Does a car speedometer measure speed, w+ dipxu*jcps-9/4; 0gb zsmm velocity, or both?

Can an object have a varying speed if its velocity is constant? If yem.5 1jxrsnny/k4hxb7h,2pa os, give examples.2 47h/karn p5oy n.xhjxm,1s b

When an object moves with constant velocity, does its average velocityp amt f,:m(gs,-pag7w during any time intem tf -7ap (apmg,sw,g:rval differ from its instantaneous velocity at any instant?

In drag racing, is it possible k5:txts 2mul0for the car with the greatest speed crossing the m xslu t520k:tfinish line to lose the race? Explain.

If one object has a greater speed than a second object,z w po7g9;nei( does the first necessarily have a greater acceleration? Explain, using enie7;z gpo( 9wxamples.

Compare the acceleration of a motorcycle that acceleraijgk47 xhg6+v arq73ites from 80km/h to 90km/h with the accele g367qgvai rih xkj+74ration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Ex.+7;b7o, rh/ewfcq n7jtgsy iplain.

Can the velocity of an object be negative whe4f be:*)im2awtj;qry dz,;aa30xoqj n its acceleration is positive? What about vic 4jdaeqqrowx 3a;*2yij;t )0a,fm :zb e versa?

Give an example where both the velocity and accelerationcqzk*+mvjv2 mxlz6:: are negative.

Two cars emerge side by side from a tunnel. Car y3)msuf f j(oz yy.+/zA 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 they come out ofy)fzy3.so/ jzf+y m(u the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acc9 x co6xok lc+g.0l)theleration decreases? If so, give an example. If not, l6o) +x0tgolch.xc 9k explain.

A baseball player hits a foul ball straight up into the ai)3ys8mvhqhxnj:2 o n u bfj,b587fwt4 r. It leaves the bat with a speed of 120km/h . In the absence ofvw,f4j:n qt 3nbojh82 8 x)u7hmf bs5y air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration d4b:aeu* m hv fu6+rg:jue to gravity — does it increase, decr4a rbuj g:vemh6f :u+*ease, or stay the same?

How would you estimate the maximum hepc 49dki7f 9adight you could throw a ball vertically upward? How would you estima94 cd a9kp7idfte the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant spn3huif *(-cg*i lyk.t eed of Then you travel the same distance from point B to another point C, moving at a constant speed of 9i3k ygl(*nfu.t *i-hc 0km/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-long vertical string 6-upk w anbr*4*nvcl,with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the ncr,**4bw up - vlk6naend of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions(v /eeiuk)*kf is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along) vke/ f*uek(i the way, a dish resting on a table?

An object that is thrown vertically upward will retx*m5jaqxruz 20 5(mry*9 )ptsvpwqc) urn 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? 9mw*qrtzax5quxs ))j0mcv5 yr (p2 p*[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 timd1-uf wrif e.2e? Give ex r1d .fwu-i2feamples.

Can an object have zero accja3 0nc dhm6,feleration and nonzero velocity at the same time? Give examplehd,n3m j f6ca0s.

Describe in words the mod9 n) 5px cy+oys5hff6tion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving o y65 cd5y+fp9hs f)xnyour hand.]

Describe in words the motion of ae vz5, 8xz7 (hc )co*xp5vylsthe object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 1xsj7q0cr )gc3.25 h?    km/h

  A bird can fly 25 km/h64gu7pz -,x ,is(mrabz yfjq . How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the..hs+n:wdoqxfg(bmv/ )k (pa side for 2.0 s, how far do you travel during this inatte.vsbdpfkm wq:n a.(/x(go +h) ntive period?    m

  Convert 35 mi/h to 0y;ze p0vxlb-m. k9 ow
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves 85* 6sigozh asfrom $x_1$ = 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)xz3wukzbml ,q .ti w65x*k:h 130 km. It then begins to rain and yo mzh)bw kl 5.x3w6q zit*:,xuku slow to 65 km/h You arrive 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 between a lightning flash arqx62ph :bd e 2v6r5umnd the following thunder gives the distance to the flash in miles. Assuming that the flash of l6qd2:re rv56mx2 bpuhight 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 quar j*,l)vb hhpu:ter-mile track in a total time of 12, :p )vhbl*huj.5 min. 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 int5 czz*v*.u k+ klc+ml 14.0cvuc.tzz+kk*l*m 5 +l s. 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 tracks. Each has a speed of te r(t7pshw:8rfkv4* 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? (Seerh:8w( f7 r t4s*kptve Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How long will it takd0hm+bwsb4 5tax be-dvd 5,gq,zfw -;e thdw-0,qfsb h+vt;w,gba zx - 5dmbd5e 4e car to reach the truck?    s

  An airplane travels 3100 km at a spe5y*a s(yi-0 fwtsnh:0-lxhz xed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the ne*h(nf-a-zxt l5xy: 0yis ws0 hxt 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 vel n55zj,z y ysbfe;ktqa, yx+hg,7u +,jocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch bre bz jfs ,,e +5 xja5uy;y+thg,n7qz,kyak, 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 ekjn+x (q)xu ln.(: , sjgq/mbind of a bowling lane 16.5 m long. Tlgqk, q:ium(x/)jn sx+. njb (he 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 m/s.    m/s

  A sports car accelerates from ro*sf cq m8q:n0 (.f*a dc/hzipest to 95 km/h in 6.2 s. What is its average acceleratis0q/mn* i .(oq ph a8:cdfzf*con in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hernn 53m8 q ;vgkco9m3kk acceleration kng95;k3 n8cmv kmoq 3
(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 acceleration of a+-*iv 52xtn rw cxthm v17sng8bouttm82nx75 cnvw s*xv g1 ih+t-r $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 bwka(v0g9ul6o (zdb0m in 5.0 s. If it then brakes and come vl9gk (d0o( b6za0uwbs 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 t = 0 and moves j26 lskt5n1b0 bj,qq:daauo8in a straight line, is giv t2us8al: 6qbjbod5 a1n,0kqjen 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 13 m/s b/8 ke20i ywucto 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constanty0w 8k/u eb2ic acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dista;)ze4trjf,w ktc a)4m nce of 85 m. What was its acceleration, assumedktfemr,w;4 )4cta zj) constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a ruv / v0p*/swod* 71l,klxj fehqnway is needed if thd,k w10 v ovhpe/7fl*ls q/j*xe (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of 9r-vtbt+x (nrv4+ llu 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 sprinter, and how long does it take h x( +vbnl4l +utt-vr9rer to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s. How fagpz.u+hg+: yxeeq z ff7(.. ycr did it x:+y .ffg yz+ ez.u7cq. (gphetravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assumingafkn *56+l hu; kexpri5(f eyr-3 8lwr a deceleration krxfyfrl8wun*6r5; l 3 (+5eiehap-k of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h striket.uo006 rq uxg6cvj)vs a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Expressuo6 0c)tvgjrqx6uv0 . 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 initial speed of 95 -v18 tsyw x-bdn .jt6vkm/h and human reaction time .t 6xjsvvwd8t1 yn--b 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 thes1ib 2cw4yrw o;q;ynj ju8 0u3 stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s drio/ t4 rqa p6i9yn1 uwxbr2);liver looks for an opp ao12p4r yriibqultn/x6) ;w9ortunity to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in f/ ymgi*t *ehe:u8z030h;jigtw8i ef less than 30.0 min. After exactly 27.0 min, there are still 1100 m t8ijue/yfge t0f wm*ez t* 83iihg;:h0o 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 appro 8)i7vxhmn4pnku /3mujb- rw*5u uow-aches 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. 2rj-uu h iw/nnwm vp8x-om)ku 47b*3u5–31). 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 from the top of a cliff. It hits the ground below nvrl(wya y.odh 2r0h064(g4 xww eo )pafter 3.25 s. How high is the cliff? 40ae wr4gvy2y( ol.h)xnr0(wwp6od h    m

  If a car rolls gently fk,:, u.cvjaq ($v_0\,=\,0$) 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 22 m/ vm z0fpu4c3w7kvv.f 0s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing q9 s*attz6.g um bohut:35 k+iit vertically upward. With what speed did he throw it, and what height d uomgi3b* ukh 9tzt.+atq6s:5id it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls underc)4 q vxqd+qgd1xi 7x us72fl* the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0u1* qxvgx +q7s72f cdl)xidq4 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5. bx37fva-m )ut20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reachv-)73bfam tux the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that th0t)x)*) ;genn f;yxp x:xqefde distance traveled during each successive second increases i)y;)f *;x qxxep tgnn x:0de)fn the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (alj-4bh xas(z e8gebraically) that a ball thrown vertically upward wihs(ba4z- ex8 jth 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 43j1k x7fj8 ohtas4z9r y.nru 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 0e qi w s40-x)vrgs) rn9f;mq m:fu3ddnumber of photoflashes per second). Assum0wq:;fe0vr df3)d mur nqsm4g -sx9)ie the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–3 /,lh2kkn zr;gd .*3llh.jp lxfu/l4i2). From what height ab,d; ulnh2 g/ .l*z34.lhlkjprxf ik/love the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean 2,c qca xku;(x1f:7ifl j2vbgis heard 3.2 s later. If the2jf( 2igvcl ;x, aq :cukx7b1f speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden h8:i ac i+pjh2dnj6*q ;s)pg fgose 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 ground next to you for another 2.0 s. What is the water8pi*dh+c6 ): jgqas g;ij n2pf speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed ,(pk 1yki 4)byuwg2ci of 12.0 m/s from the edge of a cliff 70.0 g,(4u pkkyib2y 1 )cwim 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 tovwd5isqy)48 a gw n(g1ida(4w pass upward by a window 28 m above the street with a vertical speed of 13 m/s If a(( dy i4wqns45dag)1iw8 vwg 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) Atu s768x7ai zil what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the accel86z a7u s7xliieration greatest?

  The position of a rabbit algxlrndwwj 446 (( /teuong a straight tunnel as a function of time is plotted in Fig. 2–28. What is irtwl ugdn4 e/j( 46(xwts 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 accf 6i .s(a4 )hfz7eh)ieuo np-lelerate approximately as shown in the velocity–time h-oi)hnzef7ui e6pl)as (f4.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 accelerati5,*9k3nbidi 2 ypecbyfk2 gg0 :k0qqdon of the car in the previous Problem (Fig. 2–35) when 3db0n *,bik0e 2qg: cf5y29g i yqdpkkit 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 travelesk5l ye 5m:bp/d during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement asj ap1be:m,29n9s uc xmb8j7f6s m ky+m a function of time is given by Fig. 2–8sj mmajyb799mue, :msbx 6 2n+c pkf128.

Figure 2–36 is a position versus time graph for h 76wwuh+yvyij (e+8qthe 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 dir 7+(eq h+yu 6iywh8wvjection? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a fi b4a*d do.3k 3ouhz(pvrefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37. .3bd3ou* kzh (pavd4o
(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 is5u j 0qc9e: ee(*jf)zne ,omjs about one-sixth what it is on Earth. If an object is throwj(fm :e q05*eo9)nzuseec j,j n 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 by an over-the-shoulder sw 2rje-i.;js wlo3 ,iseat belt has a good chance of surol2j,- rw .3wiiessj;viving 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 73:fr, lqkfj 3:jsyiab6uk i3below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he mea3il ,33: 7skrb akfj:qji 6fuysures 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 truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end g9 b 7gqwm sdn)3;ffrm p8h4f rtuq697collisions by hauling them up on a crane and dropping them from a certain height9f7w sftr g)b 84hm qudf6grp37q;nm9.
(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 travelsz y :iiqqb-v6re5 ,jb5qvd u-9 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 accelel n 5vo0fk3/y6di fhsb(qsdra0 7v-m 8ration from rest. The front of the train has a speed of 25 m/s when it passes a railway ws/d kr 0o(a3 fiv6d5slm b0fy-h 8nvq7orker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface inmcgl.2kya z.79a/tg e to a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the2e7z9 ag./kcm. ltgay average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit6jlwvhcixog /. vpy ,n*9i3 p: system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem,ipo,*. vph6i/wvc : jl9ng y3x 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 downio2w2bfw c.u5 when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height mustwi5cbf .w 2u2o it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is plank- :1df (2qdjs ehyw/.glx ky.ned 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. Tos:/1y jwd gl ed-kx.h2(q.kfy 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 spqqb yqd2 c7v71+sp:g ;u* scdq.d:mpr eed of 6.0 m/s Just as an empm;prgyusd bqv2 *:qd1s+. cq7qdc:7p ty box car passes him, 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 fromi:tg z ezu.cpa(ff7wnns 808, the roof of a high building. A second stone is dropped 1.50 s l7ew:zfnisp fug8at zc. 0(8 ,nater. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must aveoo4(:ll;vlfn rage 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speedl; 4:lvnl foo( must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France cjy d/d2c:*;;mec7cy)s obc uf xdzn) *a27 vdsrests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed isya;2b fds:* cu7d7cceddzvc my 2s*x)o) ;jn / 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trspf :q;nl,iwiw0iw ;4ampolines. The first child can bounce up one-anl w,wi0;;w:4qpnfi isd-a-half times higher 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 travelit fzv + ;qx)3csmavw8;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 q z 3tm8wcx v+;)vs;afcar 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 spbpk:px( l ;y1j q; we,x:vv*baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing mo *s;;qx,(wlbpepkyvpvx1 ::j tion.    $m/s^2$

  A rocket rises verticallynss. 55+hq pp57y ygea, from rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42g08rc, z73 eo- jcdtf o.5vzew. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lig ,8z ojcfr5eg3t-0e.7zc d wvohts 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 speedeoxt o7rw/e 4g.d1 uyb,htd2u 4r traveling at a constant 120 km/h takes off in hot pursuit. The police offiy4t uhox gd27e1t d4/ubo rw,.cer 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 buildi 2d2l-icuc hr3v6xyfi 9:cts.ng; 2.00 s after that, a second stone is throw6.2tc fic:ivl2 yc93dx- u shrn straight down with an 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 25f+hoicu -5/km:zqpbk/oro vertically up at 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 veloci+/kz bq 5kpuoo-o :r i2mf5/chty 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 rhvjiuj8x m 1m)+*n) 0gclz/hit take 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 resistance will restrict her speed to pem/mn 8hlzi)xrj + v*gju 0)hc1rhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgerss,0 z:v,nzt. is d1u9rda/eo i through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min),.o:z/10 au,nts9ei srvdizd?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 ehjb5ecl6zn5t u+fy 0dw*98 jtimes faster than Joe can. How many times higher will Bill’s ball go *nut85 0jefjczel95hb + yd6wthan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below yoeywgg w d99px4+ fh l5zm21:nyu. You drop a ball from rest and see that it takes 1.2 s fo4: xmy2wg9eylw+9 5dngzf hp1r 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 thed *wi,; .7zdm qzo4f;mbqlig6 height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of thei mo7lf iz*z;,qm;4d g6qdb. w building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicyc 8bd98tlwbl-dles, A and B. (a) Is there any instant at which the two bicycles have 9w b8 8tdlld-bthe same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?