Does a car speedometz yp guj8z ct;;.j6j9i9wd0ober measure speed, velocity, or both?

Can an object have a varying speed if i (w (vp:kkps2 la05ollts velocity is constant? If yes, give exampl2wa(kkp5l0so v:(llpes.

When an object moves with consiu82dv 0g0o qhtant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any in2vo0gihq0du 8 stant?

In drag racing, is it possible for the car with the greatest spe beqr:c0hpht6l-+* gw ed crossing the finiq:wteph06 +*r g-clhbsh line to lose the race? Explain.

If one object has a greater speed /hiahfmezmc u 4q *ttp8l*987 than a second object, does the first necessarily have a greater acceleration? Expl* mtti8mz f4*qa8l7h 9echup/ain, using examples.

Compare the acceleration of a motorcycle that accelerate i.5ntmcls7wrxp5 b d8mkk -j5d574sqs from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the sanq dj5lm cs4bkipt rw.7s- x5558km7dme time.

Can an object have a northward velocity alu 9ft)fwl28and a southward acceleration? Explain.

Can the velocity of an object be negative when ito r1hhdi: *0;fq)rzwts acceleration is positive? What about vzt;)fho q*0wih: 1rd rice versa?

Give an example where both ti+o ydy/jirw, .e gb 7pqz/,/nhe velocity and acceleration are negative.

Two cars emerge side by side se 8y 2ia 12vhk9zp wnf;43brn smmy- 1rs3y+sfrom a tunnel. Car 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 accele - mzbr1ssr;41 3nms +3i9way2ns2fvhk8 eyypration 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 acceldn--c;t uf(h wlt2*lq eration decreases? If so, give an example. If not, expllh(*ntcdt lw2q-f-;u ain.

A baseball player hits a foul t v 8vgztx,of*c w09/zball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistao cgt8* 0xz/fzwvt 9,vnce, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds u-)4g3 cs;kcn /ucr.v; kuus zvp, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the sa nsucck43v;s .-gu )r/;vckzume?

How would you estimate j7l e/zu6a0j k lg0ym)the maximum height you could throw a ball vertically upward? How would you estimamygz 0 )uk0 jejl76/alte the maximum speed you could give it?

You travel from point A to point B ixh)6a z; (630ew5ulp eme igbun a car moving 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 speu eu;m xpz5ew3g66abe)h i(l0ed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long verticalr/+nc shh7bk7k0/ se m string with ten bolts tied to it at equal ins /kb7 r/n 0ehc+mksh7tervals 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 mot x ,/onxclfsd57l, ;ndions is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on ,,7n x /o dlxsnl;f5cda table?

An object that is thrown vertically upward will rk;9mx+6i7 av lzj-mmont r f5.9jlc:heturn to its original position with the same spevrm6:.mn5oj7i kxj+ltl a9 mhc z9-;fed 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 motion.]

Can an object have zero velocity and nonzero acc sj y:nh73a3 4jwvg2sweleration at the same time? Give examples7snsgv34 ywj23a jh:w.

Can an object have zero acceleration and nonzero .opnv e):qw2k velocity at the same time? Give examplwokpvn:qe. 2) es.

Describe in words the motion plotte7ex7+isqrsq pjf6q o0(lp;p -7kcvg8d in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walkkpx7c( sgr 6eq+v 0f8 pli p;s-j7qoq7ing or moving your hand.]

Describe in words the motion of the object graphed in :hnwa ba)p 7)lFig. 2–29.

  What must be your car’s average speed in order to travel 235 km n2f qun;4ibp6in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? 2*-w) mx myzn uv x4zo4cvri-o46 s9qo   h

  If you are driving along a straight road and you look to the g b6clf4u wb7.side for 2.0 s, how far do yougwf6c4. ul 7bb travel during this inattentive period?    m

  Convert 35 mi/h to -cngtj8t m+ohze9m84 -hb4a p
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from pk 2gv./zk0tk$x_1$ = 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. I tny6 xkcyj. +iuyln7zyk 93+-w*fe+rt then begins to rain and you slow to 65 km/h You arrive home after drivin t -9n++3 *k7yxjy+urzi ce.yfnly w6kg 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)ah,o-fs.r/ g-kbipd between a lightning flash and the followi).k-foh bisg,r -/d pang 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 of sound in m/s from this rule.    m/s

  A person jogs eight complw2ru0) . yubtdete laps around a quarter-mile track in a total time of 12.5 min. Calculate0tr )ud.yu2wb
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, mov a-b;3arh*xbzing 116 m away in 14.0 s. It then turns abruptly and gallopsa3z;x hbar*b - halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks.m5rv8 ci2wo9r Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each ot rr 892w5icovmher? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck trav lpdm *8bik8pit n+lg*q4fu1 *eling How long will it take the car to + gqpdmi t4f *1kiu8*l8plnb* reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tax8v p.rmqncy939wqp 1tllf(- ilw qywfpcml(9 tvnp9x 1q3r.8 l-ind that boosts its speed to 990 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 ab/vo6e z 9)yxf*lkm 1ynd average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, 16 )f/eyko x mz*lyv9band the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of a b6ld s.xccbc/erl33a i7i8) of owling lane 16.5 m long. The bowler hears the sound of the ball hitting the pin 7 bcfx/.3rlod)ec83al c6 isis 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 6.2apj ...ismzruul;p1 6l )1ymi s. What is its average acceleratp.u;1iar)ulj.1 zs .iylmm 6pion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1..p/ *rqi a.i9ypypi. ev0x y(qkg/x-y35 s. What is her acceleration 9/x (g.0piy iqpyxpir v qy/*y.a-.ek
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particulay b v(*1:l;*dtvjzofbuh-7 pe r automobile is capable of an acceleration of about *ob(h;z*ldv7 pt1jf-vbu ey :$1.6 m/s^2$ 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 )3nei a-n1 lxkiwv:1s travels 110 m in 5.0 s. If it then brakes and comes to -vnk1l3wxi s e ):ani1a 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 shtz/+ml9upw v 36* bxw-. qziatarts from rest at t = 0 and moves in a straight line, is givlam9t +h .3/* xwb-u6zv qzipwen 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 m/s in 6.0 s. -m+9 ephjn. cwt ;fj:kWhat was its acceleration? How far did it travel in this tim;+cnthm k-j:pe9. wfj e? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance8 oij g(; as1uyiz lib/abo2p8ae()x* of 85 m. What was its acceleration, assumed constanz()g e*a12ib ; (aiiaouo j8x /syb8plt?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeof;d8oz 5qin p4rf. How long a runway is needed if the (constant 458nir; zqopd) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essent6d ev4giqo:9wi ,an7kzvb* 8hially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the b a:vdgw8 ,69e4 izo7vhn*qikaverage acceleration of 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/sk-snxe 5j qebw79jfc0*c9n p; to rest in 6.00 s. How far didwxfp 9;9ek5 n*-qcce jnb j70s it travel in that time?    m

  In coming to a stop,*whn5a6(s wmo a car leaves skid marks 92 m long on the highway. Assuming a deceleration o5onshwm*6a ( wf $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes(79a+ eby xksj/-phsh a tree. The front end of the car compresses and tb aekh+ -s(97/yshxpjhe driver comes to 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 a car with an initial speed ol+x j/g-2s4y+isn 5y c*md (upgddi :yf 95 km/h and human reaction ng-y+sy xduc(4/d+ ligs*52i:jydmptime of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equationl:nl 1z)i-gxw0: kpu o 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/o5nu1fc fz-qz2s vk((s on the highway. The car’s driver looks for an opportunity to pass, guessing t-2nqu zz1c5(fovsfk ( hat 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 t44 re0n)zc ubs k2sf 7dgzf2.10,000-m run in less than 30.0 min. After exactly 27.0 min, thee4k7gsd rsbzct2n 0ff 4. zu)2re are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as w-6x miqle )r5the 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 in w5-i r)emqlx6tersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below after 3.25.hia4ee4 vp -+iy(s* c* uq9zitgt ,qr s. How ,q z4ci+(rv4hq iu-9sp e*itt *yg. eahigh is the cliff?    m

  If a car rolls gently 5 x(tyjb+ r107nhnysz($v_0\,=\,0$) 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 a( /ut)6vwg 9gr3nklx bir 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 after t/4bp4p+h8 ji h0lrkchhrowing it vertically upward. With what speed did he 0b hpc4h8kirp hj4l/+throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under th;gpvi 4;u: f.mg(bvfqe influence of gravity. Draw graphs of (a) its speed and (b) the dvg:gmf.uv(4p; i q;bfistance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a h-hqz ,+xw)y;b 36a. cxeglrch eight of 125 m above the Earth, a package is dropped from a window. How much)zcag x+,3 . qbcr;hx6hlyw-e time does it take for 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 1syjpc-ju gf cr-;vz8w-2 c0s(oo du 8the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This wofw82;0d1g jp-uyso (rcuj8c --c vzsas first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicall: m+ 2mvurjb+qu; zzc/y) that a ball thrown vertically upward withz :rzu;vm u/cj+ 2mbq+ 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 upwrovt 1 wpe+7b1be d6znn 9c6e.ard with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–18 (or 6o*umwa y7t :brx0q nx15u(ymnumber of photoflashes per seco awxonbuut:1m y 6(7mx0*r5yqnd). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32);wkkq, d :u(wt. From what height above the top of the window did thdk(tk , u:;wqwe stone fall?    m

  A rock is dropped from a sea cliff, and th)9 ;ql rcnpfo,t 64fsre sound of it striking the ocean is heard 3.2 s laterrs9o, r fflp4;qc nt)6. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your gardpx 9 :dtmb2ii:en hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozmxpd:it:i b 29zle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s fromdu3wx-id3 r k(v-q) l4nx.z:e k:xq(nw boo(b the edge of a clifw)z(o ql4xdv3-i 3bx k b-r:(uonn(q:dkwe.xf 70.0 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 abodd4vsw 126pag ve the street with a vertical speed of 13 m/s If the ball was thrown v sa1 64pw2ddgfrom 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 tra i*e41rv(foxpin as a function of time. (a) At what time was p(ove4 f1*x riits 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?

  The position of a rabbit along a straight tunnel as a function of time is plojt9f7 io: 8ib3bj dq4qtted in Fig. 2–28. What is its instantaneous vbd:jqi3 7b ijoq 9t84felocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as shown in th8( oge, mg8fu 8qqi2hpe velocity–time graph of fgi8mhq 8e, q8og(p2uFig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (Fig. 2–;06f53mjyb r otnhw-t 35) when it is in tmr t fbh6yno5-w3j0;
(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 sr 1kptsbpbpr3q5a 99 3j1o*ueled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose disi;wsq:0w/ r1oc,lac nplacement as a function of time is w,qw: as; n0rl1c /coigiven by Fig. 2–28.

Figure 2–36 is a position versus tioz+,- ixr z+i9)jzqndefg 38l me 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 negatiionx++lj)zqirdf9-,3e8g z z ve? 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-s553nktb9 odx j abbsx i.l-4q.tory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Figd-. al3ibkbb so595 j xnqxt4.. 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 gravityp nc-. 4qa/,vs;rvv nu 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 wov-.nuva; cqrvsp4 n/,uld on Earth, assuming the same initial velocity?

  A person who is properly constr)8 q57j7ty7 4gg7uuir7d p m ndvhscb4ained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g’s” 47u8q p 7b 7ji 4dgng5hs7rcu) v7mydt$(1.0 g\,=\,9.8\,m/s^2)$. 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, and his pu3 .kvqu-sx 7c+tlx0b0zp 2stzrsuers 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 lq+-xzkv zp2t. ctux0370 ssbbe 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 fojn k,x ;hn1s w:8*d5 -r-z-hnn nih; ioxokw1or front-end collisions by hauling them up on a crane and dropping them from a certain height. wrz-hok o n,;sk1in-dh1n5-i :;xn8 hxjn* ow
(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 a+:njn f ;yffx*bout $10^9\,km$ 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. cm 01o 7;izksoThe front of the train has a speed of 25 m/s when it passes a railway worker 7k izc0 oos;1mwho 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’sibp9xq5l l0e 0m/uwv. surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the wqxmbp .l /0i90uv l5ewater. 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 s m jfzo8f5ug/4ystem, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a trainomz/5uf g4 j8f 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 freec 1 f.:ekc:h5zjx8mwu zuy 8ij:v9ny3 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 evasive action, at what minimum height must it spot the pelican to escape? Ass ui8x5yckn ewh 1 : u.:zjj:98cvy3zfmume the fish is at the surface of the water.    m

  In putting, the force with which a golfer st pf,e5m nn:hv.rikes 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 tnpn h5e,.m:vfhan 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 ujhoe 8s pejm+3uo(r0- .bi0l freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceleujim .0o l3 +u8s-eob (ej0phrrates 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 buildingh7/co),gy tkt itcndc*e *e72. A second stone is dropped 1.50 s later. How far apart are the stones when the secontnik 7g*cc2teydo) ech/7*,t d one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 (c9, gjn38wbmwnus/y33l-3kgdxhnt km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . wha-nb3jnnyh3,xg3 ( 8k g /swm 3cud9twlt average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he mov(jfx/2r c cq p0f-w 2 zrp*m6q/msrl:qes at 18 km/h . At the bottom, 4.pq-2: (wcr*s /zxr/6 p2rclqfj mmq0f 0 km 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 trampolines. The first chil(tq mjgoo-etl2ee+*gx ic+15d can bounce up one-and-a-halm+-1 tixj ge2*5+eectog( qo lf 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 1.10-km-long train trav )dih yh9lkgiw3;5 vn/eling in the same direction on a track parallel to the road. If the trai g3d/hl i;v5w9 nyhk)in’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 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 baseball1kdypf7l8 ay(7m bi e( with a speed of 44 m/s 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). Estimate the average acceleration of the bai 8adle1p b(yk7m(7yf ll during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerationiv 4bew(v3 c(sz1f m9q 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–hg. m hxv31ksn )*gwp9e4qcbyqg5e ): 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 you are 10 m from the first intes gh.w9c1q hq*p5mev ge:3) kyb4xgn)rsection, 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 12v ak309nx fy/b11 pggwu2,k ta0 km/h takes off in hot pursuit. The police officer ca1kt03axy, bk ugp anw9g21v/ftches 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 thattxgod i-sz bc97o1-.; 08n, mcnbylno , a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the s-dx9tc sy0o,o -;i7bc lgn .1n8z nombame 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 th zl285dq)iqls e same time. The first stone is thrown with an initial vel8 is)dq5qlz2 locity 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 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 w9 b;3syxo 3oioould it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed too 3yoiso9b3 x; perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a gril cjjgqjtx39tcv)tht;o k32/q9 3 a2 h;rbrh3z ling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is t tq9x9ajhv ;r2 t;o h3krc zj/cb hgt2tq3j3)3he 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 thaune dz)6t3ah aj (k*6* ;jv :cxivpj5mn Joe can. How many times higher will Bill’s ball go than Jv*3cv;hnea 5k j6d(*p uij:j)x6atmz oe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of n z*rak/ja85 wa cliff while your friend 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 town k5j ar8/az* 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 particular building using a b+ ra4; nlg;tkyarometer. Instead of using the barometer as aya;k +g4 l;tnrn altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A andz)+8)bnu mdaa uqf.qk5*ub6+j8zetm 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 paak b.n6tdqa+5uj8fm* u 8u +be)zmqz)ssing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?