Does a car speedometer measure speed, velocity,tp : sjvx r2i3w8v/bv9 or both?

Can an object have a varying speed if its velocity is constant? If yes, .qb90jtk51fzdvde sa: ;o+jvgive examples.5jd:b10ef.jtzv d9 v o asq;+k

When an object moves with constant ve4r1-2 t.j0cf cepqibslocity, does its average velocity during any time interval differ from its instai40b s.r tjq -pe21fccntaneous velocity at any instant?

In drag racing, is it possible for the car with the greate742,a w +bxu-meho gaw6mkv (yf-pz k(st speed crossing the finish line to lose the race? Expga h4ykb7mu6v kap+,w(- femzowx2 - (lain.

If one object has a greater speed than a second obju bzooogla* +8s:bu,.xl3x g 5ect, does the first necessarily have a greater acceleration? Explain, using exampleo x,ol.z5lg*u3o: u gx sb8ab+s.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km/h oz- ec f*u dqrbp-ax.0tsjth9 ;k, 4l1with the acceleration of a bicycle that accelerates from rest to 10km/h in a,j;h4 t* sb tecu0l1.r-o f9pk -dqzxthe same time.

Can an object have a northward velocity and a ybkc7 4pu /;kjr4h*cc( 9dpcisouthward acceleration? Explain.

Can the velocity of an o 0hn*)hld:xs2i zh 8dobject be negative when its acceleration is positive? What about vice veo d8*ih hlnd0z x:sh)2rsa?

Give an example where both the veloim1)*qscdbk3p. k m8cq1ktw ),gir3mcity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is travelin3sc 4h f63siheg with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing e6fh ssic3 h34the other as they come out of the tunnel? Explain your reasoning.

Can an object be incre6t g7,lg ba;twe5 aa -.um2lr.wcu:k n;z8hntasing in speed as its acceleration decreases? If so, give an example. If not, ex,c8..6eu;w7 amltl:b hug g2a;ra5k twn-ntzplain.

A baseball player hits a foul ball straight w:p9roiat:./wfq);qp evx d /up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resirp)/pqoxwa::d iw/vtf9; e.qstance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object sp o3ab. nhsls *w/tzl)6eeds up, what is happening to its acceleration due to gravity — does it increase, sls nb/36h.*oazw)tl decrease, or stay the same?

How would you estimate the maximum hei4 :7yfn;kq/ noqm:tlwwf :js 1ght you could throw a ball vertically upward? How would you estimate the maximum speedj ;n1 fo:wtny 7mwlf/sqq:k:4 you could give it?

You travel from point A to point B in a car moving at a con8 3 ez3 cvrxgqlthur/1c/y77yd02g dastant 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 t 8 3h yv ce3urdgq1y27c/dlrxa7gt0/zhe entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string ia4zu(-*c+ kd;:xmork x,n dv 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 clinks occur at a(+mknid,r;vk*:xoc4 uz dx - equal intervals?

Which one of these motions is not at cofpmw69bw+ a0 knstant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor makimawk96+ bwfp0ng stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its origin/0c5caltvo +l al 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 due to air resistance is always in a direction opposite to to+0lva l/5ct che motion.]

Can an object have zero velocity and no+/ urzl2f f1q728zud :bkdvuxnzero acceleration at the same time? Give exampl: ubxrz7kf182zvldu 2/ufd+ qes.

Can an object have zero acceleration)qcyuy+d 9p17( l7 u-o eqputh and nonzero velocity at the same time? Give examples-ptulu+7pceq )u1 9hq(d7oy y.

Describe in words the motion plotted in Fig. 2–28 in terms of v, acz. b0x: bedlk1e1fh lj0-3nb, etc. [Hint: First try to duplicate the mokjlx.1f0b dbb1ec l-:hn 30zetion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. lx -uol:;2tw 7;kmiil

  What must be your car’s averageh9u/f5zt +obqco0my 9 speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long d 4cbm:ydmz9 grzv 2;rty.-g3loes it take to fly 15 km?    h

  If you are driving along a straigplpx.cni (c-q n:mr28 ht road and you look to the side for 2.0 s, how far do you travel during this inattentive period? qc(:npxp 8m2. cr ln-i   m

  Convert 35 mi/h to *mlayudxyo s;4+t9;0pn wgj )
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fronl1fq da)*q1xd86 re .ktba-z m $x_1$ = 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 13kd29ji 1: odw4e wj+po0 km. It then begins to rain and you slow to 65 km/h You arrive home +ipejd d24o:ok1 9jwwafter 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 a lightning flg37utr r7jgi: s y:w5pash 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 the speed of sound in m/s fr :wr35y:gg7p s7tjiur om this rule.    m/s

  A person jogs eight complete laps around a quarter-mil 0*7vjoi8n- yqk qhh,b3ky 12l34f vnxd1jffbe track in a total time of 12.5 min. Calculatykfobh *3di hv2f1f1,4 kqvjy lb n7x03-n8jqe
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traineh08upyao(s) c 9njwub qx ,5e;r in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calcpwub,h nx8(q9ys)ej0ocua5 ; ulate
(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 eachwt-q::uwbp m; other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be :tqwp:bu;- mw before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 f5cah/ bhoyvw26*t0 t m behind a truck traveling How long will it take the car to reach the t 0ov*b6t/2wy h atfch5ruck?    s

  An airplane travels 3100 km at a speed of 790 km/lnicp.6dyxw06 m:ru r;gf31 n h , and then encounters a tailwind that boosts its speed to 990 km/h fdr 6ungic0lypm6w :xf rn1.3;or 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 avhn -ux*lz+qtw)dm2. z l/oq+rerage velocity of a complete round-trip in which the outgoingz+ ).2u/ lqq+nd* xohtm-lzw r 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed 56i3ud6k lnelbejzxqi s)(xpuf*a()u *i . g9hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his a.ei**b3zp g(e (i)5 qx6lkfls) xi 6 njdu9uuhands. 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 it ziq)sn59p2na :f6cp ss average accelerationpaicsn5f9 z6psq) 2n: in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 3clazs+a em+( 10.0 m/s in 1.35 s. What is her acceleration +l asac3(em+z
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular auna7 0fxys- js.fm3c4 1ouuta1 tomobile is capable of an acceleration of abou1.mny 0a-astcxjuu4f3f17s ot $1.6 m/s^2$ 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 tk uz c2v1.mz 7clly-;when brakes and comes to a stop in 4.0 s, what is its accelerazlv1y- .2ku;lzc 7c wmtion 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 mw zf5bt5)2qv and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleratv)zm5w2b q t5fion 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 xayc n04q-9 vimj+h2n u1wmap 1d +i8vwas its acceleration? How far did it travel in this time? Assume cou-c iwd1v2h9ma n+vnqx4+8apm1ij 0y nstant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rr5gi 2d2 lc0tkjv.*dmest in a distance of 85 m. What was its acceleration, assumed constan0 dt5. 2vgr ji2clkd*mt?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runwap,gv3z(ja )h ty is need(ha)z3j vgp ,ted if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to ess hb+zyhfx85w8h)6wxcn /u/ f. zp9y rjentially top speed (of abopw8u/.yynhx9)wx6 f b5h 8j fzrhc/+ zut 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 reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.43) t6s5nv7cgjre7kv x+l hgf0 m/s to rest in 6.00 s. How far did it travel in that tiglxgf+ ktj4 v sr35nce7 h67v)me?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. As:( pdpv4jx ;ecsuming a decex p(e:jpd4 v;cleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresl(bn h) f4. nileg8ft0ses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the4)f gh.i0f bt(lennl8 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 bx6 i qmmi9i j-17f 8eotm7)oza car with an initial speed of 95 km/h and hu)m7omoz i8txfem 7i 16i q9-jbman reaction 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 equation for the stopping di6s lc 01y wiclfsb*-p0 8,kyuustance 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 goi*wuq+iakwg /ba2 ,/y dng 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that hw+*2qg/, dbywiuaa/ kis car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 mgccey9lp29oe gtwt:/ pm*q,; in. After exactly 27.0 min, there are still 1100 m to go. The runner must then acce,qley :e ;gp/99potmgc c*2 twlerate 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 just as thwcxrx1i0rt -8 pmy5v r 5tzadn/ (tk3.e traffic light turns yellow. She knows thrc da-8k5 ri/wx vpmz t3y0(.ttr5xn1at 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 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 topnc)7 -lyqr zpyz5 2vr:v5x.2 u3einjn of a cliff. It hits the ground below after 3.25 s. How high is2qri7r 5ly3pez:nznycuv.j ) n25xv- the cliff?    m

  If a car rolls gently (+lrp ty:hs06stz ; 2mj$v_0\,=\,0$) 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+9l3k1pp 10b/oscd lkzt c-ar 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 verticall x)w*hyuw ts4i7)m 6qmy upward. With what speed did he throw h x siw*wmyu)7q)m4t6it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under theb4;*usj+cgg equ.zj16hp ( y) mdlj( o influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function l gqu6 (hgy)usejb(+o1jdz.*4m;jc p of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height ofw81yb)4wyrmvp ddv)- 125 m above the Earth, a package is dropped from a window. How much timed1-4y8y m)vrdw)bp wv 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 thaci- kr/4n,ug6+ulvrzz a9wa( t/t4 hqt the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–2viurw /ac, 4 9z(kgnrhztaql ut46+-/1.

If air resistance is nedpv22fz vhvc-)xl) u*glected, show (algebraically) that a ball thrown vertically upwa*l-d )hc)2 2vxpzf vuvrd 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 speedvoxeqqzp;/+f+ lhpz 21c n5;s 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 Figh:sfry74es cfg6h3 p/. 2–18 (or number of photoflashes per second). Assume the apple ifg7hhe 4sr63 csp/ f:ys about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s tyu-i8a3 weiw3mb z3*co travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the si833 * uwbi-3ewmac yztone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocelymio7 msye 3 :q02pf2an is heard 3.2 s later. If the speed of sound is 340epl omis2ym q 07yf2:3 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. dsdb:yjstq 7i:p1/f* pwt(2o 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 you for another 2.0 s. What is the water speed as it leaves the nt/y jwip:db 2 t1o: ssq7dp*(fozzle?    m/s

  A stone is thrown vertically upward witha/e ub;2dnxegi90(cwnx6fuf. 2yg6 d a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34).;y06d cn6 x2(bf/inu92xge. wu feadg
(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 byr1oh +c6fjcxmp(f(7u a window 28 m above the street with a vertical speed of 13 m/s If the ball was th ju(7 mpox r(ch1cff+6rown 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 thc-4+ci hdod s*e velocity of a 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 periods, if any, was the acceleration constant? (d) Whend+*h4 sc cio-d was the magnitude of the acceleration greatest?

  The position of a rabbih,,0+jsy8vunid o3 jgm0 a n.tt along a straight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneo t +, 0j,3dhv8ojyuagnm0ins .us velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in tjy(8e-rnue6*k6rc u t he velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting nrt 6( e*-6yce8uukrjof 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 Problelbs1d.8b k9 ubm (Fig. 2–35) when dkb1b 9lsu.b8it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the or gppx1.q5 .xefd boz/cv7;tm 2xx 1+object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functpd0g p)e/ nb2rotz-9g ion of time is given bp dp 2)t/br -gnez9g0oy Fig. 2–28.

Figure 2–36 is a position versu2f2b w+lf2an+aiyssk n85)q u s time graph for the motion of an object along the x axis. Consider the timel+fn ifw2 aqa8bs y2)suk+n52 interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive 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 firefighter’s u1d lg9kb h /,58w01pa5 whm r-nfifhfsafety net. The survivor stretches the net i-lgb wp/khwf055u18hf , h ar9dfmn 11.0 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 the Moon is about one-1l(atft0kg /ysixth what it is on Earth. If an object is thrown vertically upward on (y glta/f10tk the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by a. 4fo0caxlj7( ei8nzin over-the-shoulder seat belt has a good chance of sura ci ioxe7(.f zn0j8l4viving 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 abovewzz3cc r,ed4 5 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 Bon ze 4w,c5zrdc3d quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for froj*qj;7y v ,ug .ocixd:lz fhmtd-;8quek,(j2nt-end collisions by hauling them up on a crane and dropping them from a certain height;oyq,* m8u jfjqdxi g:( k7cuz2ljh.e, tvd;-.
(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 about 40tz 1kv 5uzgb$10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins u.*u2q 5 ,wn8ryzt 4.jzb hnzonniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the traizn.*j qz,ub h 42.5rzn ywot8nn 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 suqfdkjwor zac/ 5640s3rface into a deep pool. The person’s downward motion stz0qkfr65w3jso d c/4aops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit s*y6 slwj ;dye2 y*hc u.ql1y.zystem, 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 9.02yze . .y6lw*;dul yjyq*hc1s-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 ;4cp e f5c4 bv4vm-px; h2tmtjand free fall straight 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 takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? vmj - x2mptf4;4hv p;b5cce 4tAssume the fish is at the surface of the water.    m

  In putting, the force 6et 7dqyfhv,g 421tp pwith 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 pu14q6g ,2vpyt td7fhe ptt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a constant speed ofhh/9i yy 79dph 6.0 m/s Just as an empty box car passes him, the fugitive stahy/hh 9iyp 9d7rts 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 adl yyb w48komz/06+z high building. A second stone is dropped 1.50 s lata8 z yody0lzw+ bk6/m4er. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km6m j9ezb3;s0yv /jgmn/h over the course of a time trial lasting ten laps. If the first nine laps were done b/ 0mg;yjje3 n s9mv6zat 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 h k;nykvxmr 6tm*wq3(m :(d(q f4*vh zoe moves at 18 km/h . At the bottom, 4.0 km fartherwxhmm;( v: fko(tqd*( *qyvz46m 3r kn, 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 tw;p msogn5mtqef6f1 v1+l76z z o trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up ofq zl;71 f6 v1eom +zmns56pgft 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 sh 5ie4y.x8y dy9avk1traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in oppv1y5s8ay y9hk.eidx4 osite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwinerk l6 e28mj1pg 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 ave1jeempkr86 l2 rage acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, 6fb k+ap4 5op6t jdp3lwith 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 spi5 vgm;c(*:hm/ ;r nn qac4twhown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights arm;c w4m ;c/ *rq: npiht(na5gve 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 const, ybn 7zng74leant 120 km/h takes off in hot pursuitlzne4 gy,7b n7. The police 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 thtr0 0zyn fmo (v0xzz/5d;.k ywat, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the ntdfzk.0xv/y0 omy5( zw; 0 zrsame 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 tixn)wxq4s *5zsme. 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 the second ston x5x)*n4sqz wse 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 longj*a b)q; 4+r xs:bh/vabo-fgc would 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 will restrict her speed to perhq-/xhrjs;ca*) v4b+g bbfao: aps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through ar2g 9 c.mbm4 +dtbxvx+ grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must +m mxv.9x4 rbtdgc+ b2the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a balleh5, ;8cn ia f8x3a-8rgnvmjo vertically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s 8 vf5gnr; jhe max-ci8 n8ao3,ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while yopaz1cys 4;o6 npp+ +dhur friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw thcs a+zp6h1+ ;4opnyd pe ball?    m/s

  Two students are asked to find the heiy+.wh5 fj5j31 s)e +r tkroezoght of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the build jt5wok y +se)reh3j1f.z5+roing 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 for5 squh-vo2+ ir 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? (c) At which instant(s) are the bicysvru5o2hq- i +cles 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?