Does a car speedometer measure speed5aj6w5 4p5sd/cyuy l n, velocity, or both?

Can an object have a vbo*aj 89 ,spqgqr *.czarying speed if its velocity is constant? If yes, give examples.zc qpj*8g.qoar s 9,b*

When an object moves with constant fz/l3 d. enfzaydy*/jap. p2w qi.;8dvelocity, does its average velocity during any time interval differ from its a fqazld/3enwpf.8y *.z;d. 2j/ pdiyinstantaneous velocity at any instant?

In drag racing, is it possible for the caruhcf5 hw00 phy., s3cn 54g vcf0pfjy0 with the greatest speed crossing the finish line to lose the 0 f,gy 0y 3c0hfhfcj5c.v 04p5upw shnrace? Explain.

If one object has a greater speed than a second -c936w7f8ihfm gj pe vobject, does the first necessarily have a greater acceleration? Explain, using exapc7 ie96f8w- vfjg m3hmples.

Compare the acceleration of a motorcycle that accelerates from 80km/h 1ur d0b kbiqqf)-o q;hd(.x6 qto 90km/h with the acceleration of a bicycle that accelerates from rest ;.xkuqf6obqqd( h-q dir1)b0to 10km/h in the same time.

Can an object have a northward velocity and a southward abo:f( i-wocfsz 9)lz,r7 lc,ycceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Whblg46c7 gn2vjirq 7x se7y.v1 at about vice verqe 6vxglji b14277gvn .cs7r ysa?

Give an example where both the velocity and acceleration are negative.tzv 4n53-/vukva/z ws

Two cars emerge side by side from a tunnel. Carcxxd(eio0 ( l6 A is traveling with a speed of 60km/h and has an acceleratioxl 0((xo6ced in 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 acceleration decreases? If so, gi3vq n 1gh, zi380svhhtc:l89i c7+nk ttqyak-ve an example. -h,s3 av3iqh t+c1g9chyq 8tk 0li8 kn7:tvn zIf not, explain.

A baseball player hits a fo dybo8 1::kpqnzuq8rj *n5, kjul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air:5j, qo:n 8y*u kbzpjk dqn18r resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening toaee5-qsem.jqr1 48g5/ a fbx e its acceleration due to grax8j5- aesqamqee /.r1 5e gb4fvity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could thry9imygvh 582 y+mq h e.07coenow a ball vertically upward? How would you estimate the ey ey9ov+g20nh75. c8 qimmyh maximum speed you could give it?

You travel from point A to point B in a c-4qzjyjc87 p yw2+ezi ar 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 ?-4j+ ij8y2ew zy7zc pq Explain why or why not.

In a lecture demonstration, a 3.0-m-lgx3i+p+cw6c ** 9 sjmotwdhb +ong 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 the bolts be tied so that the cld bw+gp c9*wjh3*sxcomt+ 6i+inks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rr*jgl; oxed-8z8q w u/ock falling from a cliff, an elevator moving from the second floor to the fif*lxoq jure8g/;z 8dw-th floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upww) 2zg v6wrl )b -6y bxb5yvsa)ymou; wy(6cl1ard will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration du2uwbyym(vsvxra 6y66c) ; -) obyww bgz15)lle to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero aaxi* 6 uvqx7qms; ; suzj9.zi;cceleration at the same time? Give exux 7q 6jq9 s;m;sixvui zz;*.aamples.

Can an object have zero acceleration andsj6n5;ih0 qd+*p t bui nonzero velocity at the same time? Give examples.jpisi hnbtqd; *56 0+u

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hlx/zgvi: f2 9qf4 hv(zint: First try to duplicate the mo g/zi 4l vff9:hq(2zvxtion plotted by walking or moving your hand.]

Describe in words the motiurn *5m5ch6h218cz xm (rhap zon of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to,2w* pnmk/ 5e6xez+b/ ojujvq travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long h lrbh7 .u7sl+does it take to fly 15 km?    h

  If you are driving along a straight road and you look to them gam4l6(b0 i.josu 5k side for 2.0 s, how far do you tmj b(l 64s 0aigmk.uo5ravel during this inattentive period?    m

  Convert 35 mi/h to a6- jdfe o*x.l
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frommh vp5l;5w hdmk7;)d 8m0a/k3sku y kr $x_1$ = 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 km. It then becbki 03n 6ff1dgins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 2n k3 d1i0fb6fc0 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 ok(q (0p yr ac96 tya943bmkfea lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives inpo94(ymaq6tk3 y (a9ec0rkbf 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 a-. ru lu 2.j1.dnlah1ku7eed 7,mhp fx total time off-.,.e.nmj2r u lu7p7e1 duk hal1hdx 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 11mo:2b+ d zsrno;b tb8l;40n 7mp7qsof +x- dvu6 m away in 14.0 s. It then tur0z+s-n7q d7nrmubo:fmobv+bxt dpl82 4 o;;sns abruptly and gallops 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 paraaw-3 o x :e0,r8nwtrwnllel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initia 0 raow3:-x,wn e8trwnlly 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 long wihh+++lr:r;z j8qbh k ill it take the car to reach the t +hrh z8l+ih brqk:j+;ruck?    s

  An airplane travels 3100 km at+nwv :nt zp2x: a speed of 790 km/h , and then encounters a tailwind that boosts i nwz2tpn: vx:+ts 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 comp nk pyz)9wv+/jlete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the retur k +)jwz/9yvnpn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the ss4d3p tw,ugaj.n. 5p 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 issn pt a4 sj.3g,.5dwpu released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates2 r -om2v3sbiu from rest to 95 km/h in 6.2 s. What is its average acceleration isu3ovm 2b2i -rn $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 1 (/xb));exlfd ,lrcqe0.0 m/s in 1.35 s. What is her acceleration )r lf,xe)xl q/(bde;c
(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 abry g8f2m/oeyo x 8dt+*ou +8y2tmd xgroeyo/ *8ft $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it then brakes ax222 z 6p wuw/rvqvx:ob1.emand comes to a stop in 4.0 s, what is: bpq122x ueo2w.xvr6 maw/z v 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 and moves in a strhia4 ix:;jp i8-c ygl9aight li:y-h9 cga ;ijx8i 4iplne, 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/s in 6.0 s. What was its acceleration? z ;10n9gcehr7r2d hmpHow far did it travel in this time? Assume constant accelerationm01ze2 7 ncrd9ph rgh;.    $m/s^2$    m

  A car slows down from 23 m/s to rest in ahx*al/l(a ebd ri 7+t) distance of 85 m. What was its accelerat7 )t+l i/de labar(x*hion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long yn:mx y8uh 5yb )b2* x77xi-dkvzpul/.xs up6a runway is needed if the (constant) acce7z6bbvp x7/n)lk imhu2y yu xd*8:xpuyx s5.-leration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially toq 4 ui8 miofrapcx:5zm kch0w97i(; z(p speed (of about 11.5 m/s) in the first 15.0 m of the race. What is t ic(pqr m xzow48z9(;f:hm 0k7 ui5ciahe 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.e xplvi4b:w 9p3qd7a 70 m/s to rest in 6.00 s. How far did it travel in that timel xbid e 7wa:34vq7p9p?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming etb+uqa /ma9+r q38:q, chrmka deceleration /r +tbq9rukq, qaa:m3me c+8h of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h bf-g)(1isr wj strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. Whfgb)(r iws1 j-at 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 of *vbf 2 - y;uq/5upazl92ukxm)aq h hj295 km/h and human r;2-2aazlvh 5hjq9 p/ufubq) m 2*uy kxeaction 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 equationhgb;s d.0g xs8 ls- -igb20mls 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/320it ef auwm;s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car cani ate;2mw 3u0f 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 30.0 min. After:ve14 ey ucz (rf)fxmfwq8j)k 7bhp05 exactly 27.0 min, there are still 1100 m to go. Theqx0yk wf4p7rz(f5jcum eeb)1:h v8f) 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 inter6wz4*p6k u,alz+ bek1;hmk9yxr .w m esection 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 interlk r1m4zkbu wp9e . yze;+6*k,xw6hamsection (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 cliff. It hits th; jivqo-*si z4zrdz (+e ground below after 3.25 s. How high jqz -i z4so(v i+dzr;*is the cliff?    m

  If a car rolls gently 0t get9)hsh8tb35t yrj/4-8qfvy ltl ($v_0\,=\,0$) 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 +e35i9h ;rbro;z ykq:bxxmf :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 verti x+l)qj4 i-ticcally upward. With what speed did he throw it, and what height did it reach? ilq4)j+ c- xti   m/s (Round to the nearest integer)    m

An object starts from rest and falls under the u y c*8lmv-aj,influence of gravity. Draw graphs of (a) its speed umcv-,a* ylj8 and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20g8.4bp fn5ymf m ,dn3r52hwef m/s. At a height of 125 m above the Earth, a package is d4.5wnyhe5rmff8n32 pbf gd m ,ropped 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 from rest, show that e: s;;bh lf7rtthe distance traveled during each succthsr7;leb : ;fessive 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 neglected, show (algebraically) that a ball thrown verti4,rn;pmwr h(ecalreh(,4p mn ;wrly upward with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed /uwe3f d8.q5ivtt-ey:;m zwb;zbvi. of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple inma*q b/2ve:si Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple posvbms e2i :/aq*itions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28qjimb)*6;)5vl zht : y2buhyk s to travel past a window 2.2 m tall (Fig. 2–32). From what heightytv*bhk lzbj i5q2my6h):); u above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ojk +fdkr44p4mi; utjz:a8hm - cean is heard 3.2 s lda8k 4jk zjpfit 4-;hm4:ur+ mater. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose noruktm- eb57o-7cn; hf 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, you hear the u77f nkoce- -;5rbmh twater 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 spex ca+2/g knzx)ed of 12.0 m/s from the edge of a cliff 70.0 m high na) xz+2g/xkc(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 upward by a window 28 m above pdlhf01h +wrm 029 daithe street with a vertical speed of 13 m/s If the ball was thrown frr m+h2h9fd0 wpa1 0ildom 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 7/x6w jq2pa yhs5jlx : sam0y)zf*u: vas a function of time. (a) At what time was its velocity greatest? (b) During wz/yufs) m 6a: jhxv w :l0p*sj52ax7yqhat 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 along axkgb4) dpu+f1aut5lj (: 1bt q straight tunnel as a function of time is plotted in Fig. 2–28. What is its instanta1tu +qx:b1k5g fajt4u d ()lpbneous 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 wad;q 0 - 2k1fwhm7wlvd9 zyw:as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiy- fvwm2d7 0hw1w9lwkqz d:;afting 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 acadfj a-bo)20nt w i,vcvkbg ;pb58/( hceleration of the car in the previous Problem (Fig. 2–35) wheh;kobjv,btw(bn f2a8/pca 5g)-i vd0n 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, estimae:q-3z z. ypk0 sztey+m+z yn,te the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function ofnh acshe*lt9*e i/su 5s h;9f3 time is given by hs3i*9na* hs9 el/5t uesc;hfFig. 2–28.

Figure 2–36 is a positq)hpa zb dv3dq5(2;b*rdz1*1 f6foj i6pf stsion versus 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 poj sd tdr;iq5z3*dos 6 1ffq p2ph)6vfaz*1(bbsitive 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 above a firefigh (vi,m:ch,u089v t 8t5dirdtm s)h sjlter’s safety net. The survivor stretches the netlh dts5ru,j, 08hvm:i 9 v iscdm(t8)t 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on thqg4(f+jj;ldu za7 nd -e Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it wouldj;4-dj+(fq uzngdal 7 on Earth, assuming the same initial velocity?

  A person who is properly constrained tu, + g0j mdbrw.b9hj7by an over-the-shoulder seat belt has a good chrghb9mwju7j b ,t0d+.ance of surviving a 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 2 1*k6un ldfx* nsx6xqabove 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 from the bridge onto the truck to ma1 *n6n2f*ksql xx dux6ke his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its carstwkvh4oh (e5 ;dfz r28 for front-end collisions by hauling them up on a cran; ovfkhr52t 4 d(hewz8e and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels abo 9; /lun2,q;krayi eutut $10^9\,km$ 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 acceleratio(. 1niub1oqaxg/q sy7/r/wv an from rest. The front of the train has a speed of 25 m/s wr wuqn.1y /bq// vos (1ig7xaahen 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 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 a6rbnezi:g; n/a kmi3-b2 0 gfb deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the waterb f-/ n mgi3bka;0igrz2e6:bn. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit systgp zde*/(x wk8 -5iiozgcw,9v e qpw0(em, it is necessary to balance the average speed ofovi0zkp,x / wq dic5ezw8(p(wgg9*e- a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip 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 *xmrw-6p gv6d9 (k7qsh7qbz hfall straight down when diving for fish. Suppose a pelicrvhq9sxk6 6mg 7p(wq7*z-hbd an 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 surface of the water.    m

  In putting, the force with+vatc3r2cs/o tlynt f*(to / 9 which a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhoan2cr yo9l/t+(tvt 3s/ c* tfill 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 a constantn 3py4f.bajv 2 h p9vox vdbmeu6,1t4+ speed of 6.0 m/s Just as an empty box car passes him, ap6bo9 me34hu pbx4+ d,f1v.jtvyn 2vthe 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 rt o7(((u,axm dex(xhe oof of a high building. A second stone is dropped 1.50 s later. How far apart 7hx(u aoxedm(,txe( ( are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.i ttv:yy1u o7 g1,gij60 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be mainta7t ivg,yti :ujy161go ined for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountaiqphg8jeu7x8x w ;+pa4 n pass as he moves at 18 km/h . At the bottom, 4.0 km farthe4ppjhgx88w uaeq 7; +xr, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on twolz isxsd11w9-pv4..knvf 5 jc trampolines. The first child can bounce up one-and-a-half times higher than the second child. Thi x-kd4j nz.1svf9s1l.5 vc wpe 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 ov( )e*o /viu :ld-c.,4slmcvj;iq ebqwertakes a 1.10-km-long train traveling in the same direction v-:4ic.o/lqqujdvme sc w)*i; ,ebl( 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. 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 o4 ewg oc+ tjxmu3/5qtb-zxs3.f 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind thq +wjtsuo3xem z5 4c/xb-3t.ge 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, with an accelcfn. 9x;6n y l fpd,mulr(jrj7,zq.h2 eration 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 b2 x85er38xuc-h0 qrdz i( rxpsjk-;xa 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 first i;2x3i b p keur-srx 0xxhr8j-q(z8d5cntersection, 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 8ojema yzj u1,qtm uj1)-(r8a a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, m- ()18 aqz1tae 8juy urojmmj,aintaining 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,pjt wrmrckfg 7+, bx*:z j3h62 a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the sx7hbp+rz gjmj ,wc6rtf3* :2kame 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 vert oqdw-xa 0/;jsically up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a build;0qdxwajo/-s ing and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a fr8;9/cv u2c./ktyr assh5pvy tee-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the airc;/ 8 tcav yu2 k5.y9trs/hpsv resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to st*2e gpo8uf22rb u(vb+ u-fneend the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/mg(*2tu euv 2b2unpf b-o+8rfe in)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe canun 4fyz02psnv *j+:n7 ej+wqg . How many times higher wqn js: y7jg* u++ewp4n0z2vnf ill Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend 48cv4ttqqj +m 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+ 8tmc4qq jtv4 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 48o roz7jhhzijp 9e e3+;kso(building using a barometer.ee3j;soj 8 hpziro(o9 kh47z + 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 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 bs7 9xsg -yl0v*inc0 plicycles, A and B. (a) Is thesys *xilv90gc0p l-n7re any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?