Does a car speedometer measure speed, veloci 2i:ovk+/ ww;kvc k*stty, or both?

Can an object have a varying speed if its velocity is constanth3:ly-y kj x0w? If yes, give examplejy0h -x3w:ly ks.

When an object moves with constant velocity, does its aver.1e x /bi9moarnn rv2/age velocity during any time int.nx2ro /e/9r1 vbmnai erval differ from its instantaneous velocity at any instant?

In drag racing, is it possib dtn.i adz1c+9yv :6dele for the car with the greatest speed crossing the finish line to l.yc: die9td+1 za vdn6ose the race? Explain.

If one object has a greater speed than a second object, does the first ni q1elu q*.8bg: bnza*ecessarily : zbgbeu* ni8q.1lq*ahave a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates fro22 3yk vgpr 5j6,ncaux/nhv 7afm* vs4dg1f u,m 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the same timey,k2nfjasv7f4 /3d2vgv rug 6x51 aunp *mhc ,.

Can an object have a northward velocity and a souvr-95.d fl(wf.4u yv nzbqx.sthward acceleration? Explain.

Can the velocity of an object be negative -ys1a*2.q6xtja8 mh(9 dnb dqxhgs+cwhen its acceleration is positive? What abouaydmdbq8c (g 2xash*hjq+-st9n. 6x1 t vice versa?

Give an example where both the velocity and accelery+ z 0k;vl q )i++9(4iwhlyilaeone 9dation are negative.

Two cars emerge side by side from a tunnel. Car A is traveling witdi4kjevnf8t( w0t6u3 p)o gv-h 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/t3 6 8ip4d ke(wujtovn g0vf)-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 kgx;h 21de+- xg.awnfacceleration decreases? If so, give an example. If nd;xfxk+-n. gw1h2 geaot, explain.

A baseball player hits a foul ball straigz) qja0lz0.2pl, fk dmht up into 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 the caj 2z)pml.,ql f00z daktcher catches it?

As a freely falling object sqxl i+) (,)jxuoex7aw f/jdd6c e/k4dpeeds up, what is happening to its acceleration due to gravity — does it increase, decrease, or stay thj6,fldc7qe eaj+ux) x(wxdi )o// k d4e same?

How would you estimate the maxim-/n s;0yhh3hjndnid,j-t o/i um height you could throw a ball vertically upward? How wouldt//sh 3-;di-h jn0 h iodn,yjn you estimate the maximum speed you could give it?

You travel from point A to point B in a car movik hw8tnhkzm4yw7sf+3t4 d. j4ng 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 averaw+n3t zsw47f.t48hyhmkk jd4ge speed for the 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 s-a r/ kvkd9t-h ko l15n.fu9ugc1mp 5v6/mdhto it at equal intervals is dv un -t6 k5uh 1dfm9 /sk1cd.-ghl/mp9v5kraoropped 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 clinks occur at equal intervals?

Which one of these motions is not at constant a:lymm 1wkf dxnh i.)f92o7+bf cceleration: a rock falling from a cliff, an elevator moving from the second floor to the f7mn9lfd :y+fm)ifo.kbwhx1 2 ifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its oiin0f b2zzwgi (a0sni *t4 6k9riginal position with the same speed as it had initially if air resistance is negligibl0gi9w bn0tf i6(zzi4aks*in2 e. 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 zeroh e;l6hq-max6*d5 kpx velocity and nonzero acceleration at the same time? Give exh6* x5heam;6x k plq-damples.

Can an object have zero acceleration and nonzero velocity at the same time.o ahzlewcv( 5uj+7) d? Give exampllh7+5wved ( zo a.c)jues.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a,t; 4dz*.)rf wad-p udw etc. [Hint: First tr dar* zd )fdt;-p.u4wwy to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed i/fbsfq 0+ imxk(6m x9jn Fig. 2–29.

  What must be your car’s averaew 914;flh(i ,sjl tlxge speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it t cuict3c8o( c:(ypj/t*fjvpxu 5hn 75 ake to fly 15 km?    h

  If you are driving along a straight road and you looqkj- xbo)s.*j k to the side for 2.0 s, how far do you travel d*q.j jk-sb x)ouring this inattentive period?    m

  Convert 35 mi/h to vzym9o)r. xpxz;z.*a
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves2usj y;,hjp )s -3vzow from $x_1$ = 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.(n-thw hvk5g16c)du r It then begins to rain and you slow to )wn g 16(rdkvuhcth5- 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thulhj dr0yt7ym2(xzt .san5 57 ;x2jgfz2h0yoimb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate 75nhz 22j.50xfio gyzd tyjl2hts r0 a;mx7(ythe speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a total timmj2fwo4vm;ui /t2 tn3e of 12.5 m 2n/mifvw oj4u ;2tm3tin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a (xe muc+.px7xin6t 5pstraight line, moving 116 m away in 14.0 s. I5tx7p. u(6xi nxepm+ct then turns 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 parallh, ;4 gvjnyur9el tracks. Each has a speed of 95 km/h with respect to the ground. If they are initiall,ygnhu4vjr9; y 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 n ;wx,w63mw knhf r2ctld 5txph 94t6ld7, kq9m behind a truck traveling How long will it take the car to reach thnlcfw 9h2kqwdxrmt 3,,pw6td7k9t x ;h65n4 le truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounte xy6 rdqnv3j3,rs a tailwindxn ,ry3v qd6j3 that boosts 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 anw 66 5d;cke.y4 v(httan-yy zmd average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed dymv(4tywe-. 5y zt 6;nhca6kby a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveli5nsdoih z amn;m;360rng with constant speed hits the pins at the end of a bowling lam6ao ni5 0m3d;szn;rhne 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.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is iix 9khe-ex2bu; ,c .mlts average acceleration ilmeu9cx2xbi,ek;-.h n $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelfom hh.ghe*yunk kv6;jb*/cj(y1 e +7eration *jynukhc. e1ebv ;j/ mh( ohfg+ k7y6*
(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 aboug gru)q:3-)gjj/) vliu rf w;st f qlw:s)ujv) jig );rgr3 g-u/$1.6 m/s^2$ 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);rxcc6 f45va-fbzxm speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what 45c;vfrzm -f6 axxc)b is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from res7fk +qbp v70pt*wla g7sj2:qyt at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and os7a+ vp* :k77fg tj0q wqlpb2yn a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? How1y;lqrc5iq y-*jb(k a far did it travel in thi lr bia5c q-j(yy*1kq;s time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s t.8vebak,;o q so rest in a distance of 85 m. What was its acceleration, assumed o, q .av8;kbseconstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is nee8x;d 7rom)rrv7hm .zd-cz*w c9; zhs kded if the (constant) accsdh*v m8.r7;7c zoz9r d)z;hc mkx-wr eleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentut dha(:i(567 , oqno:vgwz9hmn fc5l ially 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 rea 5nl mof,c7u( 5o:w(9tqgahh niv: z6dch that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniform hs +dwjt56f 4rv;ju/ily from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in t+/d;s v546 jjtiurwh fhat time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. A0/ yd9sq6 ahfr, z 2tt03evmeassuming a deceleration odav6rf t9,30ty/esq z meh20a f $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tbutdw c+a .pdt).4pm0 ree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on?pc ddb.)tu a4tmwp+0. 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 ins;eh bm. y/khf6lz6 9b g8lt:hitial speed of 95 km/h and human reaction time of 1.0 s, for an accs/hgzh l8;6b: ybf96emtklh.eleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stoppiogmksz12h 322tnddl 8 ng 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 *by2 n afgicyn+-m:v6car’s driver looks for an opportunity to pass, guessing that his car can ac yacgn ymv*i6n+: f-2bcelerate 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 theasrn749x u)nyr1( guj 10,000-m run in less than 30.0 min. After exactly 27.0 min, there ares 4)rxuny1r 7jg(a9 un still 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 intiaw1f*l 8 y -)gecfy;rersection 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 awaycwr1e ya8f)y *if;-gl 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 cliff. It hits the ground below after 3.21o r +nc/xqv:v5 s. How hi:vqrc+1xvo /n gh is the cliff?    m

  If a car rolls gently ( nu/*8kxr4hdw $v_0\,=\,0$) 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 5vcspr54+)tfn7ce z 3ldreu 2 +or; wkstraight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after tb/ vy 8 sdrn0ztoqg/87hrowing it vertically upward. With what speed did he throw it, and what height did it reby odvts/rq8 /7ng z80ach?    m/s (Round to the nearest integer)    m

An object starts from restjf6hlzi3jrygr-xn (9 y bqa2z l*.( k/ 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 = 5.00 s . Ignibajr2k.rn zq( 39-(6 zg yl/ljxf*hy ore air resistance.

A helicopter is ascending vertx 9t(cdqi:4 :o kflnhxvn35;b mo:(ffically with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial c:nlifx5;bq:3f4 :x( t(k nmdofoh v9speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show tm u1:c9dkl0ark7m9 bj4 5xkx h8tf c,wvu *5kghat the distance traveled during each successive second increases in the ratio of succe19 ,c m vwkk u9lr5kdatug:8 5kmjxb*ch407fxssive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, sh0t:r 4hr x9 qul;d,c rozy56xmow (algebraically) that a ball thrown vertically upward with,4tx xm: urcdhzl5 6oqrry;09 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 )8dwzwr f -3mwwith a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig4:/iqunqe6 1v sqkrc ,. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple pui1s6 nc,qkv:rqeq/4ositions, 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.r(m+dt7vew a*s 0j,r x 2–32). From what height above (x*+d jsrv at7r,0we mthe top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ofc;f t*9hgju +hpt:0 a7vzkv0cean is heard 3.2 s later. If the speed of sound is 340 m/s , hfz +t gpuh jv:v70hf;t*a0c9kow high is the cliff? H =    m

  Suppose you adjust your garde ; ign pn:;6 erfai/yl5qv:p8tn hose nozzle 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 water striking the ground next to 8:r5i:e6 n;q/;gplyvt aifpn you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s fromnm1* urrl o:4s the edge of a cli4ro* 1s:umrln ff 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 pass uvyaq 6.tbfz u3 20fxe99 u(eympward by a window 28 m above the street with a vertical speed fe (v0 zb9 3ea 6yuqu2mfx.9ytof 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 train as g (ta550f)jyoaozq :n 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 cofg a a)joy5:nz(0 5qtonstant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of7wmh-7rghh 6z/eb (xu time is plotted in Fig. 2–28. What is its instantaneo7 eumhh wb-rh gz/67(xus velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as show.:7qk0 c*jur rihlc ,tn in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shicl.qhikr0,t7r u*j:c fting 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 previous Pro0h,rek5 90 )8owucpzeul ka 9fblem (Fig. 2–35) when 8pl f) 0aze9rhk cuo,wu59ek0it 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.jyyx .0edgo7 jv-hz0;,sy wv fj,d- h 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)yiy5kzmc qxvuxsy5 s-(h,41 a function of time is given by Fc (y-1qmki ,xyvh 5z5uys)4xsig. 2–28.

Figure 2–36 is a position versus time graph for the motion of a1; t7oahgwt 6( saqz7pn object along the x axis. Consider the time interval from A to B. (a) Is the object moving intw( ozq 7ga7 thps61a; 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 aba*z g7c*r0fkd ove a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to restdfc a**k7g0rz, 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 about one-sixth what it i (tx4 nn9howh5x 2vuvj 4rm;z*s on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would mxv wht r54*;jo2hun4(zxn 9von Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a goaq3)v 0x3hw 0 3fyyhbfod chance )wby33 h03hvxf ay0qfof 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 3/v6ysp faijm1a.o,vg+ e z1o on a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is 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 itmjfoa./ey+ivva 6 1 zop,3g1s?    poles

  Suppose a car manufacturer tested its cars for frri t x-ufr4 1xl:c8nj)onmyg4z4.u rah* (su*ont-end collisions by hauling them up on a crane fun - r1r ( uyrx8*cm4i. 4g*alo:zthu)4 nxjsand 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 to;xglbq :.m s55x6iluravels 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 begihhu:;;2x6 m zbkk)arkns uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railwm62:;rhbh k; )uxz akkay 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 watid 0a9/:np;i)k tavkrer’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleratio;9i)/knp dt0v aki: ran of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit s ohk4nb4 4ey7 x4o*jesystem, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a k 4sxb4j eehn4*4yo7o 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. h 0q,j3cnx1.dibki0l Suppose a pelican starts its dive from a height of 16.0 m and c b,hnl1kd 3xjcqi00.iannot 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 which1m1gh jpj 6-ke+fgh,1z pa xw7 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 Fimx ,fj+gph7g-1 1 6h1apzekjwg. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight t.z m6m.im1,:j lmvi1ogd rbsl,o8,pzrain traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive 1zmj8: gl6,.om,m1v zmoisi,br. lpd 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 hight2w93d9azb 62)lojn (ds fv wk building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one hzd nw32a(lkt9s2 6bj fw)v o9das reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 p1i7j2mp6.mgu ng*w u 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 maintained u2*.g6pi1 muw nm7 gpjfor the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain passkzv1kxhauvn+5 r l(/0 as he moves at 18 km/h aklh(x0/+v krzv n5u1. At the bottom, 4.0 km farther, 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 cfih b9,1g 6uk- u n8dns24mrpon two trampolines. The first child can bounce up one-and-a-half times higher than the6sk19m8hd c f u4n,n-bg u2pri 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 train travelik 25m:zgy 4wuzg58 yugng in the same direction on a track 5m4g2zzuwukggy y:85 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 oe:.tjwq,o0q0w.h ld f7pj .gwf 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 the average acceleration of the ball during the throwg.7:qljd o0pw qf twh,0.e.jwing motion.    $m/s^2$

  A rocket rises verticalg)fcu cf aj1,z )+n20p wtp(adly, 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. 2–42hz fal/ te1qbm7h;;m9. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at mh;abt/e9h l;7f 1qzmthe 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 constanw:homgo2*b l2t 120 km/h takes off in hot pursuit. The poli gmw*bh:olo22ce officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second rsrf8d-3+ eflx *m1ypstone is thrown straight down with an i1mf dr3p8-*+ lr syxefnitial 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)ozfmvpaph25ckqn .2p1 :md. same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should:md2)o vf. p251p a.mzkhqcnp 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 wouldu*s0ni2 xhzd h4p-.xsb a7t7*q qv1xh it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance 7x*q2hh1 a.x q4t7d x0-bs zi*p nvhsuwill restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgx:5kavacs(p hc6uf+/ ers 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 a6+(cf:h sau5kcx/p vcm 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 falvjp+5;na (ny ster than Joe can. How many (n;j+v5 yanl ptimes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the gro bnorb/, t iuvy9kd5zc:(;1caund below you. You drop a ball from rest and see that it takes 1.2y9vi5(b 1krcn; ucz/a:o bt,d s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to(t;x13hpb q;3 r 7m olvv3raiq find the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, thro; mv(htqbq3 7iax313v lp;rey 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 6i0n2l(.hc-avhni6v. wuv deposition 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 largerc. .u 6d6v-nhiv2l0 ev wnia(h 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?