Does a car speedometer my p 6m+ (i5ntmzz.h*vsme7*breasure speed, velocity, or both?

Can an object have a varying speed if its ven:3 q o7fmdho-locity is constant? If yes, give exampleo :n-qohmdf37 s.

When an object moves with constant velocity, does its ahr7 j-6u ja*zsverage velocity during any time i*-asrzh67j uj nterval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatesuq7 f--klxrddjg+it0 4;s ivf4z d5.8l aj mw(t speed crossing the finish line to lose the race? Explain 7 ifdj8lsgr ifx4u4wdvl -d;qjm tz(-5+.k0 a.

If one object has a greater s id.8k*w uut1:l ncc)ipeed than a second object, does the first necessarily have a gcd*ci 1lu). iun:tw8 kreater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90kmxch*2b9ebok g+vvyi2c +(o j,/h with the acceleration of a bicycle that accelerate by* i(cohb2+2vveg,koxj9+cs from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward accelermspum, eu; vkng,.7p:ation? Explain.

Can the velocity of an object be negative when its acceleration is positive?f)cl4 wh.;6wdpus *qu What about vice vewqs u)u *6c hwdplf.4;rsa?

Give an example where b- +rwllhsd:*z h+pan *7l, g-ww0dh vzoth the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is travxoo o kc0; zt:(hxjz:4eling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain yo ;ch xt: zokx0o(j4:zour reasoning.

Can an object be increasing in spewb,b d;vuu7qp:33;oxqp t4 f een3u+ led as its acceleration decreases? If so, give an exaxf; p3;3wqeb,ubnev:4u to7 d+lqu3 pmple. If not, explain.

A baseball player hits a foul ball straight up into tha xui q08)t yd6zmo-tm /ry28. wmm/lme air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, ho-xw m/mrmyiaut)q 0l toy8 86mm2/. dzw fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what h wnyw x31fa3(is happening to its acceleration due to gravity — do33 1yxw h(wafnes it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a6y,xr5wlo2z a 4s)iwp ball vertically upward? How wou)x z2yow6 p rai5ws4l,ld you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a con u6o7 hs/m azs/1adzzli- p43sstant speed of Then you travel the same distance from point B to another point Chmd3ali416 a7/suszz /poz -s, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical u 69y8x,jn igkstring 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 hk8uj 6iy9, xngits 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 :cg2f+jo3 sq gacceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the wqcgfg 3s2oj:+ ay, a dish resting on a table?

An object that is thrown vertically upward will wh t.z kt 5/2,6snvjzzreturn to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreci t 2nwzhztjv,. kz/5s6able, 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 sa 2i* 3yho :,ylny4uoxzh 3kaxasu1 ssr43wg55me time? Give examl5yihry s1x3 4n4ukz5 ,s y3*w2:a u oo3axshgples.

Can an object have zero acceskoj(*jxo q* r --kpm*a 3t9vca fwh-7leration and nonzero velocity at the same time? Give exa7k(pt c-rsv*- wo-j ohj 9af*m3x qka*mples.

Describe in words the motion plotted in Fig. 2 -be15qr9izv g–28 in terms of v, a, etc. [Hint: First try to duezq g-5vib91 rplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object ge( e ) 2*g5f zgk+fezqydvu2d5raphed in Fig. 2–29.

  What must be your car’s average speed in,5z qtegq.o1:orfy7i:p yl n/ order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h Howny jd t--lu n:s8ydu.- long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 udoi ++pb*v63iu a 6ihs, how far do you travel during this inud*66 p +oai iivubh+3attentive period?    m

  Convert 35 mi/h to 7a0 rl2k8km+x +ifb 1nxu ri)x
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from8 cr ;mq s9bly8eaah. t0gh,y-qu4 zv7xl+,ve $x_1$ = 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 forw/xkkwdw)a;e 5fsi0 grwv bb6-f 0q:3 130 km. It then begins to rain and you slow to 65 km/h You arrive home after drivik f:/ w5axbf-; )0web w6swgrivqd3 0kng 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 lightna;5wrpr gs,7t )+co(6 kly ;bi- qcnaying flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives iy7 5r,oybc-lsqr(ai+; wg ;)ta6c npkn essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a8s s3hsf4p4p;2n iwbz total time of 12.5 min. Calculate pss4w38sn h;p4i zb 2f
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m awayxuzgrr+ uj 8 q1qn27y6 in 14.0 s. It then turns abruptly and gallops halfwaq n+y7z168jrgux r2 quy 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 e,htljuj 7 man3*45bhfach other on 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 b fhnj,3a*j l7 mu5t4hwill it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck tkbmml7 zmo*96jjno7-,tp)a f raveling How long will it take the car koj mo-n,t9jm6f zb*)l m7p7ato reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encount t-+40 /qw 71 nsefx+oiduqqypvm3 xt.ers a tailwind that boosts its speed to 990 km/h for the next 2 + uxwt fq1v7t /0dsq.4px yoq-+imn3e800 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-rtigx. cz.4i2os8- o3 qiru, itrip in which the outgoin.g8 tiocs -ui.riqz,4rxio3 2g 250 km 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 f :v z39lw-v8s:xwkdqwo48 8ur sjlb( speed hits the pins at the end of a bowling lane 16.5 m long. :(w-zlvr 984j:8 blsq8uvksfo 3dw wx The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its average acce;c. gu 14brili fe79jeleration.le1ribj gu ;i4ef97c in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is9 qs9b*mbf zn8)an o6i her acceleration n b aozqmn98*ib)69fs
(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 n( qwngk:0jl)of about0qnl (wkng: j) $1.6 m/s^2$ 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 1104 6- s5 2cbw bk;l8plj(eth) a+luobap m in 5.0 s. If it then brakes ans4kjcp-lp (6 2ta5lb h u8o+wa;ble)bd comes to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and movess /a 4jtrm)sb5 in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each ij)/5t4 bs mrsan a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. Wo)a :.xmhp2ui hat was its acceleration? How far did it.h xup) 2mioa: travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a d-a2-tiv*r nds5g gf1gistance of 85 m. What was its acceleration, assumed corv sfd2na--ig15 gg* tnstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeofz e:wti6 m:2.dil 1j8zx kwlg6/pdn;o f. How long a runway is needed if the (const zi ol2zi1wxwgp8e6 t;d6.:nk /lj :dmant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can *iudc/.5 -m qz zv2r7(jbx x jxjs+e5yburst out of 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 thix7. yrqc-jmi5xx/+z esvz5udj*bj(2 s 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 ;p7 d/zy (odsop;bvy,speed of 12.0 m/s to rest in 6.00 s. How far did it travel in ts7 y; oyobdp;z/,(pv dhat time?    m

  In coming to a stop, a car lel,i w3r; ;f8dz/xbswkd .l8ad aves skid marks 92 m long on the highway. Assuming a deceleration k; x,rbf8ls;i8zwad.d/dw 3l 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 compresses ad;nvp 6)ps3 vs mp/a:pnd the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “:3v)sa m pv;/pdp6 nspg’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 car with an initi1g+u4z xm 74c/agtmfb al speed of 95 km/h and human mtxb m1au+4cf7z gg/4 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 stop( tw wswlb0g(3ping 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 dpvz:rwm; ;0w jud)r+ highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelervw: ;dujrzrw dm; p)0+ate 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 mine6jpb + h7d9jqil;:gb . After exactly 27.0 min, there are still 1100 m to go.6piq+lg 9:b7 bjhej;d 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 interyn,hy vs7 :4no0k9boc s07pnvsection 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 (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 deceleran4:vy op707nbssy n9vo, c0khtion 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 6e44h+ phu0c22deo9agbf5hyt ag6 c y( ty3mda cliff. It hits the ground below after 3.25 s. How high is th6ea a56+ h4py o fhgyd42c2tt0c9h3yb( g udeme cliff?    m

  If a car rolls gently (swp l nzl,rdfz7 d r2 j-ud.l+8)p0-by$v_0\,=\,0$) 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 speed of 22 m/ 5yvys zv+x6 5q1p,( walgbg4x3su 6zqj0s)kes
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s ad(+(gg+kjos y rqz9)czylz j x7-(apl xgw:- 0fter throwing it vertically upward. With what speed did he throw it, and what height zr:g9+z-x xo )jpa(-wsz0 d lgj7(g(yqlk+cydid it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravw t)wnl8 g02e(2lw nmzygn5,fity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a n y02 wmw lf(g8 zweltnn)g2,5function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.vk 2g0jql:yyesh -;9n 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:0lysjhk ;y: 2v-9qgen The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance tr(3lvyx akts1+le0 jd*g/h f :taveled during each successive second increases i/+f*3tl ejk(0at: l1x gysdh vn the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algexl5 ha(z/ do)d8d i+hbbraically) that a ball thrown vertically upward with x5+8 )ahddbdlo/(z iha 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 with a speed of 18.0 m/s ,zrte-fcdsp //v e ;x0s8b*ze
(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 rt08bes qxj7/11cy ra apple in Fig. 2–18 (or number of photoflashes pyqea/ rs0c7 t11xrj 8ber 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 k79,)iemqam a tall (Fig. 2–32). From )a aqm97mke,iwhat height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and thei9um)6bg yxw3 )zf 0iv sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/sz i39fv06mwu gi)b)xy , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. Yapse 9*kga2 t :i0xmy37il+evckya( (ou point the nozzle vertically upward at a hk v(a (e3c+ p*a29x ame0:s yi7yglikteight 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 nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the e)k s34k;2ez9lzdig bp dge of a cliff 70.0 m high (Fig. 2–33 izde k2; zgsk9b)lp44).
(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 t5r kn+(zi+kqlj-m( v9ojd 6qabove the street with a vertical speed of 13 m/6q( k nzk-ot+9mqjl jr+ di5(vs If the ball was thrown from 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 v ac 1b/:hs w3nkjyax9:1)twqeelocity of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration ah)qw9sanx1:ewt by cjk /:31constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit aloi/ )skt68ozx0y:mt r t boz7a4ng a straight tunnel as a function of time is plotted in Fig. 2–28. What is / y0am6srtxztzb:784io okt)its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as shown in the vexj. wse3-i1fl.k81 g(l5dope2w ( rw6xbozii locity–time graph of Fig. 2–35. (The short flat spots in the curve represen1l.x gzw6dorx35j8 ifewpo12ki- liw b(.s(e t 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 Procio5e97w10 m1 ,eqt tyh)okkdblem (Fig. 2–35) when it is iykeho t 197q)dmo5ekw c,i10tn
(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 traveled duri+m4-9cgt zkh zng
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whosua m5yx7xhn*a5z(o s/ e displacement as a function of time isa7z h 5*oxan/5 (musyx given by Fig. 2–28.

Figure 2–36 is a position versus)fvxmu gxu (14gt,amg0( wyt57na iy( 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 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) Finalltw(u g y1umva5t (4ni(gxaf mxg 07y,)y, answer these same three questions for the time interval from C to D.

  A person jumps from alhu2 nq +74grt 7uak lrj79oq3 fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before comingj ruhqa2t77qg lr 7uk4+n o93l to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Mpbm1 /yt, .n-4 /l os6n pesyysipw1sb )kb0c)oon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Ears)b)o6 ny pml,ns w1sk/e4ytpi-bb0p/1s .cyth, assuming the same initial velocity?

  A person who is properly constrained by an ovdkjh0w x-htr9o.926+svfcq y er-the-shoulder seat belt has a good chance of-rjtyhd 62 owsvc+hk 9.09fxq surviving a car collision if the deceleration 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 mq a:qu0o)+ a6t*oje aahkp;o +bp:w1a bridge, 12 m above the road below, and his pursuers are getting to+;j1+ a 0: :uq)wqhaptom a*6abopkeoo close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles 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 frb/6+ vlja0o5ivpr hq 2ont-end collisions by hauling them up on a crane and dropping them from a cerl 2aq+0ji/vbh6 v 5protain 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 travez1rsawpw )h66r+ukiv 7s-wo , ls 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 bejxnda/ ; +rghau,- e 94umi)vsgins uniform acceleration from 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 last car as it passes the worker? (See Fig.,r h ax i/na9eums)g;- uv4+jd 2–38.)    m/s

  A person jumps off a diving board 4.0 m above theu 7bxqqftzh n.(y-z gn 70qwip0x5f8, water’s surface into a deep pool. The person’s downward motion stops 2.0 m below t,z gyb-fq 7qthw850ix(nx . uq70npzfhe 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 transit +*( 6,z a vhakl:dn ;nwz,dvzjsystem, it is necessary 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 idea of this problem, calculate the time it takes a train t;ah n(:ad6kv+zjd nlzwz*, ,v o 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 whexa70lo1qug 0n77is7 kqif49b o ddbf- n 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 sn7s9d1k b7dulqigf-of7a7x 00ibq o 4 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 goz8 + y469(r1bawn iibvstks*dp,s0 o plfer strikes a ball is planned 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 an uphill lie (that is, pur +b6va04bisk ip8(n 1sw*sz ,dyop9ttting 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 constav m lrjn i02f5i2cdoq*;+l(xa mls)20yg rn l6nt speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceles)l nl a+*qm 6l2n2l 0oi;yvfrmc0 jd5x2g (irrates 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 zi(da)odm)- g+zd +sla high building. A second stone is dropped 1.50 s late+d)m)+d -zdgloiaz(s r. How far apart 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 pk zswg6+ xq*.v)ou 0fny1,uu a time trial lasting tengpk1fv zs x*q ,+un6u)w0u o.y laps. 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 :k9g mxx y78f3 6akbsede France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 3x 9b:smg6y7k8akf xe km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on ( o( g +c-1a3zkdobraztwo trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of-zg b3+ao rzc1 (odka( the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.lcul. y-.r1 cm10-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 time? See Fig. 2–40. What are the results if the car and train are muy-.clc r1. ltraveling 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 wr o z-td(:laijz75ef6ith a speed of 44 m/s In throwing the baseball, the pitcher acceleratestjdz zfreia6-75o l: ( 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 acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acc.zsbk4y(fh(le8uf 2 w eleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection hao hcycik ens:x:,b/6 )*1upro s a traffic signal, and the speed limit is 50 km/s . Suppose youo b6/cuxn :)irce,*o yk :h1sp are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, beas;ozsmt* )xc vb8x3s07j3passed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The 0;z c3s7t3xe jom8 xsbvb*s)a 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 seconda:mtgjm0.gt)8+w1 z ejw ynnc7zib;4 stone is thrown straight down with an initial wnejb 8yt: win74ggc0+zz .1)m;at jmspeed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same tuuqfls(+9ve dr;nsj1on +0gm /07qy time. The first stone is thrown with an initial+ugv;yunq9s dqmj s(0rn1o70 /lfe t+ velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial 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, hw ykt-*f+j*yu ow long would it take a free-falling parachuti y+yuw*tj -k*fst 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 perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt touom3 fy745teqzb:ylc7ie 81g send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in :1zmo4ubclfq8 3tey7g7i5ey burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a bal4x+4 deh gnmg4l vertically at a speed 1.5 times faster than Joe can. How many times higher will Billg ng444dh xem+’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while sjor. r33;gtj9.hfosle 6v3xql:8e eyour 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 frir 3oe;:r. 9oleh.s 3gvtfeq3j 8j l6xsend 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 find the height of a particular )qucp.b07h i/s*2n 2ycfhknd building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing in.p22khcs i y* nf/ u7qhcdb)0ts 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 graphicsz(73v ft3alj 2hy 3 bevyq;)ma79h for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is y h2j 3a (smcb;)i q tev9alh73vyfz73passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?