Does a car speedometer measure speedeuf x6kx .bb o;(20m ssspz(0f, velocity, or both?

Can an object have a varying speed if its sgst7+qw c1di jb9-xc/46 h w6p,svp bvelocity is constant? If yes, give exampl+ 6bc pi sd47/v1whpbs6cq ,tj9-sg xwes.

When an object moves with constant velocity, does its average velociw2o7i(6k,g9 plqr dl jty during any time interval differ from its instantaneous ve7(dq2 ogk9j 6p,ilr wllocity at any instant?

In drag racing, is it possible for the car with the greatest speed c g, /petl7wpi pca:i +b4,,vxorossing the finish line :t+,i /b vpp,xplcewgo 7,4a ito lose the race? Explain.

If one object has a greater speed than a second object, does the first necesskys7d ,ee4 cn l5t4a9jarily have ,y 7c4 kenj9sle5at d4a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/fwgura w5 ;stt: cj6it4:ar:8h to 90km/h with the acceleration of a bicycle that acstgu j:af;wa: tri46cw 58 :trcelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration?v:l sdly71yk( Explain.

Can the velocity of an object be negative when its accelera2z t: k1fxfxt.tion is positive? What aboutt ztf1.x2fkx: vice versa?

Give an example where both the velocity and acceleration are5mzn sdq4e5b 6 negative.

Two cars emerge side by side fzwjk bo;-syl t t0fvm3 3u;e.n (olwu s,x+o,:rom a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunn:-s;.y(+t bvew mznx; l3ofswk u,ol,o j3t0uel? Explain your reasoning.

Can an object be increasing in speed as its acceleratiocu r .*wpa6p+4 edqh6nd lq54 fjyo(d,n decreases? If so, give an examu q(njro*lfq.d6y d,4a+c pd5wh pe 64ple. If not, explain.

A baseball player hits a foul ball straight up inxj 2q6jvyxw/ 7sh e( )4*vptfito the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when thpy4j(s*6q2vf7 )x ewi /hxtvje catcher catches it?

As a freely falling object speeds up, what is happes3z0 cl y4ai7bning to its acceleration due tbi3zl7sayc4 0 o gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum heigh czbtbp9- 6 0yyr (5m7kxm6jjet you could throw a ball vertically upward? How woul96t5mbzc7b 0yrp- yejk6mx (jd you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving60om kp4v2 e94qdggyl 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 vd qmgegl6k 24 09p4oythe entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tied t(s e3k4no5 vgu89,0hjz:cfbi dk nl v5i,9zcro 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 ,u z5ifh(r4,53kd govvi cen:bznlj8cks90 9 clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock falling from:)zmvrhz j9 7 geew6i4 a cliff, an elevator moving from the second floor to the fifth floor making stops alhzev m4e96 j):7wirg zong the way, a dish resting on a table?

An object that is thrown verticaldc1coi;z/2 u jkdl4b5ly upward will return to its original position with the1b;z2k4cdod j l5cu i/ 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 acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleratw2nav c kox2y*n. ..sjion at the same time? Give exa w2kvna .cjns2o xy.*.mples.

Can an object have zero acceleration and nonzero velocity at th0td8 mp t2p r(fgyoc1pxx4 0:qe same time? Give examples. g1p0p(fxpd qr02t m:tc8y4xo

Describe in words the motion plottes . zgzbpd k(r:f-5a:ud in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motionazb g(.k: :5druspzf - plotted by walking or moving your hand.]

Describe in words the motion of the p(jw ;;3exemq+.z; cjg4 cxpiobject graphed in Fig. 2–29.

  What must be your car b8jc9jvf.9o e’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 kqime: )/t2bm*qlb ts(m?    h

  If you are driving along a straight road and yq9(o9xzq xzpw)i9 6h7 qa o1euou look to the side for 2.0 s, how far do you travel during this inatth)q (pqzxzi9ox9 wo76a91q ueentive period?    m

  Convert 35 mi/h to cvu; k33w0ojo
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves f ingwc2d9d, ckk.yt+ hm.+-rn rom $x_1$ = 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 km/h for 130 km4h lz;dfk2,p kgq 2t-h. It then begins to rain and you slow to 65 km/h You arrive home after drivingkk ;-d tg,2ph 2lq4hzf 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 mqj:iynnskl+0 **e8oseconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of l +nnlj*08e:iq ky*smoight arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in agispxjz 246n8a m 7fx2 total time of 12.54pz2sn i7j 8gam6fx 2x min. 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 7vfjir dcn5m1 u1r5a1 m )gf0xaway in 14.0 s. It then turns abruptly and gallops halfway bac1 djrnm0)gm151c rix u7ffva5k in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a spedr2h7oga ,7r ued of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–ug 7drr2o ,h7a30).    min

  A car traveling 88 km/h is 110 m behind a trui).ln.ih q5kn -e7,a dggy9 a4cv z5vhck traveling How long will it take the car to rkv-v h le9 7gc5y.i angn5, .hqdiaz4)each the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and tde lki)*xa4m :hen encounters a tailwind that boosts its speed to 990 km/h for t kd*4 aim:ex)lhe 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 velocity of a compjn r8e.8o tkw8lete round-trip in which the outgoi8o.t 8 wj8kernng 250 km is covered at 95 km/h followed by 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 spedi96b o ny)rn:ed 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 from his hands. What is the speed of the ball? The speed of sound is 340 m/s.6d:b)n9oin yr    m/s

  A sports car accelerates from rest to 95 km/h in -pf r ni.gkf/+k51f tmp edd9kj :s;;c6.2 s. What is its average accelerat +pffm:ksi g9.j1ck dd-; /rf;npt5k eion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. Whaxxvj:5v u 5 )ws.0tdbbo1;d pjt is her acceleration uwsd0 pb:tv.b;x5xv doj1j5 )
(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 accel-q c cal/; swmr4ik*,b5ibjn tr) z77eeration of abou-q*t kl7nj;,mesia 7/b 4rcir5cbzw )t $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed traveupdx w9bfc16-ls 110 m in 5.0 s. If it then brakes and comes tdp1c9u-b fxw6o a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racink d 7k;xj6k4vu7xz(us g car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following s; 64kkz vj d7xux(ku7Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6 lco:xjig9rzz;*l15wufx1 , l .0 s. What was its acceleration? How far did it travel in this time? Ass1w5olx c ij:9 lu*,xflrzgz;1ume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 8cenl3 7/lex7n3kup3vj3 zvd 6 5 m. What was its acceleration, assumedkcl3p evl6d3e/j vnn3zx3u 77 constant?    $m/s^2$

  A light plane must reach a stdq :cwv alu1/82wuw2peed of 33 m/s for takeoff. How long a runway is needed if the (constant) qt wl du:v 1a/22w8uwcacceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out oi:ps 2m qkxv2.nds4 q4f the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach4sqx 2v2 m np4sq.ki:d 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 in 6.00 s. Howh*pc iv: -rm6d far did it travel in that tipihd*cmr -6v: me?    m

  In coming to a stop,cw 81pt k25jh+b 8etrtaw2b/j a car leaves skid marks 92 m long on the highway. Assuming a deceleration o/t1bt2 ac2p 85kt hewrj b+8jwf $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of p om8ehzx60o e-xi 01pthe 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 a xoei1z 0o068mexphp-nswer 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 khls2.)r +f2tl * gx36qlcx 7eg,lcxxfm/h and human real2l*2lfg.r lxcxf6e3 t xsh)cxq+g 7,ction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation2(dkd5p hqgkp q(n(, q8xv4jn for the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver looks h 1-2nxi7txy ,jynwh 1for aw1tnhxh 2- i1xy7njy ,n opportunity to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0l88x6rfqlo* pu(*ts gza )v 5e min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at 0x*5 sat)v8 *lflp(u86 grqeoz.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 4501i3oyp vue f)r-uvq .n d68cq km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m aw u1qeqi)c -.yfvov0ru8pd 6n3 ay from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliffd1 md m-t1+v)cfp fywjr3yd-/. It hits the ground below after 3.25 s. How31 1+dtrfm--)p fdwmv/c yjyd high is the cliff?    m

  If a car rolls gently ( 9dk/h:rxx : dpr-us.t$v_0\,=\,0$) 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 sp;ph+uhufe:8kj8j l. fhi +jn02mt z5jeed 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 upwa3ax /sm6+xd1l 3y wzg -.tqhztrd. With what speed did he throw it, andz -yst6.dxm zwlg/qx +h3t1a3 what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. kkw6 6.17koa lhimp k+Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of ti+l7mkk i66kh kpa.1o wme 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-2mf;pst ne)v a height of 125 m above the Earth, a package is dropped from a windo t2)fvsp-n ;emw. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distan(h( hd)yi. qrwglwe44 y87jre ce traveled during ea 7gleywhe4)w8hdi( j(qyr. 4r ch successive second increases in the 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 neglect5 a5 zekq+dkuk4 t7rj6ed, show (algebraically) that a ball thrown vertically upward with a s 5tkd6rzeak k7 54+qjupeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upwaj.81:ke o /yvr,tifjuc 4q* blrd 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 betw yu 7qge 5lknj(zm.+2geen each photoflash of the apple in Fig. 2–18 (or number of photoflasg7 l(kum.2eqg y5jnz+hes per second). Assume 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 2.2 m tall (Fig. 2–32). Fbe. 34u,paab ovy7s*gkjwuz o p )1:q/2drkb +rom what height above the top of the window did the stone fall? /e*3u4abos2rjk b,7+dy). g qa1p:bow zvkup    m

  A rock is dropped from a sea cliff, and the sound of ik3 z:to*v9g ygl,*v jet striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H = *,ktg*g9je lvv3 o z:y   m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You p//1ozd+xvvd dye w +*ydmo:e8oint the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle ydv*/vd 1eyodm+ ez/ +ox w:8daway 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 r:xbx2xx90bu i-)a gxd k hoe9ug2,)jwith a speed of 12.0 m/s from the edge of a cliff 79ui2bh eu:j)or x2- ,gxaxkx0xg) 9bd0.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass(t/czgydap v.7dp 005ri*czk upward by a window 28 m above the street with a vertical speeg pi/zv0zpc(yc tkdd7*r0 . a5d of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a trafe4l/ o gifksq54v)0g;s, rf ain 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 consta5 e4l,sggvf;i0r 4f)qs/ko afnt? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function o*ivgo 5vq- c 7uv6f6lkf time is plotted in Fig. 2–28. What igv fi5uq-6c*7 vokvl6s 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 approximat ztbc 8o2b;ik*ely as shown in the velocity–time graph of Fig. 2–35. (The short8z*bt kbci; o2 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 ar0e 7 a5 g+*)qzexjkyprevious Problem (Fig. 2–35)y 7eja)qke+*g0rza 5x when 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 distanur2y +t x5erea 5d/c-a4/euk5hzdh8ece the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacld09qj,z w: w ipr;c5tement as a function of time is girt d,50i c qlwjp;w:z9ven by Fig. 2–28.

Figure 2–36 is a position versus time gra8au mqesc;/,t 5 :mb14ukifm t 84fmpyph 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 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 o /e4tpy4a s8kf:mfbc;uu m5 qm1,im8t r 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(y*;9 nsrj.i/loav pv a3xkd+byl+3d firefighter’s safety net. The survivor stretches the net 1.0 m before coming to redv+jv33(/i9k +nbys * lxyp aorda.;lst, 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 amja+ ,w /k ar,b4s3c.bpr w4ppbout one-sixth what it is on Earth. If anmw+ p,34ja cb,p 4rk/ws.rb ap object is thrown vertically upward on 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 afr-gi43 fhqhub)-3v r(r *gy an over-the-shoulder seat belt has a good chance of surviving a hr rb 3g3-v-4ga(ryui hqff*)car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, and h3bp 8urshp ndk: i)d).is 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 trudn) ish :bpdrk)8 .p3uck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cal ipp4unukv 5/6xv./ rn3xjt9z n6ez.rs for front-end collisions by hauling them up on a crane and dropping them from a certain .6ne9/n5x6 jupzp vnzxv / 4.kur3tliheight.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels abqxgi+jw qqt -+e23*ocout $10^9\,km$ 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 vz:g2ox (vx e6m+v+8kagm9 vc9*. xglpcvl -drest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the fron.9xv9(-ckm:l +el cv vo+vvzgg adg*mx px2 68t 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 dekd nu( le(o3ym/i9( e59estbdep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average de5o(d n3b9ile/ye s(d(9u te kmceleration 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 neegytz *fg+mlbko h92srv;5,4cessary to balance the average speed of a train against the distance between stops. The more stops there ar2tsg y, * hgb +fv;9orl4m5zkee, 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 fish.lr nt31.c i7hc 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 actiol7n3hct ic.1r n, 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 so thatp,.qgwz quy6 ddk* p*6 the ball will stop within some pyku6q* qd wgp*,z.6d small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball 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 hgqd h d.sv.40eo*k :jhop on a freight 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 *g:h4d 0k qdj.. hoevs$a\,=\,4.0 m/s^2$ 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 mk :rf:l9jr9kd.a ls3second stone is dropped 1.50 rf9s arlkmlkd 3::9j.s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial ly0s* ep0nloo,c q/2ej asting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintai ,0 spyq2ec /oe0jn*loned for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountg2dzlo5s8b988wo 5ngh9 wpaaain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . Whpg8lg5bhaadw8w2n99o o5z 8s at was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The gqwdowda+l:us;2 :h:6 uc nwa tm3vi 8qmp8)) first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the secn:w+g; l:wi8u6cqompd ) qs3w2) v:h8a admut ond child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling ing oycbc*l5j +o0++owh the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does ic+o*j bol hwc5+ 0g+oyt take the car 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 baseball with a speed of 44xs)pl7p az1 17,xwcv/ jff3x n 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 p,zj) px7s7ax1f1/ fcxvlw3n during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration + tywddbgjt+2*dxr02lhk0 -xof $3.2 m/s^2$ 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 i/n9qfrs gu5eif2 2nrs8s8w g1n 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. W2f952sefn81 wqns /s 8ugigrrhen 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 constan6cd 3 c5ez-cfct 120 km/h takes off in hot pursuit. The police officer catchecfe cc56zd- c3s 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 afej*p1l1 qfsc40jaa x. ter that, a second stone is thrown straight down with an initialpx1 cj.fl4aeq j1as0* speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The fir)ekwu,3si b+.dw s, vbfjq;( fst stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hi jbf,).;3ew swv(u+,d qbs ikfts 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 free-falling parachr(a olvfv w 40l lg67(rcl.utl::;ggt utist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would7r t ollvglucl4::vw; 0.tr(g (ag6fl 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 conveyo6u9j t zhf4il 6+wxyd6fr 7nt;r 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, whatttxhwnlf +yi6 d6 z;9fjr74 6u 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 faevul/e2 rgq(k6j15 ynster than Joe can. How many times higher will Bill’s e (2 glujenv5q6ky1r/ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the hjiwn .1xxi.5 0z or lg.;4ceeground 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 w0; oij5rg1el..ezi4hcnx. x 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,kavbvm kqu6-4 z,cc3 using a barometer. Instead of using the barometer as an altitude-measuring device, t,m k, z v6bv3qac4-cukhey 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)-uhc ty :d(e9k Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (ektu ec9d(:- yh) Which bicycle has the higher average velocity?