Does a car speedometer measure speed, velocity, or both8 f i-)hjqcudzp4uj 6/?

Can an object have a vary0px + k,4iky5lhl+vw y*:qpz.vl 5caking speed if its velocity is constant? If yes, give examples. .a: v+kl,k v5i+0y *lkwlqh5yzppx4c

When an object moves with coofjcjtrq2dk.yh15:1 3ef m ;dnstant velocity, does its average velocity during any time interval differ from its instantaneous veltkj.ddcm:;e31q2 ohf5 fy1j rocity at any instant?

In drag racing, is it possible for the car with the greatest spej.n ihu+* ;tpced crossing the finish line to lose the *cptu.nh +;ijrace? Explain.

If one object has a greater speed than a second object, does the first negu h4o ot)gfe*7kcj* +0i 2csrcessarily have a greater acceleration? Explain, using ex+) rofge0g*h2 *7jtokisc4u camples.

Compare the acceleration of a motorcycle that accelerates from 8og2m,wcko5+ b0km/h to 90km/h with the acceleration of a bicycle that acceler oog5kw2,cb+ mates from rest to 10km/h in the same time.

Can an object have a nor -j s;f;qs;ntfthward velocity and a southward acceleration? Explain.

Can the velocity of an objecjr 0fl+3uyc;ht be negative when its acceleration is positive? What about vice yuh ;+f0clr3 jversa?

Give an example where botxkj x h;okx-1(h the velocity and acceleration are negative.

Two cars emerge side by side from a.h3bi,+ :sgyg+slclw-luh),*yf en ,w odt9 d tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40,goe,h3f)9y,-yw bli *d:ds hu n++twlg s .lc 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 dec:f7zidf8k4trxg bw hk2+ -wz/reases? If so, give an example. If not,t f4bdrk+k gzwfx7 w: hz-/82i explain.

A baseball player hits a foul ball straight up into the air. It leaves -nk550zdn2r*w qcis.bonu( c the bat with a speed of 120km/h . In the absence of air resistance n55- nriwdcs b2u0.oqk( czn*, how fast will the ball be traveling when the catcher catches it?

As a freely falling ofsof ry/nt05 :bject speeds up, what is happening to its acceleration due to gravity — does it0o: fnfy /5trs increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertick/w5jxoe4khu ;bbwga 9(v :q 9jom()wally upward? How would you estimate the maximum speed you could gi4m;ke buhw w9x a (kgvqow5)(ob:9/jjve it?

You travel from point A to point B in a ch0l)b 0ri c9jugwjr6mr 3f)1jar moving at a constant speed of Then you travel the same distance fromj)w6rml cj1fh b 93i00 rg)rju 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 verti/.n;w .y*pru*nmb tz tcal string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fal. .yrmnn**pt wz/t;ubl? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at const0.3geczy-uqm ant acceleration: a rock falling from a cli m0eyz3qu.g- cff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will reyxixucm4lq u60p ;4b3 turn to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to thep b um3c0uyqx4 x4;l6i motion.]

Can an object have zero velocity and nonzero acceleration a08 o uhio8m3qmmfv0;jt the same time? Give example0 ;mqoo88 f 3jmmhu0vis.

Can an object have zero acceleration and nonzero velocity atj* ;7e sfdg9fl the same time? Give ex*e f97lgf;dsjamples.

Describe in words the motiozv1b .s*t v.ckkv-m4tn plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or*c vk1-vvs.bm kttz.4 moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. ;mp k;oi ku5duc .7x)c-tt2 fw

  What must be your car’s ahh+mxpl si-vdpcj44c 9d1*skt x4e9:verage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km?hn*a y h*;lc6u    h

  If you are driving along a straight road and you look to the sicyaa4n*gyx lgm (f4 1+de for 2.0 s, how far do you travel during this inattentive period4+ (a mc4*fnyg1yx lga?    m

  Convert 35 mi/h to h7;+ nzt n ify-1ox v.fz)2qwb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from 0-nie ;xiz 99wq 5zksn$x_1$ = 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 j 66nwe zzxp0)rixz 60rx (dh)begins to rain and you slow to 65 km/h You arrive home after driving 3 hours z0p ji)rwr)dz(6zhxe 6x n06 xand 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 lightr zeea6,7: ezjning flash and the following thunder gives the distance toe6z,arej7 :ze 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 l*loyj7s h ik;4k)nbc)js +zt4aps around a quarter-mile track in a total time ofk*z4h4yn+ b)lkts)7j icoj ;s 12.5 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 line, moving 116 m away in )qo t6 reoewjcvk6f0+9sq+ m/ 14.0 s. It then turns amjoc s6v+w9f) +6qokqt ee0/r bruptly 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 eaciwax:o *s9:js9p xq5 o4v8ktf h other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they areaoo s 9w4k9*: tpfvx xq58s:ij 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 trv)61/ur gx;qt3dnqg raveling How long will it take the car to rn;/dqt )31ruqg6gv rxeach the truck?    s

  An airplane travels 3100 km at a speed cslftzc x783t f2ia)9lu)8qlof 790 km/h , and then encounters a tailwind 8af)zi 28sf )9l 7xqtlluctc3 that boosts 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 oflu7m2--x qsu ex/ba-k a complete round-trip in which thx -q-sk27/lm-a uexube outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling/ubi/np wl7hh a 6ggz. wwh/i0 gb2:i0 with constant 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 2.506uginz.bh0wa lw2w 7:gi//hib0h / p g 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 ts5 lp x2ghpo.3o 95 km/h in 6.2 s. What is its average acceleration in 3o2 5hgxpls.p $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What i; cycv8fp7 27tzx650vnamt e hs her acceleration2xv8 0ht 5vc7 ep nczf76;mayt
(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 accele0zdnx*v0x v/ ,x6dflyration of about * zv yxnvf 6x00/dxld,$1.6 m/s^2$ 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 in 5.0 s. If it thttya*gb)dfi1ehy02 5wq)m: a) 8mvz ken brakes and comes to a stop in h)10gm iw :f m8)avdtb5*te ykzqa)y24.0 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 racin2chy ciyp6do7,e9t7 xg car, which starts from rest at t = 0 and moves in a straight line, is given as ao6hit cp7c2yy 79e,dx function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was 2dt/0 yhiyi w0its acceleration? How far did it travel in this time? Assume consta 2/tywd00hiiy nt acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What waom+vd:w;kw + as its acceleration, assumed constan+vwdko;a: w +mt?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoffj i5 rl bzznp1tq6y(;2. How long a runway is needed if the (constantr6y;nj 5t (zl b1p2izq) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of w ,ci6y u 1 2y;pdwc31h9hx (zikx7lwothe blocks to essentially top speed (of about 11.5 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 s2izxkd7 ywwu (py9,ihow 61hxlc; c31peed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to res ezzn;993d psnt in 6.00 s. How far did it travel in zd n9n;39pzes that time?    m

  In coming to a stop, a car lixg+0q fx2 )iceaves skid marks 92 m long on the highway. Assuming a deceleration of )xix+qi c2 f0g$7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h tb, 7 /sve(itustrikes a tree. The front end of the car compresses and the driver comes to rest after t v/se,7but(itraveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car wu +hmh:y8 gfm6e(2mnzinw 7.hith an initial speed of 95 km/h and human reaction time of 1.0 s, for an accelerationmh.n6zy 2fhwhieg7( m +mu: 8n
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stong/ qze.m4sf4 pping 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 driver loohp8)4 yeij h6c.ao ne8ks for an opportunity to pass, guessing j iaeo8h)ph84y c6 .nethat his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 3321 )x uadygoikk8g0 e0.0 min. After exactly 27.0 min, there areoxik 12eay3dg0 8k) ug still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersectioh/ jdxwj h /rgyl71py .b3vb -j1+uvb(n 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 cross1y31v 7+p/j d-v bj hgyuj blr(hx/bw. 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 hithsmvn.9 l0v 3ss the ground below after 3.25 s. How 3l .9s0sh vmvnhigh is the cliff?    m

  If a car rolls gently+k88 xz-bea gw ($v_0\,=\,0$) 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 spewq3kmw8w: 6 uzed 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 tt1a1i7 r1ayn9oieakz v +3 x,phrowing it vertically upward. With what speed did he throw it, and what height did it ra9vzk13ox ea 1tp 1iyai+n7,reach?    m/s (Round to the nearest integer)    m

An object starts from reiz,1mf 3ehle 9st and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, af 3e9lhi1emz, s a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascen4pt7wtj8bf be 00s y3atxk8 6zding vertically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s i8t04xyaps bb73ke jzt8 f w0t6nitial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show t9 8yd nj6izxx45k37i 6 4r8)rbtri( mcs vnwixhat the distance traveled during each successive second increases in the ratio of successivezr4b7ywdcirjn r 5xxn (38m96x6v8 4 ts)kiii odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is nevv5 w5 ypm /:15ww(vfjzkgbg9glected, show (algebraically) that a ball thrown vertically upward wf/vw5z1kpm5w :jvv w g b(gy59ith 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 uahn9o8kb( cj8di kh3 g-9- oyspeed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple intm: 0v;*s, )ijxulp) xj uj56a.snuyo Fig. 2–18 (or number of photoflashes per second). Assume the app),*ou)avpsj xtjj56:;x.ml iun0ysu le is about 10 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 window 2.kek7 2 x)jw2yv2 m tall (Fig. 2–32). From what height above thkw)vk2 yxe 2j7e top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it stb13vmy,rtnel ( -rjm 8riking the ocean is heard 1 ,tynmr3j bvlemr-8(3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hosealvd5 kevb 9l +m7q7*)0kt xrp nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the 97*0 rpl tkdma v5k+qvb)lx7e 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 from the 3v(gd mg6/fzx6dw61enmpb +m edge of a cliff 70.0 m high (Fidg e (6xbz/66+mn gf31pwvd mmg. 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 pajfsw7a- lbq 3;5dfda9f h(u* iss upward by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the stl3auf;7j hiq* fdfs( bwda-95 reet,
(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 trai)mksqmcz26j x 3ma b*:bid6iy. ,k/cl n as a function of time. (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) Whck3) i6xsjammm2,.6/ ld:qc* bzki byen was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plotte rfz t-u.pk4r6,adpk,d in Fig. 2–28. What is its i6 fpkd .tzrauk-r,,p4 nstantaneous 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 v:/4fkfv5ovt,oz0 baq s: 61ayyx8n japproximately as shown in the velocity–time graph of Fig. 2–35. (The short fl 461o0yvzatjy:kv f5v8 ,of/ns aqb:xat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (Fig. 2–35omj fpry2r8;hb7cv;s 28*t tl) s o *tmc br2yj;tpf;7hvr 82l8when 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 ob0p 3ry1,vy9aq hyi0a u18t jkhject traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functi: nzfpw - mvs3*a6iq(qon of time is given by Fipi q*-6(nfs3qav w:mzg. 2–28.

Figure 2–36 is a position cu( d/zy /f5u,dgb oi ,yzi79wversus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Isob7 fuy/uz/widd(gc, i5y9, z 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 fourtem(3 ;goxhr j4h-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before hmoxjr 3;e4 g(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 one-sixth what it r+j9wj7pbyp-3 /ikec4wb 7dzis on Earth. If an object is thrown vertically upward on the Moon, how many timey-kbw b4jrc+7 iw37ejp p9dz/s higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat b)8bgg 74zpzz1afmz )oelt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g’s” pz4 g7g1a obzf z)8z)m$(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above th.3 z5i5fyjnqvo/2snw e 1oi* he 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. 1zo5ni3n5o .2jvfqy* hw/ esiThe 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 fsj4y+ilmm psc .68e 2its cars for front-end collisions by hauling them up on a crane and p2jym8m4e6.cs+ li fs 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 aboue74;(ekn 5gcpyy cf-et $10^9\,km$ 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 wk7 v.d,9f*ul amrge(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 willmav., gur9(dfke 7* wl be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divf.r9bs e4-ulwn5 i)wgm. tp -ling board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below .f ew iur4wmpn9l-s)lg-t5b.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 is necessary to balance the averagwilo 3x ( gmcj,, 2p2 - x1qd8cil4+uub/yaksqe speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in ska, cygjxim2l+u-q4cu ( db l1x3o ,28qip w/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 do* p jvj6enpmj0 1ar:y26he mqx:)3n inwn 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 takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the6 1j hn)2npm:x 63p*0: rjayineq jmev fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is;5 i( p,so 3tuez:q0npij2g/0gfucc m 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 jzm cu(20n5;:f iec/gs p0pqgi,3tuo 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 trai)mqf(r. cbp i3n traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive)m cqip.f 3br( 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 is droppedmr4d.pzpupeq3 s7 r0 2 1.50 s later. How far apart are the stones when the sesr.r2p7upz4d0qpe 3m cond one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over ti4xowk( 1 kl sip:e64w,x8t11ipowrp he 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 the lasw(: eo8k wpi1xl441xtkp 1w 6sip iro,t lap?    km/h

  A bicyclist in the Tour de France crest2qib4bj1kl 8fr*u nwsd -l -3hs a mountain pass as he moves at 18 km/h nfjrl q -21-w48 hb3dkls *bui. 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 trampolines. The first child can bounce h+dbf czl/e*7-o -;o qgax6rh up one-and-a-half times higher than the second child. The initial speed up of the sec;ehx 6a*r/h7o f-zbqogcl+d -ond 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 traadpu:el8p u.b91x*wlpz a59r in 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 trave .l81 raepdawxbul* p9:59uzpled 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 et2s3 o3tz4 ykpno5u0rcz 8aee bc+); speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball thro e3yt)rk zo;t5 bccn2zp0s4uo38e a+eugh 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 verti h9al m-ovsy74 v) wa 5/bxn(xp-gk.mpcally, 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 interse at0ju.t2j;9xu dlf(sction 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 ajuat.2xf 9( t;js 0ludre 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 g/l7* tozi3i2c mbxo bx4 3w.dtraveling at a constant 120 km/h takes off in hot pursuit. The poli wt/xz 3*bo g2.ldxiobi7m c43ce 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 roof of a building; 2.00 s after that, a second y+xq4k2kez d20.t ahjn(o:zhvzgg9* stone is thrown straight down with an initial speed of 25.0 m/s and the t+2.tda*zxgv 2 9y nkhko zqe4(0gjzh:wo 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 qr:bmbj9ha;4 thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after ;rj bmab4hq:9 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 takgd66epq+jq,9hc ez0)vvjx2 le 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 wopl6z h9qvq c),+g2ex6 evjjd0uld 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 y60 - wmypstv:to send the burgers through a grilling machine. If the grilling machine t pmy:vwys0-6is 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 production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertical x) a 8rw;3q+r. 3arjgp:kp i9wz2nuvcly at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go than Jg aizc)2.ax; w3qrpj89 3knrp +:uw rvoe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stanp0of5g(s b6p p k547s7f wic+:rahyqpds on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws ifwfy05hcg46kp+po(papq :s 7b5 7rsit up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a partb c-uri-n,z7vicular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of thecv i-z,u -n7br building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicyc7lz-ur7jvxd 6jzf 5y4les, 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 wr5v6z7fd4j-ljz7xuy hich 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?