Does a car speedometer measure speed, v9v4 z r4ubq0ieelocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, b 4g.kwo0ofq igj25w3give exampoqoig5f2g0 4j3bwkw.les.

When an object moves with constant velocity, does )ph-j5zj2;sx *nf apl its average velocity during any time interval differ from its instantaneous velocity at any instaf n a;*x-s2jpzlj) p5hnt?

In drag racing, is it possible for the car with the greatest speed crossi:q-ce6bzg ( gong the finish line to lose t(q c:b- g6goezhe race? Explain.

If one object has a greater speed than a second obje6rmz6ibvdf5v kts o* r :5hogw0r:.g8ct, does the first necessari :zi*5vortd fhrbsg v:5g60kor.86 wmly have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle tt ( 7:gjfid.u:ux: ;8w vwggvgxt+ce3hat accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the same timew:.gi x;cg3 +et( u :gvufjgd:t x8vw7.

Can an object have a northward velocity and a southward acceleration? Ex ex+fdd*b 3w/uplain.

Can the velocity of an object be negative when its acceleration is positive? W w vij v*qjlf7d3;z ytf7;*ya f;z3f,yhat yw 3vj*yzf z;j7*vfy ,;f qfit37;dlaabout vice versa?

Give an example where both the velocity and acceleration are negative9 w,dtr2p ua0e.

Two cars emerge side by side from a tunnel. Carbz5 7 l4.zs8qdr r,hev5gok7 lx :y/vk A is traveling with a speed of 60km/z 7:xs rv8,khl5rz. ld7q y/bo4vk5geh and has an acceleration of 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 increasing in speed as its acceleratik brf(rkfo-d(d3e,2alo0 a + yon decreases? If so, give an exampl a2bf +(roy(ad,-or03kkefld e. If not, explain.

A baseball player hits a foul ball straight up into the air. 2egk4fi u7k-pIt leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the bk2i-4g7pkfe uall be traveling when the catcher catches it?

As a freely falling obj) ym zihnn 5/k( 0jcu5y-b ansn1p9l-pect speeds up, what is happening to its acceleration due to hu9sc( -10m5 -nyin/p zp )ab jnn5kylgravity — does it increase, decrease, or stay the same?

How would you estimate tdi(4w41fmnzg: i ef,che maximum height you could throw a ball vertically upward?14(,cge:i wfmdinf4z How would you estimate the maximum speed you could give it?

You travel from point Abnbw re+b .42 jkadp-/ to point B in a car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain ./b w2 j4krbdan+peb- why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolx f u*e5owc+m17l)vpzts 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 vox) plecu* wf7+m5z1between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accelhuso;bmxp* :pb:1w 5zeration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish res *:s 51zx:;mpbuhopwb ting on a table?

An object that is thrown vertically upward will retur2y*-2f)ltf1n6 axn x9 dpavt sn 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, axftvxn*pat)12 -fl 9dny s26 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 accele ..sooiy,q;d ase, 8ndration at the same time? Give exampldq .si. ;s,8ooae,dnyes.

Can an object have zero acceleration and nonzero velocit*q3v+9o 3-7wgtze mqf jghva;y at the same time? Give examplqaze9hg7f - mw;3+*j3v ovgt qes.

Describe in words the motion plotted in Fig. 2–28 in terms of (* fdgl+,fwu;f 4 iicqv, a, etc. [Hint: First try to duplicate the i(u4 ;f+q*dgicf , wflmotion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2c vxj)la(r kvd6:vb;,–29.

  What must be your ca6:ehbmlm5 b63+ qyhwj r’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long do( bu.3tb1izvpes it take to fly 15 km?    h

  If you are driving along a4kvjb;bpf0mg ot wq7728v i*f straight road and you look to the side for 2.0 s, how far ff 7kq i 2;v*8bgpvmw4tboj70 do you travel during this inattentive period?    m

  Convert 35 mi/h to 5c6,z 2ke5 h cvuvj;wu
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from ry*8g w*f639nvy(e bgihpti7$x_1$ = 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 9,kc/h, g.n h8xtfbw. myqr2w45 km/h for 130 km. It then begins to rain and you slow to 65m x,/k4 .btqhw.,wnf8rc hy g2 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 ()xla05*sj mn )w dwfhziy+c* a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in ew *dz5mx a n f)j(y*lsch)w+0issentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around g v;yvi x63mbi)0nm6va quarter-mile track in a total time of 12.5 mini) yxinvvm ;66b3g0mv. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight l6m:8wo xm ny2line, moving 116 m away in 14.0 s. It then turns abruptly and gallopsn2mx y8mw 6lo: 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. l4 d i/l-lfec -86vujs0mxnjy:r1 xs (6pavo -Each has a speed of 95 km/h with respect to the ground. If they: jljvsxy0(io sd1fp6xl4 r 8c-/m6nevl-u-a are initially 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 traveling How l:u3ly 9xx;ql+dqdc8d ong will it take the cal u9cxl:qq ;d+dd83xyr to reach the truck?    s

  An airplane travels 3100 km at+ lc xduls-vrz 3q1;c+n0g ov9 a speed of 790 km/h , and then encounters a tailwind that +ln 1rz0-o x9 vvulqc+ 3c;dsgboosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average 8a11bmd o,gw0s t(gd yvelocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-houts 11m8wo y db,dagg0(r lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pin15vp 5m9lm(h/l r yvcd4bxu- rs at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting thev c-x5rvh9m/r5ly4dmu l1(p b 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 i1qqqd(y g / tlw:9(sw5+poak in 6.2 s. What is its average acceleratio:k(dsy q(o5piw tl+wga/q1 q9n in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is .h.oe4dt-d5p 7egxs m her acceleratione 5ht.p dd7e-msgx. o4
(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 acceleration of abouf0v 0b3 wsl-lsls l0wf- vsb30t $1.6 m/s^2$ 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 tra qi./o:6i3 8+lh ednonpcgfm7vels 110 m in 5.0 s. If it then brakes and comes to a stp7 /6 mf+odcei n3.in:8lqhg oop 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 and9): x6d5t+vs 7hu jjiqmdnn,b+m o,pa moves in a straigi m7xq ndhj+6)pod,5u,n+sj mat 9bv :ht line, is given 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/swi)rmk39 a q a57s+f5 vxdkz)n in 6.0 s. What was its acceleration? How far did it trav3r9)z k7 d5im5+ax)k vfqawns el in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dista;p rlbw5:fvu 1k-s:) qet 3uqznce of 85 m. What was its acceleration, assumed rv:z3w;tb:l5eku- )1sqfqpu constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a r /(5e- 9eao8o. ckyh+0g aoenqfjfw)i unway is needed ooe h +fo-a 0i8 eqg(9eawy/j)kn5f.cif the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burqaey1a6a+ b9d8jgyc0c3 w4gs st out of the blocks to essentially top speed (of about 11.5 m/s) in the first e4+q96syj 3c ya0b1a 8gg cwad15.0 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 of 12.0 m/s to rest(+)rau a8td tbxv9om l(az,.c6* p dgugmbb;7 in 6.00 s. How far did it travel in that tim b 69b+xmpgbda.latu* ozura (,8 vc)(;dt7gme?    m

  In coming to a stop, a car leaves skid marks 92 ri9m( ru)jt+wm long on the highway. Assuming a de+t j mw(r9ur)iceleration 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 7kbm, au9l s/wtree. 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 answer in terms of “g’s,” where 1.00 g = 9. l ,akbsm/7w9u8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car wie7rr b1:(g/ xox3l0 oo s(qktqth an initial speed of 95 km/h and human reaction time of 1.0 s, for an acceleration ( q7x:( qs/eol r1r3obgot0k x
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a car is pf3i9okt.dcy 5wypx;dl 4a26rso* o9 $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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. )kgr h4huu+ ,h o2mx:mThe car’s driver looks for an opportunity to pass, guessing that his car can accelerate at 1.ur: +mhom4xg2uhk)h ,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 complk q dg+d h+zl*7:(pznoete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. T (+ kh+q zgzdpd:7o*lnhe runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an int 1 o)o3d os.d+ xvig5ey vhmc;1usb+)iersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she ted1ov .5 dvu; sg)s)+oxh1y3comib+i ry 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 top of a cliff. It hits the ground below af,r8z8 df+6w( zwqvaursm:lk n f14t4uter 3.25 s. How h:rmw+,rz 8u41vw fst4 86l zdanfkqu (igh is the cliff?    m

  If a car rolls gently9 3o,66ul wcgyt8pnos ($v_0\,=\,0$) 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 straighke/38y4xh g+ nu9)z4f lwzc fdt up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upward. With what 3 jmodem;vc1/tlu7(97z. syu;dy jbl speed did he throw it, and what height did it react19 sezv(y. c7my; uo3udjdj 7l/; blmh?    m/s (Round to the nearest integer)    m

An object starts fromh06pb.tujhw 4b c4o1m rest and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function o t6o 140hh. 4cmubbwpjf time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At hbj1msl e/pu )u1lw99a 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 spee)9lj9lumwb p11se u/ hd equals the helicopter’s.] t =__ s

For an object falling freely from rest, shot-8; 1dxg ebrtw that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 1der- ;xb 8tgt2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown verwt(81j vq y csv-z6qm0tically upward withv0zs(tvq y qmcw18 j6- a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verq2 2 l(jxr4d jdsp9izi*ctt*. tically 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 app,;gz kbr/-a ttle in Fig. 2–18 (or number of photoflashes per second). Assumekz gr-;ta/,b t the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window gqz6s :ubiryft2q3r+x ,4ni22.2 m tall (Fig. 2–32). From what height above the top of thei nr2rf6s23qqyu +: tbgzx4i, window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oceato) wl ish4hcp:wxpr:s rlu2+ +by 1.ms, g5e1n is heard 3.2 s later. If the speed of sound is 340 m/s , how high is tw, s1t+sw ho2s5pr:.m p+lrb ig )41y:e lchxuhe cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream oy(hwdb5m .hz1gho mx 75j kh8q t5)ad)f water. You point the noz1(hq mwab 8)txyg5d7ohhdmzjh5. 5 )kzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge offcyb) ztf7 yevmgpi 4k.,s,k67gya1,(yt0ig a cliff 70.0 m high (Fig. 2–34). fz.,1 bci,ksy7 p )mg4yk,vie7gta6g(y0y tf
(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 with a v ih-nqoyj- ,j+ertical speed of 13 m/s If i-jh-o, nq+y jthe 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 timek4 w(vb,f3kla . (a) At what time 3(lkab,fvw4k 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 acceleration greatest?

  The position of a rabbit aloe:jxwpzn(6 u )d e) 6+utab8inng a straight tunnel as a function of time is plotted in F) + 6d(xjne iuate8):uwb6p znig. 2–28. 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 shown in the v 4 eolc4-tlxo+3 ew(5u9h qot8 bwg 17i1fgtgoelocitlw 11 o5l8tgo towx 3 otfb9-eue(7cgq44i+ghy–time 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 w1 ofemdn2) ;gprevious Problem (Fig. 2–35) when it fendow 12 ;mg)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 ow ( 3jd1ckf)n5esa5klbject traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacemen0a- q e9tjf ((nbsda6qqaarf4 2-*imi t as a function of time9jf*ndi6 2sa0((qm a qq- reafbt-a4i is given by Fig. 2–28.

Figure 2–36 is a position veo cue;l4dx *wee5dl8y01 ,hag rsus 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 the object positive or negative? Now conch*lae 8; 0w4d 1,doyx5eegu lsider 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 . c33rg*kzqui fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before *q iuk3gcrz. 3coming 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 the3- em/us snyl4mone j(i9l2z2 Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward ly/e umz el924nim -(ns2sjo3on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoutdrob. f7+4 faq)ae3n lder seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g3qfb 7+ eoaa f4.nr)dt’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 gm8iv n ;7jmi0a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is nmjv7mg;0i i 8passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end colli.fixwh+ d r0l;sions by hauling them up on a crane and dropping them from a ld.hwr0+fx; i 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 t-glaexg3xy9 a 7.6xhp ravels 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 acceleration from rest. The front of th 53j nfiaqjyt8:m8c, ye train has a speed 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 fciyjmyqa38n:5j8, t 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 *w cxj8 /6ymmta deep pool. The person’s downward m /* 6wmt8xmyjcotion stops 2.0 m below the surface 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 istgid 1dq4l, e1 necessary to balance the average speed of a train against the distance between si,1 1tgedql4dtops. 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 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 diving for fir6 el )zdw: 1q- as,mlnc0ub-msh. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the snmql:lucd-60,a -mz)r1w s b eurface of the water.    m

  In putting, the force with which a golfer strikes a ball 2tn cdh*p4 iq;is planned so that the ball will stop within some small distance of theci;qt d2 h4*pn 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 traveling at abh ;j*s:wd: ts constant speed of 6.0 m/s Just a:jsdw; *t:hbss 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 building. A second stone is droppo jv imb e)tl,8umw.;/ed 1.50 s later. How far apart are the stonev.)l,/ j imetwm 8ubo;s when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of qqrc )i5t;4eu a time trial lasting ten laps. If the firstur45;)q tei cq nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour7olqyccm: v+7r 2t1-p,pv4-y* ex zr thr1 ypk de France crests a 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 averv y : +2yrr hxvzle1y 7qcp-1pt4m,ctrk- 7*opage acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can boyz *5cw/vn+ya r z42gq3qmoa(unce up one-and-a-half tima+(ywqa/r*c 342mvgz 5onqz yes higher than the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overteyvt, 3row8b(pm0w dme32 qz -akes a 1.10-km-long 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 car to pass it, and how far will the car have traveled in this time? See Fig.e8pv 2qmdr obt3(3 mw,ey0-zw 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 throwlgdut4 z)f7 e hcvw7+-nd-v.h s a baseball with a speed of 44 m/s In throwing the baseball,wdh zcg7e+ n-lfuv ht7-.v)d4 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 motion.    $m/s^2$

  A rocket rises vertically, from rest, ;4k3 t ypwz34x: louldwith 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 shownq(ic0 e e75v8z vud0 zbfgatp2nuo2+c66 jj8o in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the zvpico2 gq06e+ c6au5t2n f z8(uobj8 0vje 7dfirst 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 so+d6b/a(:bja a,t* ir xi mdsv1z:p,speeder traveling at a constant 120 km/h takes off in hot pursuit. The pold,:b,b*sjr: diza+ ( i 6s1 amaov/xtpice officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s aftfvs . ,5;i kliwgr1lc( 9c*jqwer that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stogj(* .q9il wlwik5sf1 ,crcv ;nes 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 a cvls*)j9a yq1t the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial ve9sqc) l*1 vjyalocity 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 res -a zo9d,j.g.o , .zfj7hbpslzistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude ob.hzalo.j- 7z 9d o,ps,jg. zff 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 conveyorj1 at qgg;/d:w( sey6 sr76khe 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 spac/: h ;(jqegt6as yewr67k1gdsed 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe sp+3wi + .ogmlxf ys9-v,z .sdcan. How many times higher will Bill’s ball go than Joe’s? +omxyg3.9wlz+ i,.sdf vs-ps$\approx$ =    (retain one decimal places)

  You stand at the toprz *(uda+zkm:z2y 6kz of a cliff while your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the6zz:k zmkry+ * a2zu(d ball?    m/s

  Two students are asked to find the height of anhx 1lk2 ptc/k60 0-xkjoof 2m particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One s-ot06konh1m0jf/k lkx 2p x2ctudent 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 positd,toxt+z7gjh5z6j z 2:w1lu tion vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same vz jgw,ht xz od+j76t21:tu zl5elocity? (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 average velocity?