Does a car speedometer measure speed, velocity, or both plmnn*.rk 2:j?

Can an object have a varying speed if its velocity is constant? I h)hi* ekj6+zza h,/2r ku3lrff yes, give exampl3)jh ark2ei+ fzhul*6 hz/r, kes.

When an object moves with constant velocity, does its average velocity durings/qwxe4i 4o4x+nee x8 any time interva4 si enxx+ 4qee48wxo/l differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crde(8u) j,fu9 smjqg1possing the finishf u, sjq8(uem1pd j9)g line to lose the race? Explain.

If one object has a greater speed than a second objecnonsu a 9u 2v.t2m1s0hm xqu*u9; ;pspt, does the first necessarily have a greater acceleration? Explain, using examplpuv2 u9nh9x1 u2s .0 qu*mo;;mpsn astes.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 9n wy2niy + sce-puuy,:.. ekg l8.+rno0km/h with the acceleration of a bicycle that accelerates from rest toce i+,o.k+s puwey. nnlnrgyy2: -.u8 10km/h in the same time.

Can an object have a northward velocity and a southward accelerationp-p0 s2y ejvp;? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wh-m5xz)vc ns)dat about vice ve5d)-n)v sxm zcrsa?

Give an example where both tm.m v0 gr/qk7wee9k hu79 thz)he velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car ammirlx( 0v)* A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is)0v(*rim ma lx 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 sk+8 ix0k;zgsj6 dhz 3(t/ jy1tzvz5ic o, give an example. If nhivs6ij/z5z+ky1kg8z; t 30( xc dz tjot, explain.

A baseball player hits a foul ball straight up into the axqa5ykf/mg:nag imy (5- c6; hir. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the balli6/ y m(a5qn;fgmk-g:a5h c xy be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration duvp6 :l kca2yx mkxb8wp3j0*. re to gravity — does it p8w63k2j mkb: ly0ax .xvr* cpincrease, decrease, or stay the same?

How would you estimate the ,sm rsj(2r3 4y;zhgycmaximum height you could throw a ball vertically upward? How would you estimate the maximum speed yohc4gyrz(y ;,sjmrs 23 u could give it?

You travel from point z:m0 ofk ne(q*uzu66dh 6cpl:A to point B in a car moving at a constant speed of Then you travel the same distance from point Bh:6d0f *qcem:(z p 6oknuuz6l 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,/d daw-fr/e 8l 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 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 clinkd-/8rwld ef/ as occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock falling ddo)k0:sj3 kj1bp)ikdl92 kg ;bd8pzfrom a cliff, an elevator moving from the second floor to the fifth s1;p jjgk :dkd)d8 b3 9dbkk0 zlpo)2ifloor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its ro122*dfhj n t*e phr2f,kyb,original position with the same speed as it had initially if air resistance is negligible. If air resistance ,*f2k2d *tfh,1o hp j2eyrr nbis 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 samevgw 2w 1jj s)4( uodya6zo,dp4 time? Give example( zg )d64wdou,a j42ow1spvyjs.

Can an object have zero acceleration and nonzero velocity at the same time?zcqa0 1u4 o-jdkkl:v. Give examcj:4-uk k z .adlv0o1qples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, et594 o jegsfe5o8bl d6ojg*a7h;1sk yzc. [Hint: First try to duplicate the motion plotted by walkin* yejo7 d1sz6fbg8ls;4ak 5e9og j o5hg or moving your hand.]

Describe in words the motion of the obq13cmbkoyyti)+ g l2*ject graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel wtn f0i7ax c;+235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? y+3p4vrow yxs)j +: j)v2dsjb    h

  If you are driving aurwz vjfk98-6av7 s4 t*1ml jflong a straight road and you look to the side for 2.0 s, how far do you travel during this inattenmws8jv jv7a-1 f trf *z9lk64utive period?    m

  Convert 35 mi/h to a6wji3 5 eai.z(ey+gnyt4m .ca cy9a(
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frd tog qkfrs4 :-/q,jz9om $x_1$ = 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 steadilyu6mtw2 j,-po-e 7mayh at 95 km/h for 130 km. It then begins to rain and you slomymt-whpj6ou2a, - 7ew 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-thumb, evzlf9iwt a7-6r+6ej cm nyben/tg 0(z;ery 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 of sound in m/s from this rule +tniz/e9aby7r6 f;(l gjntemz 06wc-.    m/s

  A person jogs eight complete laps ar0))wcna*v0 ,.mkc9 z cs tsggyound a quarter-mile track in a total time of 12.5 min. C. v)s0gmk0 wcyn ,zsa*tg cc)9alculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away nn(j(maalm- 5qb0n7 qfrom its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway backnn-a(aq 0 bmqj7(5nm l 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 o aze t8 ogk*lg(i159gyw d1d(wn parallel tracks. Each has a speed of 95 km/h with ry 5gatd leww(o1(*9zg18igk d espect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long will itcap rst3x) .g;aie3z/shj2m 5 take the car to reach the truck?tjh 3s/cge;5is23mp)r .za xa    s

  An airplane travels 3100 km at a speed of 790 o5wn8viv8zs 0 gb p;c pv35vk)4wpg lmiz568fkm/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km.z488nwbi)v5 z 0svcmkp g6ogl5i vp5wp3;fv 8
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 8e(cs- elwpys w eu7okk +epd ,//r*q:speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covereyek+oe/w se * ce/:ksw,pul8pd(q 7-rd at 55 km/h.    km/h

  A bowling ball traveling with constant jxwbt+, 8e, jacv c5bjq(e; +ispeed 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 af 8,j(vbejccjiw5etq a, +;bx+ter 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 q6*4gh. t-gx *w msmrs95 km/h in 6.2 s. What is its average acceleratiog-s.xq6*4m *mrhwsgtn in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates ff+ lm7 (yd-z8 vz 5ybq/dbdx7trom rest to 10.0 m/s in 1.35 s. What is her acceleration (b-+5x m77ft8zlv d yybqdd /z
(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 acceleration of aboo5.qy- +4py( snos gj.j ym2rwut ynwsop5 jgm(-j+.y2 4o .rsyq $1.6 m/s^2$ 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 speedx5ek.o) i cb fq93cz 7t55j 9bv8mioua travels 110 m in 5.0 s. If it then brakes and comes to a stop in 5cxqvoz7bt3 ucma).o i 8if ke9j 955b4.0 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 racidkg xt7eok+:fs 6;4fo ng car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity a 74o+fdgo6:;ekt fxk snd (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 acceleration?k1 t4d* hp rtda6x-uo6.us:0 g2vjwe)ji tfp2 How far did it travel in this time? dv 2gpfj )s *t r2-wuk1u ja:hp6ido4t06e t.xAssume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its accel9v85dgwavo kps c5 07heration, assumed w55p 8koa9ds cgv7hv0constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a rpoac.1xbrl.. *bt51oxogv1 junway is needed if the (constant)b1rcj 1 *x.5..1bgxlo ptvoao acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially topo )s,fbc5gu mr rve*c. vl/;t: speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the averalfrsvg5coe. mc buv;/t :,)r *ge acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of +*ec ,umf3l1.d zmzp a12.0 m/s to rest in 6.00 s. How far didzle1ma 3u,fzcm. pd*+ it travel in that time?    m

  In coming to a stop, a 3 9w+jk: gpw)gudk*b gcar leaves skid marks 92 m long on the highway. Assuming a deceleration of gw3g:bgp9u kd k+*w )j$7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h stri hg) 67ab4bxj y/3o7: ld,kso3pp ee-vjeu1k ikes a tree. The front end of the car compresses and the dri d 3,lx g)7oek7 ibpe4e-aj1o6/yuhkp3j: v sbver comes to rest after traveling 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 distance7uqceu9ri6v1v9e og ; ; r,dsas for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an accei;qodgeec urs9u,1a v6 9vr;7leration
(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 car ij/y3-5z6 er tulhjl- ss $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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 tr3kn.ecssstobcti0 41t . )br4 uck going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate atk s cbb0on cir)4.t1t34.sets 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-e4spp2h6a*n hm run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then a4*hsa6epn p2hccelerate 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 in.mg;84liab;h7zf 2 gq t x ese216jrpvtersection 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 inte247i gvbel jrta2mhe;1z sf.p;g q8x6rsection 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. Il90zh1/t6h ,/f.jlikx- owed7v ton l t hits the ground below after 3.25 s. How high wx/ 6tnd -/hje ,0ohloftv l.i7 1z9klis the cliff?    m

  If a car rolls gently sagsppy7v88;2 ukh ;a ($v_0\,=\,0$) 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 tobr1nzg0niplp7c tw) ,9+,6-mlgq nvhe air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertictrvk;. 1 gma; 6v3azwgally upward. With what speed did he throw it, and what height did it ra6vg kv;.m; ag 1rwtz3each?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravitydq h.:hif;one3:sa v /. Draw graphs of (a) its speed and (b) the distance i vn;/.h:ho iqasf:3de t has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending ver 6aczz/b n88pyfd.v91a uyhsblf9 5;rtically 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 initial speeds9n1d8 v5layz8yr.bcah z9pf/u6f ; b equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the dista /uto ego a)5,m2)e)/ gpd 1w s8uijafaml1q8fnce traveled during each successive second increases in the rati8m5l wtf1uoqp2ju fm aa)os/gg) e18d, ei)a/o of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraica1k5 z.c ab2wetdfe(mtymv)* 6 lly) that a ball thrown vertically up6 kvae1tm. d*ezb y5 m)wc2f(tward 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 w e4uzhn ;d(f-bith a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each pmf 5zy);lecq0hotoflash 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 ply)5zqf;em c0ositions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Figy61: b5 bwt1lpxglaj.. 2–32). From what height above the6gax l:1jbt1wp lyb.5 top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is1nis hr +;u8vewjc 5a0 ho-ez( heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H = j(zaese-8r;uc0v5i1 owh +hn    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. Y1f)o-ov0ua3;z phy b4,+ pdj ol q2hpoou point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). Whe3l4a;hd )qoz,j opufvoob 2ph 0-y +1pn 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 1 d1wim e+,8+fm,czcre2.0 m/s from the edge of a cliff 70.zmcd8ew 1ci ,f++ m,er0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a vertigym*kkx:q3am7 kqa4( cal speed of 13 m/sm x4:k akmkq* (a3yqg7 If the 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 function of timeubx/q9l+d 16l)ocezz . (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? (l 69b)qoxczzud/ +1e ld) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plo,ri3tw f1n: lhtted in Fig. 2–28. What is itsh3r,l nif :t1w instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximatef6 / yv.lmf,a:t- xnd1x/rikb9n nc-p ly as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent sp,vaxfyfi6 r/t/n-k-:lm 9x cn1bnd.hifting 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 d1b ;/h(wp(d 7- zji-zk ftexrthe previous Problem (Fig. 2–35)7/(de ;dzz pf-bh j(1wri-tkx when it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the di8.c,3qjh*f+zly fxwe stance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displac5fnvc9 qk sq;5bm5 ts;ement as a function of time is given by Fiqsc m ;n5b;tv5fkq5 9sg. 2–28.

Figure 2–36 is a positiok-*k/5kc/rd .r cealp n versus 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? (c/r.e/ 5 k*pk cdl-akrg) 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 fi ybx/vwg7+1k qrefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, +xbwq1k/ g vy7Fig. 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 gr r.gxza (0zd r7crj*zu9 )+pgravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assumi0.r )u+zcrrdp 9 zxgja(rz*7gng the same initial velocity?

  A person who is properly constrained by an over-thex7bof.*;sjvv -shoulder seat belt has a good chs.*j; ofxvb v7ance of surviving 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 the road below, and hisei+rj*:k giztv-u 5s0b2 vm*) io1hku 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 :u ob*r1k-2ehtivgk+imiv) 5szj 0*utruck 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 manufa0e9in*x *m1dmfpxbxop - 6sh*cturer tested its cars for front-end collisions by hauling them up on a crane and dropping them from a c6p-* 1bx0hm eo ps*9xmdf n*xiertain 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 Earthvwtytwjw00/ n; d4buu6jw u0: travels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from r6 hr14gr:lhd kest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from whl :g 4h1rhrk6dere 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 divinp ysx iou+;/s+g board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the personu;/+siso + xyp 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 ali)-*rdb(o 3ojda +u a4z abt/verage speed +t)db/uajra* d4oa-l(oib 3zof 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 when diving for fish. thjus5 b*m *w9Suppose a pelican starts its dive from w **b5umj9sht 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 the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so thxp6.s1fllsn:s ;q gm-at the ball will stop within some small distance of the cup, say, 1.0 m long or short, in ca xslmn;:.qs spf- 1lg6se the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a frei2ybnw *a 6xxv4ght train traveling at a constant speed of 6.0 m/s Just as an empty box car pa an*v2w6bx y4xsses 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 of a high building. A second stone isio l,iqdrm9 gssee(116f4j y wg1v u*4 dropped 1.50 sgm ,411(s *fiioy ju1gwr9vle64d sqe later. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must mabl(/4*dzd u(ctd mr)/2cnk average 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average spk2c*n/dl( m)4dr/tb z aum(cdeed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountanzq8/ 32y/ ime5phiaq in pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed qypq2mizh /3a58 ein/is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playn 0x;s bsrcy3g)5ke 1fing on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. Ths3 egy);f1krxcb0n s 5e initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling in the06kx1 )rf5t qkhf0c rsh6laj / 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 5thf06qlrx1j0fk rcsk/ah 6) it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s Il wdjeep/ e)h:fn7m-7+ gp b8ya-w8b0yuxv(o n throwing the baseball, the pitcher accelerates the ball through a displacembo )7y:( aleg/8wwv+d ef7-mh- epjbu8xn y0pent 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-. syb05k ea2h/5zi 0wlnx0bnty:cclcally, 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.v yk xh42 h0q:mlw,+qr 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 fi , hr0w2vx:lqyh m4kq+rst 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,q1+ avb3w7l5mucpup) 5l n/uh passed 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 conspqlpc5+1 n b aum3u/h)u 7l5vwtant 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 h zdpbjh*n2 gfc.l6j/;t z m /eo-+4ypthe roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the +zlde bctjj 4*.hynp-2zp;fo/h/gm 6same 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 firljj1;fp,/ 3c ws6lsa*qa wr xok;iqkt/3bq31st 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 seconaq13 f/klc3pj/*bksi; s 1wqjar; to,6lwq3 xd stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a freb h(p ;6splex(e-falling parachutist to fall from a plane at 3200 m to an altitudhlp(xp;(s eb6 e of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers thrl (kdy57e m +wfzdz5uqd .r;u7ough a grilling machine. If the grilling machine is 1.1 m long and 77ludum+fdz(q5.;kzr5w deythe burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe can. ofbr1pu*s/u.0 jx dqa4q8i. uHow many times higher will Bill’s.i uqbafo804 jr/px.u1s uqd* ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on theh:s ,y wdxw,kr bzy(6-ivpd.p9c5l /n 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 ipxddz( cn ,ws 6yyrv 5kwph/,:i9lb.-t just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building usintj61u hoc3+wng 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 differenceju6 c+3 wt1ohn does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph ;)y w c7d x526afnwuyvfor two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity?6anyyc5w;ud fvx 2w) 7 (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?