Does a car speedometer m1buh lsm+0i* t6mb 3tnr2*dqreasure speed, velocity, or both?

Can an object have a varying speed if1ddc f v1n6lny -la7k7 its velocity is constant? If yes, give examynlfdk1dvc7 n -71al6 ples.

When an object moves with constant velocity, doefrnx,y8 nnf+);gyk : ys its average velocity during any time interval differ from its inx8:y y)ykg+rnn,f f n;stantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing the a.j +e+m ynv1b tgce8mxq:6;dfinish line to lose the race? Expl1md+eenxy +. t6q8bgj:ma; vc ain.

If one object has a greater speed than a second object, does the fire 0+ff4(o )v tsyy0df;tp(enm st necessarily have a grea t )(odt0ynfmpyese+ 0;(f4fv ter acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from qeez/*s-bx ): )syghp 80km/h to 90km/h with the acceleration of a bicyc)se *y)/ phb-z:sq egxle that accelerates from rest to 10km/h in the same time.

Can an object have a northward veloc0fxtlcwa (u iw 414xu2ity and a southward acceleration? Explain.

Can the velocity of an object be negative when its accelerdgo3 38r wa bnz:0ot4j ahq)j*ation is positive? What about v8b*t wj n:jgd4 h)o aoa0rz3q3ice versa?

Give an example where both 0mzdxj :y1-db j(sykzp,b-.c the velocity and acceleration are negative.

Two cars emerge side by side from a tunne6tw f eio7+zh2l. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is pass2zw t+ hi7of6eing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing od4uf6it(tkcxr3: ce6,gengi91ya* in speed as its acceleration decreases? If so, give an examplet16(cyf i*ukxo6ec4,:dgt 9rg ai3n e. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the bat:yj ip6tfe5n*3gg j; gug. -bw with a speed of 120km/h .5e;bjt-j g uw.i n3yggp*6:gf 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 happenip,r,6w ,,dvv2 jwxoc k..w5xr2rgny uyq6n ,ang to its acceleration due to gravity — does it increase, decrease, or wr,o 6.w 6acqx.yvjryr,w xpd 2 ,,gvu5,nn2kstay the same?

How would you estimate the maximum height you could throw a ball vei,zbh9k j4fju 7 7bweql1x z7.rtically upward? How would you estimate the maximum speed you could gz. 9l4q wk x7i7j,uhezj71f bbive it?

You travel from point A to point B in a car moving at a constant speed of Then w42g 1m-cxauv*es o k(uz;,s0/gunyb you travel 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 ws1ygb ukgcow va2s-zu n4,*0x eu;m(/hy not.

In a lecture demonstration, a 3.0-m-long vertical stringjgj 1c0h sb, 83;dtvvj 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 p 3t0cshjbd j;jv1,g8vlate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock m s ng:xno.q8k(qatj;x-c(0 b ufi.7xfalling from a cliff, an elevatorx;.caj-ubmn7kqq:(xtg. (0xf i s8on moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thm oo j)w1vc6d m))u(nerown vertically upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to eodo) )c6 munm1jvw ()the motion.]

Can an object have zerum qzvpv.llil43 ,;,o o velocity and nonzero acceleration at the same time? Give l,mpiqvo43l ; vu.lz, examples.

Can an object have zero :dpgj /mlho7so6bg;xq i6u7 4*pkfb +w:6lzu acceleration and nonzero velocity at the same time? Give examples.lhjmbds: w q *ub;/+k7 flo6ixpgz o4u :p7g66

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint:6*upnt6uu 6ck First try to duplicate the motion plottedk n6uu6utp6*c by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. uhg2+lz stt3wlq 8 -j/2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 hufb :jicomup6/ :: o:v?    km/h

  A bird can fly 25 km/h How long does it taa2k,sb .sv:mt0l j s5mke to fly 15 km?    h

  If you are driving along a gz*xy7mp9-qy straight road and you look to the side for 2.0 s, how far do you travel y7xm py9z-*q gduring this inattentive period?    m

  Convert 35 mi/h to ;x1q 9 cbf*zbq;kcgjwn/.xf f (.)tsu
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fo4 4.1xdsjd nrrom $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily syn5h us+p2r.at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after drivin2r+nu.5syh s pg 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 a,3jsvze ojc de5v; ;7xnd the jo zsx;j,3e7 c d;5vevfollowing 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.    m/s

  A person jogs eight complete laps around a quarter-xk+ 0phvoq)d* mile track in a total time of 12.5)hv pk *x+do0q min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from vgqf 89e3t c(fits trainer in a straight line, moving 116 m away in 14.0 s. 9tqvge3 c (ff8It 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 gho2/,iuf) :wz 2en uxeach other on parallel tracks. 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 /w) o ,gn2x :hzieuuf2reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m b;2t6wddzybux2) 1gl m,pqw z5ehind a truck traveling How long will it take the car to reach the t5 g 1dpq;zlmuy)62,bzww2 xdtruck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounteg)gz i1 )xu45n lamn u) xh6ovv2f*sx4rs a tailwind that boosts its speed to 990 km/h for the nex1))glg n62i5fmxov4xnsvx*ha4)u u z t 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-k;z7y9hprt ap(w9 y 3ttrip in which the outgoing 250 km is coahytpy7w z r(p3t9k9;vered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pi82cjpx.j0m is ns at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed pmsj2.8x j0ciof sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. z f+oy (xww/q7What is its average acceler7y+/xzwwoqf( ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.24 8 mo5oe kev/btf;gqkcyrlq 69+ rl30 m/s in 1.35 s. What is her acceleration ev;2o rl9eg4ck63m5qkqt 8br +ol/fy
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile8 e :rje:9h3u scc 7qa4tihoi) is capable of an acceleration of about e :sa4:ei87tjcic)roh9u3qh$1.6 m/s^2$ 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 irwfw1ey6ozz rf+ ux2)5,/k fi /:mwzkn 5.0 s. If it then brakes and comes to a wr)u 1ezzr f/62fykxiofw/k ,z5m:w + stop 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 t1j 5jo:y,d yqr = 0 and moves in a straight line, is given as a function of time in the following Table. Estimat jd:1roy, 5qjye (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its r 07+lps;slpe4f7vhxk)w24e aoq2wgacceleration? How far did it travel in this time? Assume 7wg2 lp4e4r0h)7sekoq l f2apswv+ ;xconstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was za/51u5roiuv wjft 8*its acceleration, assumed constaf z/v5*1u wiou58ta jrnt?    $m/s^2$

  A light plane must rhafaf jzl u88r8t4z:pf :w6h/xwfr :a3gdh .(each a speed of 33 m/s for takeoff. How long a runway is needed6t 4afrg p /:3lh8wuh8.(:f afr:zw zfha8xdj if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spp/oj:li7 wb (yeed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speey:j p(7il wo/bd? $\approx$ =    $m/s^2$ (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 fak iq7 s9id/mds26bx/ pr did it tr72pisd/ sm69/dixbq k avel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m hqqp,ghm2(xs2xc1p*long on the highway. Assuming a decc* m1 hqg2(,pxphsxq2eleration 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 c- 85*bd-jmjzh uc qna)5xxy ;nompresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the drunx)*nb j- h5dxzmca q5j y;-8iver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with 7wf;k maudu (o*u ux:3an initial speed of 95 km/h and human reacu xouuwak;3(f *mdu:7 tion 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(zdyp2xllobavv2 y 8u06ne8 1 the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck golvb:iytt +n s)t0 2l)bme /5aeing 25 m/s on the highway. The car’s driver looks for an opportunit)v )n 0s y25b/:l ia+tmetebtly to 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 than 30.0 min. After exactlya1+-,pii 8e gxvn2nl 4iinn-e 27.0 min, there are still 1100 m to go. The runner must then accele- ivl+ 4i1 egix-8nnnae,2i pnrate 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 approacfmc29*j2h v zur.xn8n bke6 n/hes 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 intersection is 15 m wide. Her car’s .ex bm82vn2 zufjc n*r6k /9hnmaximum 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 md*f+ 6 vlt*axf*s) b+xmyag+below after 3.25 s. How high is the cliff? m*tma*ylfx bxgs d+a*6v++f )   m

  If a car rolls gentlgf((sd;:q zajcq b 9u2y ($v_0\,=\,0$) 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 straighl-1ro*r7ykbhexc 8 f ;t up into the 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 afte4zpiqeq+ kwvzbs04:1o f 1 o -hya9vw7+1sjmf r throwing it vertically upward. With what speed did he throw it, and what height didmb7ps9z o wa 141qq+zyovf0v-+es 1:fwhijk4 it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw graphswaz /g5m o1f-x3 zva0a of (a) its speed and (b) the distance it has fallen, as a function of time from t a1xvazm f-5/ 0oaz3wg= 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with g s yf;vlz))vpu:z1 8ra 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 speed equals the helicopter’s.] t =__ l)y g);pzrf:81su vzv s

For an object falling freely from rest, show that the distance traveledgc cy j)kgy4t bm- tb0,t+.7xg during each successive second increases in the gt gc4y0mty.+jg ,bktx 7c-b )ratio 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 neglectedogic5yg k(0qa8lds)) , show (algebraically) that a ball thrown vertically upward with a speed lik ag)yc5q(0 g)o ds8$v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upw.xw +2aldq8z)0e0 oe6.ah,vldj cprrard with 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 photoflash of the apple in Fig. 2–18 (or numb,p7lrptm1z 92l 3lhc ber of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but np2zc,t3m1 7l lrhl9bpot the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a l((mb sbwa0um4wvy7s/ f h/4 jwindow 2.2 m tall (Fig. 2–32). From what f w //ms(b4w 0ubj(4vy7alm shheight above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oc90,2rhcms6vpv c8l zl3yslese / 8 i3sean is heard 3.2 s later. If the speed of sound s llhy3/3ezs 6 ,c9 pri c2ss8vvel08mis 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of watvcrj*ow3 2+ m xd5us)eer. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is thex c*3rusw)mo5e 2jd+ v water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with aexk:7 yv1 ,imd kfhb65 speed of 12.0 m/s from the edge of a cliff 70.0 m6bxiy k,:h15fv7 kdm e 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 28fl460ubve h f9 m above the street with a vertical speed of 13 meh4f u6 f0l9vb/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 of a train as a function of time. (a) At whai-*.bqqwu1;ofqj dr /t time was its velocitr qb;* /-fq o.1ujqwdiy greatest? (b) During what 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 func;ikqm;:rnzu + ;ub;oztion of time is plotted in Fig. 2–28. ozb n+zri;umq;k:;; u What is its 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 approximately as(q- zk dnx3y((1p2octs3serehw l7 ;r shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the e s7r y(3xn2d -pht1 3cose(rwkl;zq(curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in5mfen zbtr6y8/s 6bp/ the previous Problem (Fig. 2–35) when it is in/5b/fn y8e ptbzmrs66
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled durbc 9m5uudp2b y-48mft z8w65zizwyj1ing
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacex/- 5tw-ubzqn )/ufhhment as a function of time is given bht -5x/zqh)n -ubu/fw y Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object along451j x +wuz(zqk n))qjddx f3j 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 th j)3z+)dq zq4kfdj1jxxnw 5u( e 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 wi;pw 6z;alkp/;7e7:pizwz-v rx ralv5ndow 15.0 m above a firefighter’s safety net. Tp;p7r5ivzaw;rk/lp lw zez-7 :;a6v xhe survivor stretches the 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 Moon is about+avmcm*h p uj ,: a:i(ebrc6z/e 5mt5i one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higherap( *z6/ta br,emcji:i:5mh+ 5 cveu m will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-w,x )y nbju0fc:s:qa:shoulder seat belt has a good chance of surviving a car collisio saq):y0wjcx :b:fu,nn 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 his pursuers b77ouu)dbc :s 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 roaddub7ob suc):7, 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 tecac1qmiz3(mfn 6mij) :ojcm0 ih72z2dn; v h .sted its cars for front-end collisions by hauling them up on a crane and dropping them from v3:dc)c(hzo 7 jhqian1mn f;cm jz0ii.2 2 m6ma 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 trl6 yc/q3rzn :ravels 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 acceleraty m,1l0 ;7ns-xnyn :,mhmejm aion 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 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.) jn -nhm,ema70:,yynm xmsl; 1   m/s

  A person jumps off a diving board 4.0 m above the waen*+zi.ta 1j vter’s surface into a deep pool. The person’s downward motion stops 2+ 1in* .aztejv.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the average jsra :(f wr8l4bln g6i(p: a;espeed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. T:saj:(4fe( lni6a;r g 8blwpro 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 dod,n cisd-.2zff m;l 0swn when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path zc 2md- l0f;dss.fin,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 witht 89e69aoarbp 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 (that is, putting downhill, see Fig. 2–39)86 aet99p boar 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 a constahp xd3a51xajp , 5vcf,b,:qdfnt speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accepj5d :3,vha,f1 cd5 xa fqx,pblerates 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 buil wl,70zru ,/b5oktcbdbme3 a, ding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached azr/,oea, bm7 bd5u0bw,ctlk 3 speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a xvi1-;qkb w5 ztime trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last la1;5 zbiv-kxw qp?    km/h

  A bicyclist in the Touga e(7u k-nh 9kxvql(6r de France 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 was his ak(uq k e9val(g7h- 6nxverage acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child caabbi(+iejw/ :2u l6 jh1-d qlmn bounce up one-and-a-half times higher than the second child. The initial spe6mhj1 :q/j+d b -2( baleliwuied 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 travel,ou5s ir r7v3*jcdg 1wing 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 pass5*or dgwuri3s,c7j v1 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 In thr-wk kp7ev+so2 owing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2 eo7s+pkk-w 2v–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an vt01)4hczmhobnv:( zq0; pi pacceleration 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 +x (tj v.h2:evurbz4rsignal, and+v. rvj:4z(2 erbt uxh the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights 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 speeszfwvk*l*)pj5-y qm8bim3 s2der 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 acceleration.*3ysv52j *zwipb-q sm klf)8m
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a secondmwb lo)wih2h p*++z1d stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same tzophwi1 +b2l*) mwh+ dime.
(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.76qf 9:qckip5xh s/epuq7 x9n The first stone is thrown with an initial velocity of 1i9p :7/ pfqkx7h 6u9xsceqn5q1.0 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 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 free-falling p. dx *hz n6bni o:;;pvqi24wd7b tq 0gk9kajw2arachutist to fall from a plane at 3200 m to an altitu:7jgtx2i0nki hkqzdwwn pa;9;obb v4d* 26 . qde 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 thrqbhgo gl xa /k 70 syw9nw13.iw;b9+hsough a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must thenh0b xy7so iaswgqk3 .g9;wh l w/b19+ 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 tkn,omsmv, b 4)han Joe can. How many tkm bm4,nvso,)imes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on t0co ah,rlzq2 )y5uv dd0n9xv5 srg*)phe ground below you. You drop a ball from rest and see tdscq0vao0,v)z2 p r 5g*ly95n)x dr huhat 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 the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of/6 uzsh dkx9hlec58 :fpq3wx: a particular building using a barometer. Instead of using the barometer as an altitude-measucqxf/z :hwps3x5el8:kh6 9 udring 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 the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) I7:g bp1.(hzhe4 4h7pnqt kv2hzwv9 eas 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? Which bicycle is passing the other? (d) 1h qhz wvk.h:g4bvn4a hzp2(tp79 e 7eWhich bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?