Does a car speedometer measure spu bk8gf(ge.; f: +tgxoeed, velocity, or both?

Can an object have a varying speed if its vel c(dkpryf p(gbqe6/95ocity is constant? If yes, give examplesrgky pf( (d9e pq/5b6c.

When an object moves with constant velww6kq v/i1gri 350gka ocity, does its average velocity during any v5r1a6w3i qkwki/gg0 time interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossupfm*-7-qi+2b c l/prl/96dvs tqzd ying the +/p z 9-q cf/p*mbl-2ir7vd6sdlyt qufinish line to lose the race? Explain.

If one object has a greater speed than a zt, to1vrtj 3xfn*vc(q/ ,3tjsecond object, does the first necessarily have a greater acceleration? Explain, using 13q3(jtz*c tvft/ jr t,n,vo xexamples.

Compare the acceleration of a motorcycle that accerm- /m l;20pil7 icbszlerates from 80km/h to 90km/h with the acceleration of a bicycle thm7lrsmilbcz/0p ;-i2 at accelerates from rest to 10km/h in the same time.

Can an object have a northwad0tf ;d dx0uk3viz-u 9rd velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its ai gmt -6zuh/o91 rdpy* e;-vizcceleration is positive? What abo- id 1*uev9o-;gytp 6h/izz mrut vice versa?

Give an example where both the velocity and acceleration arr ecckor01v.0e negative.

Two cars emerge side by side from a tunnel. Car Aw *xom;9z bww7wsj )x; is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed ofwx7z s w9*) ;;wjmoxwb 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 increasing in speeda +u: jnloyzve)n(h 9j7(azz; z5si-w as its acceleration decreases? If so, give an example. If not, explaisy7(j )zozanz:(wj9 5z;l+-eia h vun n.

A baseball player hits a foul ball straight up into zmgn /,-+s/ smssdd: qo7-iscthe air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how f /ssz /g7,qs-omm:sdn+i-d scast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happeni 98:gvaa8 zqnri0 u9vzh/ 2nhxng to its acceleration due to gravitzrq9avhxi:88/9vn2u zh0n agy — does it increase, decrease, or stay the same?

How would you estimate the maximum height you c pna2 (hd-g;u+ykjs+ uould throw a ball vertically upward? How would you estimate the maximum speed you coupkyu-j2h gs; (n ad++uld give it?

You travel from point A to point B in a car mwjun quqmnw7,e3 )x* 4oving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your averagejw e*7 ,xu)q4n q3nwum speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3. x), r+e/ xfvkhxx5iv90-m-long vertical string with 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 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+rvie xf5,)x xhvk 9/x the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration:.y(+r w1,thpkp k hhz2 a rock falling from a cliff, an elevator moving frh. kkpty+ rz,1pwhh(2om the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticalver:18im ;y cnly upward will return to its original position 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: The accelera;mv n1er c:8iytion due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleratip2 snpk7ko1y )gttk+dg7el s 5;u1:mpon at the same time? Give exa2 gk5k:ou +myp )7pn7elg;k11t tps dsmples.

Can an object have zero acceleration and nonzero velocity at the same time? Gxqxty 4jgsw)n sw5e/u8 .+b q5ive s/ qx8nx5bsjt+q 5uw y)e.w4gexamples.

Describe in words the ms qgs 0 bhfzd27:g)fk5q+b z7ootion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or movin7dbqgfs)z q0so5f k: h z7b+2gg your hand.]

Describe in words the motion of the object graphed in Fig. 2–29;mvxq, wp9 1qll(de2oum3- h d.

  What must be your car’s average speed in order to travel 235 km in 3.25 -s*n30omtg flg 3 u.5qnxm ;;wkk b(ngh?    km/h

  A bird can fly 25 km/h How long does it takeqwez0odo);t* wqg-l ( to fly 15 km?    h

  If you are driving along a straight road and 1g(cy .egolpy vr bx.09fl,(n you look to the side for 2.0 s, how far do v 1rpncl ((gb f9e,0l.gxo y.yyou travel during this inattentive period?    m

  Convert 35 mi/h to ym.0vfe5p2fq3)khgfkpb;3ld1 mn 7j
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from y3 ohyymx(0)g $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 kmser:8nlw tld:yj 0m3 q6dn3o6 /h for 130 km. It then begins to smq3 tl36:8r6l : wdo0jdynenrain 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-n z)euj9lsd06 +ye,cxof-thumb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s fromdj096yu)ns, cx+zele this rule.    m/s

  A person jogs eight complete l7arzti3 e rmu/ /wuyt6* j/q8eaps around a quarter-mile track in a total time of 12j/8y3azr7iq m/u wue*ter / t6.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a stramez)g0 *s* t xg. 2v*p0sztvnmight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 stxm0 n z *sg em)0*.vgp2*stvz. 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 spee2m;zd : emo:u3c*kfb td of 95 km/h with respect to the ground. If they are initially b; mt2mz cu dkfo:*3e:8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck t8*a* s-apcqi cu71ayj)z.j r/knjf a*raveling How long will it takenkaaj .8** afzqi 7rs/ -ccp*u aj)jy1 the car to reach the truck?    s

  An airplane travels az8a )6a8(r+hv+ct3p ykmlq m3100 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 kla6c tq+v 8kya ( 83a)h+pzmmrm.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-trip in(*ad0 tw,zwzyt 3 dfr) which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the retur a)(3w0frdz*t ,tdzy wn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed qj9k /id)y0uia2mg5s hits 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 released fro5yjik d0qi) um9 /s2agm 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.(qejlv3q i02l )b6zra2 o t4tr2 s. What is its average accelera2l otlr3zrj4)iba( 2t0 q e6vqtion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleratio nf7o p8oyf67*k:yezany eyofzk7*6: nfo8a7p
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceler9ih7 lj s6yu0l4q*mq ration of about s4i *l6yjm q97q0urlh $1.6 m/s^2$ 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 95 c0dnwurge( 1o1kvd constant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, wg509c1 vwd dno(ru1 kehat 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 racinyzgo, p:;zyz(*f2.xs fhe 8lyg car, which starts 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 functizx( ep.; y:g h2,yyz8lfofsz*on 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/l-4rvxa3 z kt acceleration? How far did it travel in this ti/4rz3lt - vkxame? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Wha v/px/tb*y2fh.ko8 epdf93v bp0 6pxot was its acceleration, assumed con9b y0k ovd6x/ 38pfpex b v.*othfp2p/stant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is neeg:xty :-fa5aokenp92 ded if the (constant) acceleration f5a p :a-x2tyo9k en:gis $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed4m.; zp8kmnkhgoz +e* (of about 11.5 m/s) 8h oek g4+knpm.;zzm*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 speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed ohb i85-i:cx sif 12.0 m/s to rest in 6.00 s. How far did xibcish8 -i :5it travel in that time?    m

  In coming to a stop, a car leaves skid marvqsp0vq:og(if4z4y k .jmoeh)r 471 bks 92 m long on the highway. Assuming a decelee40y4ozq(4 krs jp.q h vbf)gmov1i7: ration 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 ww2aj2sgy-t p0p5l h8 tree. The front end 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 on? Express the answeyw 2lha8wj- s5 02tgppr in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 km/hy*r+7 pqz1nd+s(earo 2f qf( o and human reaction time of ofd+syq z 7 2p1+a eo*((nfqrr1.0 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 stopping :,qqtw-g(p9 x*lt ynwdistance 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 2552: qxfe6movr m/s on the highway. The car’s driver looks for an opporfq e v2rmo65:xtunity 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 tha udmn c6*ig) 9y: ei)m) ivv)jho;xwn7n 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at 0.:97x*igj mywhni;c e do6 n)mv)i)u v)20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as the;-/tx3xd/f rfvroyj cbke 466 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, ort f6f;oecrr// x4dx vjk 3by6- 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 top of a cliff. It hi5 ym ohuu39)eo p:/9xenn,lnrts the ground below after 3.25 s. How high is the cliff:n/3 n)e 9e9y rxplomh 5unou,?    m

  If a car rolls gently o(nzbr,a1 el)be 7j6w fos6e 9($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of 22zp;g,cd(s 5g k 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 verticallj)w5k xvd-:ufy upward. With what speed did he throw it, and whk5v)dwuj: fx -at height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rey c tl4*h1ttx9c(fy0w/fkrj q.5vl :cst and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distanq l 4.f v0c1c*9ftj(y5rwxlh/tkt y: cce it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending verticallyhq8of+9 l dlzaw3cl ), with a 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 doesw l z,+laf)8lh oc9qd3 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 tha(8f 4izp:2g3nsywn dks /8rkl t the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This w(lf2kw/n 4:yns igkdr8s8pz 3as first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraipyiy (z,j(i54)a3ho m-km owzcally) that a ball thrown vertically upward with a sp 4(,hzwm pmj- (y 3ay)ziooi5keed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically h;x37e xmwp0v 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 apple in Fig.6i4lz:d 0h:pfeo4g (i bx3vha 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the t3af6ieo (xd z hv:b4 :pghl4i0op.]
T =    s
   flashes per second

  A falling stone takesk+4j/ca2)e xqu n*ui; tldf9p 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window dideck4/2 u9ldi qtj +*pu;)fan x the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikq./z:f nlhm+izmu1 ,sing the ocean is heard 3.2 s later. If the spn,hu:iqsm1+zzlm / f.eed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle f12zglvmt.er/ or a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (r/e .z2v1tg lmFig. 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 vertic,dwlymk z8 *swx51ipz iy.(x+y7 r4zo ally upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. yx4*(mwo,y.1 +ryl8pi 7kzxzz dsw i52–34).
(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 theg ) 4 .yujz(qrib+fl)o street with a vertical speed of 13 m/s If the ball wasroi(g )qj+ lyuzbf.4) 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 f6ef ,3l gpwcz:unction of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? g: 3z,wcf6pel (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 plottbpbbd l 9ys+*.ed in Fig. 2–28. What is its iy +*bdl9b sp.bnstantaneous 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 r4 z /;pqqosk,approximately as shown in the velocity–torq4,kp s;q/zime 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 5 fg/z9 jvk2d2-rp dpythe previous Problem (Fig. 2–35) when itkpz 2fp yd5- d2/9vjgr 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 object traveled durinuwu;*ab ob y- ro9s9pw- +v4rfg
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a fumn( d -s/q(fu0ydwqu:pg u(n/ nction of time is given by Fig. 2–28.u( qd//-pmuqfnuy:( gw n0s(d

Figure 2–36 is a position versus time graph for the motion of an object along tbks**mz yk -ay8 wbi4)he x axis. Consider the time inte8-z4y* m sawkyk)bb *irval 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 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 53u 4dz -b4, nwbccmlda fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m bnz 4-5d bulbw 34dcc,mefore 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 gd,rd;b2. rwzgtf-: pdravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, ass d2-dr: gp z;,f.wdbrtuming the same initial velocity?

  A person who is properly constrained by an over-the-shouldc s::x r02ak ozi5d;qler seat belt has a good chance of surviving a car collision if t:c0irz ds lx;2k qoa5:he 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 bridge, 12 m above the smdd8m7 b30p 3sa-(jn cp)eke 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 should be when he jumps down from the bridge onto the truck to make his getmkd7a( ds e)cen -8p30 smj3pbaway. How many poles is it?    poles

  Suppose a car manufacturer tested (6,wkf) x9ik t o.ez gceza,izzq8+*g its cars for front-end collisions by hauling them up on a crane and dropping them from a certain height. e 8i) , z9w(kztzqkx6 g*go,.+iafzc e
(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 travele:q;u:d rx1gk v 5,aja jj4-pps 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 acce/k u-(o0 hgdeks 0lbns(wk r2.u;sf /zleration from rest. The front of the train has a speed of 25 m/s when it passes a rail/ l(zsbehsuf 20w-(r osg0k ;dkuk/. nway 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 o55 o20y 3 ni+qlr ;1cjlkvprc3zqt1 awater’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surfi1qo krz53 lcrt aov0n12;5y+jc3qlpace of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necelezew3,+fy g7ssary 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-km trip ing zye+w,le3f7 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 dq :nto 1lh ps 23jr;3/:gcextkown when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 pt /qlsg3 cn;j 132ohekx:rt: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 strikesm nb: a;wsdm b.0putya5gi:79 a ball is planned so that the ball will stop within some small dist7map5.nwt0 bgai9d:ysm;b: uance 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 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 travelhb8qp 6j6j+rwe b/m* )hbe0cq ing at a constant speed of 6.0 m/s Just asq 0/ 6*eq h+rebj68 j)cmphwbb an empty box car 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 of a high bo pd ;cw,zk: rd6(zaf44o*gwo uilding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a o,fzo( cw;o*4zr :adp 64dk wgspeed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial lastizj*fqnqnf9 k9 g b3 )ky4rm-.+ni:ihpng ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maipfg i m n -+9fk3*hk4yn:jqr9b).iqn zntained for the last lap?    km/h

  A bicyclist in the Tour de France / / qcj,uojw+0c.ba xxcrests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km f0ux bc,xq.co/a/+ w jjarther, 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 t71ny 6xveqgzlfj a (11wo trampolines. The first child can bounce up one-and-a-half times higher than the second child. Thef161ng(vxz qa l j71ey 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 trainjzom 6.w0e*de traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to dezmo wje0.*6 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 baseball with a speed of 44 m/s In throwing the bnsw imq6v :e7 fb;-5claseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is releas7nb5m6ecw iqlf-:v; sed (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration of ,dm2v a.hhtt/$3.2 m/s^2$ 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 has a tkf1pv6 4i.wh0 ararl 8raffic signal, and the speed limit is 50 km/s . Suppose you 8w.rp01ar4lh ikv6a fare 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 tavk3qvk(*9 xkn0n 5xifkes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration. ( k*0xf 3vki5nxkv n9q
(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 fr8menq vf maou4y41m:r0f a:z 3om the roof of a building; 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 nzo1qf 8f rae 4: 3amm:yvm04uat 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 stv1py74dmxfk q 8oe, i ;-ie2hnone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony ofq ki17p ,8d ;onhfimxe-y4ev2 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 would it take a fre+sk h 7ogkaq9:e-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance : 7+k9kg asohqwill restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant usesh.f5o6) o* kwlaa ghuhd*i79b 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? Ifo5h i9d 7k*wau6ofga). lh b*h the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertipo92/p4h* eijzn x3jz cally at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go than*pi2xpz4jjh/n o e3 z9 Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands onx1cefp qrl5p:p x)0. t 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 picpp:.)plqx 5f t0e1xcrks 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 a particular building using 7hulue9 tkr:q k49z u9a barometer. Instead ouq994h7tkle k9z ru: uf using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s 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. (0ynwax5n/n l+ 2**cfqov .iag a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At wh ai5 0n.w*flao/nn q 2x+vyc*gich instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?