Does a car speedometer mefdr.xi unx1q2x3wc 4-asure speed, velocity, or both?

Can an object have a varying speed if its v0vrspm+ dys 6g2s6k)velocity is constant? If yes, give examples.66p+ 0skysvr d mvs)2g

When an object moves with constantpt5d6cwa h(/jxitb/ ,3l (zp d velocity, does its average velocity during any time interval diff5( p dzawc,p3hibt( t xdl6/j/er from its instantaneous velocity at any instant?

In drag racing, is it possible fooi8k-3h*yf: uj erge. r the car with the greatest speed crossing the finish line to lose r*-uejofh8g:y3.ke ithe race? Explain.

If one object has a greatekjuf6za32 4 or1wbb0(2tg1 ls5vzf ypr speed than a second object, does the first necessarily have a yffvp(ol j1gwr au56 z2s4zb3 2b0t1kgreater acceleration? Explain, using examples.

Compare the acceleration of a motl)v uehk.fd c tenm ky/1w(+d(x6lodpf-/6s5orcycle that accelerates from 80km/h to 90km/h with the accem).6 t5y wcd v/-e/(f o6lukkdel s(nd1 +pfxhleration 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? 4tual8pz5 l3d1 fuea(Explain.

Can the velocity of an objec )1vjw yg/ff3o)ijfk/t be negative when its acceleration is positive? What/kffo3/fj g) wj)v1yi about vice versa?

Give an example where both the velocity and accelerazr0es9 xfv(tngllo12u 5q 1z5tion are negative.

Two cars emerge side by side from a tuwc8kzi1 d:uk,6 qo c,f44absinnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . 46disoku: 8c,fqzic bw1 ak,4Car 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 dpp;v 1 )gjbmqamkb ).,4a,ac;uk:k7i4sl rm oecreases? If so, give an example. Iq1c).bkml7gaa,,mojmu4 ak)br;;4sp:p v ik f not, explain.

A baseball player hits a fouyvn r2ep 16 jy-wp5iqmh35 uj4l ball straight up into the air. It leaves the bat with a speed of 120km/h . In the ap5ei2-4yuvh 3j njmw6prq15 ybsence of 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 dk. k).jtyu+wfue kktj.)+f.uwyto gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height yoenf;vu5 rvvp9qy82 4 , y9dsxtu could throw a ball vertically upward? How would you estimate the maximum speed f,p9setv;v 9n 84yq xyvu5d2ryou could give it?

You travel from point A to point B in a car movi f(j5erdi)c3t ng at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Exp)t5c ej if3(drlain why or why not.

In a lecture demonstrati lzq 1- khupo8n. oc1big-+s;ron, a 3.0-m-long vertical string with ten bolts tied to it at equsb+.o;ig 8k 1nz-qpchlr 1-uoal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a )u;9su 4fqh oa, of;byrock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting oah;94ff)y obs q,uu o;n a table?

An object that is thrown verticazus )(7puosq5, r5zps8dbxvr*wdlho o:: .x ; lly upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altere*blow5,d do: puu(v8o.:q;pszz7hx 5)srrsx d, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zwla q clz fli8v2fs3bw w-61,0ero velocity and nonzero acceleration at the same time? Give examples valfc- w2w 6bf sw,iq083lz1l.

Can an object have zero acceleration and nonzero velocity at the same timzsk3hil.)ko8 w-swhp v.)2rbt2w4ea e? Give exampa rvw32i))os.8hsbw4ekt k2p w h-l. zles.

Describe in words the motion zsj g* w8:js*xajalqnr*j)kc 57 hl6)plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to du nllw: )as*6 5)js rjjah*gcxjzk*q8 7plicate the motion plotted by walking or moving your hand.]

Describe in words thegvxy0m 1(l l)f motion of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to pat0/gf49sjbi4oe a2travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h Hoh. ,bzx65qc mgw long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side fy3f,e 3ctv9xi,ust 8ror 2.0 s, how far do you travel during tfiy3te98r, xtu v3s c,his inattentive period?    m

  Convert 35 mi/h to d* ymk:tiiv6q( 1 pqhl)mkk3/d1kx)t
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moveso.,(kf .sb+ydnff p j6vh+2 rx from $x_1$ = 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 bepw n3hq7ds1 ;cy vb;4fgins to rain and you slow tovq ;d47nb3ws1py hf;c 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 t47d8yeevr;ciynq9r89 ;w cl flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed ocdyrr;t8;9e78v9cnq 4 yiel wf sound in m/s from this rule.    m/s

  A person jogs eight complet yrbtm /0 chx)6plxx64mauvg2z-t - (we laps around a quarter-mile track in a total time of 12.5 min. Cal z-4y2x c x v)0-hawltgmxr6 u(mpb6/tculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight lipgkiz( hs, 7z1ne, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. C71 p zz,hg(iksalculate
(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 a4skh;kg6 o xn;o(-vmf speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long wh-kvfo;x on s;k6gm(4 ill it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a trm x/s4fuag68rfgts1 .uck traveling How long will it take the car tf r4/g81 6utfsg.m xaso reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and thff/t*g qtgm:2z s2i q-en encounters a tailwind that boosts its speed to 990 km/h for the next 2800 km* -qmi sgg z22tff/q:t.
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 round-trip in ,uphz*ny,r: ae7 g8 lywhich the outgoing 250 ka,*y,l :yp hrz8neu7 gm is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at thew7no p m5hefh,p2o:+hz5xga/z96 rh g end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the5 mpzephax wn f:ggh o/+57r69h,o2h z ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 952y.ej-o(nsh9 +hbnu z km/h in 6.2 s. What is its average acceleration in j- +e n ob(.unh9yzs2h$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelerati42e jf k-2tggton g4f kt-2ej 2tg
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable o4bt)-aj/mtpd8 yf w x7f an acceleration of about)b-7y/tw4fmpj 8 axtd $1.6 m/s^2$ 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 -sv b9 -tbai,jszb72f in 5.0 s. If it then brakes and comes to a stop in a,t9v-sbbb zfsi- 7j2 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 fucqh)+o+m jx* rom rest at t = 0 and moves in a straight line, is givh) x+ o*qcjmu+en 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 to 25-6-, -mlzkjn ) xgurfz;-mjab m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assumerjm-z ,x ) - nbl6jg-zf-mu;ak constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was itsnnr7 wej57q3+e0il kn cdvs(/ acceleration, assumed cos0eivl5(wrcd /n+k7en 73jqnnstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How lon/ln) *y5 lsezg6 9yhchg a runway is needed if the (constant) accelerhnsg59z ce6l h/y )yl*ation is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spershyjxp( w/1 :ed (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 trw sp1xh/yj :(ake her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformlh qsmqa64) n3ty from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that time? ms3aqhq4 nt)6    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. A)a bp p/zz86xdssuming a decelexzd)azb 6pp/8ration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of)lnsy*7( ggwz the car compresses and the driver comes t )syg(l gzw7n*o rest after 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 distances for p tks.p0 ,,oaptixd-7)om6de a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an accel 70ipde)so d6kmpp-x,t at,o.eration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equationjj.5emh5q8 d t for the 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 tuh.p3 ynmukgoy7k ) 64he highway. The car’s driver looks for an opportunity to p6n7.h3o4 kp) gyuyumkass, 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 30zfxw3b + w*wi-.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must t+wiww*3f z bx-hen 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 an intersection just as the trap noyu 6zdz.7jv15t (en-cf4affic light turns yellow. She knows that the yellow light lasts only 2.0 s befoa4n c pv- dz5(u17nzof6y.ejtre 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 cliff. It hits the gmoqn ; qvr:04amz */gjround below after 3.25 s. Howz gm* jrq;v a0o4qm/n: high is the cliff?    m

  If a car rolls gently (kdkq0l he7/:n $v_0\,=\,0$) 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 oug nma4jd)j 0;qc06 ixf 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ballwn**4ko xieivzln577.) j tat-ja uv) 3.0 s after throwing it vertically upward. With what speed did he throw it, and what height lxna- w4azit5tun) iv 7)7e.k*jjo*v did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw graph h)yfs p,+u4gss of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to yhs, u fgp)s+4t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At: jdtbso6z5kl1v.w -qbn, +xl 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 reach the ground? [Hint: The package’s initial speed equals th:,s.k5 j lvq+lwbx1tbz no d6-e helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance tr v):7kf zemgv2aveled during each 2zge: kmv7vf) successive second increases in 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 (algei3dky3,qe c, zbraically) that a ball thrown vertically dcie,qk33 yz, upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a 8.c44me0vjpy wute +yspeed 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 applewv-s9+)j ybb j in Fig. 2–18 (or number of photoflashes per second). Assume th )vj-b9w+sj ybe 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 vj--e,svf 2xbtravel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the w s,j--vbfv xe2indow did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it sto 1:tv8o :ezuc4/n 2am1h,aucdhn+eo uph*f4 riking the ocean is heard 3.2 s later. If the speed of soundte4 u+41hz/v o1*ae nnc o:8f omphu:cduh,2a is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stre 65mi* nb 6ibhi.d1calfu)0caam 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*a 10 .6chbl6)5nibu aimdcfi 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/s from iz:k1fmdpe.7h :0uo eom tg88the edge of a cliff 70.0 m high (Fig. 2– imo1ef:.7z m8k o dg:0htp8ue34).
(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 win+a nvm7dh 6l2mdow 28 m above the street with a vertical speed of 13 m/s If the ball was thrown fromm7d6m+l2 nhav 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 t).ed :rf)tq fof a train as a function of 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 acceleration constant? (d) When was the magnitude of the acceleration greatest? :r. ftdeq)f)t

  The position of a rabbit along a straight tunnel as a function o w p6h1c9mpjj+e+p:h9o5zicdf time is plotted in Fig. 2–2 d 69 1c +pwmjh:9ippocej+5hz8. 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 acceler+ltkm5);qnh g uv*+tgate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the ggkq th)u +g5*tv+n m;lears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (Fig. 2–68pxtpph4x re ph:;kv8+6n pk35) when it i;xe6npx h68 +pt: kpr4v8p phks 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 trav*;tp: fjy u v12rjof4sw-gn 3leled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph8j7a50-g7kcc thlri ti 1 xbh) for the object whose displacement as a function of time i7hcg k c0)7ibt8h1t l -5rxjias given by Fig. 2–28.

Figure 2–36 is a position versus ;qebe2ld x/g7ht1rkw x6 q/0ptime 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) x2e/lr /g p7w6hkq d;q1ex0 btIs the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above db hn7y)lj7(va firefighter’s safety net. The survivor stretches the nenlbv7h)yd j (7t 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-sixth what it pemi- vlx9:c0is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assumin 0cli:9mpve-x g the same initial velocity?

  A person who is properly constrained by abksyy;u9 .do:f+8wll l/yo ns85cx7f n over-the-shoulder seat belt has a good chance of 7:l .l/oo f c8fnbwl+5ysuxds8kyy ;9 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 roa vpzt.:(su v0rd below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which hepr zv.tv(us:0 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. How many poles is it?    poles

  Suppose a car manufacturer tested its carqllp3,j 9c jel7os13nm/ y k:ys for front-end collisions by hauling them up on a crane and dropping them from a certain height.k:c 7pjloql,1ej/3 m lsy3y 9n
(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 yba.k ig xqp8)2, ei7q wp5ti/h,h0wg$10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uofgdtkvl ,:ls: )i5 .qr)zz.p niform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car :frgi.op)lkz s)v. lq, :d5 ztas it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divr )t eeycz; o.2izv -cbb8m;m4ing board 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 whilez-t;zm4 b)ebc 28revomc. y; i under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance4itz z(1+ uwvd.ze2 d8y/zk og the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average 4.e+tw vy1gz z28uko(z/ zddispeed. 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 an mms5g/n j:y mf w* qo5k*u(fzjonrn8:1w)gm4d free fall straight down 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 1yw :n/*5nrq )gjk (mg*8m4 fo jo5mfsnz: mwuevasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force wd -yw*g ehr8ghh 1s7 )(gacwg.ith which a golfer strikes a ball is planned so that the ball will stop within some sm.e*8ghg a (w)grc hy7w1sh-gdall 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 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 frk c r 0g:hb1ib2djz,4 9pv cm+z/1ov, ;wkbcbleight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, hkj zvc,2 ,9k: v bz/rlm c1bw 4oid;p01+gcbbthe 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 from the roof of a high builcisf n.-0wzp(sr)n 5k.d,ckpf7m cg0ding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a sr7.ccf- pcs0 f k)kw dg z(sm05.npi,npeed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial lastwl:k. pvj.gc 3ing ten laps. If the first nine laps were done at 198.0 km/h . whagck l 3.p.:jwvt average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France ad)fggvf0+1 ):i jzkjcrests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (injidkg0 zff a)v) g:1j+ $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampol:i ,ztf6 bty,zwaxy5 3ines. The first child can bounce up one-and-a-half times higher than the second chilw yy 5b,ta:i, 6tx3zzfd. 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 traveling 95 km/h overtakes a 1.10-kmgqc*:v b0k :)dtdwpg ,-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. 2–40. What are the results if the car and train are traveling in d*:vtg 0w kpb,)g c:dqopposite 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 sp1 f 2qx ,:iegvsv5j3;n 5wv;kx;rap ageed of 44 m/s In throwing the baseball, th3a:n25i v;ja;xx 1v,ew;gpf srv 5gq ke pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with azm+mb*h1 aud ,n 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. E g.pj8qcnm)01(j qdk9bq 7bwpach intersection has a traffic signal, and the speed limqgdjjc8nwb)p17kb 0(p9qq .mit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest,4j6i z4pkf eu: passed by a speeder traveling at a constant 120 km/h takes off in hotpiue6k4jz4 :f pursuit. 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 thatavh 2+ 4:rxbgj4/ ysxc, a second stone is thrown straight down with an initial speed of 25.0 m/s a a/xcg2vb x+hrs4 j4y:nd 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 tgv nr9jctm.944xi0sr y0 - bwehe same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second gs0vyb .i0nwej-49rm4ct r x9stone 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(npz uur67x 0i 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 perux rzin7(u0p6haps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgeq irh(4 72fufi7 l8uzcrs through a grilling mac u827z4hr7i iu(lqfcf hine. 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)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a ni61a):ubxb) wx8 o /g9)xl3gvu gvbbd7b -wrspeed 1.5 times faster than Joe can. How manx8gb w)3)19 b7ugxroxga -vdw :lbb)/v n6iub y times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friendv9wr :hh0vba,rpu6+ m6 4cc aa stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the baca9 +wh6:4h,vp0rb 6ac amurvll?    m/s

  Two students are asked to find the height of a particular building using a barolcv5 s74vooj3e0di 6lmeter. 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 the building’s heivlje0674 li 3osvd co5ght?    m

Figure 2–43 shows the positkz8,ynbl-agx v h(8 9iion vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bivy n,(lhk8 zi9-8gaxbcycles 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? (e) Which bicycle has the higher average velocity?