Does a car speedometer measure speed, velocitc*ei6mr:2 z ikl x:5.a2 sufnny, or both?

Can an object have a varying speed if yhr;yg ;25m*()xw; ilxglhjjits velocity is constant? If yes, give examples 52 ll ;;x)h rmy(hyg*jjxw;gi.

When an object moves with constant velocity, does its average velocity during 2kc2ohaj.ke// ep7vz any time interval differ from its instantaneous velocity at any instant?ec7/j2hz.ek/k2p v oa

In drag racing, is it possible for the car with the greatest spf)*2/i 8b zvw2h9:rikb utcqn;l0sf jeed crossing the fif9v/wl q kshi8 b2)bzu rjt0n:f *;ic2nish line to lose the race? Explain.

If one object has a greater speed than a second objectja2ta:b5t c5xj 6dybl7 j zy04, does the first necessarily have a greater acceleration? Ex 5zbyldc5 a7aj:jxj62t40t b yplain, using examples.

Compare the acceleration of a motorcycle that accelerates d /:;ukeg+5j inz8a0cq km r9*ekk9cv from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest 5uqv/nk*r+kkeg e9i;m a09cjc zk 8:dto 10km/h in the same time.

Can an object have a northward v(*; nzm y2 6ba3llurkselocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positiv uq ) hf0e4 c(m us(cix,/gy9p-gd(qtie? What about vice ,9 cfdt(ui/g-y gqs )u4(i0xmcph(q eversa?

Give an example where both the vele z4znmt9 vp s;akr3*,ocity and acceleration are negative.

Two cars emerge side by side from a n0rsr,4l2 k natunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/minrsr42l0k n n,a . 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 your reasoning.

Can an object be increasing in c50rjrxk mg 3)speed as its acceleration decreases? If so, give an example. If not, explaincr g5 )mkj30xr.

A baseball player hits amzo)zqt *q/ ,a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resaz,q)qz/ tom* istance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its ack51zqx25agtqx/k i / x-zd r,txyv4w: celeration due to gravity — does it increase, 5qv/xtdktx2z, 4wxiz1/:xkg- 5a qyr decrease, or stay the same?

How would you estimate the maximum height you could throyx3lcfw i6 /3dw a ball vertically upward? How would you estimate the maximum speed yiw/ x3 cfl6dy3ou could give it?

You travel from point A to point B in a car movinffqz;qm,id,os2 7,ufffcd 0, g at a constant speed of Then you travel the same distance from point B to another poi2,,q ,,ff zfc s0 m;dfdoufiq7nt 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 vert6s dy9ask:q l9rpa1(xical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be k6 qrx19 pds9ayl(:astied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock falling kk c;3 3os+ /kz72ld2jfwzkeefrom a cliff, an elevator moving from the second floor towz zdk e2k 3k/fl c+;3eo2jks7 the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward wi6+l//*g.sr yxkhr4y4/w8vufbw8 kr ngm 8r nbll return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction ylb .8rgy/g 6vkrs/w rb8 mfn*hn urw/x8+k44opposite to the motion.]

Can an object have zero velocity and nonzero * -4u8.vgxrzaws:rm nq os1 y;acceleration at the same time? Give examplen q*wamgs;:4 -uxr v81rozy .ss.

Can an object have zero acceleration and nonzero velocity at the same time? Ghcr a:jb5;yvejxsb1e/5 6gj 2ive exam5/v j c;yjhxrjbes6ge: 52ab 1ples.

Describe in words th,tywna 9uy e0 z)rh3 skql)7)3jtu :gqe motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to du yq,l)w:7k n)93yr)tus0a3tgjuhz eq plicate the motion plotted by walking or moving your hand.]

Describe in words the motion of ybv(*-zc zdvku0-3srthe object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25it)tny*r-kyq1 (46owj*cfs v h?    km/h

  A bird can fly 25 km/h How9iu ko8vy5 nt;ra9 p h,3;euko long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for h 7ddx /cr5oe1ms/p3p2.0 s, how far do you travel during thr31 d5s/pdec/m h7pxois inattentive period?    m

  Convert 35 mi/h to gz 8p p+7v(lfh
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frqrt;nk t0gn5n 2,wlm-xzujnmj( uy,1 :n ;c 7gom $x_1$ = 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 steag k0b1sl1g.b fdily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home af1gsb k1g 0lfb.ter 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-th3dicg1qlsfnl lu9;yamy ;w4 . l: n2j1umb, every five 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 essentially no time at all, estimate the speed of snl .la ;f9y ;l3u4s:wyimcnq1 d12jlgound in m/s from this rule.    m/s

  A person jogs eight complete ak,rt68 b5hlim2(*aq-,ie d; xcpbs u laps around a quarter-mile track in a total time of 12.5 hicp;-, aelqd2u a5,i* s kxm8(b6rb tmin. 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, mu2fuh +h3o /:ptr. 2uhixliq4 oving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculate ltqrifiohh x2/+4 2p3uh : u.u
(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 eam7:;mn3fcur fch other on parallel tracks. Each has a speed of 95 km/h:ffnmu7;c3 rm with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 11j48ggt z6 nxeet,.6 m lp7 nqc1j9bxj50 m behind a truck traveling How long will it take the car to r9tb5e78lj1gtx6en.j4c , pzg nq xjm6 each the truck?    s

  An airplane travels 3100 km at a speed ofhes bb-mo o.xp+1e8st l 50*(xjp q9ejxz7,ph 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km. e ,+(-zb m01b5jxeq8h*7lsopto.p9xhs pexj
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 speeiaidv*.* wh (:k0oshkd and average velocity of a complete round-trip in whii:i*a w.vd(hh*skok 0ch the outgoing 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 speed hits nal,f;* v0aeo bkv/e/ the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is th v*a/e aofvelb/,n 0k;e 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 averxhm un3m2 /5blage accelermmlu53 b/hx n2ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35ek7avf(x m4b+ 6m*pww s. What is her acceleration xf (km +apmb*6ww 4e7v
(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 cyz .+ 5rtj2d(jjll (rof abouj (j 5(tdjrlr.z+y c2lt $1.6 m/s^2$ 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 sp sfd*bd*au+ilc87 dx2 eed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleration 82badlsxf7 iu d +d**cin $m/s^2$ ? 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, wfccc i*pmi ,m2 c4fc9)hich 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 velocity and (b) its acceleration as *mmc,c9f p 2fii)cc4c 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 its78f zjo cvs2a. acceleration? How far did it travel in this time? Assume constant acca8jsvo.f 72zceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its acce+09tv;x2f8zxe xouirxpz/ 4p leration, assumed c8p4 x pz xvez9/tx+u2rix0;o fonstant?    $m/s^2$

  A light plane must reach a z2 yh/.c0olpa speed of 33 m/s for takeoff. How long a runway is needed if the (constant) aczoya2 hl cp/.0celeration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essena3pp) mroc.gu f1t-;a tially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the avera. ufaa ;p-tmc3grop1)ge acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest inlfh0n e;z 8eii0 *2pkr 6.00 s. How far did it travel in that0f0hie lizp8;n *ker2 time?    m

  In coming to a stop, a c.c pw- lbd7ty*o2lazt ;-s3a war leaves skid marks 92 m long on the highway. Assuming a decet 2.ly7a;wlo cpa* -3swdzt- bleration 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 compresses3 4gts(tm)* ppevn g:t and the driver comes to rest after traveling 0.80 mt) mt :teg 4vg*ppn3(s. 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 for a car with an initial speed of 95 km/h anja rd5ysqc8 d n0s22v7d human reaction time of ss702ard 8cqnd2v5yj 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 of a car is x/3vw k777ma,fy2:q zqiyk1g i4 aixz/lqpd1 $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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.ez2h65 wd5vs r4vgzv-;q 2hdt The car’s driver looks for an opportunity to pass, guessing that e6d-;tz vhgqvwh 5dvr2z25s 4his 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 tha;( u ivzk2s(rugj0qjy tb .)0e 10,000-m run in less than 30.0 min. After exactly 27.0 min, th(k(gs .bu0uat2z; jqy0ri vj )ere are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as the thk; 47*ydf:8vxt(g bcw u ajl:raffic 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,at u 4dcyvw*7f j:gk(;xh8l:b 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 hit73y;:0crwdnt wdh)f os the ground below after 3.25 s. How high is thndy0; hc):d w3 ot7wfre cliff?    m

  If a car rolls gentl*qs j;/ p:kqgx,x +hydy ($v_0\,=\,0$) 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:it8qj8d/7abl 5q-dc zj;lpx of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a 0tlr quxu 1w5c/-zx k;c1i qm6ball 3.0 s after throwing it vertically upward. With what speed did he throw itq 6xic/qc5wmtl1x-uzk u ;r10, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the inczo7nw4 b;oksr5uda+x) ah 57fluence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a fu5u+ 4xh7 k5db7;nzw o)asaor cnction of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascend-9.fgfz x1z r 42fc6zjf6lvmming vertically with 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 take for the paf4zjl6r mz-f .x26fm1gvf9z cckage to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, 1v 0g wt8b6ygsshow that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was firsts6vg08btyg w1 shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (alg eh 2vlb/oq 8csk3*/fvebraically) that a ball thrown vertically upward with a speed b qosv38vck/fl/*2 eh $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with m 0)35io zi8hz e5ayvnhh e;fk7 h2da*a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–18 (or numc7 j;99by(y)bs ma3w vzpf x7nber of photoflashes per second). Assume the apple is about 10 cm i3jz7 ;nb 9ws p vfyacb7m9y)x(n diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.2elkjp/32 6hi d8 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the step/6 l2jhik 3done fall?    m

  A rock is dropped from a sea cliff, and the sqdbg23ufxx m by qvr34+;;t0kound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =y0bxrx q3k;fb+qg34u ;tm dv2    m

  Suppose you adjust yief 4cvapc3 4( xma6j3our garden hose nozzle 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 is the water speed as it leaves theac433vaf(pmxje 6ci 4 nozzle?    m/s

  A stone is thrown verticallkfirl 8g,,;k 60cehs py upward with a speed of 12.0 m/s from the edge of a cli ,sr;ehkpk8,g0i6 flcff 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a wic)luiu2w+t +n ndow 28 m above the street with a vertical +uiwl )n+2tc uspeed 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.t:t .ldf0mn(r (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant?dm f: nt.t0l(r (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a fjoek -3 9 vgh13ngzo2dunction of time is plotted in Fig. 2–28. What is ijgo -ze1gk vo n329dh3ts 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 accelerat:i 8ge1n dibw8is r/.re approximately as shown in the velocity–time graph og ine/ r: 81wsd.bir8if Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of thtqultp (r7e)* 9ll w*noigyv 0y *5r;ee car in the previous Problem (Fig. 2–35) when it i(**y9p o ue iwlrl*yl); ern7q tt5g0vs 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 thc t 6 z;m;volvlcw/ :gr212:ozxcnrb9e object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object w8+l )o z2e:ygh zsd;rahose displacement as a function of time is given by Fig. 2–288gz e;)adoh2zl y+r:s.

Figure 2–36 is a position v 2;ev4 ruptg/.v i1xwjersus 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 s /x14w2 .pui verj;tgvlowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a fia3o:lq;gg4 p ui,0z,ln1fnvaqh /h ,vrefighter’s safety net. Thqo0 ;3/,p hu,vzi 1fn:gah gnaq4,lvle survivor stretches 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 Mooi/jf;9;y1bb k )q xrlmn 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,ly m;bqfj1xib/)k ;9 r assuming the same initial velocity?

  A person who is properly constrained 5-pjpfxhu8/ a :lri7jby an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g’s” i5x 7lrp-f8ja:/jpu h $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road berz 8.7vb7j(2lzmrsz p low, and his pursuers are getting too closzl7s 2zr 8.r(mpj 7vzbe 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 front-end collisix-yf wvj2 odac-tbzk. ykf 0r4)e2* t:(9zg rvons by hauling them up on a cran)zc -40a:. y j9tey-rff*borkwdv2kztxg ( 2ve 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 travm m)t5 )*qu c;psein7na +3 oal;hrg(.r whuc;els 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 uniforu*at adz51 mzx-b6 :okm acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180z 5x*u a:ztmoad1kb6- m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s h4cq8c )+ vmw/d*oy vtsurface 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 persond tcq4 /+o )vvh8ycm*w while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a ra:rx658,(k5pw5z hi.d acdavt) cns dnpid transit system, 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 to make a5t,.csi d556z)v :r8(nkp xh dca adwn 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 div uylp p o1q;v6*e1 tew8mx0j)ging 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 pe )xep;q10*epv 861w mgtyluojrform 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 w wznop*xn- s w7ek.w:2hich a 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 from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a par:w*xo.7s wz we-npkn2ticular 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 sj-nq1ytq +fcl+7(k nhop on a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugi17tnnq-(j+f kyl +c sqtive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high bup.sc:y /cr s3oilding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has rea /rc3cos:.sp yched a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial v/ s.yi*bgl9qlasting tl9.s g*qbyiv /en 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 de 9pwx (;- 3bg5ijzkq moFrance crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his averagez9 q 3kmj(o ;-gp5xwib acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child ca2d*tdh*jr qiad t86, bn bounce up one-andrdtat d6* qb8 ih,d2*j-a-half 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:gm 0f3up qpoufou/ku p6 q)t4h0m2hio +;vx0 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results u 0pp+hu;u6 ou04q0)v3/ kpi:t2q gmofmxf hoif 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 fg,+-v73 gl c58wd ptujuum- 1jdad9xbaseball, the pitcher accelerates the ball through a displacement of am1jx-gp+tluv9 g, 8 ja d57d cfduw3u-bout 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, fr*.eagecny) xaz82kz)22legog,k x n3 om rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. E- j.:m)7 6 xpmmjvp0hunnf c/tach intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. Whef / nj p6-tummpm:n7c)vx0hj .n you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a ailx suqs3 1/+speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the sp3a+1is uq/xsl eeder 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; 2.1:k wmz owxu3200 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two sto3 wxm:uk1z o2wnes 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 ver q8zy+*isr +.zuemfq;tically up at the same time. The first stone is thrown with 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 ;+ qz8r+ufszmeqi.y*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 lobhv y4oy1mjrt49z,dq7e 9 d /cng would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of obj9 ,zyq41dm7 e /rv4hcdt9y 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 to send the burgersn fzc kpt8a,c:x z n3f-*5dhe3 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 ndc5 cxa8-* hpk:f3fen ,3zzt the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically drx8 z5scez )op28 i geh4f9r+at a speed 1.5 times faster than Joe can. How many times higher wil2ez9 ghz5)ofe4x8rrdi8+ p csl Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your fr(7ai6.a+0ic mpbl+kqpndaaa;/x 6e-a srcy + iend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s f+07la/dc(p ;ay eq+raa-m66b+kp sxiian ac.or 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 height of a particular building using a barourc)e 87: zzpsmeter. Instead of using the barometer as an altitude-measurin8pcz ):7 uesrzg 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 difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two b0+8n ev *ooqrp.hff29gun7f qicycles, A and B. (a) Is there any instant at which the two bicyclen fv07quferq82gfn *p h+ o9.os have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?