Does a car speedometer measa7pvop1( ry.wvirxobdyy 9 t6aya),/ 6( d9vh ure speed, velocity, or both?

Can an object have a varying)-x,44bwns7 lw dfwq6avnv8n speed if its velocity is constant? If yes, give examps bd87q fw4nxwl nn4 w-6v,av)les.

When an object moves with constant velocity, does its average velocityxpso2 8l2oaf4v4+qqh c hu,(l bnm5+2cvil*h during any time4mqovb,l 8hvxi*phsql+c 242 2(h cf5l+ouan interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the cae 560k ztgloo*(*coaor with the greatest speed crossing the finish line to k*( *5loe zt a0g6cooolose the race? Explain.

If one object has a greater speed th l:xnjk;,;ftp an a second object, does the first necessarily have a greater a fk:,xp; tj;nlcceleration? Explain, using examples.

Compare the acceleration of a motorcycle thhixye9j c8 9m)at accelerates from 80km/h to 90km/h with thec8ij eyh9)mx9 acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a north9ou 4bdi- c7yeward velocity and a southward acceleration? Explain.

Can the velocity of an o/uu1y cels5ae5/o h,nbject be negative when its acceleration is positive? What au/nyslao1ece 5 5uh,/bout vice versa?

Give an example where both thdrtd:+ x x1,movdqb,5e velocity and acceleration are negative.

Two cars emerge side bmto*5k0 u sjk7k6d.asy side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration m75k sd0j * t6sukao.kof 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increax7 nk o pq8:e+ zmi17lm(ij2hk2d b4rusing in speed as its acceleration decreases? If so, give an p+7(8inedzu h:kx i j42r qlom7bmk12example. If not, explain.

A baseball player hits a foul ball straight up into the air. It-ipp8h6pln4jj ern 6, leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the6ejp4jp 6 r,iln-hn8p ball be traveling when the catcher catches it?

As a freely falling object speeds aeg (a-ym y96o( b;kvf1 e:eihup, what is happening to its acceleration due to gravity — does it increase, hm;ai-e9 evyobya g:k(1(ef6 decrease, or stay the same?

How would you estimate the maximum height you could throj((mkgr2o* kk . .z8 nmd7mg 85 e4agiyummuk(w a ball vertically upward? How would you estimate the maximum speed you. zd(ok. rn mygkkg7*8jm i e8m2uakm(u4g(5m could give it?

You travel from point A to point B in a car moving a)1 jt*ks . q mweyi.az6ty4w(pt a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Exp)z*ai1twk 6 ( tp4ym .y.qejswlain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tiea-31 npnr7hvhd to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end orn-hhv 7ap n13f 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 falle7 riu p:k(y-t-coa 1 ppcs2b36( bdhjing from a cliff, an elevator moving from the second floor to the fifth floor making stops cac3p(7pbi6d12je:s -yb - hupor(t k along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original posi4j2l vmy5*uf, zg(.p ,pg*nni0j xh pftion with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: 5 0nlvzi ,fjpgfgy (.mh 4n x,*ppu*2jThe acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero accelq(,q 5sq 2a5 qkw0ysbeeration at the same time? Give examplbq(qk52 sq5e ,w ya0sqes.

Can an object have zero acceleration and nonzero veloc6rbn,hz:il 333 s+ bz*1nm i srpq,vwdity at the same time? Give33r:qi*r6, p,bb 3h1ds n+vliw nmzs z examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. 2w+krdo*vznfs a9*2* rv- bbw[Hint: First try to duplicate the motion plotted by walking or mozd2+*2owv kna*bv*f rb9w -srving your hand.]

Describe in words the motionu e a *89n8nymxxxmx23 of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travw+f2 dtc)gkt ,el 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h s:zo34j ikm0jHow long does it take to fly 15 km?    h

  If you are driving alov(s lagzl3j (/ng a straight road and you look to the side for 2.0 s, how far do you travel during this inattentive period? l3v(aslg z( j/   m

  Convert 35 mi/h to piwryg*//jsd;7//ncjx- 0 uz1fi.pt dd wi(g
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves kz+kv2d zgi): from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home f/msp(hb.ik ;orom school steadily at 95 km/h for 130 km. It then begins to rain and y./p mhib(;k soou 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 lig;p/fw7 2ae g4 aexp4/;p uagdghtning flash and the following thunder gives the distance to thpuw aedgea;px/af 24 7;pg4/ ge 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 complete laps around a quarter-mnm679ay dgerqlg; u-b+v.pr54gk f5iile track in a total time of 12.5 mina6vgnq g-9 d5r;ig7 by5p4rk.e +flmu. Calculate
(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 in 8zwsl*wwkr; 7 14.0 s. It then turns abruptly and gallols*zww rk8;w7ps 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 0ps;a:;*am1ysyc s n8nf- ma ion parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they rsnsnpa:-m10 *c;a8y msf i ;yaeach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behinpnmajtc d6 ap47 sq90dvd89u:d a truck traveling How long will it take the car to rea7 dq89js0np94ddcvp atm:a6 uch the truck?    s

  An airplane travels 3100 km id-ziu)7 cjs: at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 k:jzii)d-cu7 sm/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 averagerdi ,( p .as:*xi0ecti speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed bx,p*ceia.itd(i:s r0 y a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hak. ,yg62rgry3 bwv4z its the pins 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 rele4,zyy vrkg.gr wab6 23ased 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 tod(mm,r* hoz8q 95 km/h in 6.2 s. What is its average acceleration ioqd r,* 8z(mhmn $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelhw ;ad4)x:mga 13bxv1x 2 zmmgeration 2d1gx4 m; w)b:gaz1hxax vm3m
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a partick/r;el5 ln,gxular automobile is capable of an acceleration of abouln,e; 5kxrl/gt $1.6 m/s^2$ 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 in 5.0 s. If it thcrh u6 ax35oqcpd2 iasa1n0:0en brakes and comes to a stop in 4.0 s, what is its accp 3 :axo05r sh 0ucaadc12iq6neleration 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 9g6llf)- rw uivfiqm 8zl:98cand moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) 89 lli-rwciuf)g m: f8v6lz9qits acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25utj1axwt)e) f chkk-7: -/ghd m/s in 6.0 s. What was its acceleration? How far did it thxt7/ g1w : )ctjkhu-- fed)karavel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Whatt: h1:mbh r)wk2 0ea:rq /osvt was its acceleration, assumed constaneta0) rh:ws:q mkv1r2/ot:b h t?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takevq(krn z tr3nom+b9jh4;9h8k off. How long a runway is needed if the (constant) accenrkzt9 843onv+hj m 9rb(; kqhleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (ofavo2xhfk.z+ 1, b -f gvg6dnu* about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how lg, 6z-x vh+ 1 o.n2fvadb*fkguong 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/s59m0sd 4 obdjt to rest in 6.00 s. How far did it travel in that time? ob45msjt dd90    m

  In coming to a stop,iezdrsi )6c/b6pd,)w a car leaves skid marks 92 m long on the highway. Assuming a deceleration ofs/c,pii6 bed) 6d) zrw $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The fr9f2lt( a2ox2u ,vlkb oont end of the car compresses and the driver uk b ,2oa92lxft(l2vocomes 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 spee5bl-0 l .jdx:8o-)f 2bgnxop 6zpgimsd of 95 km/h and human reaction time of 1 8x- :j0 ix.dbbzmnoso52)lp fpg6g-l.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 stoya5: 8zm;nzts cwn* ;mpping 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 3gv 4 ja6q5hojqzj9rc9zq*3jhighway. The car’s driver looks for an qjgchq4z6r5aj *3o 3q 9vzjj 9opportunity 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 50xa.w(01ed:oo nuphoe n dh .less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acc0e(o0. :a .o5who1h uxdpdenn elerate 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 skd 3.z.y/ kp6p+cx53au chesas 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 .kyhp d .cxs e5z/pa3 s+ku3c6to 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 fro+4u79mqsxa;xf bsxsh2t4j9y;/za d tm the top of a cliff. It hits the ground below after 3.25 s. How daqbs 74+ tjmz;xx9yhs49u; tfa2sx /high is the cliff?    m

  If a car rolls gentlh h c;uz37h6xey ($v_0\,=\,0$) 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 uv bh g2e+;ymx( y/,bt9zy9qy9nhqn5gp 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 afteri,wrw -kq*l2 n throwing it vertically upward. With whatw -r2inw*lq,k speed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest -0gcwf(sr5yn and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fall5-0( wsfnrgycen, 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 r 1/rf lhv6:bj5.20 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 helicopter’s.hvjr6r b1:/f l] t =__ s

For an object falling freely from rest, show that the distance traveled d yqr+/zro i5o8uring each successive second increases in tz+5ri/oor 8yq he ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglectcp.diom*68juqm re, / ed, show (algebraically) that a ball thrown vertically um de86ipr,o jc*mq. /upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically tkz -i h h yov79e:adm8p(nk7:ex4/v)ngm8j h upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple1bpid4 ))snjut1mu6 v in Fig. 2–18 (or number of photoflashes per second). Assume the bj)6pu) tv dmisu411n 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. csq4y ;xua8sr-y +4 qgq)dn2u2–32). From what height above the top of the window did the qd2y-nyug 4xqu8rs)acs4 +;q stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking tkn) q17l2-ztq reed5ahe ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is q zdt52lkre)1 ae-q 7nthe cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard strea x ;qs (i6t*sh0f1iwm0y mduw*m 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 th0*6 d;q smi y0xwsf(1w* hitume 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 fr yz(k6 x7 d6rox6kyrz lr,y57rom the edge of a cliff 70.0 m high (Fig. 2–34). yx, rx7zr6 6y5rlyr7d z(k6 ko
(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 )ztfm;-e6 knc y6nah( y3t.dnrcn2+lzoz+ *w by a window 28 m above the street with a vertical( 2hzltc)rdaonezwnz +.tk63-* + nc;y6nfym speed 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 of4e58/w5zq rqsbp +ee1-w stst a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the aww4s+btqze -etq5s85s r e/1 pcceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time g/1mp) pfsri2 is plotted in Fig. 2–28. What is its instanp i/12g srm)pftaneous 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 azm,b.7 py6vfkccelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the 76y.mkb, fpzvgears.)
(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 averageloksope-b8-a 2w c 28a acceleration of the car in the previous Problem (Fig. 2–35) w-lp sb -8c2owa2o8akehen it 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 dialyla:x ,.f* istance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t ur8 y9l4fmk-w graph for the object whose displacement as a function of time is given by Fig. k4ylf8 9w-umr2–28.

Figure 2–36 is a position vers1kjhy;yft *0 )m*crcgus time 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 )01hjmcy;*cygtk r*f 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 firefighter’su+lynj(z4t8 bk frs:/4 ftsm cv5-;le safety net. The ske8 4yvztlb -sjffltu(sm 5r:4 ; cn/+urvivor 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 gravity on the Moon is about one-sixth what it is on y j/fyxg zs :gc,g6.oizp5g; e9d3 td:Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the spjts3gzgo:i56:; g xdz,/y yce.9gf dame initial velocity?

  A person who is properly constraine q76e.kocu7yf3 ;a5s ljylnw2d by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration dfq ykaely;2n 7slju.36c57wo oes 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 (j6(7mi nflvkon a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approachingfk( vminj7l6( 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 be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufard*x r(z8.hohet8l9v cturer tested its cars for front-end collisions by hauling them u v dxh8o*r h9tz(r.le8p on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth traveli.aq x+ieyp)p2j 9gy)io9 jau6* dv:z s about $10^9\,km$ 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 acceleratiymnd0nl//k w 6on from rest. The front of the train has a speed of 25 m/s when it passes a railway worker6/y0/ nmwl nkd 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 surface into a deep (2x-cogbg 5z.y u5n zsyjcg ))pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the2 gy.sg5c 5n)z )xoy(cg-buj z average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, ith n nblu-6+h4idcqcpj a8c3j9o9ow7+ 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 pri8 +wo lc-o qaj+ 74h9hn nj6cb9dcu3poblem, 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 straight down when *cfre z+ xk63ndiving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path onc fx k+cnze*r63e 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 planned soqgsi*+3 .7v fgczw3ats s9zg 8 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.8c 3a7f3gw+9.s gq svt gzizs* 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 friwc2x9 -:lwuyd d+ nzm6p1d5s eight 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 accelerates at :pdzimd2-l y9wwx1n c+56 u ds$a\,=\,4.0 m/s^2$ 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 secon(f:jbkdhah4tu9 7 s;q d stone is dropped 1.50 s later. How far apart are the stones when t ;(jkuf 4s9:bqdah7hthe second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h ovek) roxb+pe-xj i7 -tw7un. sbj i30nu4r the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average spee7no bb0 4pu.7ku-txnx )ew-is3 rj+i jd must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a moun *pd0lxl3gd9eklf5wt1m,2*p mgrxs -tain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed,9dsp50t1l* m w-g*exfklp l3 xg2r dm 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 trampoli43o,t,/: l- +ljy zmgiznxu hnnes. The first child can bounce up one-and-a-half times higher than the second child. The inlzou,tjz+:-m3lxgy, inh/ 4nitial 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-lod : 6scmsab40fng train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the cb:scmf4da 06 sar 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 basom d57uc;ihwchn7dtbl)m 5* ,eball 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 ball during the throwing motiond mt5* ,7 )hwnb7m; cicu5hlod.    $m/s^2$

  A rocket rises vertically, from rest, with an acc85 thi .s exw-c2g5qhpeleration 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. Each intersection hl qsurbii +8v pribx -4580j1 qj9tsf,as a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. Whejil9rt +ji4 qq88vpi0s 1bbxr -f us,5n 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 tag hb;kb-j b7kj9z.flsmpn5r f:k9,7 kkes off in hot pursuit. The police officer catches up to the speeder in 750 m, mai,f;n.k:kgbf9- p kbh z95b7rsjkm7jlntaining 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 t ,-kkg;lw321thyhuv .00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones lawhy3h1vt,l - gtk;ku2nd 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 time. The first s5iwlo t2:s gg9tone is thrown with9 t ig5slo:w2g 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 resistad m+ f(fus ; otr63q+b -,qbnnw8xj)wpnce, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altidf(f;8q-+j+ ub n) ww q,xs3prmn6tbo tude 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 use9u3iq bzym 6u0pok:,b s a conveyor belt 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 spaced 15 cm apart, what is the ratikbmo69q u3p:b , zy0ue of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verticall20tehj n tjz:r0nq0 v4lt8bu7 y at a speed 1.5 times faster than Joe can. How maqnj20 r 0tz4ntl7t0j: vbe8huny times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friee h1qc: ma6w/gnd stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest i: mg/ qc1a6hewn your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the hy2 1u9h3-byr1aax xn neight of a particular building using a barometer. Instead of using the barometer asn2xaa91 y1 3xu-hnbyr an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) Is gmcpq+u-qk0coe :f81there 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 other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher av g1+0oe8q:ufpc qcm k-erage velocity?