Does a car speedometer measure speed, veloci+hc.nh cqav.7q sfw 2 al+7w8tty, or both?

Can an object have a varying speed if its velocitia(4 e jx)ien1) 5jow4bgni-ay is constant? If yes, give examples.aa)5g(41we ni-noijxij4 eb)

When an object moves with constant velocity, does itm5ptjt: x ulcz2 gw92hg43;tfs average velocity during any time interval differ from its instantaneous velocity atgtj 25 32ctg4lmwzu 9;t:x hpf any instant?

In drag racing, is it possible for the car with the greatest speed crossi3p t*obc5 v4h * y;(ntsxx:7 ssylzij5ng the finish line to lose the (y43xvxh7 5otc t ls :yszj i*sp*bn5;race? Explain.

If one object has a greater spe0bmn1)no xo)q0l)gd k ed than a second object, does the first necessarily have a greater acceleratio0ngo) 01))lmxdn qkbon? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h toz npnk4:5xmym- lv/6o 90km/h with the acceleration ofkn mmp-x/n54lvoz :y6 a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward v7gmx8 rysv5g m5 dqybb:(e1 1welocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is posi5glo8u.g 6pe 4 obs7axtive? What about vieu8 g7b4x6 o g.5oaplsce versa?

Give an example where both the velocity and accele/vqz7d 4*e8nh d,hk2qtp/blu5i dv 6bration are negative.

Two cars emerge side by side from a tunnel. Car A isxox qvg5n+s1 8 traveling with a speed of 60km/h and has 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 reasonin+ qxgv518 nsoxg.

Can an object be increasing in4oas( n0ut ,rkw:duk - speed as its acceleration decreases? If so, give ,(drk:so- u w 0tuank4an example. If not, explain.

A baseball player hits a foul ball straightm*vzavjw* e 0- up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will jv-m w*v0ze *athe ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration due m cl/a,nn;ql-ao2czn-hg)mc*; * odqto gravity — does it increase, decrease, or stay theo*n qd,og;- c;cn2z-llm)*a m/nqhca same?

How would you estimate the maximum height you could throw a ball vertically ,;b epo kv8o8bx-kgb+upward?, k8b;booxpbk ge-+v 8 How would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving y: dsspx 8y5raz9 .x;6gby-y uat a constant speed of Then you travel the same distance fs u5 -b8r .;xdyzya: y6sxpgy9rom point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts ti:tfm t)56gijq gd4x0ied 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)mt:if5t 0 g djxgq6i4 the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at co.gxm:.6:d zur da2of bnstant acceleration: a rock falling from a cliff, an elevator moving from the second flu 2 doza:6.x dgb.f:mroor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original position ns4 .a+cer m)e/rt;fg with the same speed as it had initially if air resistasrmrg) tee4 /c.fa+n;nce is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero accelera2l sh1sf(n9n5veq jt -tion at the same time? Give example tns efjl1v5(n sh92q-s.

Can an object have zero acceleration and nonzeodm) 0; zwdh,sro velocity at the same time? Give examples.w,)dsdh m 0o;z

Describe in words the motion plotted in Fig. 2–28 in terms of v, avpc* 1n2tcge-, etc. [Hint: First vpce2g-tc1* ntry to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the ob 076 okyo .dmhis6d5rhject graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in jgi /xv+72bw v3ygny,3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 luw v6 *d vh00(q:azekn7g0 pukm?    h

  If you are driving along a strap:q8gp(bj b0a2u 7kcqight road and you look to the side for 2.0 s, how far do you travel during this inattentive pp0bq 2 u(7qbakg:j8c period?    m

  Convert 35 mi/h to j),ioa;.rb ke
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves hgk.1bphd5 +sfrom $x_1$ = 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 th-rp58ijyw 5/9k0m ckoymk 7 nxen begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 miny-prm/cwky j95 ki07x m58onkutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thum 9 lt0cd5.z3emp u*wjvb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming th5djpz.*em3 clwt uv90at 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 cp()guau e83p yomplete laps around a quarter-mile track in a total time of 12.u)3p 8agu (epy5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight l rt6u)ou* n/5m qpj /0iw-qufyine, moving 116 m away in 14.w/o yui05qjun6rt*u)p- q /mf0 s. It then turns abruptly and 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. Eaa0vmsi.s,jb busv9 1g9e4x:ech has a speed of 95 km/h with res 1x9auv:b4,v ejssbm.ie9gs0pect 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 110 m behind a truck traveling How long will iti: +vi+o6zmjq1 zhnf oz :k;i8 takfiz81v:mjooi: ++q zink; h6 ze the car to reach the truck?    s

  An airplane travels 31h2o,65wo a mb8o dit4c00 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km o68 2ia mo4hbocw5dt,/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 complete rv-5 wozg:yj3 vound-trip in which the outgoing 250z:y3v5j - owgv 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 the pins at 7h7r; uzuqr8p the end of a bowling lane 16.upq7h;z7r8 r u5 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 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 s. What is its average4z2ks 8w.ag s8aom;ok acceleration ;zk kas28s4w goao8.m in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accefa23 hrs. tnk*leration hr3a*k.2ftsn
(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 accelerh3rw+ x1 ew.itation of abouwxt3iehw.+r 1t $1.6 m/s^2$ 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 18sj0r (1jyh.m0j u77 xegv)xicrmu 6y 10 m in 5.0 s. If it then brakes and comes to a stop inji x80v7y(m7ghxeuy6c 0jjr. u s1mr) 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 stlj7voiaktl0, ry.1 2parts 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 a function of time. Displa7ly, t.2kvoljp10riay each in a Table and on a graph.

  A car accelerates from 13 m/s to 25p4gokm4sqb m e, /u;5 mn.wmk( m/s in 6.0 s. What was its acceleration? How far did it travel ige q/(nk m4u,om m45bmpw;s.kn this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its ac9 i *:b po6-op,(jdfh;ka wsrjrpny73celeration, assumed consjhn-;(*sdb3 r p, :kpwrpoyo7 f69iajtant?    $m/s^2$

  A light plane must reach a speed of 33 m/s fmjjqa +.1a nv1or takeoff. How long a runway is nee.jan1v 1q+ mjaded if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially v52 v;( ap3qezt-qr81djrl ahtop speed (of about h-z;dqate8r2v1q (vp a5lr 3j11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s. q9gc./6ncwo8r/ok iv How far did it travel owc9r8g.ik/ noq v /6cin that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highwaxzu3w .grp-49mm i.kfy. Assuming a decw zgk 3.9p fi.4umrx-meleration 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. T f:z lok+za1)uhe 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 cfo:z )ukl+a1 zollisi 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 s e iw gcski(lwx r7+lt0e1-m +.wo;:mof 95 km/h and human reaction time of 1.0 s, for(+ s 7 g i1l.:kwm cxtew0smwrel;+-oi 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 c6jftqggz iao8(*1)c gar 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 onlv 3+ eu) ,cnuej(cu fr9w00ssp bzx)( the highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelu(benvz j9(3ss 0lfcx)wcu0e r up )+,erate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After+u6*8wmmxf7a gfd3oxgc5j :r exactly 27.0 min, there are still 1100 m to go. Thag65jurxcfg8x 3* w:fd+o7 mm e 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/hta+4tf0 nr zh; approaches an intersection just as the traffic ft0h +nzt4a;rlight 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 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 after 3.dbhqujsb.le352 ozyi9/hf 5ss0(pdk3-ljb . 25 s. How h2fbeqyd l 0lio/s53zhk. p- sjb.s5bh9(jd3u igh is the cliff?    m

  If a car rolls gently t5tq9y.(gcp3 qlvv k7i ,f6dk($v_0\,=\,0$) 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 wbq359vwd o k3/gfw3sa ith 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 throwing it vertically upward. With g bjem,+zx46r what speed did he throw it, and what hzr+, 46m bjgxeeight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gr:qvn (e96 fyokaphs of (a) its speed and (b) the distance it has fallen, as n(qo6:k yvf9e a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically withjy+)g,( hfcvt7 hr-xb a speed of 5.20 m/s. At a height of 125 m above the Earth, a package (tc) ryh g+7- xvj,fhbis dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from m:gg/hs7j xthihkq:v,j)kk5n*8j3d rest, show that the distance traveled during each successive second increases in dhgnm)i8s*k3,tqhx75:jk g hk j j:v/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, swo3 zsd1g6) ;,wo4,ba awrupchow (algebraically) that a ball thrown vertically upward with a,d acrw6,g)w4a uwb op3z;s 1o speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verd1 gjm+qjuw)r38t ; qr6nrp6g tically 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)e/6k9d9h w*jtv yzuf the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Uvzftu9hde /yk*w6 )j9se 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 2.2 m tall (Fw+ g1t 1 e)cr:x-de/eo/ne oulig. 2–32). From what height above the top of the window did the sto ed)eln1w+c ux o//oe1g-ret: ne fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the f8kfgs y;l5 3qocean is heard 3.2 s 5fslf 8q;k3yglater. 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 hard stream ogdtgl5( vrtttr04 /6 zf 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 thr(dttr0 v465zttg g /le nozzle?    m/s

  A stone is thrown vertically upward with a 1g tu ;g0 nol(,g+htqaspeed of 12.0 m/s from the edge of a cliff 70.0 m h1a,oq g0n;+hg lutgt( igh (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 sephpar /4u: hq e20r8ctreet with a vertical speed of 13 m/s If the ball was thrown from the street, rrh/quh pea0pc : e482
(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. acl/,r);wwpts4yr9 i (a) At what time was its velocity greatest? (b) Duringr4 ; 9)wprsta iyc/wl, what periods, if any, was the velocity constant? (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 axi 1e bjdf206 3 qtbr89mpzir4t /3ucg function of time is plotted in Fig. 2–28. What is its instantaneous x6g249/rm1p fcuqri38i zt db0b jt3evelocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in:rikps6 su fsi l935)o the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of thusp 6 i k:3isosr)5f9le 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 previoususjyv) 3k 6vru5(/ +b0o hx w.gmn*uwk Problem (Fig. 2–35) when it yr3)gsj/kvm0ouv*wk5 hn6 . wu(b+u x 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 g3;-epnsha 842p-hjjt hhu l/ the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objv0( ddb,utbt t)ipe*0ect whose displacement as a function of time is given by Fig. 2–28 )t0(0d*tdvtp, bbe ui.

Figure 2–36 is a position versus time graph for the motion of an osidr xfq7tk5zp +y7a/+nn/r-h,*w xgxc x.0 nbject along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object mfizrntd cy7 a x*0//np.kgn+wh -r7 s5,qxx+xoving 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-z6tvjw99c am above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig.-j969wz tvmac 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 abousujq*u9v b4 / gvvd4h)h+ c)cct one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher wiuh d v 4bccjvg/v4cu9s+*)qh) ll it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder nly 3xtn w0a,i5mmky /s ky129seat belt has a good chance of surviving a car collision if the deceleration does not exce0kt y3my/1wmiy9 n5 xlsnk ,a2ed 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 m4a5 + qtdie,cg above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he 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 oq45ged+t ca,i nto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by haulinmywdki*4z7r.7puh xpk / )t h,g them up on a crane and dropping k 74,pk hmzyihr/ .ptu7w*xd)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 travel6o- aw /xwy)tcs 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 . 0yod brg( +0ul9yu2z8umxqrahmc*4the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front om4u ruo+g82hz.r9 0c * (buy q0lmdayxf 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 abtt+38u f:s0 7ofsdy uhove the water’s surface into a deep pool. The person’s dowt37 f u0sodf y8:+ushtnward motion stops 2.0 m below the surface of the 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 c 6tk0;fu7 f*5 nwju8 ,boohdcis necessary to balance the average speed of a train against the distance between stow57f n ; *d0of,tbuch6jokc8u ps. 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 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 straigh6c ,:bssd(s(nn n.u ki tsb**bt down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it t *cbnus(db,n k.s sit*bn :s6(akes 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 whic3us7i :q1qqgf h a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m lon7 i1:gqquf3s qg 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 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 trte jq( 13h40iwvmw4b haveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the whm(j0v3i4qbe w14 htfugitive 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 roofe;f5t4gdnr m. of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?n g.5e4f; dtmr    m

  A race car driver mustx 4c7rzz,) /ojq+vgb n average 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps w,ro 7qzgbj+ )n v4c/xzere done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de F svl+4 irjixupxwdl *0v5.ca677 vqi8+ wyhd-rance 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 avera. qw*8 ux7pcii04s hrxll+57i yjw+dda 6v-v vge acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing7ulog rh.7j,+.fr y lw on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial fy.h,u r7 o+7wrgl jl.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 a41(yt z mo17xt frp+b1.10-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 (y+7p r tza4tox f11bmtake 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 the bp3 q-cz1-/c2f widutwaseball, the pitcher accelerates the ball -z/3up-d tfiq2 c1wcw through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerat-o8bcjy6sq ,4re 2a 5ts/ f5f p fft5cbhpet:3ion 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 inteq g4* nx/n,+;giummb,b+me ohrsection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each. n qxegoim4b*bg;,un m hm++/,
(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 yuo9j *i*h us-bt.it9gj/p *jat a constant 120 km/h takes off in hot pursuit. The pol*ts joiuit y9.*9j/gpu -bh*j ice officer catches up to the speeder 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 ro5.9p y,yoekbrxt38,g n(mquo of of 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 3t8b5yy. e,9xk,g(onu rqom p 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 49l e:1-ee63s v guk(zqig25 e/uowm pr8bhcs at the same time. The first stone is thrown with an initials8 -pe 59ws2 3e/k:ue gcv 6ouebl1z(ghmr4iq velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it td2 k/x+shx-x7c q , qyz5n0ddfake a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 k,d -nc 5qh2skf zd0yxx7d+q/xm/h .)
   s
   km/h

  A fast-food restaurant uses a conveyoj/q.,.w i n1+p nrp1ju8tlsd br 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 iswi pb j1d/lru 8. j.n+pn,stq1 the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically pgf j,k+d9a79d6mmvw x, p9ep at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball9,jk6ev7a9x9gpp d, m +wdmpf go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands o-l cvl,-lb(ey n the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that i ye c-b,(lll-vt 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 buildia 1iyfylofg6f-.a1x o*7 ,zvkng using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s mayal1* -i1 k.gavoz7fffo,6yx ke for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for tnm48vml jv0:g8 zw:sp wo bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is 0smw8n::vpvlz 4j 8gmpassing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?