Does a car speedometer measure s9q x;xv3gp fkhla;v0sdj+ 2rxs,0ni76 (uh vmpeed, velocity, or both?

Can an object have a varying speed if its velo rk-ympj:e)gyef c12 7city is constant? If yes, give exampm) 2feyjp71k ey-cr:gles.

When an object moves wix3 sbuft35drb- 4w9hiil(5 l)jh2kfy th constant velocity, does its average velocity during any time interval differ fromihj- 5u)lrd2f4bl hwy(if3skxt 9b53 its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the grear5 3t7os9hq9xk g /lpktest speed crossing the finish line to lose 9r7htg/5lkqxs 93kop the race? Explain.

If one object has a greater speed thanel mvw-*:p; bby*1jrpu1 l:ww a second object, does the first necessarily have a greater acceleration? Explain, um*ypwj1:uv wp1:bl e*r;-w blsing examples.

Compare the acceleratiov:aut1nbar 0 1n of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle101:a tb rvuna that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocit2c)5mqegng 7 oy and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleratiu- f9::p7j(qgzq*wksud vwu *on is positive? Wha vskfw-9( uqpzg du7j* *w::uqt about vice versa?

Give an example where both the velocity and ac-7eec 4m-ulo7kdx)a vk to7)fceleration are negative.

Two cars emerge side by side from a tunnel. Car A is travelingfe 45dzdub4qwfk4d1k q6 ywo 25cr1;e 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 ek15wk; qw4ub41r qd4c2of5z fydd6ean 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 acceleratlwn6,u6tvlb5ol/ l2i /a5heiion decreases? If so, give at2wli6v laob n/li55/ el,u6hn example. If not, explain.

A baseball player hits a foul tz5-a 8j qg 9icebbobu;2h;:d ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the cateod q 5c9ua8g:zbjb;;-hbi t2cher catches it?

As a freely falling object speeds up, wrq;8p02jvcqtsflgcm:x(8 5) gzx / ukhat is happening to its acceleration due to gravity — does it incrq(fl v 5mg /zxuxt2pgr;:ckq) j8 80csease, decrease, or stay the same?

How would you estimate theo c/d)xy0 p*yd maximum height you could throw a ball vertically upward? How would you estimate the )cd* p0yxyo/dmaximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of Thep.er udknd(02kzz8m w he-f ;:n you travel the same distance from point B to another point C, movdwf(2kdr :e0zeku;p8z - hn.m ing at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with t. k u6xxgf.vp3gi ,k,ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and theiggx 6v3t, .kkp, x.uf 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 rock falli:llql3a 4a 2wbng from a cliff, an elevator moving from the second floor to allq43:aw2 bl the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwardftdlqc vr4g/l y3+n-- will return to its original position with the same speed as it had initially if air relldy cng-f 4+/r t3v-qsistance 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 acceleration at the same time? Giveic/ow8iq )4 qgjg d(6i examplijd8 ) 6gcwqiig4(o /qes.

Can an object have zero acceleration and nonzero velocity at the same tim-d svjjfcb*-2h6zru:q/l ,w4eba (oqe? Give exf u (4j- -6j:o,hlzdsbr*qe 2bq/vacwamples.

Describe in words the motionc u6m hew( dt,xl+alt; gt+.l6 plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plote,;gl+6attmdwlhl xc+6. t(u ted by walking or moving your hand.]

Describe in words the moti)jkuto) 9b1 ls,i 8nfoon of the object graphed in Fig. 2–29.

  What must be your car’s average speep)ku tp*1og jt n*z+sispx f2h ld10-*d in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long doesd*0dd kka0ezr 6cbd3ebctza + 4p.*f8 it take to fly 15 km?    h

  If you are driving along a straight road and you loo ty; kw;c o8hr-4 ) yios)vr(bcv7zuh0k to the side for 2.0 s, how far do you travel 8z h)o-wi;csht vu ryo ;7)v4k(cb ry0during this inattentive period?    m

  Convert 35 mi/h to ne1o jt6b/8nf
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves c:yvkq d;0a9efrom $x_1$ = 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 steadi8u)f9,c-d)kkj3-dgpzv7cisy.k h o3g7 sy ialy at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrvh)7s -d,fd8)yjp-cakzyg.7 3gku 9i3 ikocsive 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 + to2:p(c .e oy e7;9tmlsdvxabetween a lightning flash and the following thunder gives the distance to the flash in miles dec;ovap7est mt9(2 ox:y+l.. 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 complete laps around a quarter-mile track in a total timsth- -oqa7 ss8.sm vo9p hd;9re of 12.5 min. Calculqs89 hodssm7sp-ao;.9h -vrtate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away e9xfzpm5 v(wyvzx*7( in 14.0 s. It then turns abruptly and v7p ( wezyx9m( *z5vxfgallops 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 parals9;phec3rc8z nj ;pcii1 2 p,ulel 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 reac19p uj 238pi,;;nsephcc irc zh each other? (See Fig. 2–30).    min

  A car traveling 88 km/h 3flso4oh/*ht xd+giv 1h5c r:is 110 m behind a truck traveling How long will it take the car to reach th5/sov+ o4hfhg ird 31cl:*hx te truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a taifv)-igoax ka0fi-( hk9gb z 8(lwind that boosts its speed to 990 km/h for the next 2800 kif h 8(k9vog-bxi0a- a()fgzkm.
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-fks, eefk9g(+b- hoj average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-f-b j9s , eh-ge(+fkokhour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the (p76bgd(kt yr v0ic t3pins at the 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 h0k dp3iybt(7t6gc vr (ands. 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 l+w j( ro.qssc ld4./sw 1qzx-3df5djin 6.2 s. What is its average acceleration in+s-fd(q4 s/ cjljr.xw3szw5.o1lddq $m/s^2$ ?    $m/s^2$

  A sprinter accelerates fro01x*.mzpuc.73 kdzx;f tav bvm rest to 10.0 m/s in 1.35 s. What is her acceleration 0v3p7fkz xm1adtb.uc x.vz;*
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable jtr7;+l;g70ngop ol lof an acceleration of abou l rlt70pgj7;o+o nlg;t $1.6 m/s^2$ 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 i66iwwza/tqloh- ; 6y mn 5.0 s. If it then brakes aaytlwizhow -6q 6/m6;nd comes 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 s. :j0b)d:* wzbihpo nutarts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a fun.wdnh 0pjz*: i o)bb:uction 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. What was its acceleration? How5(h5da j(v(jlo mxs:f 59nv8 uzy.h vb far did it travel in this time? Assume constant accelera9jn5bvs.h5fuy 5m(( a(h:zov j8 dlvxtion.    $m/s^2$    m

  A car slows down from 23 m/s to ly)+xa -qc mu7rest in a distance of 85 m. What was its acceleration, a 7cl+-amqxy) ussumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for jyao uhdi i 6,(0bp7z(takeoff. How long a runway is needed if the iu(zo,b ha i7y(d6j0p (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst ou-id p5 zttn 5lm8ik:t/t of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that/zld -n i5t5kmip:t 8t speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s te , r2p n8ul 9ety:zun5+,lbwgo rest in 6.00 s. How far did it t t8uuep w,yg e 9+25rbn,lzln:ravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. As8r k/6q(6qlz y7qbswnsuming a r7sqw /l q86zyqkb6 (ndeceleration 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 eg m*la (;w oibfn6mtu(:(h*land of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi ona*6ngiw*a m(obmt(ul :l (;f h? 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 distancesec9 f3 p3f1 ivxkydh 30gs*n:b for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for 3 h vig310scpbkyfe3xd*9 : fnan acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distanc+c;bdr,: 4 ykgh3dbrfq5e bl4e of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. Thz+; - wvr5j:n1dfjf ,gi+ dojxe car’s driver looks for an opportunity to pass, gdr,vd-j 1nzj5x i: +og jff;+wuessing 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 1s8c j .eegno:)h nly*20,000-m run in less than 30.0 min. After exactly 27.0 min, thercn 2g8nhjlys. e*o ):ee 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 car5 hre7fx32mbn1n36 nwrb)ux e 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 intersection before the 7 nx uw63b)nrf2eb1rhm53 enx 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 wd0 )imc xsr+sr7cy (,4a y.dothe ground below after 3.25 s. How high i,c4+ dy .m0 yrx)a irswo7(csds the cliff?    m

  If a car rolls gentlc7)/f 3f, 7x. fezvhklakcph3y ($v_0\,=\,0$) 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 :(vzak(9k: e)va ib jnstraight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after pytei *e2nox 0 we7:pm f)q0g,throwing it vertically upward. With what speed did he throw it, and what heigf 2ew 7*0), n0ot:xmegipqpyeht did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest an0fj 2c bjl-q0nd falls under the influence of gravity. Draw graphs of (a) its speed and (b) jjl-0cq2fn0bthe distance 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 4rv ab:b5 8qdxa speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the h5 b:av8dr b4xqelicopter’s.] t =__ s

For an object falling freely from rest, show that the distance travelrmrwdg;w *;cbd ,mo3f+q v9c+7e wzt3 p .9piqed during each successive second increases in the ratio of successive odd integers (9tg o im w9p+z;rmq3dc*wc.,+w vpqdb;37 fre1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicao3 hm;ybofwh0t6 k1 v+lly) that a ball thrown vertically upward with0mw v+hfobk toy 61;h3 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 sp3tsew 0 0kjqc:4s34 o ,ckdx-bk5 cbaqeed 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 numrkgxvt + ks,jf/ p.rf;u: *0vdber of photoflashes per second). Assume thvj,+t x;svff/:r*ugd. kk rp0e 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 wphammb(/o7b1 uk2m 8kindow 2.2 m tall (Fig. 2–32). From what height above the top of 27hpmb8 m(ak1 ou/bmkthe window did the stone fall?    m

  A rock is dropped from a sea clif.6nik; 03pbauiw4lhp wmun39nd,- qe f, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is .nb0i u ;d,i 3nwpq3 kpmnua96 h-l4ew340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard jn,do f6h1; l0/kz8 zk) ktq,jfad g q+y;gnh;stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fiz ;,d d6kj hy8f0on;gtk+l)n ;kh 1q zagq/fj,g. 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 nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge s5hoq1.+ks j bof a cliff 7khj.sob1 +5qs0.0 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 witc.e ;5-bjrqus h a vertical sec .-j;5busqr peed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the vam ,/1jvm;ekc3 d2v 7aeaob z.elocity of a train as a function of time. (a) At what time was its velocity greatest? (b) Durinj;v,kcz1 v/ ad ab3om 2me.ea7g 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 tus3 poscnf 5 0-osk60ntncv3j 0nnel as a function of time is plotted in Fig. 2–28. sp5oc0j fs6co0t30 n- nnk vs3What 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 accelerate approximately as shwgjdaunm /kuh153 * k6own in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve rk5 d k3wgjnuh*ma1/6uepresent 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. vf, mb2ef1s fs,ru/3q2–35) when it ,fuvq m3 b2,serf sf1/is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the obj2ctuo;+ tc z3rect traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functioef4 b;pz+g)jvxd c6 4rn of timx d) epb4jv6g;c+4r fze is given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an oc.s3i *v74b9mdsl jzcj +v.ysuyv 7 i8bject 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) su.8 7svvlj7iim4v9.+zd c3y bsyjc*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 window 15.0 m above a firntir)8b ijzw8gsko. (o -62z yefighter’s safety net. The 6ky)(sjzi tng8- wo.zi2o 8brsurvivor 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 gravityku taoeckm+5*+v44 jveoc)qf3 k*l j, zpi)+w on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many tia )c)4*u+vk, *wocjtli+ voqzp4jkfee5mk+ 3 mes higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrainv (eqzd4le.h-ed by an over-the-shoulder seat belt has a good chance of surviving a car collision ifvzhdeq (l4e. - 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 aiz 1*3 h2 +-6xvde0esb:csank lxgw,d bridge, 12 m above the 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 i:ekh g2-061,daxc + x ws3dnl be*vszthe 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 ted+la*c z 9twu5sted its cars for front-end collisions by hauling them up on a crane andawu*t+zl9 d 5c dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels about u+4 .xjodcm/ g$10^9\,km$ 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 frm 9(ay.l w1-/vh f 8tsswpnn-mont of the train has a speed of /w1- tmpm(8vn .9lnh sfsyaw-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 as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving boa,,vk7zde,9go ,cw b arrd 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 wb, okedr wc7,v9,a,z ghile under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balanc8z;0 hh tbmgx8uyk 3()mdgc4y e the average speed of a train against the distance between stops. The more stops there are, t ydkm0mg yh84)gz8c;tbx h3(uhe slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall strg 4ifxd;05p t0 vl.whcp 4xd+oaight down when diving for fish. Suppose a pelican starts its xl4. ifg;+ptd0hdpxv 0o4 cw5dive 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? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is pla cuw,(xj,5;ntbrdf dy5o4e c(nned 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(ruo ext4y,j5wbc(;c, dn5f d 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 freight train traveling akihp80j(on s8 gwp zeqh 62/t(t a constant speed of 6.0 m/s Just as an empty box osi2e08(/qh k np gt68pzj w(hcar passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof ofpj e5i+mtq 0v6digz*s-y9 i qccvv0+4 a high building. A second stone is dropped 1.50 s later. How-dvyjq t+i0c95+sv4m i0ve6 g izqcp* far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial last+/k*/2mf tf wq gddo9oing ten laps. If f om+gd//ftokdq*9 2w the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a 8bvns ygr( bt19xkb0v/ m+(ap mountain pass as he moves at 18 km/h . At the botto 1p8g(y 9bvb( bs+0tk rmv/xanm, 4.0 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. T n*l* )d dxa:n/duc 2rdy)8sshhe first child can bounce up one-and-a-half:xn*d)8 c*usd) hdn2r s ylda/ 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 trcskg1gua l8rpl f4p /l+ka .7 (h.7tlqaveling 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? Se.1. paul 8kplrf74( sll+ak/gtqhgc 7 e Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with jo/(jwsspp ls xt4083w/i/zr d5y*c sa 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 ball during the thrl /s3s4ji5ypjs ox0/dc*w (t /8 pwrzsowing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleroaa*5w3poas,+ mrv (2g jr1h hation 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 patterm:p svr 0:j3)4f4crj/udpdn xn shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppos/c4up m0:)3xfsn4r v pjd rd:je 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, passed by a speeder traveling at a constant 120 km/h takes, 2)iz8t/ ;kuyefvdse offt8 ud;,eefzis 2kvy)/ in hot 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(rccq cy ,z;2 kg,rdsqe* mc5,; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time. 2cgecqz5kr( , ,d ;rmsc*yc, q
(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 vertd1uy z+lhmi+oxr/,dx3 tk qyo, .hz1: ically up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after y o1tu+ :,/z+,31xyzldrmqkdohih .x 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-faw /sdol84s tif) ln i1*sxi1ta-lvt3)lling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speel 1lfato*s/i3d41v s-8its)lixtw n)d be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send :l ikvj174fnj,ufv-:akt b1 0wu qgg;the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate ok:tj4fblui ;vaufg-17wq ,0g1njkv: f burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times fastertmm3rb/kx15c43txvs4 j 2f pa than Joe can. How many times higher will Bill’s 31xr /j2 kpat435f bcx4vmtm sball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground belo y5g-d-y lqo/kw you. You drop a ball from rest and see that it takes 1.2 s for the ball to hgo-dkq 5-/lyyit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of av5b+gdlb+8i2 j i k:wtq-.o va 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 dv idil+t q+b -wg5.2 vboj8ka:rop 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 and B yem:* z5s2d0nqkb,)ccyhmk 2. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the othercek 2kcsmnq2b)h y,0:dz* ym5? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?