Does a car speedometer measure speed, velocit-4xb*jf u;eomy, or both?

Can an object have a varyi ,)n2w-u0pujn1wtz x ing speed if its velocity is constant? If yes, give example0iup xwz1nj-2t u, nw)s.

When an object moves with const (ewf(i 9zu(oshop/qbwl:/m) ant velocity, does its average velocity during any time interval differ from its instantaneous v:hf l9w ouq )m(/b iep(/zo(swelocity at any instant?

In drag racing, is it possible for the car with the 1hh;if; h yydsl75z g4greatest speed crossing the finish line to lose the rsf ih7h5 ;yg4dyl z;h1ace? Explain.

If one object has a greater speed4l /apyhk2r gq;ak3b5 than a second object, does the first necessarily have a greater acceleration?lrk2ab4q h3/ygp5ak; Explain, using examples.

Compare the acceleration of a motorcycle that accv 0/w5ofl+jk6k wij,belerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rekkvwf / b+6l0 jo,i5jwst to 10km/h in the same time.

Can an object have a northward vbv b6scu56om3 elocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is 1 9fh8vc7j a(ll1unpppositive? What ab1uhj( np8vlfl a7c19 pout vice versa?

Give an example where both the velocity as)4om7ptj zr4 of;:l wnd acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is travem 0dvx ( evuhr-9ego 2i flyia 3ft-h-0u56b.oling 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 th6y3t-egxiui2 m-- ev0fdofhlrv0oa hbu5(9 .e other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelerah kv;d )e:0wdhtion decreases? If so, give an example. If notk)ehd ; hvd:w0, explain.

A baseball player hits a foul ball straight up into the air. It leaves the ba rv2q5rlz9pdc/qx5 z 4t with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catr9z4 25zlprq/qdv5c x ches it?

As a freely falling object speeds up, what g-ril .(oq. ) jwyo8hm17qnt lis happening to its acceleration due to gravity — does it increase, decrease, )ltmq7y.oq g.8j1nw-(o li hror stay the same?

How would you estimate the maximum height you coult:(hy qo0co )7amse*b;p zt;bd throw a ball vertically upwarom0 s;zteab)t pyqb*7(h; co :d? How would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speedgx w4j8j nftf. -qr5r/ 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 ? Explaij5/ qg84.fr nwxrjf- tn why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tied wdq:hiqle - x+ pt(,:yto it at equal intervals is dropped froihpdle (:-,tyxqw+ :q m 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 rjxt3 u j7fe9n b(9ueihx:s, *zock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops:u9ste9z( ib,fx u7n*j3 e jxh along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its origi 3jcrw6 l2ergp)yi/p0nal position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this resuil gr p wej/0r3y)6pc2lt be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have znhk(jflo(n6v4 b+8n eero velocity and nonzero acceleration at the same time? Give examples.(f6( lbnekh+o njn84v

Can an object have zero accelerati muwkg +66moq4zy ap4q(p3o( uon and nonzero velocity at the same time? Give u (pwuaq46m gmq +3y6opz4( okexamples.

Describe in words the motion plotted in Fig. 2–28 in termspeeut0a*ul1 * of v, a, etc. [Hint: First try to dup1 *t*puu 0aleelicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the e -x5tbnjn55h object graphed in Fig. 2–29.

  What must be your car’sxs :y;lsbbwltx*x . / )fa14apx8,vws average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it y *:f8ls t7s4kla4f6sbj)k xmtake to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 s, he-/f( k2rf rw:d3sme qow far do you travel durinsff (2-mewk3:e/dr qr g this inattentive period?    m

  Convert 35 mi/h to )6qhmj fxl3 :dg-t35xh oj3n8,mjo dq
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frovaj8e caa y043m $x_1$ = 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 schooly3b ;*jdddo7+bp*7 .jhfdy od steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 kmh +pjd77 *f3dyjob;oyd.*db d/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-tf-q1z3u3 h drfhumb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the sp 3hzuf -rqdf31eed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track/v ievnvyvn1 s5))y6f-. q mzk in a total time of 12.5 min. Calcu sfyn 5/ i1n.v)qevvmkvz-6y) late
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight lskw g43:ezrm1 l yx:n9g) u6zaine, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s.xa4zzuy63er lg 1w :9nksg:)m 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 gu;-p:ap *sdxhi*w9t other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reachwx; u 9*ptg-:sd* iahp each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truckscw bub3/7 +oq traveling How long will it take the ca/qsw+3cbb 7o ur to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tail.gq1vu2b-phbjy v9 v8wind that boosts its speed to bvjv9y.- pvgq1h u b28990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-tp a 9r0j73mi5gw vof(vrip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour l9 7fija3vvp 5w0gmo(runch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed h31 io gbxg.mhg.qu4)o its the pins at the end of a bowling lane 16.5 m long. The bowler hearsb 41omihu.3g ggq )xo. 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 g (ei7 8x1uga7dsp yk;to 95 km/h in 6.2 s. What is its average acceleration inepggu71 dys;(8 k7axi $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her1z p8zv1-6c zxaf+zel acceleration1z1c+zzal8 -evxpz 6f
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a .z dws7dpz2c 0particular automobile is capable of an acceleration of about sz0dc.7p wzd2 $1.6 m/s^2$ 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 110yo1p5 (ej. n ,qgn6wmw2x wy,p m in 5.0 s. If it then brakes and comnmojyxww1n5e w y ,g(p 2,.p6qes 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 startsa d7efds jh2a*mu6vn4h-cy ,j::svq + from rest at t = 0 and moves in a straight line, is given as a func 2,u na m e +d4dasy6h7f:qhs:v-j*vjction 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 q ke.62yus4zuj3.ghu m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume c6.jykq2he .uz g3u4u sonstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in */ rd3ta .l1)re gmzjfa distance of 85 m. What was its accelera*j r3g 1f e.)dzma/rtltion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How logr xw .9g9tm0ung a runway is needed if thuw .mrx90tg9g e (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks 53iv8m le :biunqsq,1 to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration ofus3e5,mqb lnq :i18 vi this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/:j emu,/, rmxws to rest in 6.00 s. How far did it travel in /ruj:,emm , wxthat time?    m

  In coming to a stop, a car leaves skid marks )kd yc-1ot/nz wv5znky519 r8wlss6 h92 m long on the highway. Assuming a decz91l onr6cz/svkn15hy k)ty s-85w dweleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h htz j1-u x)xwmyc) ffe,mj/.w;5/vl rstrikes a tree. The front end of the car compresses and the driver comes to rest aftwl-5 ;ht //wcefmx)ruy)j, fz .1j xvmer 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 a car with an initiad5 (uc ;- uir3i.ss6m dtgo:gzl speed of 95 km/h and human reaction time of 1.0 s, forus;6(s3u id-gctd5 g r zmoi:. an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the syz kih9/s*g9fqndt:cj 3o+( (kbdg +ftopping 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 trh.cts0j tk, x y 0unstrc jyo(z-;z5dj5q77b(uck going 25 m/s on the highway. The car’s driver looks for an opportunity uyo7zj 5ht5j r0x ; -70bs( ns.j(,cdzqkct tyto 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 coewx,r1a-, *e8mey sh pmplete the 10,000-m run in less than 30.0 min. After exactly 27.08spwh1er,ea, - eymx* min, there are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car skz zh6(c*f)2dugkj+ at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the i s *cgdukfhj 6zk+2z)(ntersection 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 be.dk1c 4x)t sbdlow after 3.25 kdd4scb 1x.t )s. How high is the cliff?    m

  If a car rolls gently vm4od-az.rrik 9z,q8 ($v_0\,=\,0$) 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 spe-b7jqtc v*x :sed 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 after throwing it vertically upward. Wik-is 16mv.pp7 t 18ch5myigkz th what speed did he throw it, and what t g5z7pc1pvyk1s8.m mki-ih6height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gra88q8ircmfo q:y:hq m.q08cpcq l :t0 vphs of (a) its speed and (b) the distanceqcrp 8htmq. 8m8cf:: q00oqlqv yic8: it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At at 20c5b2d 2u dgizddj; height of 125 m above the Earth, a package is dropped from a window. How much time does it take fgci ;d j2bd 2udz250dtor the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveledx e8ahqr1e7)vbmb drhy(+6+iov 8k4 c during each succbmvh rer k68ocyd( h41b+va+ 7eix 8)qessive 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 (algebraically) that a 8ol1t4dxmzhubi 9:7yball thrown vertically upward with a h7uyz89ob:d 1 ltxi 4mspeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertile ms.vmn46s48*gegl p- f2tdcally 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 tmz)e8 .w,rgdjpp95h l*iu t8d he apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in hpd),t*z5 dl ir eg9jpw.u88mdiameter. [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). ygw4 yr/*5xo wFrom/ y *4xrww5ygo what height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff),63semha z8iqysa + q, and the sound of it striking the ocean is heard 3.2 s later. Ifqe,ya+hms36iqza s) 8 the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden ho mqac6 uup3h* h5:yxe4se 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 qu3x:qme6 apuhhu5 *c4y ickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the ed*mdlze8 mr+e,vm nh-w;s8 f p3ge of a cliff ndm8 *; w lmfs,er8he+vz-mp370.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with(:muw of ,jm+x a vertical speed of 13 m/s If the ball wasmx+w mj :(ou,f 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) q6he 4yrje o /s)/3 yc/2zsqcvAt what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, wac j2zr63s/ qh/oqees4yyc) /vs the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plote2cqat yuj .v30)j a*oted in Fig. 2–28. Wha jq0u oy3c. jvea2a)t*t 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 accyjs gto7*09u zelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting z9j0* uos7 tgyof 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 accelub3k qr*v+lo: eration of the car in the previous Problem (Fig. 2–35) when it is in k*oq+:u3lbvr
(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, estima kt3 rc.dgf( 3wyfm2c2te the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object w.f8 r6bx1ur w4hxk(lahose displacement as a function of time is gka8 xr46 w.rbf1l(xuhiven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of+b bjv07pm,6zgw 2)em5vj ko q an object along the x axis. Consider the time interval from A to B. (a) Is the object +bwo6)pv me7mjq2 ,v5bzjkg0 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 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 winds;v3 .bwkw xy g( 1fv)syz7i/xow 15.0 m above a firefighter’s safety net. The sur xygw;f/3) bxi(7vvws1z k.syvivor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to 2j52fick+ky m:qi 87d6 wdlyzs+ we+p 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 ik7 y 58s d2e iq+m2:ykw +pzw+cfd6jlon Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a goostw +(xsh z*zj;58a7xhld w- i9kyyt 3d chance of surviving a car collision if the deceleration does not exceeh js7+z-;hdw(t9y 5wy*xkis t3 x8 zald 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 t m;3m2 cwexn-dcfs20l he road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above tsdf3m ;cn2e0mlx-2cwhe 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 col-/dc3ofvbp:k81 ke5p ife0dxgde uw8ox3 ; p6lisions by hauling them up oox owxu i:0kcdfp ;p1e3k5f- 8pv36dde 8e/ gbn 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 abou28arj+wh : oowt $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front o :ml3etwll5n: f the train has a speed of 25 m/s when it passes a railway worker w53n :lem ll:twho 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 intoxy)g)zehm dm,8gb/ 8 o a deep pool. The person’s downward motion stops 2.0 m below the surface of)zm,/88 ydm boh g)egx the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balanc 9 rbra2)um*trz vvx8-dd5b5w9a r i(ce 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, calculate the time it takes a train to make a 9.0-km trip in two siuam9b 5)rb2iv (a5r-td9drr*zv wx c8tuations:
(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 downmnae a,n 6*yd. 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 per.edn 6*an, ymaform evasive 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 with which a golfer strikes a q;58/lqky j)6eo)mj3kjiv r sball 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 dimj3ro/ji5 6 q8ysv kk le)j;)qfficult 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 c w4r*d:fkr0v 7qizog-u;q+z c2flv sh2 4fh1a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car k01lc2-cqh f4*hs+fd4zwvr z uq7if :;2 vorgpasses 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 from the roof of a high building. A second stone is dropped 1,d jjj7idz291f(x4i x*rkepn.50 s later. How far apart are the stones w*4 krj,n (iz 97f12dxepxjidjhen the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h o g6z7; ima4i7cxbbzu7 ver the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for t777 z4m6cixgub;bz aihe last lap?    km/h

  A bicyclist in the Tour de Frx/n53 roi5vgk nr.r j*,yqa/aance crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 7/ /gx5 ,y noari*kjrra5n q3.v5 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 trampolines. The first child gy9:1x*plwx7fze-c72p fkcyj 5+pa acan bounce up one-and-a-half:yg x *7 -p +l7ja1 9fpxwa25cczefkpy 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 traveling 95 km/h overtakes a 1.109ny a2*.hdrz;zn l fesofu 5who k2 ):(/qhsq.-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling o2hqq 5:o;/ n9f2hs)yde fakh. zurznl*sw .(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/sl- t0)jbl/ /b w:beagu In throwing the 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). Estimau)/te0l-lba :/ gbwj bte the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceljj m.m,7tbnrs4sb.sg a+ wy :.eration 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 Figya- )i7xftn dp:7t:kj . 2–42. 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 y a- d:t7k jfy:nxt)pi7ou are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a consfndb, s gl4)n9tant 120 km/h takes off in hot pursuit. The police officer catches up to the l49 bfd)n sg,nspeeder 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 bjyfc 14dn 90kx 3v i2vp3c62jfvpllx4 uilding; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 mk f3lf xvjv412p4cyi jvpd2l063cn9x/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 vev:1/6 7oxji-h ;n8 ka8waxlxhcs rp; zrtically 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 buil;8o njxh7wl:6ak8raxv-1x pz; ch s/iding and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling parachue/jcnwn0 tfwjd m;6b33jp+rn) e0m *ytist 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 re d0c3n/j rjf)ww *6n;b30mmp jy tn+eesistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send q.+hmggt )up)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 )u+ gh gtqp.)mmust the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 time;5t b(quyqe pza; pco0 /c:v1ms faster than Joe can. How many times higtppcau(v ;/ beqy01m 5 q;:oczher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands 1 uxa);m0czv1dxz* 9as2yf xf 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 im11s 0xfxv;z9d *2x fa)uyazcn your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to finrhz(m j:;y02an;h nxcd the 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 n;0han (:; rxzjchy2m make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph f kp 908exbcuu7 ov4w,qor two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (buv87 obq9p0wxe 4k,uc) 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?