from bysm - i,tj t hbat bpr)0j7 +:0zx18io-hdb/gthe 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 t3mtyhqk* 7z+n raveling at a constant 120 km/h takes off in hot pursuit. The police officetm nq3h* +7ykzr 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 z wh6-8a6qpkdk+1 imf roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of mf68 -pkwahz1dqik6 +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 thv8l-v i .mdov58t1 uhce same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 1vvoild1h8 8 t-5 um.cv2th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling pard84vqpbi 73cxy/lbq 7achutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pulll8bq4di/q7c p b3v7x y 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 bur azz4 e2f/zf*sgers 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 zf4e2/ zs zf*athe 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 ;q*i qhk4 nl.w :ysw: y9jqk9tthan Joe can. How mjy4 9qwwsq*tnk i9y lh.k:q:;any times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a / cz3b haau33qa57wha h1 hlv4cliff while 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 the speed with which your friend threw the bal7lbv 1/a5hc4 q 3h whuaaa3z3hl?    m/s

  Two students are asked to find the height of a part1k-y7:el)p+ bljk p dticular building using a barometer. Instead of using the barometer as an altitude-measuring device, tklt7ejp pyd1-):bk l+ hey take it to 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 an 4l* dw:eq6qxud 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) Which bicycle has the higher wd:qlq*e 4x6u average velocity?