Does a car speedometer measure speed, veloizq w eerj)x0,)4d c(at x5a5ks8n cn7city, or both?

Can an object have a varying speed if its velocity is constant? If ymyccn m)3g7eil:xd, , es, give exampley ixm3):m,cdec7l, gn s.

When an object moves with constant velocity, does its average velocity dz cmc fx3v( i+pdrs4/miboq2q: da;* ds2 -9rauring any time interval differ from its instantaneous velocity at any s;oc9:3d24dx cimqzb dvm/2qr +i rp *-afas(instant?

In drag racing, is it possible for the car with the greatest sb u,g*,r1)+pho )5l mfavphtmpeed crossing the finish 1,fagh)m+p)h b,vout*5 mlprline to lose the race? Explain.

If one object has a greano 9o :xix eg+wx+5u.dter speed than a second object, does the first necessarily have a greater acceleration? Explain, using exampl nu e+5:o xdgx+ixw9o.es.

Compare the acceleration of a motorcycle thahanwm z h7:8b)t accelerates from 80km/h to 90km/h with the accelhnmah :zw87b)eration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acce:cn-ks /hwkm jpg1c.3 * g6ndel kibz1wz /7j/leration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wh5sn 2muwre *3m8 ilg2eq+hf,mat about vice versa?2,mi 3f+w5 hgmmu ln*2reesq8

Give an example where both tt 8oj qhw uc e)9e;g11v( 6f8ovfu7ajbhe velocity and acceleration are negative.

Two cars emerge side by side w 5dcqw )wqt6c4w 3m4hnp43bg from a tunnel. Car A is traveling with a speed of 60km/h anp)qd45th3g6 4ww 3nwc4wcbq md 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 decreases?)3dyhihd 8v6-k;+s dnmsw lu. If so, give )v k; hhlusdny-m3.+ 8siwdd6an example. If not, explain.

A baseball player hits(v bazw 352ijf a foul ball 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 ball be traveling when the catzfij3wa 5b( 2vcher catches it?

As a freely falling object speeds up, wh,g juy5rbu -/te.gz l4at is happening to its acceleration due to gravity — does it increase, decrease, or star5-.y 4g/,ej gtlubu zy the same?

How would you estimate the mzzqvx 57qln + h yt9*o/5u;qfaaximum height you could throw a ball vertically upward? How would you v;/xzlz7q +qha*fnu955ty q o estimate the maximum speed you could give it?

You travel from point A to po:wep p:-gnqqfdz5d e1d.:- vuint B in a car moving at a constant speed of Then you travel the same distance from point B to another point. -:1fq 5-dzg depudwp ne:v:q C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration,a g oue6cm0el:x,8ym8 a 3.0-m-long vertical string with ten bolts tied to it at equal intervals is dropped fol x :am, 886eey0gumcrom 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 acceleration: a rock falling frc7v 8o+ap g69cnia6 f3m +n/ncghu1c6l5 vurfom a cliff, an elevator moving from the second floor to the fiftarv9cf583 +cmn7co/gv6 n+hiulc1g 6 6fna uph floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original positiaf8lb/x8dfwxjd2j / 6 on 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 dire/8jl6fj2b w/8xfd dx action opposite to the motion.]

Can an object have zero velocity and nonzero ik iw* w;rk:k v,u1y7nacceleration at the same time? Give eiwkv:ik7uk w*y;n,1 rxamples.

Can an object have zero acceleration and nonze o-l--lybw0hc ro velocity at the same time? Give examplesoyb- -hl- 0lwc.

Describe in words the 4b x) +k9kqqsmjb pe3-7sxg)lmotion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate th+x q43q- )bjsgpm)l 7kexks9be motion plotted by walking or moving your hand.]

Describe in words the motion r6a cy x5h ns;g2e7: at4mjf.aof the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.2gt9llq1k j 8c349sc df5 h?    km/h

  A bird can fly 25 km/h How long does it fbo44hyf3,a.elw g u23s7s mntake to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 s, a-lmrs/ 3l:s z3c ldv)how far do you travel during this inatten- )sll vsacd3/r zm3:ltive period?    m

  Convert 35 mi/h to 0xke57gg qhw,
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fn -+ csu189+dsq iycsarom $x_1$ = 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 schoph9l70xck- n wol steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home a0p7w xcn9 l-hkfter 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-q )s6l 4erj o1*q8etplof-thumb, every five seconds between a lightning flash and the following thundere*tpr 6l se8oq4qlj1) gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mileme /lqmd(0;) z xzz2rzsi;4z j track in a total time of 12.5 min. Calculatd i0mzzxm(2ej4z;q)rz;l zs/e
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its tr1 yoi/7ypeknf9y4.(7 q:i0fd xpd hydainer in a straight line, moving 116 m away in 14.0 sfip y.d:q0 yyo (dfhyipk/nx7d9e4 71 . It then turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracb pxiofp+zt) *0g6n m/ks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? nfi6o )/pgm p+b*xt z0(See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travelii.+ox .j nw0mtng How long will it take the car to reach the tru.j0 moni wxt+.ck?    s

  An airplane travels 3100 km at a spxmcov i/dn 2b): t(5+ 2ftaveteed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2votfca bitt( :dem/+22 5vx)n800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a cl 6ax+v/ )occje*nwtmg +k y/(omplete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0te(6j+ynk//*cx awgc+) vlm o -hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of *zr /wkhe*)np qs2/ei,a2rgxa 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 he)ir x2e**s 2,zwrpqk //gnaof sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is itsf8qu ( j-fyl6x average acceleratiq yl-(xff6uj8on in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hmn91i aig1 tto0 ms8q7er acceleration 1 io910misq8tt n7a gm
(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 accelerag ad7tptw6:3yoyq -i,ien+q;xht/ 9 ition of aboupd6-y,;wtenq+7h ixy/3:tqi giat9ot $1.6 m/s^2$ 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 atf g 6h-;cn plvor4-ehw1l ;4w1oce 4y eb.drr. constant speed travels 110 m in 5.0 s. If it then brakes ar-;n f41rcbo -r l6ehl4e .p yvdew4ocwg.1 ;hnd comes to 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 at .j 9*izt m3j7c6dwimgrzxj vk q9 1+4r8anno5t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b4*.odzjj z qa6nr7m3 kj vi9w5+9 ci8ntxrgm1) 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 q (noe/ u.()bi tl:vuy6.0 s. What was its acceleration? How far did it travel in this time:t ouqv (ulbi)y.n(/e? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of t gzqs;j5f y) rp fy76k6me6n*:1i hdh85 m. What was its acceleration, asiefg t7sf)k m6: j5z1;hq6hnypry *d6sumed constant?    $m/s^2$

  A light plane must reacfk9l d;5.phqq3ng tw8 q2 mt,ch a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) accele53t;wp 98 qltqdqh.gkm cn2,fration is $3.0 m/s^2$ ?    m

  A world-class sprinter canknbk; j gde8(* burst out of the 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 sprinterkdej 8bk; *n(g, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to re; hhimk*ai/ : e5zhy)h mq,/nost in 6.00 s. How far did i*, o/zhy/ :)k qm;ni hhihmea5t travel in that time?    m

  In coming to a stop, a car leaves skiys6;j py6o :qid marks 92 m long on the highway. Assuming a deceleration of 6os jyqi6 :;yp$7.00 m/s^2$ 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 cvm 6 )sz2 v9xz4.wuhjsar compresses and the driver comes to rest afters6z9xu 4.vjvh2msz w ) traveling 0.80 m. What was the average acceleration of the 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 distcl frk 78g4;y /epcju1ances for a car with an initial speed of 95 km/h and human reactionlej1p8/;u f7g4yc c rk time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for l26 a.8o fujwbthe 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 trur42zy3ec :yiytrug 4u 9tm*vp,so9 9kck going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, crygv ir: p9m 9t2 euk4y4stuoz3*9y, 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 10ftb -od6zx -k8ye1y5g8-mpn i ,000-m run in less than 30.0 min. After exactly 27.0 min, there n8yzox6g pi8mt5by -- d ek1f-are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches. *sn muj (kcyb7 ,a0ief*dd*w 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 jbs 7kcda*d( i.nu y0ewf,m** 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 fdtg9f0ne+ g1uj:lo, zrom the top of a cliff. It hits the ground below after 3.25 s. g +efzg:ul1dnojt 0 ,9How high is the cliff?    m

  If a car rolls gently :ut(,tph+ -8e7(ktysrop hu y($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

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

  A baseball is hit nearly straight up into the air with a speed oylmao9b( 9fidt8q5+ of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ba+wjqkcmyvl)c4 ;r *k- kj x,m+ll 3.0 s after throwing it vertically upward. With what speed did he throw it, and what height didyxc;mvrlk k4jm) kw+ -q j+c*, it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity/l3zlfh2o+b h r1ta l/. Draw graphs of (a) its speed and (b) the distance12z3 +blo la/frth/ hl it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height+e ojfw-c9 j(ow5n nw9 of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach(of -w 9c+n9ojej5 nww the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, shrb9.myje +x *sow that the distance traveled during each successive second increases in the rat*9 s.bjmy+r xeio 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 (algebraicalwb*; 3no;5cv lww3ziaib*v j01x.po mly) that a ball thrown vertically upward witha w1;5b 0mlvjb3*vi;inw.cop z*x o3w 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 zy+etcy u+ o-d*ne2d(upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–18 (or numbe a+ qqfn--4o jxqc(g:vr of photoflashes per second). Assume the apple is aboutq o -fv4a-c:(qgnqxj + 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 0.27u +u /)t en54t, zl5x9alibsbaq+ qia8 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone falatziiub)l5+ lqb,+ n5eqa/ 7ut sx4a9l?    m

  A rock is dropped from a sea cliff, and the sound of it striking iq4 e3qwi3,hd( b3fezthe ocean is heard 3.2 s later. If the speed of sound is 340 m/s , hd,eiz4 fq( i3w3q heb3ow high is the cliff? H =    m

  Suppose you adjust your gaay x(4yuxxeu+2,9y*nky k qi1 rden hose nozzle for a hard 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 groun xn9yi, 1xuyakqke*u4 yx(2y+d next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward wit +bm,dzmx6 y d58/y5etp t+ehzh a speed of 12.0 m/s from the edge of a cliff 70.0 m h + /e hxdz,myy+t5emzp586tbdigh (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 wis3p-y.x (/*u(k 2;unolko)koaj man8k7 p dlxth a vertical speed of 13 m/s d(nlnaj l-xkm2x su;p)8po.k7/ y(ko 3ouk *aIf 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 functionx*: e:j 2txrulrokk73 of time. (a) At what time was its velocity great xk jxr :7o23u:*kletrest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a st mmuz*hye*1qott rm zv d267/mi7*s+eraight tunnel as a function of time is plotted in Fig. z7mqe+r h6* 2zi7ed* tyuv/s1o*mmmt 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 approximatk;o esbhc+.e, ely as shown in the velocity– k bs;.+eo,echtime 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 carlzzd,;i it( /4wqmm lu8.b*su in the previous Problem (Fig. 2–35) whem lwi/lu(. d mbtz*q;iu, 48szn 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 the object traveled during 1ec ttdf. 46xq
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t gs8bf1*qamh820 jp b wtraph for the object whose displacement as a function of time is pq t1h wbma0f* 88bj2sgiven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object alo+6.q y ui9eajing 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) Isi jqi9u.ay+ e6 the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefight qs(i-3i rex1hm2g c9yer’s safety net. The sergi29s- m1 xqih3yc(urvivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixthz /:hq i9nt gaam3:l,ona :h3o what it is on Earth. If an object is thrown vertically upwangaa/lhi9n3 otmq3, h::oa: z rd on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properlybjf)dk8/sl,(jt wa.eei) z0j constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not ex8ka j.bt l/sfj)e)ei,w0d(jzceed 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 ark*.ei 6d9ndw;tan6qjk p5z-bove 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 thekjp5d6ditwe 6n n za*.rkq-;9 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 itmq5us+2s z(d/nx )x5n3j9/r agdv wzbs cars for front-end collisions by hauling them up on a crane and dropping them from a cern2/ xav3nsg(w5j5u+dr dmzbzx q /9s)tain 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 travklio) 5ezg0/ k8fysi*els 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 accelerah:wl24 bz)xo ition 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 to:)b4wzi hxl2he speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving b,gm9mf1ml 2oyoard 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 deceleration of the person whilgo9 fm1lym2m, e under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it qqf*i52uvk c32cbq962l agylis necessary to balance the average speed of a train against the distance between stops. The more stops there are, iuag*cy 6l 25lfcq2b2q qk39 vthe slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fish. Scgs++ cf0mqy0e+:jx (: wdgbx uppose 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 pelican to escape? Assume the fish is at the surface of the wxs0bef (+++mcgg: y cd0:qxwj ater.    m

  In putting, the force with which a golfer strikes arc5joe07ovl ) 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 mil)o5ev o7 0jrcssed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant spgb :i-f(lr1as gfn/xn/mc lhp 2e8f:(eed of 6.0 m/s Just as an empty box car passes him,1e2fn pbg(c(l:a/g m8n- rsxflhf/i: the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from1 3;othy) pebzlcd1g ry2esi x5-/f .i+ghj+l the roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second c5rgsjdtyhphi z2xe1elf l oy13+ g i ;+/)b.-one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over 9 (p)o 7t k5rizt+fwyythe course of a time trial lasting ten laps. If the first nine laps were done aio9+yt5k(7rytfp)w z t 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 ma,n*s)7 q.cajknv; ncf;x p2pountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . a.,fanp7xvpns2k)ncc; q j; * What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first ckx -jq2wb a-i)ry-l (bhild can bounce up one-and-a-half times higher -(jbrxia q-l 2yb )wk-than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveli2u t evtv:.,iwylgx ;/ng 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 . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–,:wu ityxlt; e2.v/v g40. 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 m9 -bgh0. /fcc9)jkzja uwok-z/s In throwing the baseball, the pih/jco9-bkfu )zacjk-gzw. 90tcher 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, with an 491 7-taou1wntsz lmdacceleration 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 shz,z+e/k,c:9dj dcb. buam go.c 3zpn.own in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving uc/ dg,mbcp9..o d ez3:njz kb.z+, cafrom 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 at a constant 120 km/h takgysbxey8w gj9-,jcc45:gq+lanh0 z-a6b ) hmes off in hot pursuj 8gyb sg9gczmn:6y ,-a a-blqjxc4 )0wh5h +eit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that,z2 1fd,,a8l 6 szducmm a second stone is thrown straight down with an initial speed ofmz6dc,a f,2l muzs18 d 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at /gkj,/2ws xt;wvtd+l doe+m5 the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balco s;lmot 2kj/wdtd e+,gvw+5 x/ny of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take o1a7k8ic yyh; a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resiyhay 8;71kioc stance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers thrdv*cpr8dv/ m.ky) f9vough a grilling machine. If the grilling machine is 1.1 m long p dm*cy/8.dfv9vrk) vand 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 faster than Joe can. How))pfn 3w2myr x many times highermr2 )3)y wpxnf will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the grouncgcw31;c0 p tdqq/vz 4d below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball? w qqgc/pz41c0 d;v t3c   m/s

  Two students are asked to find the height of a parts)qf.1h5 fq(ajqlb4 5rx fui6icular building using a barometer. Instead of using the barometer as an51qar(xbh.fu5 lqi4js f f) q6 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:comm.pe ui03g j+zys 7 hhn6: 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 b0m3puh i+ nj6sgm:o7:ye zc .hicycles 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?