Does a car speedometer measure speed, vrhj7p;o3w p: relocity, or both?

Can an object have a varying speed if its velocity kz3 m mpz0.s sg6sowx284b(4hissxr :is constant? If yes, give examples.3(4:6siwxo2 8 bpzrxszgm .s hs04smk

When an object moves with constanz)e )k6*bi)mdfmu1 cox() so rt velocity, does its average velocity during any time interval differ from its instantaneous velodkb*o 6zmcu1is o)mrf))e x() city at any instant?

In drag racing, is it possible for the car with the greatest s w0j upgh028hft1e cw.peed crossing the finishwutwpe8 jh.cfh 100 g2 line to lose the race? Explain.

If one object has a greater speed than a second object, does the /rjbygwcx :4 ,first necessarily have a greater axc 4 rwj:gb,/ycceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelehj1seo:on- x )rates from 80km/h to 90km/h with thenoo-:1h xsej ) acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a so5dp:,z h6 wvvzuthward acceleration? Explain.

Can the velocity of an obje6-((p l j p4kkuh:v,;smertld ct be negative when its acceleration is positive? What about vice verspk4h(; sml ed,6 jpl:v kur(-ta?

Give an example where both the velocity and pl4 f*;* tyqifacceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling grzie+ qi* ef0,t 0vd8with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/minevr*00zii + t 8ed,gqf . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed 4-f; cusl, vvsas its acceleration decreases? If so, give an example. If not, explav4-; vs,u sclfin.

A baseball player hits a foul ball straight up into the air. wen5yh lg5mx3pt5c, a28vn7j 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 cat3l 5xctgjhv,y 258napwmn 7e5ches it?

As a freely falling object speeds up, what is happe n+clk p3ei bx)kjs-56ning to its acceleration due to gravity — does it increase, bek) ji ck6nl s3p+-x5decrease, or stay the same?

How would you estimate the maximum height you could throw a ballar 2c(;metf 7m m i;g44t(bmqd vertically upward? Howd4tc4mime g(; mfb q7 m2rt(;a would you estimate the maximum speed you could give it?

You travel from point A to point B in a car movingp*w01 lydor fl/k43p r 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 ? El4oy 3 *lp rdp1f/0krwxplain why or why not.

In a lecture demonstration, a 3.0-m-lon rw kuqo- l+yb5cql4.o/ v74jmg vertical 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 4o-rwlqqy k4 om5/.c7jbvu+ lthe fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accd1(a*jyi7* fpgakg5ieleration: a rock falling from a cliff, i g dayjp7 fak**g51i(an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original q04 i*:kxmc1v;mzfugposition with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to;41z mv* qxk0 :uimfcg the motion.]

Can an object have zero velocity and nonzero acceleration og ,kg2qpo (*h h;hpw(at the same time? Give e(gp,hh gk 2;hwqop( o*xamples.

Can an object have zero acceleration and nonzero velocity at the5p rbc3 qj ja/b-ptx;; same time? Give examples 5j pta bjr/bc;-qpx;3.

Describe in words the motion plotted in Fig. 2–28 inm9z8oc6 a-nz u terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving your h9 oazz8unm- 6cand.]

Describe in words the motion of the object graphed in e*wskk ka4a+r2g6 p +4gn h6wtFig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25r* 3uxj:lxf5u h?    km/h

  A bird can fly 25 km/h How long does it take toki*i jhbqi5:od.ujx3b 5nv9.g i 3, bx fly 15 km?    h

  If you are driving along a straight roadirwf5;dv: x:o*n:x. d vsna,x and you look to the side for 2.0 s, how far do you travel during this inatt5oxxn drw v:idvnx ,:.s* af;:entive period?    m

  Convert 35 mi/h to rz86 m,y j:k d6u-blrbi -m4yh of,+ax
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves;g tz68uoi/0669 cteljmk/g2d g plfm from $x_1$ = 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 begins wzg4 nkwky8 -ner7wu*2 o*tr(to rain and you slow to 65 km/h You arrive home after dru*w(7n t2wzognrk4 8-key*wr iving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash awr:z/en (a3 klnd the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives nk :a l/3e(wrzin essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight comp+p 8n;1w tkcd8 kgkd51 ()hanr)ba pjjlete laps around a quarter-mile track in a total time of 12.5 min. Calculc+bpkdwj) r 1g(j5tn;ahn k 818)ka pdate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight l 3koplj5+4 gr,gl ;zl bwtbaz5+cdk.6ine, moving 116 m away in 14.0 s. + cr .b5 kkd54;63zwtapl,g+lzgjlb oIt 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 parall: zz nqcaip/8kbkf/3, el tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.k/bpz ,3/ zfk a8:inqc5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 1n3hg/ b5jmja: y- :davn 4lef710 m behind a truck traveling How long will it take the car t5avy3: e/ajfhmb : l74ngj -dno reach the truck?    s

  An airplane travels 3100 kmuh8pyu1rvo:bk b+ 2u 3 at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km bv +3:bu12orupkh8yu.
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 avera0 *-1i r3f7*aojt1rtpmf. h5uaevo hy ge velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followeaempvrih5 1a1 t *30 furjt.foh-7y*od 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 the pins at the end p wsp9d1pf-kr w fh)46of a bowling lh f4w9)kw6pfs dpp -r1ane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6. 2 zlahzr y.i8hw j-0f6a.sl)b2 s. What is its average accelerata20)ia h jw.f.rsbly6 -l8zzhion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates frommha*p n3kn3a+1q ik*w rest to 10.0 m/s in 1.35 s. What is her accelerationak*qh n31n+k wi3*apm
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleration of auqf :2vi+/n 4yduj:zdbout : yd/fuv+zjn4 iuqd:2 $1.6 m/s^2$ 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 vc w4 w.nbg(tha 1eh ez106k*pc1vb ,qat constant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its accelerationnba1cb* kwwpte1zh1 g4(,v .qh06 ecv 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 frohqxv . y)2)mgia1zrw4/3 dujzm rest at t = 0 and moves in a straight line, is given as a function of time in 3wjx)u .1zzqar)2vy/h4 m gidthe 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 u4 v 3zjk8j:ibeu o)kts 6g:0r6.0 s. What was its acceleration? How far did it travel in this tim6) 3ir: j4ujsk0ek :v8bugzo te? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dix8jpn(9j f)k lstance of 85 m. What was its acceleration, assumed k)p j8(lj 9fxnconstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeof4/byg,8 bbk7a e,;ljn p in+bpf. How long a runway is needed if the (constnjp4ib8,p; yk nal /gbe, +b7bant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out ofp1- / fom5yvpi2yb,fc the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and -o,m 1/2i5pbcfy yf pvhow long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down unifo.byt:b7c44 )xyti bwk rmly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel 7.bwkx)tc: y4b t4i ybin that time?    m

  In coming to a stop, a car leaves0 s.b,x1tww cf skid marks 92 m long on the highway. Assuming a wfbw .x,s0ct1 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 end of the car cd. 6giy mby4ec42do6 0g* wvxeompresses and the driver comes to rest after traveling 0.80 m. What was the average accelerbme6xvwc.g 4i4 * 0yydd26geoation 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 cua8*npvy nl* ly a,0 ks5d4ko7ar with an initial speed of 95 km/h and huma5ok*vsal4 u,p na 0d8ly7* yknn reaction 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 the stopping distance ofrr:/jr 6 3r*h;qz cwyt 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 lookk -/cscjomz41s for an opportuccmoj/ z-s 1k4nity 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 min2o n4oq,s u4 tqty5dj2gco. 4d. After exactly 27.0 qydu5o2d4 ,go nq4tc 2to.4j smin, there are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an interse3ts ma:nwcx;3 9vd0dlction 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 c03x tw van9s3md:d;l 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 a cliff. It hits the ground below ppq zylh; g skba.0w-6h f+7j0after 3.25 s. How high is the c s kz aj0;h-wq7phy+lgp6b0.fliff?    m

  If a car rolls gently icmb e 6ayg:1p m3s4ob6oc9f. ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a spe 3b q ,l,*e)d:jk xat3elvryp.ed 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 throqoli-yq2 .,rd v eb6(pwing it vertically upward. With what speed did h-oi2l. (rpve6 qdybq ,e throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under t6fxm3s;y+k.-wiy h(vm kf ,zuhe influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of timexkh,z6y3;u +s( w - fk.yfvimm 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 c m23g tcx5y)iof 125 m above the Earth, a package is dropped from a window. How much time does it take for the packg25ixmcty3 )cage to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled du p:xv( 12jmwmuring each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 ajp( mu v:1x2wmnd 2–21.

If air resistance is neglected, show (algebraici xx8-u)hp -hvzy0m)cw6 sc:v ally) that a ball thrown verticalh6cy)8c--mpu : w )xvv0zxs ihly upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward wi kzddp, ,pi8hgw8q8a)m (e ou7th 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. 2a;+6bpq :zj4 zi 3qfxn–18 (or number of photoz3fz x :6pqqbi 4nj+;aflashes 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 iq-lw f4lq5d v+tz :,tkt(ea7to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window didlt5- zi:lew7qfkq (+ttv, a4d the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is bvxc14 a p+k7yheard 3.2 s later. If the speed of 4c kxa7b1v py+sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream osov: ;. jwfn, nq2 aqy/fwmm h+l.2w8gf water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the no +n w.:awq2/mgof sw. y,nlfm8j2hv q;zzle?    m/s

  A stone is thrown vertically upwardvi h o+rq6f)wbb/3 3jn with a speed of 12.0 m/s from the edge of a cliff 70vnb f)r i6j3w 3b/+qho.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the str;si4d/mw( lyz eet with a vertical speed of 13 m/s If the ball was thrown from(i ;4z/ lwsmdy 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 velocitxbt1ug 7mm-7d/fj(bb - wsq k9y of a train as a function of time. (a) At what time was its velocity greatest? (b)ukb d17wj/-7xq(sbbm -9 tfm g During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a strair )e4cn9nnib94z zj7 sght tunnel as a function of time is plotted in Fig. 2–28. What is its i n9)ben49c 7jrn4szzinstantaneous 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 approx+b f;l s.f24 g. t,sdjk3fhdfdimately as shown in the velocity–time graph of Fig. 2–3bsf2dsf , t fk43.j h.gdld+f;5. (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 the previ/*h 8av9ho tuuous Problem (Fig. 2–35) when it9auu8 hto*/ vh 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, estimatep l5e0nae*y y06n-j;vtsosr 3 the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t +h hiwf+nteix: )7 kfbis;9s*graph for the object whose displacement as a function of time is give* f7 kxfin w+is+i ;)sthb:9ehn by Fig. 2–28.

Figure 2–36 is a position q k g(a6w)/gezqxh 9j7versus time graph for the motion of an object along the x axis. Consider the time int(jq whkg96ex g7zq/a)erval 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 three questions for the time interval from C to D.

  A person jumps from a fourth-sv()a p:7n 0 vajyyal0ku3 1rcrtory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.a v0 v0akc:r()jyy n1prlau73
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-p*6 bp:ohqhdvn0cah 8n b23 5zsixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher wihq c p o62bannb03h*hz58p:vd ll it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat n(ibcke8f e9d4(j+x sr ,aq.h /*qds0qct.q mbelt has a good chance of surviving a car collision if the deceleratic.qs9 0adr(*qjk ibcn +hf,q8eq xs 4 t/e(.dmon 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 th qeqwhq3x2y9p3 54ir te road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 253 qqrqyih34 w59xet 2p m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end colli+gh d1xil:-e csions by hauling them up on a cr h ixd1-c:leg+ane 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 : 1(+sb7oe:p jmz ,wjv uy5xd8ohwqz+ about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of rm:(rr0rr7a cthe 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 trairma0c:r r(r7rn 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 ddadq+6-czd8( n3sofboard 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water.zn(qad oscddd8-+ 63f Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is nuwk u2)m5 j9hdzdc0i,ecessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an ideimw0h2,duz d)5juc 9ka 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 whe0(;*aa g.ha;iqvlvqv. c z :len diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface oa(0. ;lava:*ivq ;hcge.v ql zf the water.    m

  In putting, the force with whic28 bjtf qmhyf4:s 8p ctyd8jvm6kr1, ,h a golfer strikes a ball is planned so that the ball will stop within somc4k fy p8sf t,q82mj:r1j,mybdvt 68 he small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a 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 constanuxf3fe:n9g/ dqa2s9-z3hc) ud fn- dst speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and ae29f3dus:g sdxz/)3d a9nhnfcu- -fqccelerates 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 mqb+rz h4r4r7 is dropped 1.50 s later. How far apart ar+ r4h7rmq4zb re 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 time trial lhie+ qgq yx/78asting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must/h+ qexgqy87 i be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as hrvs(b53 jrj9fe moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h ( brr3sjfjv95. 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 u s6guby o+*g: jimdz+,p one-and-a-half times higher than the second child. The initial sp*dmbgyujgo+z:+s,i6 eed 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 ovzt7 44+axcjs kertakes 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 tzstajkxc+4 74 ake the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the basvbq 4rj .7a il0xz8yb3 yy(j:qeball, the pitcher accelerates the ball through a disqyaxb 8j0yrjb.ily3z7v4 ( :qplacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an b9gh4 tq3eopus-oj ld3c38+ 39rox vwacceleration 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 pattern0bnk1z; z x*lp(j ro-l 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 intersectibxkp l zzo1-n; j0*lr(on, 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 aw5r f:pjru2(b+m y.ue constant 120 km/h takes off in hot5fer. b2j(umwyp u :+r pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a seqz x)o:w7 ned6cond stone is thrown straight down with an inioqxdzw6n 7e) :tial 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 verticallylj y/c87c qd)+cjc;d+m27 n3fzbwguz up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-flooz2 7 zcc c8;)j7 +ujglny3bcqfw/dm+d r 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 frx in4.nd nudvx77 i,w6ee-falling parachutist 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 resistan wd xu76 nd4,v.xin7ince will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers jpf*bh;ad1kv ty c0,- through a grilling machine. If the grilling machine is 1.1 m long and the burga0h,ft*b1 cyk -jdpv; ers require 2.5 min to cook, how fast must the conveyor belt travel? 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 fastell2ut bkt88up f+p5g+r than Joe can. How many times higher will Bill’s ball go than Joe’skpt u8bf +tlp+l25 gu8? $\approx$ =    (retain one decimal places)

  You stand at the topb.m g7 g91n .frg3m:1iqlncixi 9pi 6k of a cliff 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 ba1k xm lqiic. 1riig9f.n: m6ggbn73p9ll 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 ball?    m/s

  Two students are asked to z3i9k no5xp o-8qbu 2yfind 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,3uz-yb5xo 29qi 8o knp 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 .0zuqhs+rfigvm+gw7f(r d-;tc:p l- ;- cgfaB. (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 ar(twip-+gra7l d fuc;m-hs0-; g .qgz+vcff: verage velocity?