Does a car speedomet jyd (isjcm,-3s*/akv2io hh2er measure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, givs.+ucsa et6r* 6:do ;ez0i6vy p8odnue exa+rns* stu 68zy.uc:v0d ;o6di ao6 eepmples.

When an object moves with constant velocity, doelw1ltaizlixwk(bjt* ( 48:; z s its average velocity during any time interval differ from its instantaneous v(l t*libzw8ziw4;:a (kj 1txl elocity at any instant?

In drag racing, is it possible for th))hr qjn4m5rre car with the greatest speed crossing the fini mnr5qrj)hr4 )sh line to lose the race? Explain.

If one object has a greaef i-t8us/o kgoyn54j.rvt-hadz 1-)ter speed than a second object, does the first necessarily have a greater acceleration? Expv tjn-g hr.--8auotz i ksdy5 4f1)o/elain, using examples.

Compare the acceleration of a motorcwcx-mj8c1: j:tvmz*4e uq5 yqycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 1 w8::ecmjxt- 54q*qv mc y1uzj0km/h in the same time.

Can an object have a northward velocity and a southward acceleratilog.2hdx-l+yqm4d ;auy9k hy(9 7upqon? Explain.

Can the velocity of 51sch/at v,-zhhoiwj8 4j2 qsan object be negative when its acceleration is positive? What about vice versa?-z8 4c1tj5 j ,oqws/isha hh2v

Give an example where both the velo kyt.at*g3e *;( i ewqnsyg8-jcity and acceleration are negative.

Two cars emerge side by side from a tunnyj un5p sma).3el. 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 an u.jm)n35 pasyd has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases?d;o+.eafptxoci, az h9xf ugc.x5*(1 If so, give an exampla +,xdpc o;a* ziho(9f.g.e5cu1f xxte. If not, explain.

A baseball player hits a foul ball straight up into the air. It leavesse(g ug99 apoei:q)s- the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when ts9geqau)( p-go es9 :ihe catcher catches it?

As a freely falling object n;z zkiz6sal d42-k 1hspeeds up, what is happening to its acceleration due to gravity — does it increase, decrease, or z 4l 1nz;6ak-sk2hz idstay the same?

How would you estimate the maximum height you could throw a ball vertically d;eqyd5/ j8yy upward 5 ddqyyey;8j/? 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 spea7upa8ngrblk 7-z 4us8 -w m4red 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 spe -akra 8zl48mrgwp n7bu4 7u-sed 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 wit* 8c-jz9pug,8tt7*(h+aqihzbemi q ph ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture jz7bt a -c qph+pizh*eit*u(8 m89qg,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 xuxn2+dar92 c7kv1( g bxr6lwat constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops alonbxdvwrx12 u2k n6(+ 97 lcaxgrg the way, a dish resting on a table?

An object that is thrown vertically upward will re1nefukv5:ipb kj066c turn to its original position with the same speed as it had in5jek fb6i :0u6pcv1kn itially 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 acceleration at the sayn-r o i2iik60me time? Give ex0r6i i ny2oki-amples.

Can an object have zero acceleration and nonzero velocity at the same time? G67 dnipapi 91( dppod9ive exampli9d61dnpa 9ipo p(dp7es.

Describe in words the motion x3;p exq76de mplotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplic pqxx36md ;e7eate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2j 4+ frg-pm: +6ccpqkg–29.

  What must be your car’s average speed in orde/ry0s x0 1udc,pxq ql4r to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How longp o7 4/gu,fiab does it take to fly 15 km?    h

  If you are driving along a ss/vp:m .hlfgq 36e us9traight road and you look to the side for 2.0 s, how far do you travel duringsp.9 /fhlve um63sq g: this inattentive period?    m

  Convert 35 mi/h to 6+ms:bn ,tld bx(myq;
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frlr ku*xz. p6z 4an801skn:g-abib/ pzom $x_1$ = 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 scp) lu zkzw :0fw57v:c ,elg8fphool steadily at 95 km/h for 130 km. It then begins t :f f5l l):c0 wpp,zu78zgekvwo rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flbx 1jukxvsf85; 0mm8n xit a2*ash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentim 088i;x*1vm5 s an 2juxbxktfally 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 quavel(46q)3v;tqj b5a0vx 9 x3z jr hbvirter-mile track in a total time of 12.5 min. Clr)b;39q x5jhi jqz4t(a 06e vvvb3vxalculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traiz1 :fku k6xu-35dgobv ner in a straight line, moving 116 m away in 14.0 s. I kvfb: u6o35gzxdu-1kt then turns abruptly and gallops 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. Each has a speed of+7819iv-mjg: tst plfc )szkc 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 oth9-j t c8p vc1sistf)+g7:zkmler? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How o 3d3p::npz d4gfetub .q/c n/long will it take the car to reach the truck?gd.d:3tnuofcpe 3b/ :n 4p q/z    s

  An airplane travels 3100 km at a speed of , agf t9or:42 sfnsubo:w,9j b790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 k,g4aj,s9buo 9n:w sbto2f:f rm.
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 comguowzofpvz0c5.2r; vx tw0( u19nt (tplete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the re 2 ;01uo o50tcn9 (ur(twgvfw.zvt xpzturn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hitsg753 2vnw4 uojes2.7 lzsda(nj* mlgn the pins at the end of a bowling lane 16.5 m long.n7* .4szwa7e 3mgoj25usdjl g2( nlnv The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its average tiq)ds*( 37. azq50nlyditofaccelerati y 3 i75l(tsftqi an0*o.)qdzdon in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleration sedntav rbl0,205.lz2yc y y7 tv z0al lr02snd2yey, 75.byc
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automob mp o,04 y+)ilwhkpcq9ile is capable of an acceleration of about m w9ly,)cpp o4ikqh+0$1.6 m/s^2$ 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 constanx8*o gd; gx.bzq+ad 5st speed travels 110 m in 5.0 s. If it then brakes and comes to a 5;8box +dqg.adxs*z gstop 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 starts from rest at t = 0 and movesf7p4oh7yyp2 zssaq( . in a straight line, is gszy7 q.ofp4s7yh (2apiven 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. What was its accelerat; mu 8q)4g;.dfphj rzbion? How far did it travel in this time? Assume coq j ;)8fu.4mdhpzrbg ;nstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to r imqstn0*av96 est in a distance of 85 m. What was its acceleration, assumed cons v0at6mqisn 9*tant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is n)i 9ti t.mbw-xeededt ib9wmixt -). if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spe)a uf/8srty.7oxg:3p08yas smqn8f w ed (of about 11.5 m/s) in the first 15.0 m of the race rs g8sw qyf .:f an78m/at)y0uo8sx3p. What is the average 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:hmoosolvkg aff 04p 6j 853z6 from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that time? 8oo6sjl5gp4 3k0:f6hvof zam    m

  In coming to a stop, a car leaves skid marks 92 m long ;mxu ,m k6njm/d8)kwlx/i1ffon the highway. Assuming a d,m j6d/kiunf/l8 mw);xfx 1kmeceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresgfqkgl -(f-l*z.a* bcses and the driver comes to rest after traveling 0. lla zqgffg-.bck**(-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 dis0 : bv-5m .w8t6yrqttfck4 v8; ocdgtrtances for a car with an initial speed of 95 km/h and human reactio.6-tcbfdtr v5q :gk8c;v8wm r0 tyt o4n time 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 equation for the stoppik hc34u/zx,s wme/w 8wng distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver lom,fmz6y ie4e-bi,ihwl oy97 * oks for an opportunit-4yyhe 7eibomm*w,i 9fiz,l6y to 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 complete the 10,000-m run in less than 30.0 min. Afgo e p-7-ql(zzter exactly 27.0 p lq(--zo7 egzmin, 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 at 45 km/h approaches ao hwb 1s k qx(d4 i(aj+t-57aisg-ptv)n intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s kw1tbg-aq 7xdip)so-+a h5j(vi4s(t before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the ts(r rx ws;wk.+op of a cliff. It hits the ground below after 3.25 s. How high is the cliff+x(wsws;rr k. ?    m

  If a car rolls gently g+ayz*t:q dr1 qyb.b.zq r r5, xvu7:p($v_0\,=\,0$) 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 airzqsdrv( ad,n-8u q7, l 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 throwing it vertically u icy m .tdn;9;92 cc:.vhyzotnpward. With what s . zvnc n c.ycim;yd9:2;h9ottpeed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw(z3 okwh k+t:p5x mo8h graphs of (a) its speed and (b) the k5+:mtpo 8 wh( kxzoh3distance 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 0y9a8l+ pmft ;amjd ei2almkd:c8f:. of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a +::f2pm 9a .tf8dyj;ie0dm8mkca all window. How much 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 the digw+5wyu,n ji 3stance traveled during each successive second increases in the ratio oi ,+nw3ju gwy5f successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is n0 immk0).slmopn, mp4yx2x- peglected, show (algebraically) that a ball thrown vertically upward, pp.poxk40l-s 2y0 i) xmmnmm with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upwa35p)mevhc wi* rd 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. 6;n j-mel8osz;9fin cdw)y54g-ozd z2–18 (or number of photoflashes per second). Assume the apple is abo4;w-e 9y zig6sj zo)m8f5dldonznc -;ut 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 wiw,g/qpmqu9srknl(0 bdv*g5 3 ndow 2.2 m tall (Fig. 2–32). From what height abos bv(*q5mr ,ng/u09qwkd g3plve the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and3abiym dnx. :vtdk1y d4,)td, the sound of it striking the ocean is heard 3.2 s later. If the speed aikyy.td,v)dt:d d n1,bm3 x4of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You pofayvotf2 7 ,wnbtn.28int 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 speed7,.2no8t fwnya2f t bv as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed t)y5g:tt8 bxd of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34). y8bgt dx: tt)5
(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 wij s; l q lig*z(1e+pgtc,m;v1/wvvu n)th a vertical speed g(s nl1tw;z*1vciqu/lpj)eg, +mvv; 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 velocity of a train as a function of time. (a) At what.mdr c+g3 *xfwyie2 3q time was its velocity greatest? (b) During what periods, if any, was thq3 xd2yc we+fgi3*rm.e 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 plot.q6aspmq r5lij5. xl; ted in Fig. 2–i5q. x.5ajmrq p ;lls628. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as show t m6zke,lixv+s. qc-dr00um 0n in the velocity–tix00im,mu6lc+tkzqde 0sr- v . me graph of Fig. 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 . n k0dt/ztjjr (knc95m(8 hrm(Fig. 2–35) when it is .(m9 mnn 0 t(zr/dr8j k5htkjcin
(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 diss6hh-iw+.kfkj;+g b fizfvajj,(z : 8tance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose disgj (5 1eil;y: yp2s5tp1mo.tyt2bpr nplacement as a function of time is given by plg:mitbp1 y yjoy5 15(2e2prs .;tntFig. 2–28.

Figure 2–36 is a position versus time graph for thetpv4m4m gig:lbqm ;o.c( e8g. motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive ;. g c4eo8p.: i qmmgt(mvg4blor 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 firefighter’s safety nem5 )2c2 xd vbuo;m(ebct. The survivor stretches the net 1.0 m before cocvbbomd2cue ;) (m52x ming 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 gravityxn;yx o,77loejg- i9 t 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 i lxooy-t ;7 n9,exg7jhigher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by 6xx q)8kx/oo d-8il x3w3dai pz7 lxo/an over-the-shoulder seat belt has a good chanq a-p3 o)k/ o7xd8xw8o3/i xd illxz6xce of surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a dt msj2v9rw 48u0cvw)i.ta g 1bridge, 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 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 shouldwaw2 .i91gurv)84cmj ds0t tv 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 collisions by h 7a:.b k//q8fiq ithqrh5*gw:zc; olb auling them up on a crwtkh5lzb;go.r: 7cqfi/iq: h*/ab 8qane 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 +5efzuy .hflp x74gf5about $10^9\,km$ 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 of the+*v8e65 zzgpyny 5w2 wpohd 7r train has a sgzv 5wr wz7yp2+y85en hd op*6peed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car 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 s,9*lhilz 9gt.ys-dwx urface 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 while undszgyl -wxdtl,* i99 .her the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit sysyu uav9q3k;6 xw9f-gu7fj, pitem, 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 train to make a 9.0-k uxff99g;i63 k,py-wv uj uq7am 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 frey:m 98ls apgq(1kpu kn2fex aqc0,;e4 e fall straight down when diving for fish. Suppose a pelican starts its dive fromm 1kacn ,yep aelgs 04q 98kfxqup:2(; 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 play)wy x)+whzg5 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 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 decel+gwyhz5xw) ) yerates 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 at a constant st5eit k+. nm)pl6sdr(peed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceleratetp k5(t nr6emds)+li. s 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 stonm60uj u;p)pr,m vdi1c e is dropped 1.50 s later. How far apart are the stones when the second one has reached a spiu ;16pcmrv,0umd p j)eed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial la cd9x rhj*pd;j /5/xfysting ten laps. If the first nine laps were done at 198.0 km/h . what average speh c/j*/9j;f 5 dryxpxded must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests apq lufk(p09p+ dz 52xwca08lma-0 ahm mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his averag p2d5 lq -p(h0 wk8xmuplmfza0a0a9+ce acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The firstv8 qhjs /gh/ zz):t ar4;tckh+ child can bounce up one-and-a-half times higher than the second child. The initial speed up of the sech:r 4;/hc/)zt v a8gqzjs+kthond 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 traveling in thet uxnah*l+h ,bj715ct 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 Ftn*a xc5 +,bjhlhu7t1ig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing thexeb/k +u2u,f zzn2km8) y mq.j baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, fyuj 2fkn) bz.qk/8xmu,2m e+zrom behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from resnl,9w) h2 1 ix*v/on,zjtzce ft, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42.irhyq2w /31b s Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are drivwqs3b2hyri /1 ing 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 trave:v.pzl3aq/ quling at a constant 120 km/h takes off in hot pursuit. The police officer . p3qz:v qula/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 build,z6 lne9axep-,lye o :ing; 2.00 s after that, a second stone-yl,e: eao96pe nzx ,l is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same timewag/) o+yc8fqdz6-u z. The first stone is thrown qz/ f+uc )ga6odwy-8zwith an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second 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 wouldov e ;.(8kwbu/xoj ts, it take a free-falling parachutist to fall frex ukwoo,.v 8jb t;s/(om a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belu cfx:u-j+y6t t to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spacy-j c t:f+ux6ued 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertpya-td4vx.slprn 9 -9 ically at a speed 1.5 times faster than Joe can. How mt4 -y d- lnvs.ap9rp9xany times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a clifmz)lq p6m +/.che v+ww hxysqc/bm9v;+* cgp4f 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 to r+b / evpm4*p+y9hv+c; sqzgm)/.xqlc hwcw6mest 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 aekx7t.8ex,y building using a barometer. Instead of using the barometer as an altitude-measuring device, they ta78xa t,xeky e.ke 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 positionj,:63 w yr5lkedr0ugr (w/urf vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bijr rw3/6lfrgy, ek(:u r05uwdcycles 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?