Does a car speedometer measure speed, mlf(tl:e2(g i velocity, or both?

Can an object have a varyz *y b6aqosb3-ing speed if its velocity is constant? If yes, give examp *qb3-say o6zbles.

When an object moves with conpu)6 +a to/kvmo5 uy/v.c.sl ostant velocity, does its average velocity during any time intervals y olo+ua6.c5uvv .o p)/t/mk differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing t+ ffayyoi,zu h 19758gdi(ue rhe finish line to l7guz ( i ury,51ffd9aehyo8 i+ose the race? Explain.

If one object has a greater speed than a second object, does the first necessas4lo/ 9dg al8orily have a greaterd ol4a9s8/ogl acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerate, pmoo-r tc6+ts from 80km/h to 90km/h w+mc ro,6ot-ptith the acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Ek2qs x1o)www ,b:8doaf pcw(7xplain.

Can the velocity of an object be negative when ithi1)v,9:q r 5*ubqgntw pmd(es acceleration is positive? What about vicebuq 5:*,9mvrq )dn ew1 g(thip versa?

Give an example where both the velocity and acceleration arkt)v hp ef6-p-*fz3 lwe negative.

Two cars emerge side by side from a tunnel. Car A is traveli0x bu79i,lwb- ujjfqa6c1v q 8f1 aam1ng with a speed of 60km/h and has an acceleration of 40km/h/min . Car B hasaxw1fbu,q- j961ca 0f ml1 ab8j 7qviu a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If4q cgw7g 9qxi aqa8+0l so, give an example. If not, e4 g7axq 0+awglqci98q xplain.

A baseball player hits a foul ball s(b7 rozvv9 xg/traight 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 catcher catches it? v/zo(rv9x7gb

As a freely falling object speeds up, what)fz+daia4owy-d;3ja hv8 qck :dla 11 is happening to its acceleration due to gravity — does it increase -;4ia k cyqd 1ad)+ z8f:adlj13aohvw, decrease, or stay the same?

How would you estimate the maximu ijqz.mr8*hz xjm6k-* m height you could throw a ball vertically upward? How would you estimate the maximum speed you could give j.hq8 -*xm j*zzk6irmit?

You travel from point A to point B in a car moving at a constant spee3wp 5axhq2avp7m,jh/ m .2zs:h2p r hod 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 ents,:qa m z25vp ./hjoha37wpm2hh xpr2 ire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-5o/l. te 0ytrn-l:mib long 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 n mot/e :-n50brlti. ylot occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a r:nnr6hz4s o d6ock falling from a cliff,nn :4o 6rshd6z 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 positiq(y1, xkjhf) 9- mgqal 3owl7ton 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 acceler()g y3waq7xm-flj,thlo q9 1kation due to air resistance is always in a direction opposite to the motion.]

Can an object have zero veloceh dx;j 3ue-.(jbw1 ( i;lomvqity and nonzero acceleration at the same time? Give 1 vu dwj-i o.e;;mjb qhxe(l3(examples.

Can an object have zero acceleration and nonzero velocity at the same timrpf+;3+bu )r tgg6mmke? Give eb)g3f +m6 gr+km; urtpxamples.

Describe in words the motion plottei q rpb-,i-mbr 3d-zv;kpb.9zd in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walki;9r3p-bm ipri .zvd ,kbbz -q-ng or moving your hand.]

Describe in words the motion of the object graphedf rfb5:7vfo( z in Fig. 2–29.

  What must be your car’s average speed in order to tr 6.t5os- xr m0vcu9qrvavel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/+zc.rdal 5u;y dwp. jv6 3wwp*h How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the sf t*vp+ ude3ei:pwtn:9)z,s7 )ofvbiide for 2.0 s, how far ipu)sz:pidt +n) e7ov fet3fw9, b:v* do you travel during this inattentive period?    m

  Convert 35 mi/h to t 6q c qpqq7/o7a;,hol
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from v(3x5fs-8hcoqlpkg 7i3/t xl $x_1$ = 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.15d,dnndd p c* It then begins to rain and you slow to 65 km/h You arrive home afterp* dd 1d,cdnn5 driving 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 lightninr fwx lnm5 yg0y.22c7m t9znns6zm/8 eg flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the szg z t rs 9w.n/52fy ym2mm8x07cl6nnepeed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarteri ; spt3zzcm(z:n75 nd-mile track in a total time of 12.5 min.stdc:pnni 7 mz3 z;5z( Calculate
(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 away ziu6l-)r5 8gja 5b8,pi h:otb)2r ,gdr jtwziin 14.0 s. It then turns abruptly and gallops halfway)glr baj g 85pui)iw ib- 6t:,zjzdot8rhr2, 5 back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Eax eti7p;r, 7ky-)m*q nz uebw)ch has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (Sew qxe -*,eiuyztp kmbr)7);7ne Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck trav )jmyl c 2ypodx5h2u5(eling How long will it take the car to reacl5 5m2dyuy2 (cjphx)o h the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a t7 2)3uojl n ymp v-/x:edjt7b(shucm *js8 3lfailwind that boosts its speed to 990 km/h for thep8x m(duv/yj7 lt*l)h7jubj3ocn-3s:me s f2 next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity opu6x xgk8z69 wf a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0 wux 866pk9gxz-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling wito;jj4hm + er9dh constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sood4j;j+remh 9 und 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/35wruu y sx3mdhi z7rp3ed:he2 r(*4bh in 6.2 s. What is its average acceleration in r4ud3ridm: ( b7e 3x wsuphy35*h2zr e$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35zwyc.e z 3bo o.t9*n,s s. What is her acceleration9z.t*ce 3 ws.b nyooz,
(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 ba .zzbr8p4:l uuy*x+ jg;b(iof abou4jabzuzblp.(y; x8:* gu br+i t $1.6 m/s^2$ 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 1szsh)c z rl)0axbxow l/9:63t10 m in 5.0 s. If it then brakes and comes to a stztxl o)h :r3/ 9l6sws z)a0bcxop 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 cyz) 5jd:n+cc zar, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table.zcdz )+j:5cy n 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 1vont06ok1;w v.yrcm to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume cmv1vr.; ow yk01ncto6 onstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. 8gl9dy6 clov;y ;r7jgWhat was its acceleration, assumed constant? jvrl8dyl6o;gg 97cy;   $m/s^2$

  A light plane must reach a speed of 33 m/rv p4dkc u74/8aeinq88fj3 mgs for takeoff. How long a runway is needed if the (constant) accelr /d44k8cn 883p qufaeg7mjvieration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burs-x ua;78lx+ kchexkn71 :ojwjt 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 acj+u;1xx7-8 kkn xclahe:w7j oceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.0bor .8 aqxmw8wuo3(b9r3ybt0 +8t 8mgk:imv w0 s. How far did it travem(v ra3 xw:8m8ttkm8qbyg. r3u 9 wibo08wo b+l in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Ase xucxl 2d2k2 ju0 rysczo q:*bq73)7rsuming a deceleratio*ce)lyj22 bu q7xs :r qx307zdruk2ocn 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 compre a1mvf*c*8dpmtmxpzz)r ; 7z/ sses and the driver comes to rest after traveling 0.80 m. x;1*8trp* fdcmvpm/a)zz7z m What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances forqwssa6vi voso8l9 cgf 66557z a car with an initial speed of 95 km/h and human6a o5 vs6ssfo8qcv7l 56 wgzi9 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 oq5 6zww w sam:*ix.nd)wnw*b9 f 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 driverwu lpc.))bl+br2,c6m hxf 3xg looks for an opportunity to passh6,clxub3 g)p)2bfrc + wlm.x , guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After ex4g 8/t .qvff3 ,1-wzbbc nrkgmactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at bz4,kcfvbm-1ftn wq r/ 8g.3g0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as ov5,e 9-jti6cn vehqj)m29c h f4ml4p the traffic light tn-h4v 5fv l9jpchoq em)c6m 92tje,4iurns 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 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 aftj 7xoyrn l0.bqp+t,3cer 3.25 s. How high is the clif7b qr3jn clx0y+o.,pt f?    m

  If a car rolls gently 7/pgx qpiv/ bv;alw6 9($v_0\,=\,0$) 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 2:qq)91jnhp jf 00l lvt2 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 af8xyni* 2 9l1qurc(cj iter throwing it vertically upward. With what speed did he throw it, and whac1xjn uc*iil82r 9y( qt height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest andgr21-g d o4wzv falls 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 s . Ign gorz4-v2wg1d ore air resistance.

A helicopter is ascending vertically witdw sov1j*k 7ooi8*lah1 ig;v8-uj:pp h a 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 ;7jwo* ipvp-8*1ghl:iku 8vdsoa1oj take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freelt*1 a1zez+ccqz ( bhrin:q.i; y from rest, show that the distance traveled during each successive second increases in the z (r1 cbi:ztq+ cn1qazh.ie ;*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 (algebraically) thtuxi+;rns7v4aim*f 0 u) ;yr rat a ball thrown vertically upward with a *rmsauri uy;0t;r fx +74niv) 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 rm vi j5mi3;bl y1g0uotp1 tq736ci +mwith 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 betweds g k9s64e4p7 ky9zm u,4 9ftdlnpo(ren each photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two ndus4,9ppey9 7dz(gm kl9ksf 4or4 t6apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). Fronyt4pmj;n3;(i-4jurr yth* km what height above the top of the - uttny;jyk4h*( ; np43ijmrrwindow did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocmvq,r1c m90 ulean is heard 3.v,mm l10cur9q 2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a,,; m7fl lcmv 7n ojcq6xop:l1 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 quickl ml,o6cc:ln 7m1v7px o;jfql,y 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 wihfhr-yfsu/gpq* i2 lgi6-ar4wmw6 6+ th a speed of 12.0 m/s from the edge of a cliff 70 s/ hgia-+ 6rf -f4 pwgh*yqlw66m2uir.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 to34wmhsw, rt8s pass upward by a window 28 m above the street with a vertical wssrhw438mt ,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 function of time. (a) o+ ccphwc),oikst 59b+)0 mqdlg5w o-At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what)h+i 0o-oc)lkc5c9o wsbwd,+g p qmt 5 periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function )zg5psevy-/.j4q mpn of time is plotted in Fig. 2–28. What is itg5jmz -e 4p spvy/q).ns 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 v-dx ,c f6woj.s 78z-6 kkgeqyfelocity–time graph of Fig. 2–35. (The short fjo6f8 y qd7k,-x-wcez f 6gsk.lat 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 p ct/d1gig8uw );vl 4fgrevious Problem (Fig. 2–35) when idvw84tggl ) ;c/f1uigt is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled during*y2pmyk3 (aa p
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement 1u7fb re;x x92p 8ydqzo7t8xvas a function of time is given by Fix; b yq8rvx d 78uxoz2pe9f17tg. 2–28.

Figure 2–36 is a position versus time graph for the m esd)ysj z)zp 8t(.3nmgb7i/s5w 4qfnotion of an object along the x axis. Consider the time inters)4wp n5n7/djesi s) q3g fmz by(tz.8val 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-story window 15.0 m aboveu+ c nc itlhd7.;-3ddu;*hbmx a firefighter’s safety net. The survivor streti. +cut;lxdc;-d7 mh3u* n hbdches the net 1.0 m before coming 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 Moo9kuyf; mdex9 (n 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 Earth, assuming the same f ky;u9emd(x9initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has anxfj lb8o*w*v-x 55 vl good chance of surviving a car collision if wf5n-8ll oxx5v* jbv*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 a bridge, 12 m above th p( wkuv4f+*,(dfj237e avigis uzk- ue road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passdg*i4w+uzv p 72 (ue(ka,f- ujfsk3viing 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 f l9b23 ki,rqxmront-end collisions by hauling them up on a cr3 xilr b,mk9q2ane 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 tfmca,, 1.1ctp fhojc, ravels 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 the train k k;(bo)jkga:i t,wkk03mz4pn 15f;xxffv 6 qhas 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. Wk x56ak4kjwgztq;m )31bk vi,0(x:;pknff fo hat 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 aibp id*dl3zbskx-5.b3 q7e2 cbove 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 average deceleration of the person while unke.xb s*c 5z bd327dibi-p3lqder the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the 4ui0 jsem5v 2haverage 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 probu02 mivhsje4 5lem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fish. S+lfjw65r c: ypuppose 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 spotr:fc p65+lwyj the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so thassjljz y1-q46 np 82brt 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 (t2 qr81 n4-yssz6jbl pjhat 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 tryzc+psp3 36dbf(12;xv njdiaain traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from resp 2+japfn31;dsdx 6 ci(z3b yvt and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A seco4qm l.xpmmk5(o0if +tv) nv/ qnd stone is dropped 1.50 s later. How far aparti.(qvq olt vf+4xn0mk 5m/ pm) are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver mumiq hfzy+ig t9gx3k9,k6 fq: -st average 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 avik-6m tgh3zf9x9:y+qikg qf ,erage speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France cark28 6s :h*ntmd*vlqrests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his stmrs*: vl2kqdn* a86hpeed 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 trampol 7jfl94tb/do7; buqs ra dk0v,ines. The first child can bounce up one-and-a-half times higher ttsdljq 0b7kabf d o/ 4,7ur;v9han 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 1.10lr/visstc x/ op: uidb -p+;26-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:/c2vx p- r i+ploi/s;stbu6 d 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 throwin)h6uqht2n u w j9hl6r:g the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body tl: 2h9 tu6 6uh)qjnrwho 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 ana;r r,j(ak 2t)zs ,fgy9w/io k acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street p 7pzjvf;*pin1a)m k;0ncxz m*attern 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 amcz;p1v;xpk 7 z fm0*i ann*j)re 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/h tak:f0s7n0 3up3u5uda :ram tumres off in hot pursuit. The police officer catches up to the s0apr7m: 0smna3fu3 5ut ru ud:peeder 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 second u(e )t7im97bolau -;k9o x5yfeh) pd ystone is thrown straight down with an initial speed of 25.0 m/s and the tw5)yahi7ut de7b l-)yfxmoue;9(k9op o 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 x7 9b lu*blv7w 0+ekmgtime. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and 90l77eug xblbw*vm k+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, gsme 7yu5(q9r how long would it take a free-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 resistance will restrict her speed to perhaps5e( m7yq9grsu 150 km/h .)
   s
   km/h

  A fast-food restaurant use*h/au+ :af3q u(mdiqc s a conveyor belt to 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, hoauqai *h/+ d3 (cf:uqmw 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 ai/e)5ti 2ec (yqyh 4 vbmdp8h; speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go than Joe’s? e 8 y;4)iv2id/b(qepy5mhtc h$\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stau n,(oz92m**a4; c3o trq*rvsxfk fbo nds on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which 3ks*af*9n v ozbo,rtuf4x;c2omq *r(your friend threw the ball?    m/s

  Two students are asked to find the height of a partnnafu m.c +:u8cz*ufbejmrt bf(( )9 ot0. k,ricular 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 fall time of 2.0 s, and the other, 2.3 s. How much tb 0a,mc( 8ufbzokj9.fr (.ut+:fenmn * c u)rdifference 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 b4d m;m.ycq 0kbicycles, 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 ins4 cmybd ;.kmq0tant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?