Does a car speedometer jf9 f,b o3;;;hlezp2h af+h osmeasure speed, velocity, or both?

Can an object have a varying speed if its velocity is constanlsz,ja ( sh58*vstc l.c+rgqt qp)l,4t? If yes, give exam.rs 8l vs* l( )at4qljpzht cgc,,qs+5ples.

When an object moves with constant ve*w,o0oyuqk; qe1qq8 klocity, does its average velocity during any time interval differ from qq kyw;*1 eku,08qqooits instantaneous velocity at any instant?

In drag racing, is it possible for the car with the gr/e,(4jsv5aele5 bec dl /z/dbeatest speed crossing the finish line to losese badc / (//b54ee,lvjd5lze the race? Explain.

If one object has a greaten 0(ya5lloy4+ fg.eve r speed than a second object, does the first necessarily have a greater 0o. enyel5v(l4+yga facceleration? Explain, using examples.

Compare the acceleration of a motorcycle that acceleratey-4d ilou:d1ss from 80km/h to 90km/h with the acceleration of a bicycle that acc4o-uy: sddi1 lelerates from rest to 10km/h in the same time.

Can an object have a northward velo6ddb8bi- d ap xql ,2qgv/-2rccity and a southward acceleration? Explain.

Can the velocity of an object be negative when its mgng yx/.pud ifl*,0b46cal- acceleration is positive? Whatnfu a.gpgy 0 xcdl/,4m6-*lbi about vice versa?

Give an example where both the velocity and acceleration are negatii5y(waq u:9q; 3nzd-; yfxkjx ve.

Two cars emerge side by sid; vrg(cdz:iudi 0 ui8 2;+acsde from 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 . W vd28:s ;ci0guiaicrd; (zud+hich car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration dd9;1 qnb)zkgefizi .*j1s n8decreases? If so, give an examplegdfei)s .18k;1q nid *nbz j9z. If not, explain.

A baseball player hits a foul ball str l 4t;-kmymcpol0pr1, aight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, howk-1lp tycm4,o p0mlr; fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to id m qv gaw3/*g1+ry3ists acceleration due to gravity — does it increase, decrease, or stay the same*av m33dgy q+sg1rw/i?

How would you estimate the maximum height yc,y:g *aqk4nxdk3 vu (ou could throw a ball vertically upward? How would you estimate the maximum svkqy*d( ,:c4xau3 nkgpeed you could give it?

You travel from point A to point B in a car movina + dc;b0 fud9z,w4sgig 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 fr sicd9; fb+u0zgw,4daom A to C 80km/h ? Explain why or why not.

In a lecture demonstrati*j0g/ji;/x wgvqz i: ( suav*zon, a 3.0-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 thv i;0 wz x/asivq*g*/j: ujzg(e bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant kh l-1f)h-ydl acceleration: a rock falling from a cliff, an elevatork-d)l-h1yflh moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its originf0g h4l9ll,lbb j+l h6i0-tb eal position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this rb0il9-jl, hlt 6b4gb0h fle+lesult 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 nonz5np * jox*mjy5;zwa-fero acceleration at the same time? Giveo yj 55jfw za;n*-xpm* examples.

Can an object have zero acceleration and nonzero5seqw 6 kb:0n-ti; wqdrch-) b velocity at the same time? Give exampleeh qw-;kq b)cit6 -n05r:dwsb s.

Describe in words the motion pl bn)zxtpv 5; rv7ovsi40l vfz,58l-taotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate th;lnlv) vzs7bvfv5 r 0,iao x zp-t5t48e motion plotted by walking or moving your hand.]

Describe in words the motion of tm7nbxys7 jb29 he object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travelw6jr3cqnd : (4f4pm4s fe.qm w 235 km in 3.25 h?    km/h

  A bird can fly 25 km/hl6r. ngt oi0o;zd4 ts,u*op 8,li )gta How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for,58x;nbq;dxkdk3 ts b. nz- kv 2.0 s, how far dbkxn ,.53zdk;bxvd t- 8skq; no you travel during this inattentive period?    m

  Convert 35 mi/h to /3k w2qlobz.w
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves g5s tiq0 qvw(2from $x_1$ = 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 x76x3sdyy d p*at 95 km/h for 130 km. It then begins to rain and you slow to 6y*3s6 7xdd pyx5 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 yru5-tojy+rl +a k .y-9nse5kxz6a ;va lightning flash and the following thunder gives the distasktyaze kluj9o.n5y -ya5xrv6+ +r -;nce 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 from this rule.    m/s

  A person jogs eight completes s)/bi ,kbe9e:bc+ix laps around a quarter-mile track in a total time of 12.5 min. Calcula:eb ck+e9,/x s ibbs)ite
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, kyb2yh- 4inh( h,4nn/gpvgz0 moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Cal,g2bg (0-/nhhykhnyi 4vzn4pculate
(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 p, qes6 dr2 gk f-gemg:9ih97uaarallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long wil-29 9,uirs q7gdfheage6 g:k ml 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 long w4: np,gn2pf yvt,n, unill it take the car to re4yvn u:gp,ptn ,,n 2nfach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tau+ cct+ 4lav;7vl 0dajilwind that c;+4a+vul7v ta0cdl jboosts 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 velocity of a complete round-tri30ehh+; se9ylnl yv1nqe 8*el p in which the outgoing 250 h*sen0ey+hne 1v3lly8l;q 9e 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 speed hits the pins at the end of a bowlxg6tlp .0; rpjing 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. Wharg6;t xp0l pj.t is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates frodne+4o : nv0cmn((yyt paty p*nw,q3 9m rest to 95 km/h in 6.2 s. What is its average acceleration tmn vyw ,4 pq9y n:t3p0+(e( ydn*onacin $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from reca-h ikps*a8 i8cy .biq2) sg6st to 10.0 m/s in 1.35 s. What is her accelerationi 8iciy*c6)shgbsaqa2.- 8 k p
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablej yz tcm.q 8pyv5 /*q019mg .ajncj8tu of an acceleration of abou cqvnjmt90q.tzp acy58mj 1 /*yg u8.jt $1.6 m/s^2$ 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 travi ,i361wihhq zels 110 m in 5.0 s. If it then brakes and comes to a stop,iz ihwq61i3h 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 racin.-mo5sgm.g t tg 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) io5..m ts g-gmtts acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acce56oed sw1-kypmq f8f 7lapf. n4. f1pxleration? How far did it travel in this time? Assume constant acm6sy75f4po.fkpf.f 1 xn- 1a 8lqpdewceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was i3z2qs h;cynt xz-l(e+-bb) dr 0cp0cqts acceleration, assume;csc0tycbxrqd n3z2 hz( e l pq+)b--0d constant?    $m/s^2$

  A light plane must reach a speed of 33 gxa74 -2um 5ab xfj:cp;:lwk xm/s for takeoff. How long a runway is needed if the (consx5 bc-;p xa7 :maj gl:uwx42kftant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter canfw)cs+ lmc p lk1i0jh6an,8(p burst out of 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 kw0j6)s( n+1aphcm fl8c,pli take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a g)h90. krixbl speed of 12.0 m/s to rest in 6.00 s. How far did it travel in trb. )hl0kgxi 9hat time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the hi9lgh 4 tp (adae6;:gtkghway. Assuming a degghlat9; 6:(ak4pd etceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 kmzj:9z; d2tw oudf c,/y/h strikes a tree. The front end of the car compresses and the driver comes to rest after travecf;w ojtudz:9z2 dy ,/ling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of95/um ycanl y-fhs /7o 95 km/h and human reaction time of 1./h/lu 5 fnams 7-co9yy0 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 pmb w 9.:lye( v/:;muyfm5b*faja7dbdistance 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 trucr54wp kapale0xs .+ 8:d7 kmalk going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his 4+a .saxrpm570:pew 8kkaldlcar 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 10,00lao/ fsm2nf:y4g t 5ouh(x 7l3px9d00 cpfl9x0-m run in less than 30.0 min. After exactly 27.0 min, there are stit/2onfsam0d(f 9fo94lpl 5u0cx gp:3 x7hl yxll 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection s + tcys+8f.d8mb) c4lu)fc spr:tmn- 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 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 deceleratio+dfcn.msm )ru:pfs+4cbl- 8yt 8 ct)s n 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 afteo.nosro 3g4v,wo h+ p+r 3.25 s. How high is the cli 4 po w.3vnoh+rs,oog+ff?    m

  If a car rolls gently (afpgi9kuw;/jo z8c)wo sm1-0 $v_0\,=\,0$) 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 spq -pafxp0gcy7-cexr-9ax 1 u6eed 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 upwarded bw,u:pwup eqh40 3l yk2wi ;k,8v:j. With what speed did he th: wukq3p4,ypw d80;e v k huel:wb,ij2row it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rwox 1(iz y;h-,hs tj:aest and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t si(whj ozh1t;xy,:-a = 5.00 s . Ignore air resistance.

A helicopter is ascendingbd8e)yn6 r o t6swmn,o4x90ki vertically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a pack 6enotyo4) dkb 8sin6 wr,m90xage is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely fro 2nv;a73r0iz nfqzmeg88x .bim rest, show 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 Galiegvqn8b 8x3zfi zm 2;n.0iar7leo. See Figs. 2–18 and 2–21.

If air resistance is neglec(ab -naq kpvh vr6o 4(ne8g9i5ted, show (algebraically) that a ball thrown vertically upward with a s-(nhgv kap o i(aq86brv5 9e4npeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0ki q :+6t : qo+xavysv7qn0wqlkf)r3: 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 9he+avuamvv n;-93 hwthe apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two appl-;m9h9w3na+ evuvvah e 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 (Figh5t/m 5a.*x9a vwfmab. 2–32). From what height above the top of the window did the stone hb/a* mxv.a5fw5 mt 9afall?    m

  A rock is dropped from a sea cliff, and the sound of it strio gxw)f6usaa77bv s6-king the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is th 6ufs76gaba7o -wvx) se cliff? H =    m

  Suppose you adjust your garden hose no3*msf,mm fs.4v/++nu /lj act+ necpb zzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, y +s/ asfvpe4+mm/tm.n3bcu,lc+f * njou 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/0*bug gtz3utp(l (vn1kd: xqz ,xo75uyho u(3s from the edge of a (lg3( t*:ztou1pxuquk z5 u0dn7xg(by hv,o3cliff 70.0 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 pa)ittuskwj8,1ik w;o 6 ss upward by a window 28 m above the street with a vertical speed of 13 m/stio k ju;wk 16s,)w8ti 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;s29pa.s msj5xj3+t (iye8z pdtdx+ j train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what pdxij+ s29 mp8adj(+z jss3p;y5. tetxeriods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straigir t x.q4 utf54, behi4.jk.qwht tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous ver .4q,f.t bje44kqhtx ii5uw. locity
(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 w+, 2b1ub urbd5.vuuxelocity–time graph of Fig. 2–35. (The short flat spot+2 v5ru,u 1uxbbw.d bus 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 ofzb)mdivr ieqg0 -u+ +yc8-to 6 the car in the previous Problem (Fig. 2–35) when it iidv)6 oy8eg+ucb mr0-ztq+ i-s 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 thea6;88a1hy kq5 i xiznd5 rgpn00ukg/w distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose disi e/daa8lt:5splacement as a function of time is giveni5ad /tsa 8e:l by Fig. 2–28.

Figure 2–36 is a positivogoaui/kb4i k - ;www 2o(n10on versus time graph for the motion of an object along the x axis. Consider the time interv-av/ 2 w(b1ow owuinikg 0ok;4al 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 a fourth-story window 15.0 m abo4e w2f4n odru7ve a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Figrd44fo neu 27w. 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 gra9gp / ri :ia6,pi8guwvvity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moogpiir/6 w a:v p8i,9ugn, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by4aw8-j 0)vl 4odllids6o)/qdu l m xs1 an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does nvo6m ll- 18wsu0) jla) d/qsl4dx id4oot 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 ayd,ad-as+ 7+r 4i pr6ducx2hqbove the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down-r7sprd+2 h4qd ycua6i +,ad x 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 colei-)it e.o0dl lisions by hauling them up on a crane and dropping them from a certain heig ti0-oied)le .ht.
(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 Earthxmjt ov +v ,pt33nzs4( travels 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 hzj 3mz(b1 9jb3n gb jmx0w.;vthe train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of 1 3 3bjv wb9j j;zg(x.bmn0zmhthe 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 mw72p4opy3dt(r7rl0 bdl dfd+ above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surfrf blr (o+tdldw472pypdd370 ace 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 rapfx c6w*df9xdvxd;(cxlzt8 6 8id transit system, it is necessary to balance the average speed of a train against the dist xx(8lx6c98dfz*dc6 d t;xwfvance 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 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 s16ab3r.j )hj(tk0kivce tf mbl:* ) yvtraight down 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*kja) vyt3 h1(il c):t bem0frk6 vb.j takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so that th0fbuep*ey b;7yzt)shz u :62 y5 nqc2me ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelepy enhzs2);6fu*:e7q 5y uyb0cb z2mt rates 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 spx;o71gue snu *;hf. a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the f7 fu*. np;usoe x;1shgugitive 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 secon* + oaqc4 ; vfr8pvtbv+dko4d7 svikg-28un 6cd stone is dropped 1.50 s later. How far ap2nf486gdk*o v;a sk7i+odt84quc v +-v pvrcbart 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/hv3/r e 6tsknsch20+r r7j1c tl over the course of a time trial lasting ten laps. If the first ninej1 2r03k vec 67lhsr/ crsttn+ laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 km/h yqv q3cpb+/*s. At the bottom, 4.0 km farther, his spepc /sb+yvq3*qed 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 two5;s1 3 visgjpbpza-l. trampolines. The first child can bounce up one-and-a-half times highers .g-bp3i;p s1lvaz5j 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 overtakes a 1.10-km-long tuhzc)vldpg 1 -pt :0wg: ,ny*crain traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . -hvpucp1w0czg ln:g:y) ,d *thow long does it 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 wilg asr0p gtz33ce /:h(th a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate ptgge3 l:/rh ascz3(0 the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically,,j y7cknk). tjd7uq m. from rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection has a traffici 98f mgljm(-z)6-vd: j eusrzw/iv:e signal, and the speed limit is 50 km/s . Suppose you are driving from the west:r mjz jl9 mzi8-sgeuie- :dwv(f6v/) 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 120hrxax41p8s h)(op xq : km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 )a(4 r:x8x1phps oxhq 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 after that, a sec o 7 99pzjvjw/h8bzpi:ond stone is thrown straig:8 wbjhzoz99ppv/7j iht down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stweb 6jx)0 56*cj/rwztmif3 cg1w m*vzone 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 wwibcz f6m5cxm tw*0j zr1we g)j 36*v/hat 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 resistancer zozg3vz5a7f s)o3k ,, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 35o) 73or5,zfvgk sza3 z0 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers thrtbb*i),m p z16roz7yxough 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 burgers6 zoxt7mz *yr,i bp)1b 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 vertically at a speed 1.5 times fasterr*chcu(z vj 8xb35pn 83iv ayie:so;: than Joe can. How many times higher will Bill’s ball go than s8x3ec n:vj ; pr8yb5:uoc( vzhia3i*Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below yo7jle;*;y yfv:pi m*z ou. 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. Why eil;ojfm*zpy* :v ;7at is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building usi cw*rby;1x-cz bg .7x f6m:rqing 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 student reports a fall time of 2.0 s, and zf rwmi1x.7bbcxc;*gr:6 yq-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 poaoi p-ig1) ak8sition vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration?)a81kiao -i gp (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?