Does a car speedometer measlr;uruwx0 c1i3 iz a29ot *jx27jnlu 4ure speed, velocity, or both?

Can an object have a varyingz)/6as0pg c bb speed if its velocity is constant? If yes, give exampls b0pzc)ag/ 6bes.

When an object moves with constant velocity, does qx5 t2 l3lbofru+ 5uqez2 od:+its average velocity during any time interval differ from its instantaneous b2rotlx ++: 5fu deu z5oq32qlvelocity at any instant?

In drag racing, is it po e0nqrztrz 1nsp-/n*qjy5 d02ssible for the car with the greatest speed crossing the finish line to lose the rac0z *zq2rrtd0e/q-15n psjn nye? Explain.

If one object has a greater speedb;f1pdf* 0qjf 7cxp. b than a second object, does the first necessarily have a greater acceleration? Explain, using examplebf.0x1q pcfj7*d;b pf s.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km/ pk *umqgnk:lpa26e /s0xk(r1h with the acceleration of a bicycle that accelerates from rest to kkqlas0mn2e(pxg u1 /r:*6pk 10km/h in the same time.

Can an object have a northward velocity and a southward acceleratioe5:.xqy rr:mi n? Explain.

Can the velocity of an object be negative when its acceleration is positive? ,yk m7(24ec7ngxut bgWhat about vice versyx7tm2be n ,c7k 4(guga?

Give an example where both the velocity and 8pdvbsy (r5az3;t9 km8d4:nlisa yx1acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a spee18ay 2dw qmx73m 1gq o6uls,ksd of 60km/h and has an acceleration of 40km/h/mix3kgq8lmq2s 1 1ysu6ado w,7m n . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If *(sy . zj l1dbuy0jfl,so, give an yj0 y(l,.zufl jd *s1bexample. If not, explain.

A baseball player hits a foul ball straight up into the air. It legqx0bs 1g/g 2baves the bat with a speed of 120km/ bg/2qg0s1gx bh . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is hapsjh7 ndwyx. o86 hw.q-e.gv+rpening to its acceleration due to gravity — does it increase, decrease, or stay the sameq +d8wrsvhx 6.e-yg.hj.wn7o ?

How would you estimate the maximum height you could throw a ball ver-f7 mb opk u+gpijk- 46sv70nt5vwb5ytically upward? How would y bog 7ykm-u ts pv60nbwkif+ 45j5v7p-ou estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of T: (3-rqw go+j7y9h m5yxkp okfhen you traveyj(5r:+3k-go7yfo hkw pq9 xml the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstrati nqq3rp .z+5lf ,uuvr9*;k* ;rkzujtmon, a 3.0-m-long vertical 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 k+rjq5n9,k * 3 rz uzl;uqt *;rpfvu.mintervals. 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 h8gy n5dph ai1rm)sx z8)-c j3h;up,hnot at constant acceleration: a rock falling from a cliff, an elevator moving fzj ;1u)s-i ) 8dg, ypnpchr3mxha8h5hrom 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 return to its original pos0 .ragebh)dy7m 7:lqdition with the same speed as it had initially if air resistance is negligible. If air re0 dg l7q:7 ye)rhb.amdsistance 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 acceleration at the same cpxbaji,46tgv:1- qz0 e k jn)time? Give examv-bznge 41cx)j pit qj:0, 6kaples.

Can an object have zero acceleration and nonzero velocity at the sdb.t3ybw; nuh +r/y+rame time? Give exampldtyb wrbn3.r y;+/hu +es.

Describe in words the motion plott-yjs) x a+gys9 8xx1mked in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion pl9ksg y1xjxysa+m)x8- otted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–bo:awi-h9 u;plek f5 -p uyi4929.

  What must be your car’s average speed in order to travel 235 2hc0t7 r s/tb9g/dssf km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15hm:vrotu4b( z;16 6w pjs.ae p:(t wqw km?    h

  If you are driving along a straight roav6e h0;fpfi*rq;3c efd and you look to the side for 2.0 s, how far do you travel during this inattentqff* pv0;e 3;6cifr heive period?    m

  Convert 35 mi/h to d190 .xyoyjv-tpi35ua f :n5s9gypjc
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fropwd2060 qvgc7 fchh b0m $x_1$ = 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 /2c s5 ikqinxq 24:ebht4 b/nfschool steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You t4 i/n/ xbhb4n qfc252q: ikesarrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every fi.i)*7e guy li,x9 f5cze(2zjr h;vpb wve seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives2r9g,hvzwelp .jfi 7(;bicz )u5xey * in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a total ti)xi-aks,n ydr h7 n6eczr7r2 5me of 12.5 min. Calculater7rnha s5cy2e)ri-n , 7z xk6d
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a str41d; iqtgt wa5aight line, moving 116 m away in 14.0 s. 1qtt5igdwa4; 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 tracsq7 - 0hr5kk-thcxi: iks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each otherk:7 -qih hk-xir5cs0t? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long d,*c.k(6: qdt c9se iha 0e qfen4cf(qwill it take the car to rc: 6kh 9s dieq4 n(.acc*fdeqq0,e(t feach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters u 9mn/tskyq *eig .8j.a tailwind that boosts its speed to 990 km/h form.uksn*ej y/gi 8q9t. 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:f r37o y0ymfvgv4*bat fn88 a speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/hfgo r8tn:a3 0by7 f*vvy8fm4a 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 conv :w6n:4njxb a4ykn*g, sc 5bqke5/cw stant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound o*n,5nb/ 4sy45g6qjcx:wb:c ekk anv wf 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 ij:ztl u42(x7gdsoz bbuv0 ,v.s its average accelerb u xuz v(gztl.b jdv,s0:27o4ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s.h x+.ol 2ozakid:gj7j3p z ,s9 What is her accelerationkg ji2z7a jps:o. xl h+3o9,zd
(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 acceler- ki4:/rsuy*ykgocvno 3;u q.gi)m 7ev2)nohation of about u*4qr) )h u7oevgm/y: vi;k sy3coi.n -n2 ogk$1.6 m/s^2$ 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 at75q 0-huxqf93zvlwo x constant speed travels 110 m in 5.0 s. If it then brakes and comes to a s9v wh f zx0lq-753quoxtop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t =c(zq (t 1x2hf3yijq o, 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a jxc2,t1fqq(o3 hzyi( ) 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. Wgi6kr12iwu(qa3t /m g1n2qh fhat was its acceleration? How far did it travel in this time? Assume constaqr nm1i g git2fu2hwq6k/31( ant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to 6 x8g:i5exu/hsq usp uwu(1h*gxl0d5 rest in a distance of 85 m. What was its acceleration, 0u5: hiu1u( qpsw/x ggxh s58du6ex* lassumed constant?    $m/s^2$

  A light plane must reach qa8gv1d nbt3 n 8sk3hbe14ts1a speed of 33 m/s for takeoff. How long a runway is needed if theb3teqsba 1 4hd31gkn1n88s vt (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can b0rtv4/d6y*y +rojas eurst out of the 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 hovtjso rae*r/4 dy0y+6 w 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 814 1u/z r(mycgwf +3tgzeenz 12.0 m/s to rest in 6.00 s. How far did it travel in that time? 1 y4(8mg1 r3e eutz+zg/ nzcfw   m

  In coming to a stop, a car leaves skmisy3l2z 2 6fmiw: *ubid marks 92 m long on the highway. Assuming a dece23miwu6 : y i*lfsb2mzleration 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/q fj . pzhl,08ynifqdcar+(1he 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 tqfl0 iycfn/1djphaq 8( .z+r ,he 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 g5,sy s;*8h,n (*fkcbbjskt ua car with an initial speed of 95 km/h and human reaction time of 1.0 s, f(k ts y,n j,f kh5*ubc;b8*ssgor 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 disj2m3oq9i g t9bc0+ dootance 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 ;cr; cryf,)kbdriver looks for an opportunity to rrc fyb,k;c );pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less thrq9f6c2r go.m an 30.0 min. After exactly 27.0 min, there are mc9 grr62q fo.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 anz u26 zk)mbpjk, ab+0g intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from 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 is6 bm2upzkz,+0j)g bak 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 groun fq7.,he6wljwb.w : sed below after 3.25 s. How high is the clifsjw6.wqw.: ef,7ble hf?    m

  If a car rolls gently e z y.gabglmc8. 9699sf 5q;bnxyjc.j($v_0\,=\,0$) 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 2(mdvzg fgu1r q 02rnf(d9/:g o2 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball(kih9x4;j c nz 3.0 s after throwing it vertically upward. With what speed did he throw it, axin( 9z4hc;kjnd 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. Dra8m(, ep*- j9zsjk s ch*3kopeyw graphs of (a) its speed and (b) the distance it has fallen, as yspkpsk8zo-h *93jcm(j*e,e a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At ag(mya *,f as-g height of 125 m above the Earth, a package is dropped from a window. How much time dom ya* sa(-fg,ges 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 rest, :2/ad xl rzu.ombt,q1show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). Thisuo2r xb.ml1 /,aqtz:d was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown vertip+ky: tf9 j qtdw;g1; epzt.n5cally upward with a e: kf9tpwdq5g jtntp 1+y;z;.speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 mhlbim;au 5nvl /5rv3 m-9hd5v/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 in Fig. 2qs 3,8wwd( gwr 7m;dgo–18 (or number of photoflashes per second). Assume the apple gw 7qmo,3;sd(r8 dwgw 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 wk9 a 3r6 zf.zltiy) f *:alilfp4x7mh5indow 2.2 m tall (Fig. 2–32). From what height above the top of theml fi *f6kz 9.hilya)453azptxf7:r l window did the stone fall?    m

  A rock is dropped from a sek4n0d a65ksdtzh.(u2n q f d4na cliff, and the sound of it striking the ocean is heard 3.2 s later. If the spen4d4dn (kn2 5qsf d.6hakz0tued of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of watkqt35u , d6imf5nc9dqer. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the iu3c,5n 5dt6qqkm9 f dnozzle 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 witf: ra7kqshof9 v 9l6ttt9m :)oh a speed of 12.0 m/s from the edge of a cliltof)k h:9omatv:s 79 fr9 qt6ff 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m abovj; x-ge3zy:sk e the street with a vertical speed of 13 m/s If th :3ykgjx- ;szee 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 velocity of a train as a functioppou+ abwi e9n 3-x,6rta3(yrn of time. (a) At what time was its velocity greatest? (b) During what+t y pr a93-i,6uxep( rbna3wo 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 a function of tim swb5 sk)hj f9+a6*qulkd9sf21 e,s xme is plotted in Fig. 2–28. What is its instantaneous v596s+)k sffdkmu s*eqbx1 j ,2hls9aw elocity
(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 acc;g5 bf*y4ok .h;dduu0 )b.mcxerzk3w e87zjzelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the cur c f7;48uk5 j)wzmzu.d;zb *ohgb.3 0reye dkxve 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. 2–35 cljx 4l;kkir 2d0mv4;) when it is irk;ci 24mjkx;dvl4 l0n
(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 thecz nw ,dslu*z04)a:uz object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the 5hv+e1,pggy 47mui0ont yv*m object whose displacement as a function of timeygv5,+thm*v e1m7 po guyin40 is given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motkz ,q;c,uv 0u awl-uy.ion 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 tk ;0z.u,-u u qvyal,wcime interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s 5i1h)9tk/zrj n o/ ogosafety net. The survivor stretches tojk5hr9/otn ) zg oi1/he net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the nyasp sd4q) *v9;c,obMoon is about one-sixth what it is on Earth. If an object is thrown 9v;4*a)yco ,qp nsdbsvertically 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 awe ).fj /t; qigihf4-zn over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed abou qfw/g z;het.)-ijfi4t 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, d2lm siz -76*ze/dc:/ ny(i7sendroi 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 lrzsn y2eimzo e:(7-/ c 7n*/diids d6down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturvfj ag4t(0 75i3i 2zswf7fy qver tested its cars for front-end collisions by hauling them up on a crane and dropping them fro(47s3 z5igv yjqa fffwi7 2t0vm 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 trvpf 9m-p sh 71seanj51avels 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 u*y8azua inhhw ke. )qzs) bb/yp-:6d0niform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from wher0ayhnb6w8e- ) q*kz .i/azypsu:h)bde 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 movv) )o aaf0d/dyun5 8 above the water’s surface into a deep pool. The person’s downward motion stops 2.0v05dyfano)8 u o )d/va 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 is necessary to balance the avbhc bsqr2h2-eb +nl)o7vw5 8f erage speed s82o 72whf)q5 vcrhb-b n lb+eof 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 two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down whedjnc*t1y 2*cp n diving for fish. Suppose a pelican starts its dive from a height of 16.0 2dp1cy* *cj ntm and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the forclk;celh *v.1v2csh :ke with which a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (th:kklvh* vch lc;.2e1s at 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 traveling at 0edf+ v5ga jt8avfx;5 ,fd ;j r0xh8tga constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelerates at a gj8dvfh05tg;x+8;d, f5afv xtjer 0 $a\,=\,4.0 m/s^2$ 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 thee.iu c05.-wvbxk 2dgy roof of a high building. A second stone is dropped 1.50 s later. How far apartywu2 cv.e0kxg5dib.- are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over tbar20wqd 0v .khe course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . wha2bk. wrq a0dv0t average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountyok 7 xm3o;y;te/g b.uain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (itogy7omu ;;3/.ebk yx n $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can b23r a tu7yrsd3 -iqz+zai*mq5ounce up one-and-a-half times higher than the second child. The init+* -imz2q idz3rqsyta 53 7aurial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train t*upins- y og:)ky6hs(raveling 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:kyisp )y( n6go-shu* 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 thzb) xyln6 *9i.1pmm hje baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, fromh 1iz6pb y)jx*9 mmnl. 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 accels:p.+c9cc.hra, b rdl eration 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 showp *)osrl+px putdpl7/koo/fm, 66c 5jbh ;1 ksn in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. x6* c5 bl)ho71 puspo;mjp , do/r tskl6fk+p/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, py1:5d5 aryr.chh;81f tcz:e svait,eetku3 / assed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant accelerationzavf.e1d5i3;u 5/t s race8yr:tyk,:1 thehc .
(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 tha2a; q i7p-tuc 5r(avbyt, a second stone is - ic5v ;trb7yqu p(a2athrown 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 t.tbn7tyci +mcc:2s p67 m4jlghe same time. The 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 should the second m6s74.pyj2ct ibn+c:g tl7mcstone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling pa-k/7l(a e fihx hi:;weu;itr 7rachutist 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 x-r(t77he; iuf a; i /kwh:leiwill restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor bz xjg8(t/7t.w 5et6n+xcnmyyelt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the x8 xzc6 n+tnj57y./ gtemytw(rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times fastadhdefyx k1mio/u* -2+rw3/cbf0;ds er than Joe can. How many times higher will Bill’se bxk ;/-fd *fu wrc2i 1+h/dadmo03ys ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while p(shu l*v2 h5 fp5wm91tkua6 jyour friend stands on the ground below you. You drop a ball from rest and see that it takesphwuj1 mfau5h p6vl( 2sk5*9t 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the heighy/s4;uw)rf 9mc;ui 5 4tmdpi tbp8dk1 jl yi+-t of a particular 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 mi4u bi- 5+ dpk)psr8l /tydftcw;;u 4mjyi9 1time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the po3 nzl7b :4h fw/yi5nkl/h-jkusition vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two b/5w:klk/hj7 bnhfiu ny-l43zicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?