Does a car speedometer measure spee5lrkv wza 7ivq .6j8:ed, velocity, or both?

Can an object have a varying speed imhoavs+ v g.w ema1:wxi++7x,f its velocity is constant? If yes, give examplm7xv ow a.wie +1+s:vhxg, +maes.

When an object moves with constant velocity, does its average velocoawsiy sf3mo* 92e6x,ity during any time interval differ fr yos*x, 63imow29fas eom its instantaneous velocity at any instant?

In drag racing, is it possible for the cj)z mddhc/g+cgt od9 cp/5; e)ar with the greatest speed crossing the ;e+c)5hmdt ozcgdd// gc)j9pfinish line to lose the race? Explain.

If one object has a greater speed than a second object, does the firsb, ar75p dqj:ct necessarily have a greater ad5,q jp7r bc:acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates(- b9(,rnq cuv , kdu(wv:tehg from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10kh qtu:v wen(,g9(cv, kru(db-m/h in the same time.

Can an object have a northward velocity and a southward acceleration92h ;y qny/1odmc42. +ytm 7jjcgnyfl? Explain.

Can the velocity of an object be negative when its acceleration is positive? W q,vr1idk*tpq9oj77 h3hvx q:hat about vice verth*oq d hkv:q,ip79jqv x7r31sa?

Give an example where both the velocity and acced,cm4rfogr -o(e 7)+5qv j ciqleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a speed on6s.ihstze 2n l1 .h)wf 60km/h and 1h)t.lhsn sn.z iw2e6has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreasebzp 4r7.e0l5 w 5paepvs? If so, give an example. If not, explainwe 5ez5p4b7lp 0a.rv p.

A baseball player hits a foul ball straight up into the air. It leavesglu 2 *a 0ypwghwa:u6( the bat with a speed of 120km/h . In the absence of air resistance, how fast will g(:g 2 pu*auylwh60wa the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happehr sg3f cq);n:ning to its acceleration due to gravity — does it increase, decrease, or stay th fg3rqhc:sn ;)e same?

How would you estimate the maximum height you could throw a ba 52ptv )v,bxa(n7y0vcl. oxw kll vertically upward? How would youycx(a7 ,5txl0vnb okv p w2)v. estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant qgbe /;,oufy +speed of Then you t e/b,;fu g+yoqravel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long verticay;q 0j9 z b8de5hvov1zl string with ten bolts tied to it at equal intervals is dropped from the ceiling of th8oh; 9 yqjz zd05vbev1e 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 at constant accel1c zt*ts+ bb-le1mpbh +7zm/zeration: a rock falling from a cliff, an elevator moving from the second floor to the fifth+mhle1tzt- zz+7ps b mbc1/b* floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return t r3z.r0i jg8xubotisl ed-6.xec6 + c3o 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 alwa 6+reg 8itj c6z3uxeisrcl b.0o.- dx3ys in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleratiqt- upw9ebkm 9uc klb9 ,5x29bon at the same time? Give examplesb2b99q wp mc ul59eub-kk,9x t.

Can an object have zermhde:z8 yl tu0f,35r ro acceleration and nonzero velocity at the same time? Give exalmey83h, :r 0 zu5tdrfmples.

Describe in words the motion plotted in Fig. 2–28 at0q s+tso .3pin terms of v, a, etc. [Hint: Fi sp +q0tsao.3trst try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object ,yjar039d9-tkbd uwt graphed in Fig. 2–29.

  What must be your car’s average speed in order to1y qd1ko. 3) 6jyf6k si6kjpjr travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How longjdaly(j gcyrb cwn2.. m-:p,- does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the si*s- m tn.rgn+5swg3sdde for 2.0 s, hss5-.m snwt r*+g nd3gow far do you travel during this inattentive period?    m

  Convert 35 mi/h to d,x l8bee+j ix.lo5+ 3oo, fdde1p j4k
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves froq1n 4pb82zd4 l/ dpgdlhmd;5 ym $x_1$ = 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/hl:lzd1re ;sh) for 130 km. It then begins to rain and you slow to 65 km)zlrh;el d1 :s/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 andb,h ,s qf*lz:q the following thunder gives the distance to the fqs:hl* ,zbq f,lash 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 totaloulmt3*kw8l wj (2c p2 time of 12.5 min. Calculatl2t mw83l*ouk (w jpc2e
(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 aw) ek7:ef4yvfp uyv 0um9)z5wf,q (j uaay in 14.0 s. It then turns abruptly and gallops halfway back in 4.e4)a: 0vp,vz k)yfyqueu9jf5(mf7 uw8 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. Each has a speed of wnjz k6e99tz)95 km/h withe969t) wjnzk z 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 sby eo68lkya/j2 s n 19-re8th110 m behind a truck traveling How long will it take the869h /s2 okba81yy nr jselet- car to reach the truck?    s

  An airplane travels 31tk+ y;r;s pq3p00 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 r kpy; 3pqts+;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 andz xj ,yqwo+49c +wyqf:5l0 hil average velocity of a complete round-trip in which the outgoing 250 km is covered a+ q+ 5w4xyo9:wfllzj0 c, qhiyt 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 tfep /k3e-+9jwz a n3ihits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hittingjet 3-zk+fie/ap3 nw 9 the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 mmkrayo6n:0j,b:; /l q z5tf9uwj mp5s. What is its average acceleration in maj f mqb:5tkl z: o6,p/m0nw;jyu r59$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is he50qv1 ob/ ufzq8rpa ,x0k3y 74 bgdsigr acceleration18b qgyq7 ov z05pa/0furbdi g 3sx4,k
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile i*v4 tp xu+g*ats capable of an acceleration of about*vt g4 p*xatu+ $1.6 m/s^2$ 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 trav(zgqa, fb71f.x iil k:els 110 m in 5.0 s. If it then brakes an(bfl7i kz,f :qxg.1aid comes to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t =ra:fr/eh7g 1bg1 o;7ww/kxcvpvf9 ,u 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 / 1ru9vkbe,1x7chao;/pwfw grvg: 7fas 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 acceleration? f0 /6 af6obdixHow far did it travel in this time? Assume conafix dof60/6b stant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its . +whv c h0azgic-zqi81u6*:nyqp; or (zk f5uacceleratq:z0up;civzacofynu hk .+ 86-5*gr(1zwi hqion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeo q8vkz,j7hhi// htzy 4 j t.4xxovxi/1ff. How long a runway is needed /hqi,/j tzhxtji/xv.ovx8yk zh447 1if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially p(ulf d) t4n-jvplh;u -e,qfvbjfn4) s;c 2k3top speed (of about 11.5 pflk2nq ud4;u)nh -vv;4 fs (ftp,)bj3e-lcjm/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a sp.0ka:e sp :srqeed of 12.0 m/s to rest in 6.00 s. How far didr:se qs:ap0 k. it travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m lon0.da wgkm zszr3(n85 eg ht9-tg on the highway. Assuming a decelerationg9zs m w t-ahknderz83g0 5t(. of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h s q/m(+ b8 w6nsu:goxgvtrikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleratio: uwsgo/gvn+(x8q m 6bn 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 hft n:nk 18ljx -f6-gkinitial speed of 95 km/h and human reaction tig1:-hl j nfk8x- kt6fnme 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 stoppgs6888wc c vog9sr nk :igd1mj4.4xmf q(:mf ning 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 gohu0ze(ebgrdt 8j;k2h j7zm ku -9mn64 ing 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can;7kb0 rde (2e4 uutj98h 6h-nmz kgjmz 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 lebjyjnr/,p 97css than 30.0 min. After exactly 27.0 min, there are stilljpcb7, j/rn y9 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 45fk03, ,ekpk4/ezx , n6rr7iwys w8ly n km/h approaches an intersection 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 tsrp, zfk wrkne/8xek4l i, ,w0736ynyhe 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 kpqa.uqe5*b8a s*o-h a cliff. It hits the ground below after 3.25 s.h o 85qaebqpaus*- .k* How high is the cliff?    m

  If a car rolls gently (x6w,ywjwd7 *0.3szxdk jnzzfn2 u .s *$v_0\,=\,0$) 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 with8 )iiv*nx:8i vev+ lqb a 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 b34zf7tm/pz,1(j+iv.cs rfj h myv bhj54z s7throwing it vertically upward. With what speed did he throw it, and what height did it reach? cs3zh (7.jv mrjv s,j/y4fhpmbt+f14b75ziz   m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravitymo. 6218nax.5lki sgh0rr7d w: dbif v. Draw graphs kxl.ohwvi ra: ign8. b2rm7dd1f50 s6of (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 resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a hei+ wy5cdoz:hws2kjl )s/9hg1 nd2f ; heght of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed eohsz 2+c5dwd l1w; n )f:jkh/egy2h9squals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance 0rw h1mv) r0cytraveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was f)r0 1hv0ry wcmirst shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball gvl slyw9*i3 c/- .iwtthrown vertically upward with a speedgiwcv t*l3l/i9 .yws - $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertica7 d5x-jav 4.qvjrl rtj338 znally upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of tm bcn ge s8nz,:1gv5)zhe apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 )emnb5n:zg,1 8c zvgs cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a winl t;w dncoki6,c -c(bn j lm97xivx(*5dow 2.2 m tall (Fig. 2–32). From what hc,t ;7kdcjm(-bcvn x 5(ii*9l6 nox wleight above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the lc34k: ihhaozgq5z86sa;6wl ocean is heard 3.2 s later. If the speed of sound is 46ziwlag83: h c6sqa5k l;hoz 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard strexnqdrlo 5y:5 tkdn0(4am of water. You point the nozzle vertically upward at a height of 1.5 m above the 4 d(5nl5t y0:kx dqronground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s )hbv9f7r p f.5s*8ux4 fcmj/yd thd.r from the edge of a cv .jr9sx 4h 7yhdrmub p)c/*fff 85.dtliff 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 window 28 m above the street with a vertis9)st:lwc* zmcal speed of 13 m/s If the ball was thrt9lscmsw) :z *own 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. s9r+w 7hu ij-x(a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magniw -7 ruhix9sj+tude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as m.: o .c2xtdzqcg ee/;a function of time is plotted in Fig. t.qo;cmgcez :x.e/ d22–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile ).vb4xrz * nracan accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiftrxzb)an.vr4 *ing of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous P1+w x *7q6q 63s0uij sn.esqwqa4 fkbnroblem (Fig. 2–35)qbnj67 e w n0i+ a*u s6xs1k3wq4q.sfq when it 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 zffmx 86rpx* /8yl 4.su) yucptraveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object wh9z/d36 xsbhobose displacement as a function of time is givend/63bzhs9o bx by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motio8yqoep ;y ,2xpn 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 slowi82xq,oyyp ;pe ng 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 wintfn*2 xl2* zmq/+du+dk nj y0bdow 15.0 m above a firefighter’s safety net. Tqx/2m*tdnn2 u+bkj+0ylfd *z he 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 Moon is about 9fv ;:,a9nsjqq bp/dhone-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higherj 9 :qh9,s/dvqna;fpb will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by eg.94-fn *i2woz dov kan over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration do2z9n w o-kg.e* iovd4fes 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 the road below, and hisr7hcg 0xd i3-m bz ;eu vc/j/4,jnaxx64)yfgx 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 trucgzje3icr ;x u)gfv/jm xx6d07axhc/b 44-yn,k 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 colli7s,qv0)).qd8qqp(4ujgc,ebdqf k x bsions by hauling them )qf8x 0dqcu),b4vq.sqd(jqbp 7eg,k 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 travels apse kpzcxo: w/*k))u1bout $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train beginr58yceu l9if6l8:9alokr t y;s uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the luc le8tl fl9 ;9ya58oy:kr ir6ast car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.wy- iaxw:/7e v0 m above 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 whi: vay/7xw- eiwle under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, i 7,thl7wys0l tt 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 ls7,th 70y twlmake 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 strai;z5xhaz8v yb0vo05j lght down when diving for fish. Suppose a pelican starts its dive from a height ofhz0xv5ab 0 zov 8j;ly5 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which -ueij(f1:4uxz*n nns 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 particular green the ball decelerates const(z *nu u -f:jesxnn41iantly 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 f-1706 f9 j ddvriinbx wktxx(kg9q i((reight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelerates jik(16frq9 i xx0vbi-kt gx(9wn dd7(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.c45 0 :ie2mdijpyzd- 5) an 0rtulu2ex A second stone is dropped 1.50 s later. y una0)ep:x c5jrdet di2i205- mul 4zHow far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 8;ev + ij*nhiy200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for thj;ev8ih i*+ny e last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he hx :x5ghmt:j:moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average accelert:xg mh:j :hx5ation (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first chi5zzb:o j/) *rj ;xj(z tl9t (lgcet9zbld can bounce up one-and-a- /e ;:jco 9)ttzjtj*r(9(5b llbzzzxghalf times higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long tr g*uc. zk,/b oa)mk;zvain traveling in the same direction on a track parallel to theauzv;c kmkbo. ) *z,/g road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are 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 tfce:3 e* h3lqlv4mqmm+ksu17he 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 (Fig. 2–41). Estimate the averagqmveul fqcl3 e+km3*h4sm7:1 e acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an ;0b. wcx2liwvacceleration 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 ha2n6:w5fud kf5 exv*pattern 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 limituwv5h:faknex2 d* f65. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/hr+ 72/qfp/ sas-g ri ploiq)8t takes off in hot pursuit. The police officer catches up to the spe/8pqlr7g s+iaps-ot /fri )q 2eder 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 bui.xkeljr1r8 dnmab,tn se3; . 8lding; 2.00 s after that, a second stone is thrown straight down wmrn;.s 1 8rtde38b x,j nlkea.ith an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is throwha8/ vc xne) hmh7(t1yn with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and/ ent18(xyc m)hah 7hv hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling parachutjoo o fm3+ec gb9,i9c:; (kxtiist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? Whatti(;,ob9 mfigej3+c :9oxc ko 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 burgers through a grivw4t d l-3t7crlling machine. If the grilling machine is 1.1 mt74c3 dlwr -tv long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a-h-yh nszeqim0b9gmqfo;5 4gex +z3 / speed 1.5 times faster than Joe can. How many times sg3z +e;0hi noyfmx-m5b/eq4q gz h9 -higher 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 below yv+sb h/z.ap0m 5e8v+i49h nclgt +d dyou. 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 ths late.85hc yb4pinzh9+v v/g+d +dm 0e speed with which your friend threw the ball?    m/s

  Two students are asked to findud;d/ pb8 mej8 the height of a particular building using a barometer. Instead of using the barometer as an al8d/pd j;m bu8etitude-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, A and B. (a) Is *gg1d g:y4rk ythere any instant at which the two bicycles *14: krdyyggghave 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?