Does a car speedometer measure sptz4agkz-h8; yb*qy-wx+ jo r 7eed, velocity, or both?

Can an object have a varying speed ifg1wqzh8 . hpbmm(m j,4y mt*,h its velocity is constant? If yes, give examples.,4,wjt.zp 1mgh hmy( bq 8*mmh

When an object moves with cwgl.)zjkl gt.,-i ,yronstant velocity, does its average velocity during any time interval difyk jw,), g-.itlgr.zl fer from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with) d h,kczz/-2kzmt o*e the greatest speed crossing the finish line to lose th, ze td* oz/-z)ck2kmhe race? Explain.

If one object has a greater speed than a seconl +cw,whosz7. ct6g( cd object, does the first necessarily have a greater acceleration? .zhcow t,c (6 sgcl7w+Explain, using examples.

Compare the acceleration of a motorcycle that accelerates gn7,p8 umpzg5t )cq6afrom 80km/h to 90km/h with the acceleration of gc tzu658 7q,a)gpmnp a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a north k.kvpzbg2 0 ixcdovg7w*/19 lward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceloets(eqd fr1 uc90b0 (jx, ax*eration is positive? What about vic xu0(o9se0xt,c b1f(d earj*qe versa?

Give an example where both the ved0 i9ef/pv1tz locity and acceleration are negative.

Two cars emerge side by side from a tunnel. Caqsn v zt(re33,wb4, bar A is traveling with a speed of 60km/h ae4qr3 b w,zv 3na,t(sbnd 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 out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreaseap*3)zmo l.ob i h:c-byv6 l+)bcc(cas? If so, give a bp c:6b3-o) l)+ciaa*l .yozbc(h mvcn example. If not, explain.

A baseball player hits a foul ball straigc;wys7flx46 a ca ;jb;ht up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the balb ; lxajs76;cc4wy;f al be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to it*:assjgaj,r8 9f7 vex+ke6 )*uutrnks acceleration due to gra6ax kj*8t,+7)a rgs*s er k 9:eufnujvvity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball ,ko uc9wb,x9kvertically upward? How would you estimate the maximum speed you could g9ow,x,kk buc9ive it?

You travel from point A to point B in a ca46 w sti8ufvmx f(qoz0,7u t8ip75tghr moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 96xtit88(uf07 z fp, 4h7vms5gw oq iut0km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstrabl2c hda 31d+ 7vw5gbdtion, a 3.0-m-long vertical string with ten bolts tied to it at eqba 5d1 vgc237 dlwd+hbual intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accelerationanq4- u g bi4uudh;z-.: a rock falling from a cliff, an elevator moving from the second floor to the fifth uz -un;ha i4-d4.qg bufloor making stops along the way, a dish resting on a table?

An object that is thrown vertically upusmd /)j +n bihwqn64i020bqbward will return to its original position with the same speed as it had initially if air resistance is neglig2+q )di n inbhwum0b04b6sj/ qible. 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.]

Can an object have zero velocity and nonzero acceleration at the same tsf3+gmm3ys :y-,im9n;g enk lime? Give examples.,: 3kglsm nmgn feys3;9-myi+

Can an object have zero acceleration and nonzero veloci1oucoe6zv(c2;4+gx;n bdu cu ty at the same time? Give exampluc;ce v o og6czub( ;und4+12xes.

Describe in words the motion plotted in Fi69h + 9imq/qgnf ft eq./q6whyg. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving yy 6g9 9+mtfnqew/q6 qhf. ihq/our hand.]

Describe in words the motion of the object graphed in Fig. 2–27*1 fx(xxhkoe ;kva 7m9.

  What must be your car’s average speed in order to , 9berxset8oq42; c1di emp vd)s47cptravel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h Hfaf: a7cfs.u( rug1g0vtt(*oow long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2 - sfb(oo2z+ 3ttgt.wz.0 s, how far do you travel durin otzz -s+(wt3gtof.2bg this inattentive period?    m

  Convert 35 mi/h to ; 4mn8,hye poj
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromz +3y4in pi5)gs/icxm $x_1$ = 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. It then be 25 eo ;jvs( rbnindz/v2wk5.rgins to rain and you slow to 65 km/h You arrive5.( iz2wno vjnrd sb/v2k;er 5 home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds betwe(txeutt om-n-- e/to )pk2 )xjen a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s f-m )tuxpjx)/2toet- -n ok(etrom this rule.    m/s

  A person jogs eight compl,c px8 a5htf y2p6t eqwqh.uago01,8dete laps around a quarter-mile track in a total time of 12.5 min.qpho g e8 y2 du8phqfxt0c a61.t5a,w, Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away in 1uh1kzi(mr6 vtk.k hh.(d0 . vt4.0 s. It then turns abruptly and gallops . k(.tz hhrm ukt dv06ihv.k1(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 each other on pntw*/98tsx tsarallel tracks. Each has a speed of 95 km/h with respect to the ground. /twts*tx 8n9s If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/g(l)y 6ko:zd,a uhks( h is 110 m behind a truck traveling How long will it take the car to reach kl6uy ) za(o,:g(ksdh the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then enmu)uje7a4jw sxzvk( l.5 q 9s,counters a tailwind that boosts its speed to 990 l vs, e4muw7kaqj.x(9us z5)jkm/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average-q j*k/l1 5wonrd ana3 velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h lwkd qr 1-/jn*oa53na 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 h5 dt.l8 dkcya5mr5x +m 9;iaxkits 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 yr cxdat5x .a;k 5mi85lk9m+ dball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its ave*l,at1di2s w:lhny 5q rage acce 12st,ynih:dw a *l5qlleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What / 3p.dq1y+4u lr udxsgis her acceleration s+d.3xd ury/qup l1g4
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablev- 4rehc, pygq5z.3 jq of an acceleration of abouv453 g- erchqj,p z.qyt $1.6 m/s^2$ 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 constantt3bq( bohco b9*lpe70a,t((-wbhz ot speed travels 110 m in 5.0 s. If it then brakes and comes tocbw739,-( t bloztpb0*oh (a eh(oqb t a 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 atd;soys odo: im9(./ cp t = 0 and moves in a straight ;/9mssio(co :doyp d.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 in a Table and on a graph.

  A car accelerates from 1pyemxt 99-qz cw)j :d+42ggah3 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assumepgc9 :9z+qd ea-ytgj4 wx2h )m constant acceleration.    $m/s^2$    m

  A car slows down from 23 mkpf/ay8op p)i642izz /s to rest in a distance of 85 m. What was its acceleratioi8afizp42/p)pz 6 ykon, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for ta7lj g hefyj9j5 bf,z1uduxt8 hk;-( :vkeoff. How long a runway is needed if the (constant) acceleration l5yxj9uugfe-1jht;bz jd8 : h(7,kvfis $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially t23n fj(l;bklyop speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average accelfl;b3n2 kyj( leration 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 o/(wohzr ;q5uxf 12.0 m/s to rest in 6.00 s. How far did it travel in that; xrzqo5 /w(hu time?    m

  In coming to a stop, a car leaves skid marks 9bo 5 z)njdx(r)2 m long on the highway. Assuming a deceln ozb(rj5d) x)eration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresses and ss snupdn1k3f yh)68)ti b6(k the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi osu 6shkbyt n6n) (fpksi 81)3dn? 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 an 2z7u4l. -jtz oil il-minitial speed of 95 km/h and human reaction time of 1.0 s, for an acceleralu-j.l 74- i2tmzol iztion
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a car ise. m9a3 v r;6x0vqbuxl(3jqbx $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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 ih*cfmk ,ujn* /0kqqbwms2 2l2 3rs/r going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can acceleratsl qr2kus/, m/ 0w 2b*3i*c hmqfrnkj2e 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. j , )in ngdmrqv k-09n+5kstn6After exactly 27.0 min, there are still 1100 m to go. The runner must then 69ns+-5gnqnk0)im, dknjvrtaccelerate 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 approaches7gx/*- *9* 2 aknyujixturiv :i,vwld 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 crov*ij*/u:vd i x9 rylxnka27, *wui tg-ss 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 from the top of a8ud8 9 r)xze/q-+xoxzidrl(p cliff. It hits the ground below after 3.25 s.r +o-ddp/uzx8l)x 9e i8rz(xq How high is the cliff?    m

  If a car rolls gentlc( s1r+ y/ ai-g3iftcbcsx76jy ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of +8/is;frrb r93emsg y*i+t zf22 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 sh,5vu 2q g+octhrowing it vertically upward. With what speed did he throw it, and what height did it reac2 5v u+,oshgqch?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence wj qp,lnfx r*,p3y( 8fof gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 xfqp*nfr(l ,,3p jw y8to t = 5.00 s . Ignore air resistance.

A helicopter is ascending)h4ai: -6o0skgfoh t c vertically with a speed of 5.20 m/s. At a height of 125 m above the -oai g 4fh6 otcs)kh:0Earth, 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 =__ s

For an object falling freely from rest, show that the distance tra2 fegxdo+gko, sf,3xqi w*m/p/t; fi 3veled during each successive second increases in the ratio of successive oddqt ;i i,f*p 2xxmf,d3o3/f sgeo+/g wk integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglectedyk5lw/vd g 6y*, show (algebraically) that a ball thrown vertically upward with a speek* vlgw6ydy 5/d $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with (re1z3vph ykuwce+q j x*b5l3:h6;w m 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 nuopzuk,hd,5roue:1k yt6 nv8in6m. -smber of photoflashes per second). Assume the apple pmz :6ek,ryn8.- noto,us hdk5i1 u6 vis 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 (bs*vm4 l.dj4lw4esm *4a sj vto travel past a window 2.2 m tall (Fig. 2–32). From what height above the topwjvlsv*4e( 444 .s bdmslja*m of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikinlo2wnpdf a u9 /ccw4q9dn 5e5,g the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , 2c4f qd5epnw95ua/,lo d 9cnw how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream r z6bokbvrp6et ql 5*t.:6gn .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 the water spztrpqg*.ner o :b. kv 66b5lt6eed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the e6*1emvsc6wt d ljwl5-dge of a c w6 t6lsmc*vd- w1e5jlliff 70.0 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 above the street withm,w*ouwcigz5z 3cw v(w.t 4 )k a vertical speed of 13 m/s 34i.zmkwwg ,t(wv zc)cou5w * 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 wh-sb (ue pmt5ym70 ja;uat time was its velocity greatest? (b) During what periods, if any, was the velocip ju(7m0eu5ys;m-abtty 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,ug zwoi-u2/d along a straight tunnel as a function of time is plotted ind,uu -igo2w/ z 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 automvlnsi6 s1v 3h2obile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve re vss v23h1ln6ipresent 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 previous Problem (Fig. 2–d:tfi5zt :1y-5 6f qjczhon.f35) when it is in y1:-j5f fzndzotfh.:5 i q6tc
(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 theew/wi08ihz1 hpt6pz 2 distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object wh bu zpd8+1bga;9sn-y*myv uv-evu w 0v x)y75jose displacement as a function of time is wv j;b1udx-)+8s y *gyu50yn7 ve-bp a muz9vvgiven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an objecl; h dodm3aco(ljqor-4bq .sjy3 2 3x-t 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 ofa 4.yh3-;d odcr-l( o x3o sqjjbl23mq 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 window 15.0 m above a(c4i gw;,d6lpf)b4jkue )rwl firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.pw,( 4fgwkllbc 46 uei)r;dj)
(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 Mow1.hiel av7r /on is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go thanwerv/h7.la 1i it would on Earth, assuming the same initial velocity?

  A person who is properly consts63webe+vw kl-b+i3 7 rax4rbrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleratir - e6ww43rs7+k ebbl+axi b3von 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 9uwjl5 4pk2zy on a bridge, 12 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. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the trucz29p kwjy54l uk 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 m v 5 smk9 vkda6e2:amskhrqk7(hd2 46its cars for front-end collisions by hauling them up on a crane and dropping them from a a m6hvh :4e6sksakm(k9 227 rvdqdmk5certain 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 travels-(x1y.1sf 2op ebfek9n e,c oi 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 p. 2zkgg49r 9loqsv 2prest. 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 g4p9r9kp. zl ogsq2v2will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4k7mkl6k;mmkl6 d 9 vy4.0 m above the water’s surface into a deep pool. The person’s downward mmv lkl6kmd 6m;47ykk9 otion stops 2.0 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 rv ,9brk zm tn,3cs tg49yce+s2apid transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slowctgsysr 2,39ve+4m 9,tb k zcner 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 c/ 9 vgn70bdwjq1ma4iwhen 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 takes a fish 0.20 s to perform evasive action, at what minimum height0 ivw47/ca9jg1mb n dq 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 g7yw)z l 4l6khtolfer 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 Fi hyz6kwl4l) 7tg. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to h )a0* (x-ldysm;fjdj sop on a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts fr d*d0js-) lmy aj;x(fsom 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 hig;.d;0gui5bx ;a vzwzsclc 8,h h building. A second stone is dropped 1.50 s later. Ho a8 bhxw5;z ;.l dgc,ivc;uzs0w far 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 course of a time trtfxhgs/ k5.k(ial lasting ten laps. If the first x fh.tgskk5(/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 moves atlwl krgk.-gv.y ;/ll xt3 +3dy 18 km/h . At the bottom, 4.0 km farther, his speed is 75 kgdlt;/ll g+r.wk.y v x 3yk-3lm/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. vxr pgdn wd1xms 703 /+dl-sj8The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chl7 dx-sxdwrvj1d/ n 3m08gsp+ild 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 travelinpqf/dg),d a)u kzl;:pg 95 km/h overtakes 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 . holdz:/pg )a pfu;,)kd qw 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 opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the bas .mznn*,v xms8eball,.n8mz*, vxnms 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. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, wiv/nww;1ebccky5 8 a4 4 c+ 4xub+qpefhbh*5ejth an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2– uh 1rcey6as/142. Each intersection has a traffic signal, and the speed cur1syeh61/a 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 speeder bth+.6w sgzv 24 l0d :01k a4beodxu*letayh5traveling 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. 5d+4dau6*bby :0ze l . a1wtosxk2gev lt0h4h
(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 afyz+a+6;w f 1h auo8ckcter that, a second stone is thrown straight down with a yaf6owu1c8a++h;zc kn initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up ga:,o veej;su i h,d8b2f; f*qat the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone gqe8;h ,jvu;*ai2 dfo, sf:bebe 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 flnek s sv3u,0ed:l5gc02( ph resistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 lk20vs eldhn 5u3c(,ps:f eg0 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 burgeyhmcwr8 * rpej:x;/w9nx f5azi6 0 5yprs through a grilling machine. If the grilling machine is 1.1 m long and the burgers requirwphxmpy ze5an8/j: 0*ryir;cx w5f 6 9e 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster thaneqb+zp .( unrkehp ,1q0,rx.h Joe can. How many times higher will Bill’s hzh1r,pe(rq 0e xn., qubk.p+ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top ofa q/i1z;cid 6x*dzi 0c a cliff while your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your ha1di;6 /qzxdii*0cca z nd. 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-f5gi21d jcc g barometer. Instead of using the barometer as an altitud152-jg cidg fce-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 po0ls f+ipwc y5xx0s.*s .xovepr 5gk74sition vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Wx.x5s70 50p.fscw *l oerp+si g k4xyvhich bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?