Does a car speedometer measure speed, velocitwmfq k) wx5zt*5p93q wy, or both?

Can an object have a varying speed if its velocity is constant? If yes, ggp;;2zkyk o;zive examplgkp ;zk ;2yo;zes.

When an object moves with constant vin0i0 k(,apkq6 xfc.x elocity, does its average velocity during any time interval differ from its instantane00pciqf6 axk,n .k x(ious velocity at any instant?

In drag racing, is it possible for the car wit,moh9bq y0dg57 h 5y2pltne lcn/nq5:h the greatest speed crossing the finish line tn5tng 5lyh yhbe9ql,:7opd0n mc /q25 o lose the race? Explain.

If one object has a greater speed than a sehlh* ,oeuhckb+a 6 (w,cond object, does the first necessarily havcoa(+ hhh wb,k*elu,6 e a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcyci9vdqes;9m./ 8.ir;zf dlp asle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates e;asmf i .zr ;vi8p s9/9d.lqdfrom rest to 10km/h in the same time.

Can an object have a northward velocity:p(lhu*oeg wxt 8x, 9z and a southward acceleration? Explain.

Can the velocity of an object be n7)28tfoi7kc*w;k xk ja5 bk mzegative when its acceleration is positive? What abzck57kimtx)wjfk7 2 kbo;a8 *out vice versa?

Give an example where both the velocity and acceleration are negative.ap ). +;yyuahv

Two cars emerge side by3 y5 ,t.uimxvg side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleratituxv, yg5m.3 ion of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? Ificl-yb8+vn.ji :c xlr2 4hdt 7 so, give lyi c47 bj+v 8 -.xr2:dictlhnan example. If not, explain.

A baseball player hits ax4k1-k 2xxnfj foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the abse xxx214j n-fkknce of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object sk8c3 5wffi +hkfip xk60yor4 -u sc0h5peeds up, what is happening to its acceleration due to gravity — does it incr5 kf5 6fpkoxhcsr0k+yhi-i8u4 0 w3 fcease, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball ver::zm2 s4pec5bpbf;,4 u,xte zptp/h n tically upward? How would you estimate the max,e4,z4 c/::5uzephtp pmpnbf2s tx; bimum speed you could give it?

You travel from point A to point B in a car moving at a constat 2)6oke c.ikant speed of Then you traa)k ko2e6tic. vel 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 demonstration, a 3.0-m-lonu:1bx a-btake8ap2/ff sna8l6 sf g(1g 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 wi-b 8gf e8sful6b1: /aaf k1(apxn st2all 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 const.n c ohv9k0+ydant acceleration: a rock falling from a cliff,9n dh 0ov.+kcy an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original poshc- +32u cimg,eg9jss2l m2oq ition with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result bmo2qisjc , g2e9lgu23c-ms+ he 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 nonks+cg,,qmbe/ zero acceleration at the same time? Give kb +ecmgq,/ ,sexamples.

Can an object have zero acceleration and non .ffo1 vxuz 0cyrgw5ki//x1b0*.ss wj zero velocity at the same time? Give esb1fygwuo 5*jcw10k. /0zvr f/x.ix s xamples.

Describe in words the motion plotted 3 w cdeock3c3//d7tgy in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walkin /cy3coet3/dgk 37dc wg or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–295i2puepo:z1f .

  What must be your car’s averagfi16oe4h+;zdmwrog )e speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does i cnte(-dp(gjd+-mo. qt take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 g ;ooyomdci1 (5(amp;s, how far do you travel during this inattentivcymg poi;o5a1; m d((oe period?    m

  Convert 35 mi/h to 4i(. dfr,oyybnz m(z:3 hwbc do5f4y-
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr)yn *7c z5*qrrr hzhz+ q38jizom $x_1$ = 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 sc.gjm6jpz , a6yhool steadily at 95 km/h for 130 km. It then begins to ra,ym gajzp.66j in and you 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-thumb, every five seconds between a lightning flash and :pcpr qan48 ,lthe 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 spe nc4 a8,prlpq:ed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a qux3xt t8/z(w nzfh e+l nc(h-3narter-mile track in a total time of 12.5 t +3l nn z-twfznhex3h8x(/ (cmin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line,2*g ju joih(s; moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calcojs;(h 2g*ij uulate
(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. Each has a3kx b2ee2; umk 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 other x2mkke2b;eu3 ? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travelings506y3 fhehomu*z*rbn c n5uj9o0 fb4 How long will it takeum hyj5ohur 4f60bf3*9zsneoc n05 *b the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/hhf kot pl; e3exh55on;*d 3d3x , and then encounters a tailwind that boosts its spehek3toxd5; x3lpef hd o;5*n3 ed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average sp)i 7poxu1lg**bp; c:x zjxag b/t 1+mneed 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-houg)t*/+* jlbbg u;ip1xp1c 7axo:xz mn r lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constt p( 70c xqi*pz 2wbxvhgluob 1rp,/73ant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hearsx, 2qh 7 b7p3(p*ugrwo1 zvtp/xclbi0 the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95x , gwz6/mkc1nfhubm8e/1rd(ocd; c : km/h in 6.2 s. What is its average acceleration in6/g;obxcdcc8d enr1m(,z k/wfu:1 m h $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelera4pwa h1yvkstzx95i +9pd5jk .oq z) .ytion qkwyt 5pz i9+va)zks d.1jo h45.xp9y
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable9pjv a0 .zrs* tk+1gcy of an acceleration of about k z*s 0gv+cta 91r.yjp$1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it thenwq z,9csu r;2ep:c8pw brakes and comes to a sto: 2sz9;u prqe,pwc wc8p 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 fr lof0*b 6c-bstarts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a fu obf0 lr6-c*bfnction of time. Display each in a Table and on a graph.

  A car accelerates from iv q( k-ovtkig;v:6k:13 m/s to 25 m/s in 6.0 s. What was its acceleration? How far didk6: ivi tkg;:v- (oqvk it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance nxz( u1m* z5haduy/ht* sa/6jof 85 m. What was its acceleration, assumed co zat* uy5as1h6m/ u*hjndx(/znstant?    $m/s^2$

  A light plane must reacd 90erzsxi0c0g 5 b5uzh a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) acceleratiodrxzzcu 0905big 05esn is $3.0 m/s^2$ ?    m

  A world-class sprinter can burstgz a c x43l8h)reos 0b+9vai)j out of the blocks to essentially top speed (of about 11.ier s)o+)lh0vgc x8aa49 3zjb5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s. How f5jgbymdt o, cg 7a)/f9ar did it travel inbdjfa 5mc/ ,79yggo t) that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the hsio onel29r (j y7il fl9r:s+/ighway. Assuming a dec oly:/s7 (io+fr 9jls2i lrne9eleration 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 and 8n*fw016fciys tbpl gys.g 2( the driver comes to rest after traveling 0.80 m. What was the average acceleration of the 1g(6gf .8nc sywptly0 bf2*sidriver 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 stoppin 8/yw7ksih, nrg distances for a car with an initial speed of 95 km/h and human reactioh/yr iwn7 s8k,n time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of+jg3-j azt*k1bzpebm4; 9 zs7tz o5zt 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 highwa f731dkp eg wqbzr2w0*y. The car’s driver looks for an opportunity to pass, guessing that hi f1w*pzed0qb3kgr7 2ws 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 tu lg3xsh. q089ksyl-wdq+gv;han 30.0 min. After exactly 27.0 min, there are still 1100 m to+ -l0.wy sqgdqugsh; 9 3lvxk8 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 niz1:i; dh42n alb,6gr (uflm45 km/h approaches an 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 intersectio ad f1l2(nur;g4m:hb6i lzni,n is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below after 4vaft98 wom05rz cfn/7r6jer3.25 s. How high is t 9t8f/jrwfnm ro47az05 vcre6he cliff?    m

  If a car rolls gentl y:yley)p9oo1 y ($v_0\,=\,0$) 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 hkpp)9wt 7 )hxs4 w)huair 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 aft/3 wk.cvq y(imb+k/ erer throwing it vertically upward. With what speed did he throw it, and wha ybwkc/.3ekvqi (/+rm t height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw.s-(jwboo2m.dcz dd : graphs of (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 re-o wscdmz.:djb 2od(.sistance.

A helicopter is ascending vertically with a speed of 5y6ataco q 42*v:il4 fx.20 m/s. At a height of 125 m above the Earth, a pactlfiy:2 a 4a qoc*6vx4kage is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely frreovrozg* xn)oc1 zz* mfj5a79385jge 0iw / wom rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. Seefzcw19zrxm z 5e)5 jivga g8/orn 7 j**o3oew0 Figs. 2–18 and 2–21.

If air resistance is negb cdy)o 1i)g)2 x7:wpw ee)nwcl-a .cqlected, show (algebraically) that a ball thrown vertically upward:xpdiw7 cy1c g2 )a))qnbo-wl.)wec e 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 speed of 18.0 m/a w04.taj; wh1ponh r)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. 2–18 (or ns 8uptpvm8+x +umber of photoflashes per second). Assume the apple is about 10 cm in dipx+m t8s+up8vameter. [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 tra;tgi-51juss iw,nx)-u* rh yh7z,m nzvel past a window 2.2 m tall (Fig. 2–32). From what height above -),u hjru,*w1-t;7 5 mz gxin syzhsnithe top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strik;id; om9 wbxap*5n5c7: fmhpd; p4 lcxing the ocean is heard 7w o cb pd*afxd hpx55;cml49;mi;:np3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. Yom6cw (w+2 qc0q.yggpwu point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water s.w+q2 cg6mw p0yw gq(ctriking 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 sq;t6wn dz5h1ab; 4gv2 ec y4fapeed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34). h;2zdwy;4 gv5ncaq6f4ea1bt
(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 stsrt bhf*.ct4;2 xmpg3 reet with a vertical speed gh2 *3xttpmbr4. ;csfof 13 m/s 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 offm a7n g7l0jp(y+6agbl9e*g r a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the vef6 mna7 y9*( gegjrga7+0lpbllocity 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 stkp7o8dj;/r.so/un) j uxh 4ew b q,b.araight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous velocity r b8bo, ah7/ nx ;.djuek/ow.4u pq)sj
(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 vel hk7 t 53vjwwp.8+qneoocity–time graph of Fig. 2–35. (The short flat spots in the curve represen3v+w5o7qj.8hk t w epnt 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 accelerd9:ig -kj.2z 0edqd zsation of the car in the previous Problem (Fig. 2–35)dji dks0 9z-ge :q.dz2 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 distance x6haso)(ajb 0.8xk2t( *skwrq iaqb 5 the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for theg*a)j+:jh) g5 w;cig+pi w,fie qwm ccy nb2,3 object whose displacement as a function of time is given by Fi cwgi)yh:+jnbw,m)jgwi c2f* p5,g3q+a i;e cg. 2–28.

Figure 2–36 is a position versus time x(yxj)st0 4a 1 82htnv6valg9t *ari ygraph 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 the time interval from Csxvg(8yn2 j )60vix*tly t4ar9a 1h ta to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s safety doo 4sp- c)dzvxb3, cipa4y4f-*s-p rnet. The survivor stretches the net 1.0 m before comin p)- ocai34 y-*s4scvxdf,p ozpb-r 4dg to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sign31evl g5e -0iemh 9nxth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher wil5g-emg 3e hn10e9n livl it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder se6. x,po1smgkf at belt has a good chance of surviving a car collision if the decel mokx1g.s,6p feration 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 bridghi de tp+.xb/ 3o)0faie, 12 m above the road below, and his pursuers are gettinge d3 axb).p hii/t+0of 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 onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested itspqtd2di j/ .j8 cars for front-end collisions by hauling them up on a crane and dropping them from a certain height. 2/i. 8j pjqddt
(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 tj3dgyd9;psb w:7*sg k0bz r8vravels 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 n,l. do(ryylzw-8ug/uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is stan/oyrg (. dz-uw8 nl,lyding 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 4.0s, g rxff,6pu( 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 person whil,x6gusf(rf ,p e under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balack vnod; 91*zlnce the average speed of a train against the distance between stops. The more stops there 9c do*n;kv1lz 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 forrtfz xqqc 56:1 fish. Suppose a pelican starts its dive from a height of 16.0 m and z f1xtqc6r5q: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 plkb/5.p.fwv 6ueh8 pplanned so that the ball will stop within k .wpppbl/v6u 5fe8h. some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume 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 ate gz3 4v;ezzfe s1b(e/ a constant speed of 6.0 m/s Just as an empty box z14/; z3vegz ees (ebfcar 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 of a , lpg ,mdsb .h(,kuf4yhigh building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has,( fpgk,uy4m,b dl.h s reached a speed of 12.0 m/s ?    m

  A race car driver must average a5ue*d60e aso200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . whs05 aeu6ade*oat average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Franceddqawx*+u x :a 8 9vfg*30pqyw crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What : yauq 3*+vx wqx 9df0gap8wd*was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playinnzt rugjfa,* lk4tx4z kl339x,ac; d 2g on two trampolines. The first child can bounce up one-and-a-half times higher t*ltd4tk2za,x;l jau 9n,3cz4xrg 3 kfhan 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/h overtakes a 1.10-km-90ocox hrjcsmh tzp.fkf w-5) 9-w4s+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 tc shcz.jp9s k w-hxo5m-9 wt4)+0rfofrain are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the basevnt(*gq 9/x1uzna fr *8fy )mlball, the piy mntafq/lg r*f )nzu*8x9(1v tcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from2k7;0tl5;qdkbc d gjh 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 us 8c u;9 m8ry6id+pexyl ri(1signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When y ieuiydp8+s x;rrc8961 (luymou 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 by a speedz8;wb+hdx x4 -;qotzgj v17czer traveling at a constant 120 km/h takes o 4; -cxvxb1;go 8d zqzht+7jwzff in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a.0 wxhdxg0 w 4p tbqo/qe(j6vjv( 4)vd building; 2.00 s after that, a second stone is thrown tw0 (4j( )dqvvdwpqxb v06oe/j.ghx 4straight 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 samec go5l9+*u wa-usg3yb +kdr+ s 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.u3+wgdc s++yb lu5rasogk-*9 With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it 6f 13yr,5) mdripubvn take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her sp6bv nyi 5 )fdu,prmr31eed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor b6d.o*w6k7 mbjx hqbh:elt 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 thb*q7j6ow .6hb khmd: xe rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 tiu:: oq4 tnac+x cz,7ivmes faster than Joe can. How many times higher will Bill’s ball go thazvan ,+:i: xccoq4u7tn Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend v2m0k3v z7wt ixdi5.j stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is thk52zw iix7. v m0dtj3ve speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular buildingoaw -0 u h4lqbxtco(r/ )vv.q g29otu+ using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of thguuchw (-x0q2t+bt4v )9 ./orlo voaqe building’s height?    m

Figure 2–43 shows the posiw ap2;kb-xg1n8 8gbzution 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) are the bicycles passing each other?-8gkbg; w bnza12pu x8 Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?