Does a car speedometer measure speed, velocity, or bk :(e;i kgl (aheu*zj)oth?

Can an object have a varying speed ixza8nsb4ffr ws6 24 0bf its velocity is constant? If yes, give examp rz8af swx4nbs406bf2 les.

When an object moves with constant velocity, does its average vebgxpo,l2;yxk*8/ spy locity during any time interva, osp/bxyg*py2klx;8l differ from its instantaneous velocity at any instant?

In drag racing, is it possibthaiiniwk d l,8*8wf*t:2g6 yle for the car with the greatest speed crossing the finisi82ii8 a* fgltdnw,y h6* k:twh line to lose the race? Explain.

If one object has a greater speed than a spd )6i2n6c+ tao fe2tyecond object, does the first necessarily have a greater acceleration?6c2yo+nie6 p t2fdt )a Explain, using examples.

Compare the acceleration of a motorcyci2ku +mcuei q8t-;om d /ac.6jle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in 8/iu ;icj.tq u co +d2ae6m-kmthe same time.

Can an object have a northwmc;1 2:c.jx yica/zut kkr/qkl+bv 4,ard velocity and a southward acceleration? Explain.

Can the velocity of an obv2p( b8b. rw1;wvf fppject be negative when its acceleration is positive? What about vice versf2vpwv( wpr.1b; f8bpa?

Give an example where both the velocity and acceleration 1- (rg ebxyqu3are negative.

Two cars emerge side by side from a tunnel. Car A is travelg -o js.k pzg4ezku75w;j.5qq ing 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 pas-us .geg 7;qq54ko. zjk pw5jzsing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If svn0z:a+qo /g+jbs4od o, give an example. z+ n 4ojdgbo+/q v0:asIf not, explain.

A baseball player hits a foul b.rs b/qdm5s yw +*uhp1all straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catche u5/1rqdp shm.*b+sy ws it?

As a freely falling object speeds up, what is happeninmir4f kadg8s .p/a,k )w jb/o)g to its acceleration due to gravity — does dafko a4,r)/b/) wmjpgik .8 sit increase, decrease, or stay the same?

How would you estimate the maximum height 5 x4 kiz //otrr t;1jy1x4gkuvyou could throw a ball vertically upward? How would you estim1xk/ ;4 x 5ruzjry1ovk t4it/gate the maximum speed you could give it?

You travel from point A*mhhmp1+ ihm4) aytx :77 adep to point B in a car moving at a constant speed of Then you travel the same distanhm4xa h +h*d1iap)mey m:t7p 7ce 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 vertical string with ten bolts tiedwbi;u*owdtc , pqzn(gy6*6 5w to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls 6 qd,nzw6wcg (uiyp;wtb**5o 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 acceleration3je53;a4)bimdjs /sh dp g7bc : a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops alonsd/5icj 4 h)gd; ambe j7p3bs3g the way, a dish resting on a table?

An object that is thrown vertically upward will cm eeweb35:3 lvknp;;h a:e. mreturn 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 the motion.m;bn.k a elc33mee:e;vh 5w p:]

Can an object have zero velocity and nonzero acceleration at the same time?;- 15dccbwyt o Give examt;c- y1cbod5 wples.

Can an object have zero ass2 p)u6g 3fjqm2p.c l 3bman/cceleration and nonzero velocity at the same time? Give exampg 62/mnc).u33pqsfj2pams blles.

Describe in words thef,j.cev-d*3k cappifr,8f c / motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: F f3cidp ra,c-*v f.p ec,f/k8jirst try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29 ryqs*8u a+aoclde;wg(,7f ;r.

  What must be your car’s average speed in order to travel 2354z ; oyw3 9-(kolhayvv km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? )huo*t7 5lizo   h

  If you are driving along a straight road and you look to tho26 :;ag deowt v1ze-yi kko6.e side for 2.0 s, how far do you travel during this inattenti:egw2o yei1d-a kz.66t;ovokve period?    m

  Convert 35 mi/h to (wud2 ,gs.jhi363kj o2kakqa
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves froa1k. epd j;d/xm $x_1$ = 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;)bqs2n8jndzi m aoo.k2+a a:. It then begins to rain and you s8za n2 n jda2b.i+ ma:oq;ok)slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thu5nba 2u,xohl 4mb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed 5n,lo4xh2a ub of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile tpzjqjoi3wz - b2 :is)*rack in a total time of 12.5 miz*owzs 2j-3 j:pbiq)in. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from i6z9vgt4dnq10gs7u n gf-qr j)y- cl/ats trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculateda s4gf)9tun7j 6y/r ncvgg q0z1 --ql
(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. Eachsum;uc(+)v2 ccy cib2i 8lb.5 p tl;bb has a speed of 95 km/h with respect to the ground. If they are initially 8cib.;sluc+ c2ul tb 2(pcvbymi ;5b)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 yph1hp17t7i / +csa(q vstak5)kp;qpbehind a truck traveling How long will it take the car to reach the t hqts );7kphipa(5qp1 7 /kcya 1st+vpruck?    s

  An airplane travels 3100 km at a spez--v (ku.po /u /qa 2muo8xjnaed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km.-/a 8.ujk2xqnuo - (a vzm/uop
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 round-trip in whi4t *hxq;btj.i hn-2r fch the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and ;-hth.i r 2 *qfxtjnb4the return 250 km is covered at 55 km/h.    km/h

  A bowling ball travem.*;cs p iog 8jxfacs*jvv2(4ling 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 2.50 s after the ball is released from his jxf*v ccsoi.gpmjs48 v ;a*( 2hands. 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 ag)y 1l uz18m0aj+m mreverage acceler 1zyeam 0u1mlrgj8)m+ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates frluk9y1 0 wsto4667; eh djrrriom rest to 10.0 m/s in 1.35 s. What is her accelerationjr 9u 0ti;dl ks46 yh6ow71rre
(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 acceleratik:lh.4 oibm.l on of about 4.lb o mk.:ihl$1.6 m/s^2$ 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. I1l3 lsoj x-k/yf it then brakes and comes to a stop in 4.0 s,/xly kjs3- o1l 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 = 0 and 1(au 3nl0 *x 5xdd x1rfji,wlcmoves in a straight line, is given u1cw*alxx xfi3r( dd50,1lnj as a 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 its acceleratsf0hljs3p rvbj6r73iau 6)t 7ion? How far did it travel in this time? Assume constant acj7tabf v6i0j3l3s) ru6rhp s7 celeration.    $m/s^2$    m

  A car slows down from 23 m/s to ret;bc+:eqn v9d xegk4/st in a distance of 85 m. What was its acceleration, assumebdc ee4:+qn/tgvk;9 xd constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How ly:p9q g l0: pt1oat6aaong a runway is needed if 0gl:6t: apaa9poqyt1 the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentiallyg3s- 9umw yd(g 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 tms3-gd uw9yg(hat 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 a wf9xslxd-;/ 6.00 s. How far did it travel in that t-;fx9lxwa/d s ime?    m

  In coming to a stop, a car leaves skid marks 92 m lonw .i9 5jwp:qvuah1,h tg on the highway. Assuming a deceleratio1iq : whu w5,t.p9vjhan of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresses -kl4w:e. p 8kzxwsizt o:(k:sand the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi ztwo kwsk p:s-x( :k4eil .8z:on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 km/h and act, hb:m1 4kbhuman reaction time of 1.0 s, for an atc: 1 ,ma4hbkbcceleration
(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 3,+* setrkigd 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 cz3- s73fu3h x,s (rkr ptew;riar’s driver looks for an opportunity to pass, guessing that his car can acce-pthwr z;ui 3 fkssr3x7,3 (erlerate 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 t(s 2dk 4hrw+ergx265k gyq1 tsmltb(p :,r.rexactly 27.0 min, there are still 1100 m tos kp r6 ty 2+(,(1rbl5t:gq.4tskh2rdrxw meg go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as the traf u6qk zab 53e-c9pnab+p9u .kwfic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The interseckb 396b5.aqc9 n uzkp-eup+wation 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 aftpq2cm6x1: 71 hznl jzrer 3.25 s. Hzl1 x6jrp mzcn :1hq72ow high is the cliff?    m

  If a car rolls gently ((vudi jeb: o+npj3wij 63t;ud cz01 e4$v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of 22 m/s*4lnjm+ set7b f1 bwn:
(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 upm+kix jfbi04 )ward. With what speed did he throw it imxkf)+b 4i0j, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Dra . jh3-wdk ch:ux/2ugkjsh15hw graphs o51xus jj2 kch/g: 3hudwkh-.h f (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 vzo.mcn;(pv:b9 n h l*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:: * ;nnzob(lvvp9.h mc The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from r1ieeva pq7t* nt3cm (+est, show that the distance traveled during each successive second increases in the ratio of successive od1(+vempeic tt7qa 3*nd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebrapcl0w0vxw5g *3:1k dn dq0leqically) that a ball thrown verticalqvdpnk3wq 5 0:wgl1*cx ed l00ly upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speedi*5-qc2tv 4jd qbvf(bqjmx07 4j/ doq 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 photoflash8e) oeql +51vb/j dhvchsz9mz;mg*i7dhp:r6 of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear odzv+1:)plohb e6igdj7hvh ;m8z*e / q59crsmnes at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past 5dme0 av;nrlkrj 2*e*ni a6s5 a window 2.2 m tall (Fig. 2–32). From what height above tj6r;20drkvne* 5i saln5m* ea he top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sou c.(n-a b*ntru :tvhs:nd of it striking the ocean is heard 3.2 s later. If the speed of sound is 34t(a u r:*:hc nbnt.sv-0 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard 5m- 0l jbvvcs00nh9/1uq agv astream of water. You point t0v am0jvu1 l5q-b0a 9ghvsn/che nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s fr 0bp 5qono+ivrq56l5 eom the edge of a cliff 756ovqoqer nb0 5pl 5+i0.0 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 the9tv fs(nqc u30ouy(;qpdgj2jm,d* v: street with a vertical speed of 13 m/s If t:qd,s39jt(duy(uc n j2 vq*mogv0fp ;he ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the vqgd-u7hr( k (sfhq j+0elocity of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was th f -k7jqu(0ghsdq+( hre 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 a funcgg k4jnlyy1(l lx+my+21r2jd v1lem/tion of time is plotted in Fig. 2–28. What is its instantane(+ellgy4v2m 21 njy+k d x1ljm/rg1 ylous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in the veyl-it hi20 (cjlocity–ti 2hi0 -lijytc(me graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the pref3h vxxs1f o0- e:sr-kvious Problem (Fig. 2–35) when it is i3fx1 xkv hs:fs oe--0rn
(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 traveled during +qo*c5mmdatyw /saesw/c 1/7
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph forpj.u w,jkf.yq ,fjxs..(/m :jy +l adf the object whose displacement as a function of time is given by Fig. 2–28.+j(fy ja f/..qmkf u, ,.l:d jxy.swpj

Figure 2–36 is a position verd+mp(csmto6o q (.s3psus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or 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 theq (cm.ptpo 3( ss+m6od time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefight w9m0(y1vp.j6,6 gjubr.yx xkz7ifqser’s safety net. The survivor stretches the net 1.0 m before coming tjfqs,6wjyzm1bx(vi6x9ry0 upg7 k .. o 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 Moonw ;9wu qoel(kehd1fele ,82b :lna. kk*j,xy* is about one-sixth what it is on Earth. If an object is thrown veru9 :* ,edhl j b1k lexwf .e;y*naoe2qlk8(wk,tically upward on the Moon, how many times 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 seapv:iv9 . /al5 0nocelwx j+bq(t belt has a good chance of sua9(j v5pxlw+ v/:nq l o0iceb.rviving a car collision if the deceleration does 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 th.,qfht2 hwwtca/+4s ieyo l2w78l gu4e 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 tcwt/,.whysaw2i e l+h2 4u7 o4 qf8glonto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested itsrqd1r4. rt bk, cars for front-end collisions by hauling them up on a crane and dropprkbq1 .dr4, rting 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 trj v l0z: 5e dxni/8g;y.gxls6yavels 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 fro ow6oh8g, 8)4 fbm /uay9gai geka+wp2m rest. The front of the train has a speed of 25 m/s when it passes a railway worker who ia 96iyk a 4h)m8w f8b+ wapu/,og2goegs standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m abovee r7p(7ex,5 v* thcyb6pf3 dzu the water’s surface into a deep pool. The person’s downward motion s5*hu3e6 fb pt dzpy,7xc(7 ervtops 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 ra)rwq0 t/427oxbo)kyb,y (gn. uh kkzbpid transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculah/zo7 o2w ur b(y0b t,yk 4k.bq)nk)gxte 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 a(ujopemw/8hz*na*w v5rl x(8 nd free fall straight 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. Ia w88h(e/por u(*5 zwlnx*vjm f 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 a golfer strikes a ball is pla/hm l oi)/7ddxnned 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 d7xilmd)/oh/ 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 fresd6 2j;qsrl;prvih 70 w5 i5whight train traveling at a constant speed of 6.0 m/s Just as p isv;jw2 l6 r5irs5h7q;dhw0 an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof 7 :waf7dbbf ;4 t nrf(x0glv;iof a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the secb7t; x4gb vaiwnr0 l;7d:(fffond one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over thh k5)8,xhm tjezkjk-:e 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 f)5k h8jkkm h,-tzj: xeor the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as*ql0 m p:q4gqd he moves at 18 km/h . At the bottolgmqq* p:4 qd0m, 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 up onk2yusja)e 0 h(mnp6 *be-and-a-un2myj*k0( )absh p 6ehalf 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 3w7ll 8w3deodwco;5z/h overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite direc8l;z3d 3wc75lweod wo tions? 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 y qo gf axbwp*)ow3./a86g;li a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Figaogywg/o q *abxip)f 6 ;l.3w8. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, gw0h4+u k08*+nw sfbonik3mifrom rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection has a traffic gf6r4e/z -nw.l.c rfrt5 vm)msignal, and the speed limit is 50 km/s . Suppose you are driving from the .ntm5.rr ef-)/4wvzlgc fr6m 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.
(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 bx.v2.779v npy zhsfwiy a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to .i2xhpzvnyv 97.sw7 fthe 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 afterxbcrfj14 wf;8 that, a second stone is throwc4xfjrbw;8f 1n straight down with 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. Thy8f7gdal wkn-3.j, pz vz5az. e first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity shoug, waal -pkvjz d73 .z.8zyf5nld 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, hlv:+ t-.xl bvhow long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where t+-vhl lxv:.bshe will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the btp.5fpt gtulp ml u;,57-6thqurgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cooph 5tu gt- 5;6p 7fmt,tqpllu.k, 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 vertp j njqje23.3bically at a speed 1.5 times faster than Joe can. How many times higher.3 jjjn2pe bq3 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 thhuj.zb 6;:0j3andy tde 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 it just comes to rest in j063hjt;d.az :by dnuyour hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building using a xe*42 off76k gov7shmbarometer. 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 othefkg s7*hv46o7 m2of xer, 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.a qt-.(r kokn position vs. time graph for two 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) ar rotn .kqa-k.(e 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?