Does a car speedometer measure speed, velocity, or bot k9 ngk:xu4sdmlrjh00( s3;blh?

Can an object have a varying speed if its velocity is constant? If yes, gq0ub2 h ov1.8iyc rkdm3/d/k pive examples. 3kc ym.kv2idr8 u/ pb0dh1q/o

When an object moves with constant velocity, d+mpca,mbifwzx *t e m)8 u)3;wfb+l /foes its average velocity during any time interval differ from its instantaneous velocity+me8fwi3pt/fl+mmbw c); x),z* af ub at any instant?

In drag racing, is it possibleq1w :qylrv *s*p:n ;lu for the car with the greatest speed crossing the finish l*p wq;*s :1u:r qnyvlline to lose the race? Explain.

If one object has a greater speed tha.jx /g: x xlr477vv15 qadklnin a second object, does the first necessarily have a greater acceleration1x xvq vgj.nr 7x:lkai dl457/? Explain, using examples.

Compare the acceleration of a mot0jpqo9f4z q +corcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the samez0pf j4+cq9qo time.

Can an object have a northward velocity and a southward acceleration? ul24kiy nl2p8 2t /d7fia-ogjExplain.

Can the velocity of an object bl y/ qysef5djk2*8fd1e negative when its acceleration is positive? What aydq18lj/2s*k 5y fdef bout vice versa?

Give an example where both the velocity and acceleration are n 2 wb1ylj5gp.negative.

Two cars emerge side be,)mm fzzmi :7y side from a tunnel. 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 passing the other as:,f z)zimemm7 they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speu j o(5c.hl)jrx 45ctoed as its acceleration decreases? If so, give an example. If5 oljc )(45rou.tj xhc not, explain.

A baseball player hits a foul bal;e 7uqc- (ilfkff mf(nhq *,.wxvn75jl straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ballk hfcf(l7x-.*7qnnifq;(mje , u f5w v be traveling when the catcher catches it?

As a freely falling object speeds up, what is happeni uj(. pl f9hm6hw )w8/+fhluigng to its acceleration due to gravity — hu wf m(wj6)h.8gf lhi+lpu/9 does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vlgpq4k / ,mj:pertically upward? How would you est :,k q4jpp/gmlimate the maximum speed you could give it?

You travel from point A to point B in a car mgb)*q7c drb2n enr-3goving at a constant speed of Then you travel the same distance from point B to another point C, moving a)qd cg3nr 27r*-ebbngt 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-longr5n5l k s a;t3jasar.)an+qe- 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. 55s 3aaakql-n;a.ejt)r+ rs nThe 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 consta3o l6 e xe)2j0pgps/urt l3+ynnt acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish restings6 n+x )l 0pey g3p2tu3jleor/ on a table?

An object that is thrown vertizvhcq1:nr,6w/c u.cccally 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 the motion :zu,/6cqw cv 1nchc.r.]

Can an object have zero velocity and nonzero acceleration at the same tiui*sb5fen p2d( 5):sz rr7vhtme? Give u:*7s5i5rnfdr phz bs)2evt( examples.

Can an object have zero acceleration and nonzero velocity at the same time? Gi,tvpj *gq 9ylz6rbz8 *(p5k(bd 6vhy dve et(*j9ddvyz(vp6,z6b p *8hqbl k 5rg yxamples.

Describe in words the motion plotted in Fig. 2–28 iwa3 70v 5tc :lfvtctw0k.zp) xn terms of v, a, etc. [Hint: First trc.a370zt5f :wlt0kpvxv ) c twy to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the obl*8h 7g (v)kzmo xet9s(0*vkvmrr 1wvject graphed in Fig. 2–29.

  What must be your car’s averj7g 5twmj52r oage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long doef8mdw r3,gywndhl 2soo1bb 6 (kk.1m7s it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 s, fks/5kmk9 k( b dxx/* h9sv(;kycihf(how farx/(kb9k;k9 f 5yfhids c(h(xkv/ ms*k do you travel during this inattentive period?    m

  Convert 35 mi/h to iqpbb-( -pxs,
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from5v4p c4no; hv*chro.bqjx,2 c $x_1$ = 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 f z-:b7rhdzj8j or 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 mz78 -d: rzjbhjinutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, 1a,rllptv nvh0l(/a x, +w5yw every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at allhl vw,,(py0 tv5l1ar/wnx al+, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a qh6 xddgq. jre o:p(39nuarter-mile track in a total time of 12.5 min. Calcuj .qdo:rh g9n6e( p3dxlate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, plhnp6t b ii97q(h5cce466ktjj o3*lmoving 116 m away in 14.0 s. It then turns abruptly and gallops halfway ba6b47p ejitnjt(ih cl6p*l coq3h659 kck in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other oqgmv25k0x vwnk+ c 4,tn parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, +vk c45tgxm2, w vqkn0how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck tra0kl*s b fme3.qveling How long will it take the car to reaems f30.ql *bkch the truck?    s

  An airplane travels 3100 km at a speed 61.f9mtmald,bxik n6 of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h fo6 ,mdkabx tn.lmi61f 9r 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 speed and averag d4igm(pm f bm/gj c*ptc4(,a8e velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered atg(/dpmm,8mf*4ictaj (gb4cp 55 km/h.    km/h

  A bowling ball traveling zwqrxonbtcf:4:8riuvl;7*m w -*ul3wof3 ) v 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. What is the speed of the ball? The speed of sound is 340 z w3ru*vw4 txc*fonvlwf r ):l;i qb mu3-8:7om/s.    m/s

  A sports car accelerates ko* k)n*qeak1 from rest to 95 km/h in 6.2 s. What is its average accelerati *nkk a1eqo*)kon in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelerassuon+fc 94se+6 zm 0 ka0sa+s45 wbmftion f0s+ baf+0esokm6a4 usc 9msn z 5+s4w
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleratiorajke-dme-1sn/8n: *a p(zgtq s u6.wn of abou- 6s(1sj/w mpadgnkau nq8 r*tze:.e -t $1.6 m/s^2$ 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 4e2dr jdp o(i2wjx/2f*ph u0 fspeed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleration inihrpu*/dw4 jo p2x f 2(e0d2jf $m/s^2$ ? 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 froox s5 fse.mrtf3:+ldpovgp c6ny5 284m rest at t = 0 and moves in a straight line, is given as a functio85n v rp3lf5oe2gms.4 oytd 6pfx+ :scn of time in the following Table. Estimate (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 k(icpa h;/nug t 19hr1its acceleration? How far did it tri9u;h/pgn hrt ac(k11 avel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 8dl4ykhs.p-0c2z q8cc(gctsv. 4 s q f75 m. What was its acceleration, assumed constant?c ssdhcc p gztq.vc74-2k(48q.l ys f0    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway iewdbj)u -h rr+/ a0(k +rnzr6r0f ehj/s needed if the (constant) ru( e+anf 0rhh0/drr)j we/rj- 6kzb+acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to o/gd(d;ne1: 0)vtnr(y gaskrhnz6 ) c essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acc ; 0go)sa6z reny n ((dd)c:gnrhk/1vteleration 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 12dk/: cibc/ xy76++ r*vkpsryg.0 m/s to rest in 6.00 s. How far did ityvkb:k+ c/+*ic/r x gdypsr67 travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highwa2vfpc/a2 fno 5y. Assuming a decelerat5van2pof2 c/fion 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 f/k 7wst;tog/vr2 chf:ront end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the/grcht /of7v; w:skt2 driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping dw+ s3dlgez+w 0istances for a car with an initial speed of 95 km/h and human reaction time of dw30ewg z+ +sl1.0 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 thk)9nry(o 4veb e 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 k91 f6kg- tip5 mve1zdgoing 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that hkz6edvfp9-i1 1 t 5gkmis 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. .pfan;/cwg5nl8ce; a;uo ( :bs c-c 7plxwih9After exactly 27.0 min, there are still 1100 m to go. The runnocscng x (p9l;f: u;/.7awl- e5 bacp ;ciwnh8er must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches ak,et r.9he7p vn 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 f .rthv ep7e,k9rom 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 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 fromqb95wrq218p * iz mjdc the top of a cliff. It hits the ground below after 3.25 s. How high is the cliff?1crdqw m jq2b85 i*p9z    m

  If a car rolls gently (zqn8h(9x cbsf- ab ,e5pok*f :$v_0\,=\,0$) 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 near5 ewu -e0;ayhw: dpz+ipv7 :wfly straight 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 after throwic*h q+ 0e(supn9u )hhzng it vertically upward. With what speed didsh)hhc+ n 0( uepu9*zq he throw it, and 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 graphs+5r4fr sxmv/d -0 g1rx7yzauk of (a) its s r+ yu5-4 rgkv1dzfmxs 0r7x/apeed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically )2odhdiv y(d.gm 5-x taup(0owith a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take fo.d(d voi udxg0 hy2()m o5-tpar the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, sh(h+hj.z ssl2;zt tk2 kow that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etts(+z2jshh ;kz tlk2.c.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) vj)kwc- wjwhe 3e/t v , d6 hnmtm1z/86,+xwvathat a ball thrown vertically u-3w1x6vt e6cdz,/ +/m v,hjahkww8nmtvj)ewpward 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 4xwr b 5ee-p 2xk;5qkyspeed 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 th:rj 5. d,3if-dihaldee apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two5fld3,iied. : ah-rj d 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.yew ry2*7j7 x37ldusr2 m tall (Fig. 2–32). From what height above the top of the window didjw7l3ydx7u2* 7e yrrs the stone fall?    m

  A rock is dropped from/m0 ffa 6ba36ch3z6d tuzvp6 u0cx-pc a sea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff?0a6xpca-u /03 p mtvd6uf663h zfcbcz H =    m

  Suppose you adjust your garden hose nozzle for a hard s8b8q 74zz qlvn (jeitq8 wi+8otream 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 to you for another 2.0 s. What is lv8biw4o jzqq+i(7zn8etq88 the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upwardhx) )9ok8tx5q l jl(p 4r(2yzvpyz5 bn with a speed of 12.0 m/s from the edge of a cliff 70n5b)xh42z)z( lyrxjo 9 8pq( tk5y lpv.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m abovelh7,hib t761ymk yhmoc ,er;/ the street with a vertical speed of 13 m/s If the ball was thrown fromm lh7b, 7ciyko/e 1m ty,h6rh; 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 f0 :lidk05h95hzgpodtrain as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the k 50olzighf50ddh: p9velocity 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 along8l(vs/ (j zad(qdz7ks sks:n/ a straight tunnel as a function of time is plotted in Fig. 2–28.k8dvd:s(j/l /s(7 (a zzssk nq 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 a 1 o*o c.p((b3ye guisw33usbas shown in the velocity–tay 3b1. * up(souwbceg 3(3oisime graph of Fig. 2–35. (The short flat spots 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 inkm8,az(lm h /l,* m1poi, vzgu the previous Problem (Fig. 2–35) when it ismg1oz* , v puh/,(mkazmlil8, 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 l (+vbsa2856ex r,vrn jr,poo distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as ux+x(nbp/tun-x+z;8atpk )z l *dm* ha function of time is give8z nnx *mx/ub-zk);+ duh* lta p+xp(tn by Fig. 2–28.

Figure 2–36 is a posyvtywp8r;x/ 2c1zc4a auu , c*ition versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time intu 4pt ;y*x/c 18wuy vr,a2azccerval from C to D.

  A person jumps from a fourth- q)lum(5mtv+ cstory window 15.0 m above a firefighter’s safety neqv m+(u5)lcm tt. The 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 g/fkq p(gt(.kgravity on the Moon is about one-sixth what it is on Earth. If an object is (gf /k.q(gp ktthrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained bytj;re, 2o )ni zwit8q:8in2po an over-the-shoulder seat belt has a good chance of surviving eitz8p,rqoi;w:2n8)ijot2 n a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road be6kl9w6 6hrh7l89yr5fhjgj 2u3 dnd co low, 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 tele9u6 c f6 djo6krgnlh9 2hld87yhw 3rj5phone 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 tewtdu)ixil p) ifv* htg.6.-n6sted its cars for front-end collisions by hauling them up on a crane and dropping them from a ce.hx ugtin*t f6dv)-w).pil i6rtain 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 trav) k4 7btxe2zvqels 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 uniforml,dv 6x;, ko 7oqp;psm acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed ofx;l,dq m kspoop;v7, 6 the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a ;zi egr 0vej76deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estiv;ezi 0g j7e6rmate 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 sysx*a*b x a/ik(w)cl0f5 vnb5ettem, it is necessary to balance the average speed of a train against the distance between stops. The mor fck awa(ie5lx /bx*05vt*n b)e stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diviy pf i;u0:a3bv me,n(yik*4cyng for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pp*:n v3yi a( fm b4ue0ick;yy,elican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which s1 nhf tm9+dzot :ioy7m6h5m2a 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) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantlmofodnh2:6m+y1 hzmi7tts 95y 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 freightuu84 swp /ub*l train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugu4/lu8 w p*bsuitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stok1bcg9 qr*a*waue/4r ne is dropped 1.50 s later. How frqa u1*/ bwr9ae*c kg4ar apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the courbnhfg-vk m/yt-r n,7uexq* ., se of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be makq,feb-r* gx7v,nn-yuh / tm.intained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mou,d )nu lqpn,vp zd4l66ntain pass as he moves at 18 km/h . At the bottom, 4.0 km farthl) 6n6n,, qv4pudpldz er, his 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 twqfe8.gt:; eggf2rqo8o*; suz o trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initiaoe r ;8gtg:gz8s*. effq;o u2ql 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 overtakt/xz 2p2r6u k10srm vies a 1.10-km-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, a2z62r 1/ rvsiupkxmt 0nd 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 basel js1*e (bi4uoball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a dispjie (us1 *olb4lacement 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, from rest, with an accelx8* lqj:lm1a 4 oa3umjh*z.js eration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattp9r ggncie ,yds kra(*. 6kf,3ern shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you arerrec6an,g *sg39,kipy f (kd. 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 any3qn.:giej z- l(f9nbhflc 0. 2or*dt a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 75o efq*n(l:yjf gd r 9hz2. -li0nc3.nb0 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 building; 2.00 s after 9a)r;+ofe zvi that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the twofi v 9;rzae+)o 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 same time. Thefp )l: lke+)pg first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second f)eppk l+:lg)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 fre:ink9 (z du,pie-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she wi:9z ikud(, pnill 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 thro.p whed iy7xp:gzd; +-ugh a grilling machine. If the grilling machine is 1.1 m lx:7.pg -;p dwheydz+i ong and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times *4 vf7 su;wh8: -18jnbuxh)jyikijkmfaster than Joe can. How many times higher will Bill’s ball go thann1 k hj8-himx j;jf*v 7u8w k:b4uy)si Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top ofv5 rr9n 3 axrpgco-n61 a cliff while your friend stands on the ground below you. You drop a ball from rest and see thaacrro6n-vp3 9nrx5g1t 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 a particular building using a rqq39k .-7lp l ,jejscbarometer. Instead of ,-pq erq7sj3cll jk 9.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 vsxpc2+39ihp/4q cai4 vq saum 1. 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 ac3+qc4mpa4h91 cu i pqvs2 ix/aceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?