Does a car speedometer measurede4c7i2cgl + :kl m9pl speed, velocity, or both?

Can an object have a varying speed if its velocity is constax93 zu(6xx6zybk.bop h gg6t- nt? If yes, give exa6y 9oh-36.ktp6b x(zxb gux zgmples.

When an object moves with constant velocity, does its average velocity during euz(hy5.yboz(o ,,l c any time interval differ foh y(lz (e.,o,c yu5bzrom its instantaneous velocity at any instant?

In drag racing, is it possible for the :r (;i5 -)gv6omgmf f )qv3eftqcywi9car with the greatest speed crossing the finish line to lose the race? Expg)6)w(efmgrv qv tic9f3 o5m:q-y;iflain.

If one object has a greater speed than a second object, does the first necevhrse0 d8 u3* q;wgm088u vfuussarily have a greatermf80388e;w qsuvudur h*v 0 gu acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerate-i(b ir5nuhg3*1 mj4(lr6 nhbuuc d; zs from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in-5; 4u( (i*blncrr3mb6udnhiz g1u hj the same time.

Can an object have a northward velocity and a syl:uz,two 4) wouthward acceleration? Explain.

Can the velocity of an :tcpffcu2vsey. 4 tc.4-vkba: 3ucx6 object be negative when its acceleration is positive? What about vice veru: c.6-vfkstuebvfp3. 42y:4cactcxsa?

Give an example where both the velocity and acceleration are negative.si nmy/(wfc17j jlww6 vy*y(6

Two cars emerge side by sisdt) i..swjz7xz6 r,g(emi0ede from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has..g ess0z,x(ir)emi wzdt76j 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 av4 cwb900xpcnq( zeej; w)zu1 s its acceleration decreases? If so, give an example. If not, ev0e0 (qwn p 19)u 4ewz;cxzbjcxplain.

A baseball player hits a foul ball straight up cuf,vi,+(dmrm 1r6m7gm p:w tinto 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 t,1um7mctr :6m,d+ pmvr g i(wfhe catcher catches it?

As a freely falling object speeds up, what is happening tov98rkslx3 hkf-d45b 7.zctor 1 ozg4p its acceleration due to gravity — does it increase, decreoz4 5ob3lr14z-ptkd9f7xr.c s g khv8ase, or stay the same?

How would you estimate the maximum height you could throw a ball vertically up d7q1v.go;uv/ j bnr;lward? How would you estimate thel;1gv u o.r;dv/7jbqn maximum speed you could give it?

You travel from point A to point B in a car moving bszq-5ntg5j 33wkxcrt(vb/ :f 4f-l v at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip frog bjs bx3k lt/t5r-(f5c-fnq wvv3:z4m A to C 80km/h ? Explain why or why not.

In a lecture demonstrlo2jj) npl4 +wation, a 3.0-m-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceil+n 4j)p olw2jling 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 tied so that the clinks occur at equal intervals?

Which one of these motions is not 6wo mr,z iw(z7at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table,( zm7o6wz rwi?

An object that is thrown vertically upward will return to it 8x-g9vwoo73krrla +q s 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 opposite to the m- oqx3arw97ogv k+ 8lrotion.]

Can an object have zero velocity and nonzero acceleration azt / 0tpmx8pdjiz ;-x6c6q we8fa;by(t the same time? Give -;m/ jxtapfp68zbcx08wdt(6e iy z;q examples.

Can an object have zero acceleration and n 4 6044fhikqihp a.di vg;zv+monzero velocity at the same time? Give examk+ a ihqh.4p6gd4m0z; if4ivvples.

Describe in words the motion plotted in 3 hdnximc28sc: q-y) t 5cmwym85i jv*Fig. 2–28 in terms of v, a, etc. [Hint: v-w2n85) mytyi d mh3x c8m:j5s qc*ciFirst try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the / os.vm8z +fp( ysnn1w1cq8pyb29qkx motion of the object graphed in Fig. 2–29.

  What must be your car’s a ,gxxrt/aap1jyq* -t/ verage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h Ho 8qnbhf1d2bdx7u 3c,ow long does it take to fly 15 km?    h

  If you are driving along a straightnzz- g9 ji-o*b road and you look to the side for 2.0 s, how far do you travel during this inbzi o9*n gj--zattentive period?    m

  Convert 35 mi/h to ,e m. cv(xu.xq
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves f1s:qag 7r 5bl; r3jhxurom $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km. It then begintgnwypu31cyz4 -r+nzf+ +d1qs to rain an1g3+q 1wu fnp4nzy+d-yrz +tcd you slow to 65 km/h You arrive home after 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 lightning flash and t zqu o5s-plart,;ja;g*k3v m9he followinoumq9r-lz* , av53sktgpaj;; g 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 sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a touqd6k..arov5*t:5nvh+m+z l e q vd1b tal time of 12.5 min. Cae. r+mhv+ ql5q dunvv 6.z:dk5o *t1ablculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight liyu6rc 8m nyemj7 n689zne, moving 116 m away in 14.0 s. It then turns abruptly a 8 me796cnm8ryjuz 6ynnd gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks.mdo(pk::9:pt-umwz u Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 zp:u(wuopkt:mdm: 9- km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long will it ta- c 4e wtxp5f2f:h.xdyke the car to reach fphdec-f2 xy t4:.5wx the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounterrd1ki.-z6i l rs a tailwind that booszl r.6k1ii dr-ts its speed to 990 km/h for the 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 of a complet-92 00ha qsgpx v/luqae round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and thq0glhx02u/avpq- s 9 ae return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constuh web0ncu3+r 5h;5yzant speed hits 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 afteruwy+5 bz5rh3eun0 h c; the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2-mps 8p awde:;otjuu m:10yo9 xg 4c3u s. What is its average accelerju-wodc3 om1apys: gu4x08u t mpe :;9ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in z jjqxk:sd 65- 9sbw4c1.35 s. What is her acceleration c xs:z-q5k4j9 wj6bd s
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a zl1v0xhwhgv39 cn3 e)particular automobile is capable of an acceleration of about1e90zgv)3nchx w3h lv $1.6 m/s^2$ 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 110 m ine0w t4*4e9w x8f4dgbow 1rbby 5.0 s. If it then brakes and comes to a stop in 8e1drbb4bwfe4w ow4t* 0g9yx 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts frus rp6m s2sw)xo34mn3om 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 ms3pn)2mx6uw4 3sros (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 accelera k:gnq qau69o. 1,vchltion? How far did it travel in this time v9q:ga on, qk1uch.l6? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distanc/y p1nxzrz zl +9cdt.) hxkk73e of 85 m. What was its accelerationzpdztn)+y c r .kxzk7l9/3xh1, assumed constant?    $m/s^2$

  A light plane must reach a speed k 0l9h-rb9gmlof 33 m/s for takeoff. How long a runway is needed ib90m9r hll k-gf the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (ow( +*)*i 2i4 5 r,kl9ytjo;c dynjnuhz2vm mmkf about 11.5 m/s) in th2 ni; ,ry dnjtu)*l2c vk mj+kihomy (*mz5w49e first 15.0 m of the race. What is the average 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 d0o, 8w idsuq 8,it4ocbn: bu7rest in 6.00 s. How far did it travel in that td4w8u,sc0 inb otdq:boi,78u ime?    m

  In coming to a stop, a car leaves ski /bpt1gn1 k tz/ru4:w/p5ib:ifze.kw i3(qxhd marks 92 m long on the highway. Assuming a dece/:fb kp n//x1te3rzqg.4 iph:1ziwtwbu 5( kileration 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 trxey y:jf 2m1289 nha7d ,jlwhzee. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” w1n 9:xhlf2 da8wyz7hyje,2 jmhere 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a chp(cx. zi ih76ar with an initial speed of 95 km/h and human reaction time of 1.0 s, for an accelerati( 6hi xip7h.czon
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the i(t/4u +poutv 9nzyf6stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s dri7j:j e(0abt1-imd,wyk 7h m kiver looks for an opportunity to pass, gues :kehk jw7i0(1-t i7mdmayb, jsing 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 10,0 ysp;vy3uv cp 5:p2e7n00-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runnuye v:32v p7cp5py n;ser 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 intersecti;+yi;t y3h asaon just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m ;hy+aast3iy; 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 a b/sx( n kcb54i*rsyy-fter 3.25 s. How high is the clif/ bknisxc-( y b5s4*ryf?    m

  If a car rolls gently 4 ;ic7 ej/phzq($v_0\,=\,0$) 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;;(vbgb9mc 5lo x: ahxm6zm i* speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwiv2i o7v.kl qf,ng it vertically upward. With what speed did hel vqvifo ,2.k7 throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw grap-m7hb r9by3;dz0a)yd6keq jvhs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistanzm 9jd0dbyh6rq)-y kveb;37 ace.

A helicopter is ascending vertical/2-/nsq/ umzg2e8mfexa s 2cv ly 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 package to reach the ground? [Hint: The package’s ini -/2 e/eu/ qsmnzx 2ca8sgmv2ftial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show r8 ldscv.mvq4ux, :qah/ 7*qt that the distance traveled during each successiqq *7ud l84sarqv:/c.txh, vmve second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that8n -sw gv fd.*n j4t3(dm+ehhp a ball thrown vertically upwardg.dmenw4 h 8-pht(+sj3nf v*d with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18nf8:qz*toss:g .pv fr-k*h7s.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 iqo rbc2a rs++3n Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 r qs+b r+a3c2ocm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window w :wstclmn l3j (c1 umut6s*102.2 m tall (Fig. 2–32). From what heisluw :tm(mlt0s j 1*n163ucwcght 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 tj; ,zuz 4cg:hkhe ocean is heard 3.;kh4,z gju:cz2 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 rvk/ z/om09y p h7p(agdta86yhard stream of water. You point the vmpyh rd0kop8yz7(ag9/a6 t/ nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 mg)0.5nk3k3g 7vu ui iz wt8atg1bfva ./s from the edge of a cliff 70.0 m high tiv.t1k) 7fgguz.0ba8w ak gvu i3n 53(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 ptbd8 8fw rjq)g./ybr6ass upward by a window 28 m above the street with a vertical speed of 13 m/s If the tb)f8 8d/.y6g wr rjqbball 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) At- gs3mx -san+rmstwrc84x )3m ; w+vkw 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 matms+m4w- -c+r3vsx;krmsx83 w) gwn agnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a func8/shu+ c;qedo,e. m vvtion of time is plotted in Fig. 2–28. What is its icdevq/ o.;uv s+em ,8hnstantaneous 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 inbxe2 5,cxq(7 ase l5az the velocity–time graph of Fig. 2–35. (The short flat spots ia xbse7e5 5a(c,l2qzxn 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 prevhtcpw 3stm bg*2 8 (0 y7qxtmsml) w.ija8tz:9ious Problem (Fig. 2–35) when mtm88yichja * zw tt7mx.s l2:t)09w q3ps(bgit 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 travelz8bwme6uf x a2pe 47ohy6q)s6ed during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for o*- :g1q7qsfk*m;un du9x aauthe object whose displacement as a function of time ifun m9a1uu:aq 7q* x*;od-sk gs given by Fig. 2–28.

Figure 2–36 is a posk+pc7ioy) qr2t6svj .ition versus 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 oyvp)7 .6 s2qjick+r tthe 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 above a firefighter’s saf)pz 2kb oz 44/vfng;hbety net. The survivor stretches the nezg4 fb/4;obp h2nvzk)t 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 ,f h v5w5hygm7on the Moon 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 ,f7wv5h5yghm would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the(;b66 sbp 4iieac q ,a;5qmagt-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “gaab p ;mg6( t54iscqb; ae,6qi’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 the roa8g1 nb-zyvcatv112hxgs7 x r-d 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 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 brigsbrycavg7hn8 z--v11 xt12 x dge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front- 0;o(l*7 mjgs2 fc)myjv2v xfmend collisions by hauling th m2xmvf2yj( s)jofl *cm7g0;vem up 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 Earth trib;j0ax; j7gnqcf)9ravels 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 t+k;9y/dir y9 js un.(4qqf njnrain has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. Whatj+n s /kdy(fn.uqn;q4yij99r 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 vg: vmw7+z.h6 q/y cy4 -k75yfy metnfm above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of ttqmy+c vk567/-hyg n fy.4y7vwze :fmhe water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it ex:cmq/d2 ql; is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slowc: ;2q/lqemdxer the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when z l uq-f26- *egfrhn)qdiving 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 perflqf n-rh-*6fqe g) uz2orm 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 whicxn8 c:o+/7y d:org zish 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 :i/ n y oo:gx+srdc87zon a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a const4wco,0oa 2 jbkant speed of 6.0 m/s Just as an w4oo0a cj,bk 2empty box car passes him, the fugitive 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 building. A second stone istehw*mo q- ,z( dropped 1.50 s later. How far apart are the stones when the second one has reach- (tw ,m*zqoehed 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 last3p6*ka jey 9nzing ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the lkp*j96a y nez3ast lap?    km/h

  A bicyclist in the To 8*grpmvjz+8 cur de France crests a mountain pass as he moves at 18 km/h .8vg zc+*mj8 rp At the bottom, 4.0 km farther, his speed 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 trw8q 1alr rx9yb3-9jrx-7*nxg s yc v;jampolines. The first child can bounce up one-and-a-half times higher than the sejy-xy-avr xgs8nqr1l9b ;*7x 3cwjr 9cond 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 hrcst1t 24j0- k.idxm 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 ts.t d0 xr-i2kjt1 hmc4he 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 baseballo.x) s9ugs j;wtl-p6 t with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Flg)t-96xwpj to s; u.sig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises verticalw)+c/lqghp o; ly, from 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. Each intersection hasrotvwy3c7 2a3d)n ru, a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s or3w)t a ncyvrd7u2,3each.
(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-ky /jk. imehc+.xb2s at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a icsyx- bm h/2k+jke ..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 ofb 5z63 h,ixubo-osgk6 a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two st6koxh6 3 zbo-gi5,su bones 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 fia3 bpm,p9bf6yvrpid0xn:0,r ia,/ ywrst stone is thrown with an initial velocity of 11.0 m/s fi,xp b 0ad 0pwripr9a,3 6y/,ymfb nv:rom 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 b ;bq(:96o0xjo9mevz4xgdxrfhw 6r tq fe:, 9-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull xq9 94:o tgv; e:xob09r6er ,mxqbzfh(wdjf6her 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-;njb4jgc1wmr4g 2 by 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, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger prod4b-1cr2jbm g4 n gjy;wuction (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5apcxd*- *(pwe/zpdp + times faster than Joe can. How many times hip*(pa /p*e cpz-w +xddgher will Bill’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 belo+ t 6tqemt0 4d4wd(g( hi3fsfew 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, gt4fte3(dtwdhs4 fi(e 0 mq6 +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 buildinglpecy nkw* h0fj 61e0; using a barometer. Iyj n0ecpewl 01k*6hf ;nstead 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 difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles,xp)99f4 *-l.ncmpfen*ix xbg A and B. (a) Is there any instant x.mxbncg-* )f l4pi9x9 epn*f at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?