Does a car speedometer measuredclou5/ ;2lp7q 8e akk speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, gin 3kn5vl fz:42nfa8/h kud i,jve exampn2d4k,ivh z3uajkl n5/ : f8nfles.

When an object moves with*pbbqr0o a0 .r constant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any inso*ar. brqp0 0btant?

In drag racing, is it possible for the car with the greatest speed cmjy; +uy0gk9*tc f*plrossing the finish line to lose the race? Explaiy t0p u*9*gycjfm+lk; n.

If one object has a greater speed than a second object, does tj x3d8m)+9xway q *luvhe first necessarily have a greavxyxualjq)+*w m98 d 3ter acceleration? Explain, using examples.

Compare the acceleration of a motorcycj pqwptavf,ys 612x ;3le that accelerates from 80km/h to 90km/h with the acceleratiftw2p36xjayq, ;vp 1son of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleratuwlt1gk 5*wx3 ) nc6wnion? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wi;ryqwcm )4:-p8ja-j kx) kgchat about vice m kji)8-);-q p4jygkc cwxra :versa?

Give an example where both the velocity and acceleration are negativ2pgyv m,+- (7vczyztv f7 go3ie.

Two cars emerge side by side from a tunnel. Car A is travelint2kpub v leo9zaiwwuaup **6)6/ v/v4 g 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 passing the other as they come*/u4u pb zapveuo6/kvwtlw6a2v*9 )i out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelewj1daocs 8w4s7 f 8m5gration decreases? If so, give an eo ad7g 58w1s4c jw8mfsxample. If not, explain.

A baseball player hits a foul ball straight up into the air. It leav vemcja8m( 7skfbwbie7v7 w(6m1szif)9 -z h.es the bat with a speed of 120km/h . In the absence of air resistance, how fast w6ze)smwbve1ms (i(wi9mz7cb . 7 78fv-khjfaill the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to itskz6 a xeb blg1lqw7l2,wj:,q- acceleration due to gravity — dlz b 17j, lgk-a6x,lq 2qwewb:oes it increase, decrease, or stay the same?

How would you estimate the maximum height you could thy k ht6nqwuk7+6qky 2 :b6/xybrow a ball vertically upward? How would you estimate the maximum speed q7ktuy 6qk/ n:b+6x6yhy2wbk you could give it?

You travel from point A to point B in a car moving at 6 aa/kt4dsv3wa constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed foakwa/sd64vt 3r the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-lon5wa 5 *bh*e*6 0ajqzpyl nuhm9g 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 *a0hp5m9*a jbwnl h6 eqz5y*udecrease 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 falli+lt+l)1vg c-.j ri bs2 3evncjng from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?js cl3vgn) .bic +j+-vl21 tre

An object that is thrown vertically upward will return to its original y b.)gs(ifbx9position 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 oppobgf(9b .siyx )site to the motion.]

Can an object have zero velocity and nonzero acceleration at thb-5(be2)8pedbg e q; em9zpgle same time? Give exp d q-)z gb9mbe8e5 2l;beepg(amples.

Can an object have zero acc.q*. e +e gjrgp7mq4jivtj,b-q /(ol zeleration and nonzero velocity at the same time? Give ex7gpr.qme,/ gi vte*(oq4q. jjj-z+ lb amples.

Describe in words the motion plotted7n kcrvn/ j;p0:05 qfugyfqo8 in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving your handy 8/ nrn5j:7c q0pug;qkff0vo.]

Describe in words the motion of the object grsl 7410p)(toe c eldppaphed in Fig. 2–29.

  What must be your car’s average speed in o* btu4k k28hl5ly 0cxorder to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How jywi ,qk(vb0nek .d*;long does it take to fly 15 km?    h

  If you are driving along a straigosk (- wgiyr5;ht road and you look to the side for 2.0 s, how far do you travel during this inatri;5(-skow ygtentive period?    m

  Convert 35 mi/h to +.upup;x;iqzg tg 8c39 ;h pjh 9ep(ia
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves bamkf./ks2 ytk 2+ v+x19gmw xfrom $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 km/h for 130 km.)ui9h bff,nu4qdnhuct6*p td9 dea)-v 6:ye * It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours6)dve:dcy fp,bh u*u- eq)9tnh46i *nda9utf 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, ecm 8-utwh:) fsvery five seconds between a lightning flash and the following thunder gives the distancemc-tuh s8)w:f 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 compleb3** wigoq3vmte laps around a quarter-mile track in a total time of 12.5ob** q3wig 3vm min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its train l grkq+s-+h+,qwi .keer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calsh.,klkre+qw+ i+q-g culate
(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 a speedx nrpp 9uyg4,he69 9ab of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before the9pph a x gnu4be9yr,96y reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long will olkby5hu *0ivy--.mp it take the ca--u0ohvy i5 mp.bkly *r to reach the truck?    s

  An airplane travels 3100 km at a speeyyv0 9 y3k,:xd3c)f *ejahe wyd of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the n v)x: yk3eh09 , dyfc*ayeyw3jext 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 ar ;+xwnk;:zt+c 5f oqg 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 covered at5;rkxt; :+ofqg+ c nzw 55 km/h.    km/h

  A bowling ball travelingwef f ba/.d1g;jy81:ckn2g4 jzsnn a1 with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. Whjk2 cgjnybfangn8.zs /;e141f:1 da wat is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h pz 2vs;fxsa++sbd:z6in 6.2 s. What is its average acceleratpsf2zz+vsa6d: ;+s xbion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelr* 8l gtkrkf/ -ski/w:wl. a7b9ymx t,eration a/k k.rx* wgi-7f:8kt l,wb tlys9/rm
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particularm rypik)-+.n;d6bsnl vvxa+82 .cdkn automobile is capable of an acceleration of abousi+dvc 8l.k;ray 6bvp- +d.) n mnk2xnt $1.6 m/s^2$ 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 atq9x )6hmanwp98 ue y2t constant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0h )9n2ux pyam86 we9tq s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves in a p p.)z-dsml7 s/ ja-fyb4vbgl-rm8 r:straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each i: 4sv js-r/-llgm)7y.rz 8fpda b -bmpn a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was itkl9,(hn9f *d*gnhmt ns acceleration? How far did it travel in this time? Assume constt9h9 *kghnn*dl ,(mfnant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was b6jb9/l:ld * (bxkpn;vbzcp 0 its acceleration, (pj;0 k:bbcnx/ blb9p6 *v dzlassumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s forckav072 p8epf takeoff. How long a runway is needed if the (cons27 pp0eckf8 vatant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of th.dg kb: nq0 hjpm6ws5x+( n xq9rf:(mre blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, ab+pqj:9d 5nhkmrm.ngr(fqw(:06xs x nd 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. Hom.y+ we3sx7fu w far did it travel m7xfwysu+3 e .in that time?    m

  In coming to a stop, a c n/ d5q)3sqipygp fcp:-,9ght ar leaves skid marks 92 m long on the highway. Assuming a decelppt g)3dqgns:5h iy, fq-/c9peration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikefpamy -u0. 9hds a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the ansua m.f9yd -ph0wer 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 discx6d3gp wd.v7 ln87h,zpfi4y tances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, forl7 dfv,icwpzd748x 6hy .p n3g an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation fubhzrh7 b)g/u/8 dx 2wor 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 going 25 m/s on the highway. The car’s driver looks(8segjwzcz e2 f,is3 - for an oppo, si8ee(wfj2 3 sc-zgzrtunity 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 10,00hx r7ul8;rkmk- p)f;e0-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accel hxrmf)er7;k;8-uplk erate 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 approachj x0, *j:x-o hzu:zbzvg)ux(yc,cy- tes 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 intersectionxbzvx0j),t:c( *g oc,h yzux-yj-u: z 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 6qn1a8 lm0 ugv7ci8dwi2-k ewcliff. It hits the ground below after 3.25 s. How high is -v6l2wk qc8dm7 w1iiaegn u08the cliff?    m

  If a car rolls gentl-sfwar4wq8yy o -k zkw-9jn-)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 i1dhey3 pq6+p6) cwo,x; jd wjjnto 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 after throwing it verti 0 + qw-5jgcuy teh(nmvy8sm/;cally upward. With what speed did he throw it, andqw( jsvcy n5 t0hm/+e-u8mg;y what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw g4 pp ,upi w .o9jeyh-uxbf.wkj:a 7o27eq; rl6raphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 77.koxep ;q 2epayrphj4ij lo6- w. w9bu,fu:s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.cx9 c )rmrd1 t(+yy8yp9x+f e2uz/pon20 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 helicoptercmef+py9pdy )(+92xr8 o/u zcn xy1r t’s.] t =__ s

For an object falling freely from rest, show that theof-d4 iilux76:a8 wxg distance traveled during each successive second increow :a4g f76ix8-xdul iases in the 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 neglected, show (algebro zz4/ 1-gykhnaically) that a ball thrown verticalk z-/nyhz1 4ogly upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward wituzp3fl -x)q .2pahl0gh 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 os1t p*max i8iyb5rkeu* g2cpb9y (/0each photoflash of the apple in Fig. 2–18 (or number of photoflashes5p bg(oemy0yt8p* x i9u/c2a s*k1 irb per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). Fr4w6 -va s.pwv7 y+lqqeyr24vx 5qwy9 kom what height abovq2p w6ew4+a x .lvvwq94v-r5s qyyk7 ye the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound ofunw47u cm d bed 3w/0eci4f56b it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how he07 u4nwb 53f beduwccmi6/d4igh is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a h no-c6 aygmv 4kd0l)h6ard stream of water. 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 to4d yclvk g)6 0mnh-a6o you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward w+jpmyub.ut.2o g3fem /kl-)dith a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34gdmjp 3u +.2fyt-o/eu.ml)k b).
(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 verth2mt9rghhf7ht ;duc: cn 3)-aic3m2h uag;f)-h hh rct7nc:d 9tal speed of 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 of a train as a function of time. (a) At w i 5oe 0:ytlxnit6)z ;;hfs.sthat time was its velocity greatest? (b) During what periods, if any, was the z0t.x on )yli;st h fe:;s65itvelocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plott i2(36tz(lx uup t -qi6;wavoned tpz ;ui6i(u3 vx lta26o nq-w(in Fig. 2–28. 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 shown in a +x3kwhd1 q3rthe velocity–time graph of Fig. 2–35. (The short flat spot31kr3d +xaqh ws in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the pr7wyx k/jp,ckj9ne kvn,ac) /y.5c x y)evious Problem (Fig. 2–35)ckv ))a,jyx,95/ kc.nxwynkj e7c y/p 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 thelu d2x6z+t2 ep object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose dise beoyc* (qt*h )n6i1d9ate1z placement as a function of time is given z1t1t6*9qenoe)ay *hb(i e d cby Fig. 2–28.

Figure 2–36 is a position verrxzfyd06 8f(3w vts4asus time graph for the motion of an object along the x axis. Consider the time interval fromr6sfy 80ftwd zx(v3a4 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 C to D.

  A person jumps from a fourth-stm kfch.zh5 (6f1x(yjv3o jjm*ory window 15.0 m above a firefighter’s safety net. The survivor stretches the net6mcjjf yv1*3f xh 5hzk.j(m(o 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 o +jdi4r ;5-orsk,ekl 2cmw:1 j/hepipn the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higi+j1ck pl5;:pm2wero /ek- ir dshj4,her will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-tar z9.ujr2o2x vzvd01he-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not excaoj v 0dz1v.ru22 xzr9eed 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, 1wby +u18rznd .2 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The1+8uw .b nzyrd 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 its cars for front-end(ndo)m.1sse szq ti-snyn5d2 -t /pw; collisions by hauling them up on a crane and dnmq25)sn-/ydt .os- pwi(1e ;nsdt s zropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth tl v r8 )ff)htv.pv*5ueravels 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 rest. g hlj4/dbi9j3 The front of the train has a speed of 25 m/s when it passes a railway worker whoh b/l4d 39gjij 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.)    m/s

  A person jumps off a di 6g.(va:5pmtfn1iouzving 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 decelp.azg ft5mn:(6uv i1 oeration 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 necessar3xoc frf/;fw4o t ux4.y to balance the average speed of a train against the distance between stops. The mor /o r.u44xcfw x;otff3e 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 fre h-zsc, lrj98;nwfgh;kh( i8h e fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it tak8h;-fkgh h ;wrh8l( j, is9znces 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 strif o ;+/i1jicdgvr*+aikes 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) is more/dcrifig1 *ova+j + ;i 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 constant f8n. owbo55m kx2.n hlk 9xz3dspeed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceleratesn.hzw 5d 8knx2b3xo.mkl59 fo 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 high4p4ejw l6rzx0k *(m1f irby,a building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed ofl fa p(y6 bwek0mi41 *4zjrxr, 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cougx /3 ,:uuodtnxc/x6yrse of a time trial lasting ten 6/ / 3u,xxg:onxtduyc laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he m 7k d65bjijq9roves at 18 km/h . At the bottom, 4.0 km farther, hisij6j 5k 7qbr9d speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampoli 6unpbph)f)bmh o,zqaqm1)4h i;9qe -nes. The first child can bounce up one-and-a-half times higher than the second child. The initial speed u1ha6qfh ),pb eo b-qup ;))9qmnzim4hp 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 traveli il c*14 x.)vhm2r t7dljybh47n irlr6ng in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opp162r7n. rilvlbj yc h44* m7hxrd t)ilosite 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 wity+xolo5 (rm*ch a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of *l +mo5(oyrx cabout 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,ih.o85 iws8 d:tve;c i 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 pa3a2m v:ti5 fmrttern shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limitv rf5 mi:23mat 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 speeder traveling (4gx9ko+* i3 horvyd 6) h fxnbx.fid1at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a cd (fy x.6ih)19kxb* 4i vfgodnxr+3 hoonstant 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 th2/9szppf8 e u:, xusiie 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 same 2 piup: zsif/s xu,89etime.
(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 first stone is teecugx. ho ,tvl;:x6*b3: epc/nj9 av hrown with an initial velocity of en; , tpxug.je b93ox6/ l:cv :hcav*e11.0 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 airdg(7ye m /ti-c v .,)hydpj, pr;thk;n resistance, how long would it take a free-falling parachutist to fall from a plane at 3200r(y pgjdv,- ; p7dthe; tk/h) n.ym,ci 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 speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a gks54 h wzkw2/k91(njl 4oxlq zrilling 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 jksw4 zl on2x4 q1(l5hkk/wz 915 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verticar -e(jb+u2n2tnix9 oqlly at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball g ub- +n(q to2nrei2xj9o than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands nvr*k(0lckz,i oh : q/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 an z kv,kl*/ir0 (qho:cnd 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 a particular building using a bflw 5fwf d7lm4rypuwld aju1 )03;- ejbx*;q0arometer.dj14uplfrfbl -ufey3 wdqm; 05)waw;j0 *l7x 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 the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) m+d),sbze q f57tk q6q9ym2gaIs there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c),abq t2dy9f6m+mqz5 e7sgk ) q 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?