Does a car speedometer measure way4pw(o - yv6speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, xaf;am n95gp1give examp5mpga91 x a;nfles.

When an object moves with constant veloci;35nfjos yrlq- e80vjty, does its average velocity during any time interval differ from it- jroe0 38 lv5jqn;yfss instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest spou f wmc,+4c5zeed crossing the finish line to lose thmwc,fc+o4u 5ze race? Explain.

If one object has a greater speed thani1 7y: emyq;d/s6ubsr a second object, does the first necessarily have a greater acceleration?is;ym squb1ye :dr/7 6 Explain, using examples.

Compare the acceleration of a motorcycle that accelerates frbe1g1mln4 v9d io,w9wom 80km/h to 90km/h with the accelerat dvl,w9g1nowi9 b em41ion 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? Ey84 ncc*zwt 0rxplain.

Can the velocity of an object be negative whr7 i(ledw9+b2 xnna-ven its acceleration is positive? What abou2 e7lr-xndbwa+ i9n (vt vice versa?

Give an example where both the velocihbxsn 0tmll- jq9o/ c/6;p d6aty and acceleration are negative.

Two cars emerge side by side from a tunnel. C1.t+90 stypt/ek6wf78a. uzv sz dghxar A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your r0k/ x9twt.tvz h.ue8zya6sf g71sdp+easoning.

Can an object be increasing in speed a75raa 6 +snbqrs its acceleration decreases? If so, give arb75 qn+a6rasn example. If not, explain.

A baseball player hitsx7n ;b4xil/j k a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air b 7nk j4xil/x;resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happdz)q p(hu3ze8p+k h*xxmn5 k2ening to its acceleration due to gravity — does it increase, decrease, or stay the sa+*n(zx25pz ukq8m de3k)pxhh me?

How would you estimate the maximum heighpyk( :79vugsj t you could throw a ball vertically upward? How would you estimate the maximum speedp( k9u:yjvg 7s you could give it?

You travel from point A to point B in a car moving at a constanu(/hvt9uxnc)x * qjg) t speed of Then you travel the same distance from point B to another point 9jqu *(xc uth)n)xvg /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 3.0-m-long vertical s2:+ nroak x/ ad-yg3cwtring 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 tim:+wx a2d gy/aoc3k-n re 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 accel wy5rqq m0gb(x+6wbx;eration: a rock falling from a wy r bw0;xg(6+5bqxmq cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its o7all8 ) o7hhyxriginal position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion7a ll)oxyh78h .]

Can an object have zero velocity and noe7b+2/td g ya u+tcmo-nzero acceleration at the same time? Give dym2+g/+7totu c -beaexamples.

Can an object have zero acceleration and nonzero velocity at the same time? *dn l51l j4gmsGive exampg4ld j 5*ns1lmles.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint:p ,mp3f/) ldwwryex98z;yhg 2 First try to duplz2 ,3e;rdh/ 98) fxypwmpyglwicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed icwsf o5 lln)wc 1zgr5 l+:hzol)hw197n Fig. 2–29.

  What must be your car’s average speedch 4x /f(llui, in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? q,2y o :fbztqp 1b*ww/   h

  If you are driving along a nlp 2q,.y:prkp;h xp5c- vc ;gstraight road and you look to the side for 2.0 s, how far do you travel d vx2;ql ch-:;5pppnkr.p, y gcuring this inattentive period?    m

  Convert 35 mi/h to oc g,91 dizfg*)gt5et
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frjs;eogp w-0-s; dm cr/om $x_1$ = 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 beginso*4iqaqqy7 3k to rain and you slow to 65 km/h You arrive home after driving 3 hours and 2yq o4 37kiqaq*0 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-v/zm l dz1+w n ,ap26qa9 :bspo3gvx,xthumb, every five seconds between a lightning flash and the following thunder vq3xspxzw/ao 2mv,,: n 1gl6p+b9adzgives 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 completekykjg0zom 2. p26 8e n:(zsu)mtea8am laps around a quarter-mile track in a total time of m8yotk:g p.8a(26a)z0z2n uesmjemk 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away fromoj tnb /n7xz6):rckbg-)huo3 its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calkb 76nzcur :bng ho- )o3x/j)tculate
(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 track*3mtye/yqp o t8n:cdsf0 mttam4z/5(s. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 oym53/ p8 ymd0tt:e fsmqc t4a*/tnz(km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m beh*ce le2/cctcn3-ki z :ind a truck traveling How long will it take the car to reach the tru/lc 2zikc*3 nc-ce:etck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tailw p;inmlq b53, ,m2wuoeind that boosts its speed to 990 km/h fnimq,l,;35o2pmbwe uor 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 velocity of a complete riipbkw )zm:x;, /mda8qf7 yn 2ound-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-h imzbdyp i,x)8;kmw2:f/n q a7our lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant5jfs;5 t5.dmoj k (ho p8zmt+c speed hits the pins at the end of a bowling lanfkc tho5+mjz( .m5jtp8o; d5s e 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its ave2g6 sc+yim ocwo8h;2arage acceleratihcaoow+8m ycg262is; on in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in tu *9nd2vxl:)us mc1:jbi 7eb1.35 s. What is her acceleration7l 2* x)ubec: :n1vutdm j9bsi
(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 (m 3tqx8rigd) twtkb6(y 9zp2 of about ypr6(38bzg id mqxt9( w2k)tt $1.6 m/s^2$ 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 m in 5.0 s. If iva -arzqi09 exk 9rr5)t then brakes and comes to a stop in 4.0 s, what is its avi5rxqa zrrak)0 9e- 9cceleration 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 sl t7x*dte+ob46ci+s in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display ead+4sit+xtec *l6b7 s och in a Table and on a graph.

  A car accelerates from:z*vd gzyu -z3amw 6bp -;xg.b 13 m/s to 25 m/s in 6.0 s. What was its acceleration? How far didx-b 6 vz-wu;*gzzagbp: m.3y d it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to nh*brvh0 9uto) v/tez2 ila4 ;rest in a distance of 85 m. What was its acceleration, assumed consrva/9*heov hn4 0bl)tzi;u 2t tant?    $m/s^2$

  A light plane must reach a speed of 3 1p gezlrngh05.2t i:c3 m/s for takeoff. How long a runway is needed if the (constan0ctp el512zg nrigh.:t) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst outba+2z* .nbnin 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 sprinter, and how long does it take her to reach that speed*b +n.2bnnzi a? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down unif) 5z 1fpk lybk dg. 9)mwhbbi(8r5-qbeormly from a speed of 12.0 m/s to rest in 6.00 s. How far did it t5 y m kbwb-9hgqk5) erdb1z)(8.lifp bravel in that time?    m

  In coming to a stop, a car lybon- 5(tkfhb;/9u,j rj5nn seaves skid marks 92 m long on the highway. Assuming a decelbj n5t jysn (hn-r k/bofu95;,eration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h st +ooeucl+d)jkn 1 ub,-rikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleratio- d)nujokuo, b lec+1+n 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 diswa9o( (rkkwm( tances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, foww k(k r9(oa(mr an acceleration
(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 yf0j+0yk(zfo n )es3xa,n x,fis $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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 2k laqprecn3t9x)3m)2-bp g 0w5 m/s on the highway. The car’s driver looks for an opportunity to -m kqe)2c3pn)9rx tgp0w3 lb apass, 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 less than 30.0 min9y o94sdorty uo )a1,e. After exactly 27.0 min, there are still 1100 m to go. The runner must the ea or s9doto4u9)1,yyn 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 *izfe2- xsq1 to+4mstwyve* * an intersection just as the traffic light turns yellow. She knows ms-oxw4iy q *vt+eesz 21t*f* that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The 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 az+a 6f gh3u(uqsk,d7cliff. It hits the ground below after 3.25 s. How high isu,gfa +7s3huq ak6 dz( the cliff?    m

  If a car rolls gently+ r7m2th vhs 9,p*j;*qxppluk ($v_0\,=\,0$) 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 tho ihq1qw6kinsgkp ,- b0y( 9/je air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s af c1zjn*gyb4c4+ozr 7l* x/ tynter throwing it vertically upward. With what speed did he throw it, and zj bcy*/41txgln zy *co4rn7+what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from reil p0 )y3pf,1 hqjkai.5fovjv3. h -dlst and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of fokjfl0hl1 aqpjd3. v vyh- .3i,5pi)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 hepd1, 6az yjs5qight of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The pac ,jq5adz6 spy1kage’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distkcx6v,(wfm t tc2m.z9 ance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. Sefc6k(ztxmt 9mc,v. w2e Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicapu*cwt .y 8v8glly) that a ball thrown vertically upward wit8y.uv8p tcgw* h a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 m/s eom(ub05524 g(rmdo wi c/fvd
(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 ofrit p45d a,2p1na.5infv 2iu a the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diam5uf4 ni2i.arav ,5ppd nta1i2eter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32).j c;gjvyt6*mzd05/ja gc 8u n. From what height ab6cj0gnt /daz .j*g;u5 m8cjvyove the top of the window did the stone fall?    m

  A rock is dropped from a sea cliffz qogn(i6q: k96 c ,nmkulx8gmf5y z*8, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? Hqc5g( z8ou ,gmm6zk lnxi*: y6 f89nkq =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You poxybp4jyzkqb9 e0d, -4 int 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 veb0p4ek dxy -j,z 9y4qbrtical, you hear the water striking the ground 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 with a speed of 12.0 m/smx:v:h xs*c)ptn0w cx7 f z;2t from the edge of a cliff 70.0 m high (F2s x:x:h*v w)f;t7 tzpmx0cc nig. 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 stree72e;j y w-zrumt with a vertical speed of 13 m/s If y2meu;w-7z r jthe 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 o h+b- m;j +ci1nkwwx*bf time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the accelera1 b ++kwjcxim;*h bn-wtion constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tuny 4r , tf;tn*lxuia72ynel as a function of time is plotted in Fig. 2–28. Whtr*f,nlt ;uay7i2 4xyat 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 autoptsdof.zw,)rxkf. . o2mb4+e2b r2 abmobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flatrf)dp.+b .rm o2,taf2ex ksb .4 zb2wo 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 carn((y:1 ijb oykq-eu;mwx a(n 4 in the previous Problem (Fig. 2–35) when inw4koea( jxm1:u (biqyn (y; -t 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 dn+:l na -mfbo2uring
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacementg8m mdmm8n45h0i+ gea as a function of ti488n+dh0 ea mmgm5igm me is given by Fig. 2–28.

Figure 2–36 is a position v*da f3f, 6-nqro .+1ydx( vrqaay urp+1rj.ytersus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positivenv+ tfd6-1p.x+ fau3 1o * y.dajarrry(y,qqr or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth- 2hlrz8jq,h d2story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37.z22 jlrhqhd8,
(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 v+n u0pw )a3euto gravity on the Moon 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 than it would on Eartp3+e)u0 anwv uh, assuming the same initial velocity?

  A person who is properly constrained 04qcyrni m/ p,9h*t atby an over-the-shoulder seat belt has a good cha 09/tnt*ry4piah m,q cnce of surviving 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 below/3hx e+ zkuv2b2pix9 )cmka*k, 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 truck should be when he jumps down from the bridge onto the truck to make his getaway.x /m c2b 9ka3pv+h)k*ixz2uke How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by hauevj5hq6/ rvdrj:a- y0 6jg4 neling them u 5e0qae6-jrv6jgrny/ djv:4 hp on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels about g2z ul9tu:p,p$10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train be.i0 p7d 1.pk4 gn6s kplb; 1pkpkc(evggins uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing n6.lp1; 0pksvkdpig pcpgb7e41k.( k 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 shc8c1)r chsv5z-ol ,eurface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average devce-lr s , zcc5h8o1h)celeration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit s,f9 ,y-up, q(qr3rzjpebgo7k ystem, it is necessary to balance the average speed of a train af9kuqp, z g3oe(qy-j ,r7prb,gainst the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fishsptpd 500voveq //meiv *0a djg4: bx). Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot ij/vp :db g0v vsed)x0 pm5qo4/e0*tathe pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer hh+shl*++dwhis ia 64 strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constant *iss+ha6 h+h4hdi+l wly 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 speed of 6.0 l+iubvk z4 ik;/k15g tm/s Just as an empty box car passes him, the fugitive stku45ivk bi+lkg1 z; t/arts 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 fd:em6 krnml 5(wth+ r+rom the roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of + k (6m+h5wrn emtlr:d12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the ey9k0utwa y5j9/ qz5c0 0lxvpcourse of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must b00z5l wkuy p/qxt5eajc9 9vy0e maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a gm 4x8lybu ;p ,h4k-ybmountain pass as he moves at 18 km/h . At the bottom, 4.0 kml my;bh4gb,48k xuyp- farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two th: sr:k(siz) xl(wzn::a9ghj rampolines. The first child can bounce up one-and-a-h l(h zshk::jz(g:)s nxiwa9:ralf 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 travelinup(s)s ig+ 2:gic m6+y*ryruu g 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 loi6(:pu +yg2uig rruc m*+ sy)sng 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 9fs6i.rank kj2oe3j* 44 m/s In throwing the baseball, the pitcher accelerates kr*.kja29 jef6in 3so 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 vertica,g x,znydvyl8.zan1 -lly, 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. 2–42. Each intersection hi -5;;gzikob vas 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 firs;ovi;b kg5z-it 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 1 d,b3gt/u9k zl7 pu-ag20 km/h takes off in hot pursuit. The police officer catches up to t 7z-/ ,glpua9bguk3dthe 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 t/3ztxkkg * aw 8:pvr0ohat, a second stone is thrown straight dor 8kpak/vgx3w:0tz * own 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 vertically up at the same time. The first /xkin-4w svz 2stone 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 n vks4w/ x-i2zwhat 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 a free-falling parachk kz*(bdh5 w(j7bq7p iutist 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 h i *dk(q(5 jkbbw77zhper speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt ppkc,oz *ez 1,to send the burgers 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 o,p*cez,k 1zp 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 caz5 vtx3qm6e x:6 p pg+bra)vy2n. How many times higher will Bill’s ball go than Joe’ v re6m56vxa qpz )+t:x3pgby2s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stane(xt;ww-7 t uwds 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 youxuwew 7-;tw(t , such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a parti7 z9if0dxcgr3y5ott)e9v 0 ngcular 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, tco i 57)tv9r9eyd03 gtx 0fgnziming 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 fobs5) eq rve,0p.csbv8 r 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? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? 5r v)08bsqbsee .vpc,(e) Which bicycle has the higher average velocity?