Does a car speedometer measure speed, velocity2*i 7nz-dcxb: hsq 4nd, or both?

Can an object have a varying speed i6;raz8pie7a n.): 6qkqbeu n ef its velocity is constant? If yes, give examples. aaiq;ep rz8en). ub:k67neq6

When an object moves with constant velocity, does md)cm a k0:8wxt w.n9gits average velocity during any time interval differ from its instantaneous velocity at any instant?t0 9w. acwmg8) mdkx:n

In drag racing, is it possible for the car with the greatesti 9ksdzg86 avf9t u ,4g /-ivs/jhvo5s speed crossing the finitv 6/jsigvvshg94,sa9 ku8 -/i od5fzsh line to lose the race? Explain.

If one object has a greater speedx jw;p;wjd f7 1xl7+0q15gw qx8oyyjt than a second object, does the first necessarily have a greater acceleration? Explai; wwq5tjlxpodgy1 f7;10xqwjx7+8y j n, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km (/bvrdz0ofz(2mu6 tl/h with the acceleration of a bicycle that accelerates/mofbz0(dz6uvr t( 2l from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleratib:e88ks1ms anfukea 5t1/ b q.78muvyon? Explain.

Can the velocity of an object be nex. 5fapxd8:/6 fy1ubqyy oxj(gative when its acceleration is positive? What aboutq61 :/ fy(u x.5afydopbj8 xxy vice versa?

Give an example where both the velocity and acceleration are negaawpfnc utwx)0 752ac 0tive.

Two cars emerge side by side from a tunnel. Ca pmp)a2apn:-mb 6;m dqr A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has p-:;6 maa2q bp)pdmnma speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speu)c pvk 6+813w4xmcf4d tbbg jed as its acceleration decreases? If so, give at3jxbf84m 46d)k bcup+ cvg1wn example. If not, explain.

A baseball player hits a foul ball strahky uq30m 3g1(:k jxuright up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the c k xqm1rgh30:jk(uu 3yatcher catches it?

As a freely falling objectqze9e 8 1lj79dkgqpt*5tcze - speeds up, what is happening to its acceleration due to gravity — does it increase, decretp-1 kd9jtelzqq5 8g79* e ezcase, or stay the same?

How would you estimate the m)bg*mtgizhb qx ,rqy(y w,,50aximum height you could throw a ball vertically upward? How would you estimate the m im5xy,grtgz,*bq)bh ,q(wy0aximum speed you could give it?

You travel from point A to point B in a car moving at a cqa h ri+eif6f 3;-;vhronstant speed of Thenhefrrvi6f ; iq;-+ha3 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 or why not.

In a lecture demonstration, a 3.0-m-long vertical string wir g 6ew u2:v.mg .epj60jib)kith 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 cli kw6v6gg)bp:.ejiue2 jmr 0. inks 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: a roc)u ):x 0)l**iio.bn ostdrvdsk falling from a cliff, an elevator moving fri)*n0t )rs od.x o*ivdu l:sb)om 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 s+2n7jo4zd lsibgsrr ch /dyd * -bw0v* )52ogposition with-2wgdr h+4/lbsd5)ios7s02orz g vn db**cyj 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 the motion.]

Can an object have zero velocity an3w.tujx byz96 d nonzero acceleration at the same time? Give exampyzbxu3w9. t6jles.

Can an object have zero acceleration and nonzero velocity at the same timeq 1db1m 5 l8y46zkuugb? Give exam du6u 15k1zlq4g8bymbples.

Describe in words the motion plottfzlm*d9dl6 n+ei*kl8ed in Fig. 2–28 in terms of v, a, etc. [Hint: First try to dzfdi *lend lk69*+ m8luplicate the motion plotted by walking or moving your hand.]

Describe in words thesh,) sgx0c734zb uxkk motion of the object graphed in Fig. 2–29.

  What must be your car’s average sph zdhd +)bj0x,eed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long7b(pj2q l km q hps*d6b1ze/3a 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 s, zwnj ;k 7dbm (k )(irzxs-2sgc92qg ,bh k9bg(2(skb xrd n-gim,jz sc;zq7w)2ow far do you travel during this inattentive period?    m

  Convert 35 mi/h to plxvxhoy5 /zj f e3x6w9y;2;v
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves7n n0s:k*mq 2ybr(zri 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 steadilalf*5wd(f wi2 tv.w(py at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours a v2w*tdl(pwi5 (a .wffnd 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 s /:c,www1m,/mg1bk;f3 m*k hndm) l4nvtfzh seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in ehh1n vm;),k g,tf3bs:nw m/* d w14z/mwmkcflssentially 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 a tota oo2.cmoeicnzm+ng2 pv.r2)h6a h7 2pl time of. h n26zoog2m+c. h)ip7 o2vaep2 cmnr 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from l*epf0 y po6z tr548eoits trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops orp opzt*0f6l4y 8ee5 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 paraln5f1 p:1 v,c is.wjnbslel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each othepn n1.:c,jb15vf ssiwr? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long wil i:qf*z*+u4foy (fdmzc2on( ( wlx)kxl it take the car to reach t2 u xd4xz(f ()ic(lzomfoy*nq:f+wk * he truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encountersm f2 gulclkzif18+8(i a tailwind that boosts its speed to 990 km/h for the next 2800zlug (mii1c +k8 2l8ff 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 averoq )usq*e7xuj0x u0a0age velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h foll) uqqou07xaj*usex0 0owed 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 cws7,jo/ x9 gsvdguvts0,2if5onstant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hea5 wgj,,u79sgx svvftdio0/2 srs 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 kex 8 e.f,4dhr8mdoi3 tm/h in 6.2 s. What is its average accelerat83r,hi.4 xet dfe mo8dion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acco eszv*qin .ew (3zmz1/n6j 0meleration i3 mez*1v/ze 6 0ozqm( .jswnn
(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*l:d* 3mc.e yetybb4*g-gos x*x* rsk.0adp d acceleration of about tbgrx*de* 04:y.gc3lyssxe*-.b mod *kda p* $1.6 m/s^2$ 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 constant1+ sri*.fnb78/ kwqk n dj3w. b/dkull speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, w3*. ibsr./ wwljfd+l8u b7 k1n k/dkqnhat 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 tvfwd,/ums m25eu,:c car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity5 2ts , w/dfvc:u,memu 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 acceleratiomc25bucg;qg awxq8 f*8ej ulh1l- 96 zn? How far did it travel in this time? Assum2-c685bcqaxj * qm9h gz wfll81 ug;eue constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What w d ey :zw( r)bu+p41ngvxl3nd;as its acceleration, dyw1:xlg3 v dr(ep+ )nz;4bun assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runea3u2 19tn- v 3otwainway is needed if the (constant) acceleration it32nia13ea9nuo w tv-s $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out o1;u kwya b:*wgf 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 how long does it take her to re gk;y:b 1wuwa*ach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to r )nx z;muana) .vo8e/west in 6.00 s. How far did it travel in that ti)8/)au eoax.n;v z mwnme?    m

  In coming to a stop, a car leaves qd f0h,3 xb6/tw7l hu-v)w 3)u 6zpjawh2eohrskid marks 92 m long on the highway. Assuming a u3q7)w6-ahu,le vxhwhw2dbrpt0h6oz3f)/j 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 compresn, yu:.5tm ;2tps labjses and the driver comes to rest after traveling 0.80 m. What was the averagl5a:.jy n2;stpu m,bte acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with 6r 8by*-c owcuan initial speed of 95 km/h and human reaction ti* cuwr8c6ybo- me 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 distz*vtno) flcw4pw: i6*ance 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 highwg lbdyzi6h *xt/, r4g*khrf08ay. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate agr4dfg0kr*yi /t*x6 h,h 8 zlbt 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 zeai x0 hpfuv+/.g:+s n +q6esthe 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at./g0h q:e+up+nf+iv zs6saex 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 intersection just l9t dz, q4 j;ip/gww/+ie dif,rob:1gas 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 zgef tig ,lqbwp /1/od4;diwirj9:+ ,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 op;; j9rcjfd6n 2;+j kx-wbr .nyfgp3qf a cliff. It hits the ground below after 3.25 s. How high;.npf; wnpx6cj32r9q rjjkg+ b-fdy; is the cliff?    m

  If a car rolls gently (5js wpdb6.l 2 0fxvef6$v_0\,=\,0$) 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 of1e6kdp3afej6+zy p k: 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 throwzj0yv9z vgcsm:af:ie 6* 7( fming it vertically upward. With what speed did he throw it, and what height die:*f sm mfv6:izz 790jgycv(a d it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and fal )fq4ycxv9/ jwls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s4y jv/ 9w)cxfq . Ignore air resistance.

A helicopter is ascending vertically with ( hzptc/;0ilba speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the heli0lt(zi pb/;hc copter’s.] t =__ s

For an object falling f(i7(nnw ;jsy freely from rest, show that the distance traveled during each successive second increases in the ratio of (s7jn; yn(fiw 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 (algebraically) that a ssy.r*- .pph(yl,yg; jych6dball thrown vertically upward with a speed.h,6y j;r-p.h*ys(dp y cglys $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertixozs -8 k,w)oically upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of 90ly2fazw xxd2ay4o/ the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, bul 9af2oy0xa xw z42/ydt not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past3hh x1v 5(xf eizh1z.c a window 2.2 m tall (Fig. 2–32). From what heig1 hefixx (hvz1 hzc53.ht above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oceavq) :p)bycg* ozts08g n is heard 3.2 s later. If tc p) y)*vb8g0t qos:gzhe speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose noe 5y2c8et6u z.kunzg:a iq3k8zzle for a hard stream of 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 is5kcza te86 3iuqeuk.z2 :y8 gn the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 1/hqd 6mbq c*/m2.0 m/s from the edge of a cliff 70.0 m higqmc/6mb /h qd*h (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 z l-w(qp+u5x1 6avxwra window 28 m above the street with a vertical w +65 w(apxlqur-1vxz speed of 13 m/s 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 velocity of a train as a fu4r smu.oj5co wf: p)y,nction 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 constant? (d) When was the magnitusyo )pu ,5 .fcwor4m:jde of the acceleration greatest?

  The position of a rabbit along a straight tunnd- dk7lxe hdle(cfv.ck15 ;d*el as a function of time is plotted in Fig. 2–28. What is its instantaneous kdlde1ecvx(5. - d;7 hldfkc*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 showns: - pp23i9rq3) fx aowtx8acov ku3,c in the velocity–time graph of Fig. 2–35. (The short ws2a c3-rc:9vpoptuk a xo8 f)qi3x, 3flat 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 previous Problem (F6w3wo fe6adm8ea 8b6vig. 2–35) when it 8e3 of8mdae vawbw 666is 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, estimat u k+,3fsb6 ozq,g0qdfe the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacemente.aq8 si k0p-w as a function of time is gqka8 e-w p.i0siven by Fig. 2–28.

Figure 2–36 is a position vel8ix wt0b)1 6mpmrc6kln+ f/8 ln6zvfrsus 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 acceleratio+61p nzilw xlkfn rlfmv8tb/6cm 068 )n 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 firefight , js lsvpt3tvnd82s6;er’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–dv63ps ,t;tl j82sn sv37.
(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 ab blc;w *yz /a9+(ki6k2 cpppj rg.d*tcout 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 Earth, assuming the same initia6l/ydkjk+b9gr *wpc2.ccitpa z p *(;l velocity?

  A person who is properly constrained by an over-t29hglfgqoma3c2xt* +he-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 hlof9x +* mgc2t2gaq3“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 7gr/,hw qwglw 72lri ubo910u, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he meagworw huirwl7lb12u0g q,7/ 9sures 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 ca*5+ tn . hjg0lxnct:ai3;djfi/ 2dois rs for front-end collisions by hauling them upat nsjidg:* 3x.idn c+0 l/oj;ihft52 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 Earthb2ky x*j2:grt0ykpb s6k3q+yp2e l6 v travels 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 um/ -.dk6j,skzwr9jr/ap x qy7niform 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 fjrd76z, / wrxsj-yp. a/9kkqm rom 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 aboveiravk8op ;kw6.* cuw6 the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the *i6p.wu ; r8kc6ow kvaaverage 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, eb94dg -2z;t k0qia ylit 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 tbi2zeg4 d9ql ;-ty0akakes 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 ol+/rg5,y zi.g)lcgthk 7t a9wings and free fall straight down when 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 surfaca/l. zgg7okithl5+ ) y ,g9rtce of the water.    m

  In putting, the force with which a gmoj2)nsp2r )golfer 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 frnsog2jm) r2 )pom 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 travelingp48 prcpl.mc2 at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelprcc.p p8l2 m4erates 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 b2mv;bu52bsnk) ej 9sguilding. A second stone is dropped 1.50 s later. How far apart are the stones whebss29 2ug )kvmb5;nje n the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must as (o93p 2cr9kcqz tz*fverage 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintainedckt3( s 9zzo92rc*pqf for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountacda*xio e;6.su.5vvy g) ; abcwkm(9yin pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his spw 5kxu9scgvymvd6.;yb a*o;)( e i. caeed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. t+l)z gl(ebw x-vrian2j5 ,*oThe first child can bounce up one-and-a-half)onielag(trwl bx , jv-5z*2+ times higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train travd ywn8gwm,; xf -05zcveling 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 w,d gmx0zyv ncf8w5-; 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 bauqwlq(f6tiyo us03.4bj pr6 + ,oq7ebseball, the pitcher accelerates qubewfi4y3j(60q 7.,6+u oqpo rts lb 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 accetrjht. s*)kr 1kixnzi5+ gj98 leration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown cu9ij7r(v 7m sccfppd) 0hk+ol*l9l;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 td9lkllv7p*sc;h jmr0f7cp) c( o +u9ihe 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 s 74q4r i7 8ie xdeq0jzo)a9fmad )sni8peeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining 40o7m)ds e8aq)fq74xdaz9 r8 in jeii 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 after2fzu0)7l )yd kiy r.h sy8we/g that, a second stone is thrown straight down with an initial speed of h/kl gyy8i u2)ysr 0w.z7)e df25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The fir)koj z8t10bo6tc, qd zst stone is thrown withqt 1o,ktod) 0zczj8 6b an initial 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, how long would it take a free-falling parachut9v (vegeh.yxym+hp 5 k2l tjo78sxu/*ist 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 pet g+ 5u /xey7epx *k8s2.v 9(vojhmlhyrhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to sen vwlo:15er7ma r(z/z*oix7 mnd 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, o/m7x1orzz:i57(mnw*vaer l 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 faste1.m vl.0lia sfr than Joe can. How many times higher will Bil.vflilam01 .s l’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below yo8s( mknbs -iz7u. You drop a ballsin(m zb8k-7 s 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 ball?    m/s

  Two students are asked to find the heighxu0sy g:cj5(w t 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, timing its fall. One student reports a fal0g(s yjcuw5 :xl 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 gr 8+yftf2fnjj ;aph 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 bic8j2jn t y;fff+ycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?