Does a car speedometer measure speed, velocityi8u8f v/uz0 cw, or both?

Can an object have a varying speed if its velocity is constant? If yes, give ek vakk.nqttbiva.w tyw+6 0l.9*) iu0xamplky6baltk9 )u w t+v.i ain.q*0.0tkw ves.

When an object moves with constant vzo5: j1.hyoddelocity, does its average velocity during any time interval differ from its i1 z.doho5yj:dnstantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing the j3x07hazw01e f7zeiw 2 n :ocifini iwnofj 7:32x0eaezc07z1h wish line to lose the race? Explain.

If one object has a greater speed than a second object, does thexc5 eels-.suwzm, ex0; w,hb) first necessarily have a greater acceleration? Explainw,.-sm x;esu wl 0zbex5c),eh, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h texlnj e9*.kx c-l4l w-o 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the s*lx.j lek 9e-x4lnwc-ame time.

Can an object have a northward velocity and a southward ai3k) 8cm/0 (nyd8sl rz/gtkwj cceleration? Explain.

Can the velocity of an object be negative when itsfc8b*45k4b, kf e blty70lujc acceleration is positive? Whatt4b7 0fk b lkfle8,uc5y*bj c4 about vice versa?

Give an example where both the velocity and acceleration are negativebdd*o5j dc47.q kv9 vy.

Two cars emerge side by side from a t4updl 34c,,: waqxq)2sj yro0o)cdhnunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passuw s 4 ,hd4x:qpcn,2dc) oyra0o)3j qling the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed asbdct o.e0x8vpwy7- rc/ (o 8zb its acceleration decreases? If so, give an example. If not, exb- 8xoz0/8cwvpo.(r db7c yetplain.

A baseball player hits a foul ball straight up into the air. It lew f24xdzb2 zut1wnyb q; *sm()aves the bat with a spex w4 mnb*buf2;t( dszq)z21wyed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling objel)2tl+ b o* zl6f qj0fia1n+eoct speeds up, what is happening to its acceleration due to gravity — does iq )6 l0i +1ff2 le+j*otobnalzt increase, decrease, or stay the same?

How would you estimate thevn.54g(ou so n maximum height you could throw a ball vertically upward? How would you estimate the maximum speed you couon5ovg.(u4 sn ld give it?

You travel from point A to point B in a car moving at a p4+) mbwhzm 9oconstant speed of Then you travel the same distance fro hob)mm zw+p94m 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 ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long ve0)at+krf :qir08yx2s b8dj w rrtical 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 thej8ktx28 00 ar d+ wfrrqi):bys 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 acceleration: a ro/3:z ()dksielss oz5 uck falling from a cliff, an elevator moving from the secol :)izk /duze5sos s(3nd floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically up ge 8tn7oh4i;qm dym-0cbye0:ward will return to its original position with the same speed as it had initially if air resistance is ne; q:d y0yn mgbo4 7ieh08etc-mgligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time? Givz *qt9wto qfg9*4bo:4bti ck.e exbgzk4.: wc9* t9bioqoft4t *qamples.

Can an object have zero acceleration and nonzero veloqjrjfmq :+nbrk y.ar5168becpe- 8 9r city at the same time? Giverkab je :e9qp5+ -jrm1n8 rf68.yqcbr examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v gfsy8 z gxwp8c9uet-l.lg;69, a, etc. [Hint: First try to duplicate the motion plotted ;zxgyg898 g6s pll w 9euc.ft-by walking or moving your hand.]

Describe in words the motion of the object graphe5du (zgo:r r/rc 7bv(a6w: dvfd in Fig. 2–29.

  What must be your car’s average speev :t7s oqhams4seqm1m 3b:9v0d in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long doe 4w(a:c xkkatuea:lnr:8f* 0 era/q6ds it take to fly 15 km?    h

  If you are driving along a straig;/oo6 ck gmqctp,e) +vht road and you look to the side for 2.0 s, how far do you travel during this inatte;etq p cc/k +m,6vo)gontive period?    m

  Convert 35 mi/h to e( .w2x-xtpqz
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves froo7 bzzl kh 2o7u.2bhkr1 0jm9xp.kme1m $x_1$ = 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 9pe l9dj /(pwzat 95 km/h for 130 km. It then begins to rain and you s9l/djep9z (p wlow to 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-thumb, every five seconds betwiwi.5x j gvfem20 8niaub(4 0peen a lightning flash and the following thunder gives the dista4ai0p8mgf ini0jvxw .u52e(bnce to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track inf )w8ompsi n. -,nfji; a total time of 12.5 min. C 8n f n.owpm,f)isj-;ialculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer 8gmd+ac3i xh5q/a-hn in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallopsd-hix/ahng + q3ma8c 5 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 eai f sdm7av ,:2 ofm19up2fo:cbch 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 beaoif,c2p mo2 f1 fvds:9umb:7fore they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling -t rz+tox m3c (c ,m/wtcq.gw kww040v How long will it take the car to reach the kcc3mw -mqt, 0t+wvo. xt40r( gwczw/truck?    s

  An airplane travels 3100 km at a speed of 790 km/h 1-y ;m+e mn6zve. hfja, and then encounters a tailwind that boosts its speed to 990 km/h for the next 2800 +a-nmz 1femy6 ;h.evjkm.
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 avero (:c p9x;tekrlplro.p v.t80 age velocity of a complete round-trip in which the outgoing 250 ;.8:p .or(o rt9xp elck p0vtlkm is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the p-+-fvt/k kqw 30rsbdqvrd 6c6ins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pdw v-k b/dcr0v-q6r+6q sfkt3 ins 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 scp (2hg(tkv,ic2gb5 l kkf3:h. What is its average acceler:kgfghb t52 ckh2v,ck(p(l3iation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her,ktb 0,s*(/kw ld7:siaf;q ffqead4k acceleration dqf*,e dfsatfas 0 i/l :4wkk bq7k;(,
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular au,vj5p k-2r- xpkpb ga4tomobile is capable of an acceleration of about vrp - p2bx-4j a5kgk,p$1.6 m/s^2$ 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 sp5quvgngj66q kqet 4rb o4l21+eed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acc n2v 4+1lgugqk q664 rjtqe5boeleration 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 da wn9g-7mgua1)8 i5bew 3rnaand 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 amwgadiug1ean7n3a9b- w5 8r)nd on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. We6m8v m987he s4ymzvihat was its acceleration? How far did it travel in this time? Assume constant acceleratm6s mzhv eei887 vmy94ion.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was itsu g20t7p7*)sggvypuz ev gk ge*fj+83 acceleration, assume e*es2kgpg f7u ugj+gtv 0 y7p*8)zg3vd constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long ah-gnz4a9jt j9hev3/ c runway is needed if t4v3t-z 9naejg j hch9/he (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprintl)k6.n, brys- olcvdg9 lqhj8v 7y,-ber can burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it tab,, .s cjnyllvyk-lv9q7 r) b-d8g6hoke her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s.sm0,bd ;nw6ywo o 3vo7 How far did it travel in thatv nod06w 7w, by3oo;sm time?    m

  In coming to a stop, a car leavesczi jtqq9 8b1) skid marks 92 m long on the highway. Assuming a decele18czq i 9tqb)jration 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 c.x u3 yo4a9:73yklsbupqw3ipar compresses and the driver comes to rest after traveling 0.80 m. What was the average accelerawy:uu7oq4ak 3lb9ip.3 p sy 3xtion 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 inz7m3fge9r :o5y onhi1 itial speed of 95 km/h and human reaction tie9oim3 ryz7 5h ngof:1me 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 f). fj grehz, -wvjm(s2or the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on tht5sg74njo t+ ke highway. The car’s driver looks for an opportunity t57 +ostk4 jgtno pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min(jpzj(sd: (23h /zijkf e4vqn. After exactly 27.0 min, there are still 1100 m to go. The z/i((jj4qnz(jv kse2 :hf d3prunner 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 intersectioni ts:lfnv;z,: just as the traffic light turns yellow. She knows that the yellow l:ivft l;,s :nzight 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 top of a cliff. It *oq4)jyt d 8-b.m kfpghits the ground below after 3.25 s. How high *poj4qtmg.kfb dy )- 8is the cliff?    m

  If a car rolls gently phud: sd54/i*0yw abwvz29oy ($v_0\,=\,0$) 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 /f1.fa.d 2byt scp/ c3s.0io1boxqfrinto 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 vertically upward. With wre66j vjt8 8nh:ayod:hat speed didtd ae:868jhrnj:6yov he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influenc9 w j7yk)*b.eq +niipde of gravity. Draw graphs of (a)d *w ibn+7i)y9 pkq.je its speed 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 verticalp(ga3( *nhvully with a speed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a wg(uhnapl( *v 3indow. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance tra,6 c*y dszgbx+armr9tg8 r6)vfbn8: eveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown dn+t ,cb) s*rma6ebgf xr9v gy6z8r:8 by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, sho, z/ nby(ky*cpw (algebraically) that a ball thrown vertically upward with a speed ,*knybz c (p/y$v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upwrvh7oj 43f a8 +llhyw-af0rk 2ard with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash ofoe we+,:tb 0ji the apple in Fig. 2–18 (or number of photoflebt:+ ,0jewioashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes i+kh 2vntu- 1ru(ez /a0.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the tokhvr i21/z+ tnau ue-(p of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and pru+j klxb,n :kx3*q8 the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/ urx*k:pn3b8 jxql k+,s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard sthgeqfz.2j+ x7ream 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 you for another 2.0 s. What is the water speed as ix+h.f2j e7qgz t leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/p0mt /: gc3h q wfx50iazy6a*ts from the edge of a cliff 70.0 m high (Fig. 2–3xf:ch0 3ma ap/zy5wg6t*q0it4).
(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 the street with a pg1klf9 -mp1m -rfrx7-w7 s7qi0jb dc vertical speed of 13 m/s If the ball was km71 r- jcb7-9 p dfg0rwipsmxqf1l 7-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 a function of time.pnva :v 8yx55u (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, 8av x 5yn:vpu5if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is v;/-lscyn9xe plotted in Fig. 2–28. What is its instantaneous velocv;9lxnc/e s-y ity
(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 au( 6shxagp4 q3bf 3pzv0tomobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting oq6x4z ha3pvbg03f (psf 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 acceletg.cv k9 s 6gkc5iba+,ration of the car in the previous Problem (Fig. 2–35) whvica,+bk9 5kst g.g6 cen it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object travelaosk9 l f99vak.;j 1ihed during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph forn*7hfh. er+za el8lcjq.w ( e1 the object whose displacement as a function of time is given b+el*(.ah z7c1lh w 8jeefnq .ry Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an rvg 41ylr; w1vobject along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or 1;1v4vwyrrlg 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* ut 8(r5 b4usbuqql-1n7irdw ter’s safety net. The survivor stretches4*lu iusdrb qqb5- u71r(w8tn the net 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 the Moon is about one-sixth wh brgq,y;e 6o.a2f;vwg at it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity,;bv.go;q2ay w egf6r?

  A person who is properly constrained by an over-the-shoulder seat belt hana.f.5c1f3o ix.5cnzk3y +q r ewq+mos a good chance of surviving a car collision if the deceleration does not exceed about qck5+woa omnfyz .q31cx+ fire .35n. 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, a*(lbtsy/;m sfnd 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 / s;bmlyt(s*f are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by ;t x1 9c;qxvdcvxp1+0.wstse hauling them up on a 19 p 0dt.ctwcs ;;x1qx svv+xecrane 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 trac ,alj7bh 7(nrvels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. The front of ylzh,+dko-c4gs ay, : the train has a speed of 25 m/s when it passes a railway worker who is oc,ay,k+yd gz :l-s4hstanding 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 surfaceev7hveo hj6kacq(e.n (j 9+a 0 into a deep pool. c a6evjv 09njeo7+ a(k.hqh(eThe person’s downward motion stops 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 system, it is necessary to balaf ivlfxpkk1gss6 9 a:7 k97vi*qo/ah4nce 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 9.0-km trip in79g*7vv aq f4fk:19xssii/l6h kokp a 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 dowsmpo4l 46u )x)mqb z6 b+qus8sn 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 peli bu+sbxlmq4o)puzsm6 4s)8q6can to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with wi4w mpsgi84i 5hi 9vepqubij;983rx ;hich 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 difficue8im xg iv 54h9sp3p iruiq9b;ij48 w;lt 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 conso9 .uh .xrc2ittant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceleor.xhi9 2ctu. rates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone ik(dmvjs6,.h ys dropped 1.50 s later. How far apart av.(,ksdmy 6j hre the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial last) +b,( t2l e74cjvlmvwexd jk1ing ten laps. If the first nine laps were done at 1v+ m)l4xd27kceejj,vbwl1t (98.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he mn;c-.m 2v;j 5bkmtm2hkn8s 7alj ak; joves at 18 km/h . At theh mbklj c8mj .5 n2a -7a;s;;nvkj2tkm 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 playint+s- p4qzyoofs8ydu0, kxb;4 g on two trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed uft-4, u0xdoyq bksoy4;+pzs8p 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 tran sh(,/y;syh(b2sw3ecj:fgyt8 bu z, veling 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 opposite directite shbg:sbhs 2 8/z,,;3yny wy(jcfu(ons? 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 Izp/-+,9 c raj lpdj(mfn throwing the baseja(, f+ 9lpdc/j-m pzrball, 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 throwing motion.    $m/s^2$

  A rocket rises vertically, from resk(+:zhf3 fyn ft, 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.czpi* u7lm,.5973 jpuw (eno3bcwg lm 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 lightg.w,zil olmne5w7 up c9p* (m7 3jbu3cs are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/h tat 3by:(s8xc/ d* etwytkes off i ty8 sxy :e3cbt*/td(wn hot pursuit. 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 thatu/12ohvao)zx:om, a7kx bb z 4, a second stone is thrown straight down with an initial speed of 25.0 m/s and:uo 4a2kb/hv7bxa 1 o)zmx z,o 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 id661.u/ 21m zuw p 0jhwcywifup 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 buidi yw6z20h fp./ujm u c11ww6ilding 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 free-falling parah118t.ke1l2fy7 ks g )jiq uqwchutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed 11.8kuj)wk1 ets2gqh7qlyi f be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a+8/o gk u(yus5wz/3m*ev rgr x conveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgsug3* u/xer ko( yz /r8mwg+v5ers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Jo i4eiogn ek7ve+2:sc o- y-,lae can. How many times higher willg+vnek,iee- l4-c7o oy a:si 2 Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your vt6)1 +)9y sb(kj yjyhs /is8zf.brusfriend 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 restir1jky()y6/fss)v js9+h8y.bu zsb t in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked toef9o/h;(ip uq find the height 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 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 thpiq/ouf h9; (ee estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) Is cp7*y8 /mc6ctl1p pyp a tb8rcz6:1iv there any instant at which the two bicycles have the same velocity? (b) Which bicycle *mrty7: 1v81 y6pp86it cppalc cz/bc 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?