Does a car speedometer measu:g : khfntekza4zh corg;4d2 rc5 u(*5re speed, velocity, or both?

Can an object have a varyinslgm0nef7 b (*g speed if its velocity is constant? If yes, give exampless07l(engm* bf .

When an object moves with constant velocity, does its average velocity bd0 kf56l (gn58shdvf during any time interval differ fro gffdd50 5hk68nslb(v m its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the grea5o*svl0ha)xn test speed crossing the finish line to lose the race? Explxonh5 a)*s v0lain.

If one object has a greater speed tl-pt0 7*gnpelmt*hxx y0g0 e n 72o)fshan a second object, does the first necessarily have a greater acceleration? Explot *n s0xgnp- )plxf7ehtl0yeg0 *m72ain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80k2xwmagt;ha 1lqbv7tkg q: 5ef 35 wb2;m/h to 90km/h with the acceleration of a bicycle that accelerates from resw2g5w; fak3m57v ;gb2 q tlahq1e:tbxt to 10km/h in the same time.

Can an object have a northwaca8v2zlb1m*qey/ cx ( rd velocity and a southward acceleration? Explain.

Can the velocity of an 5uy4rzgbz; r: object be negative when its acceleration is positive? What about g:;r5ybzzu4rvice versa?

Give an example where both thdfmq- i16vqz)l 6mhs rdtkye ;p*7,q(e velocity and acceleration are negative.

Two cars emerge side by side from a tutad +f zb/o0y4nnel. 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 passing the other as they come out of ayo4 ftd+ z0b/the tunnel? Explain your reasoning.

Can an object be increasing in spj49jl+lk2qa. mv o i*ieed as its acceleration decreases? If so, give an e9 vak+ im jl.*i4l2oqjxample. If not, explain.

A baseball player hits a foul ball straight up j- t 71wrzcfgu1kmb 7(into the air. It leaves the bat with a speed of 120km/h . Injkf11r zw7gbc mt-(u 7 the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to fbh sz w4*0ec-its acceleration due to gravity — does it increase, decrease, or stay the same?c0 wfe *-zs4hb

How would you estimate the maximum h*argz,*z3qh l eight you could throw a ball vertically upward? How wouldgz z*l ha3*qr, you estimate the maximum speed you could give it?

You travel from point A to point B inh :)s;5i,ajy b0 t,yrevuvu8t a car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Ehivaet5s8btvyuj)0 : ,;ry ,uxplain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string w3vz+ct iv7)v x4nx-teaw. vs2ith ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin platv7t-c4sxvv+ e.a)3 z iwvn 2xte, 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 9w) d syud/viq+q:nj-y;t p4vacceleration: a rock falling from a cliff, ays tpnyq9:- ;vv4dqj+d/i u)wn elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original positiodp/5kdx6lc4 nn with the same speed as it had initd5p6lckn/ xd4 ially 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 the motion.]

Can an object have ze* f4y;megrkjyd1avatn+r )63 ro velocity and nonzero acceleration at the same time? Give examplesdyy6mg +anvk 3; fra4jt)1r *e.

Can an object have zero acceleration and nonzero veloc-+dra6ijd e:kcuh, 0x 85oqhqity at the same time? Give examplesro: 8k5a-dhu i +c,je0hxqd6 q.

Describe in words the motion plotted in Fig. 2–28 in terms of vt7 0hdanwqk91a2odl 2 , a, etc. [Hint: First try to duplicate the motion plotdhnqdkw2ao 9 207al1tted by walking or moving your hand.]

Describe in words the motion of the v(xkznjlfp1875 es.n object graphed in Fig. 2–29.

  What must be your car’s aver /70xv e(m,;mcdbpct/*iz l omage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long dvz n 3q,cre*.uoes it take to fly 15 km?    h

  If you are driving along a straight road and you look to t; 1kqk5.d wob.ewn(fmhe side for 2.0 s, how far do you travel during this inattend(kbw5eo 1f.nw.q ;mktive period?    m

  Convert 35 mi/h to 9u/ogo1kno,l/5 ivau
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fiwg :agni rli9(q4b;h6b6f,v rom $x_1$ = 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 i*:+a xii80qbl,eaw7o af*.iis q -8bh5t hxbschool steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrivaoxqbw-tiibl,hi*7 bh5.a8if x0 qe s+ a*: i8e 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 bt) 6m9zuq8ci5dk/n hf5ti7 pjetween 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 the spenq5tdi8fikp)mcj5 7h9ut 6 /zed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps* 9hl- djqbmv;k6qa9l around a quarter-mile track in a total time of 12.5 min. Calcubmjvq6d-;*l l99khq alate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its tr4g6bwykw; i(z ainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 6wg (4;wzikby4.8 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 parallel tracks. Each has a speed of 80fj8m6,;pc z ifu jxi95 km/hf0jp 8icxm jf ;6,i8uz with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travelin q0tlepg*tr ( :c4hq:gg How long will it take the car to reac* th:eqtqg( p4l: rcg0h the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and t gx)ogo 11,iifo 0jyztsl 2(8then encounters a tailwind that boosts its speed to 990 km/h for the nextoy g ixfl8ozi1tj)s10,2o g(t 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-trip iwckh +c)0w5uj iyr. l5n which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the5wclr i+ 5)j0 hkwyc.u return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins h;qzpep+nfu bc q( 8;.he6e2aat 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 hands. What is the s.eh(n ubcfph2e;;zqa ep 6q +8peed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerate9cvh bta-jskps -*31ds from rest to 95 km/h in 6.2 s. What is its average acce ss 9hd v1tbac-kp*3-jleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s j8qf+t4i 6euj (:hi ktuwid2, in 1.35 s. What is her acceleration4kitt,fu6 i j8id(q:hue jw+2
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a88b5g gn xsvx8 particular automobile is capable of an acceleration of about bgv58x8xg ns8$1.6 m/s^2$ 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 -jmy*vpa,l mwgj2 x59110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its accel*vgj5 pxma-2,m9yw ljeration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and mov0f ,:nv )-j+(zvd pkji nh0nzzes 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. )f:hkznij dzz+p(00nn-j ,v v Display each in a Table and on a graph.

  A car accelerates from 13 jwwc qcmi*-bv+on/)4 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel inw-i/wjocmbv+4c)* n q this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its ac0sjv57 t0zr s8w,vwhjceleration, assumezt vwv0hs,jr07j8 5swd constant?    $m/s^2$

  A light plane must reach a speed of 33 m/ebsl 6ql24g+ j)b -hvqs for takeoff. How long a runway is needed if the (constant) accelel)-vqbsh +6g4lq e2 bjration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out oq/xj1r3 +ne k7e1h(n pear+d:uhy kf)f 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 taq a fkn3 e:/1dnuyrp j)rhe7 (+khxe+1ke 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 t md s)+poa7t)jo rest in 6.00 s. How far did it travel in thaad+toj )7sp)mt time?    m

  In coming to a stop, a car leaves skid marks 92 m w09hla+ 5n r6 v(rskqslong on the highway. Assuming a decele5lnva(q + 96kshrwsr 0ration 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 7hb.1pvv g(x*g1g 0h+ vvr5 voqfjj20gpbfx (end of the car compresses and the dri0 .jgpbgj5r102 7xvf(gxghf qvvvo vp+h b(* 1ver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distkx 8gx fx fml,0)nc*;vances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an axx vn ;fmgkcx) ,8lf0*cceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for th 5mln1 ewb0 fd9hx-;eye 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 the highway. a(enl*g3k f;wn m9db/The car’s driver looks for an oppor9n;(gwbae/ dk ml3nf *tunity to 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 t/4 v c5gid( zmexxr-8jhe 10,000-m run in less than 30.0 min. After exactly 27.0 min, there ar(i-xg vexjmc zrd/485e 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/t; i36o;5 s2mjfnku okh approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light tur 26sjko; un fi;mt5ok3ns 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.gy rq 1e,ri5d6m cfn12 It hits the ground below after 3.25 s. n6eyd2r ci511 qm ,fgrHow high is the cliff?    m

  If a car rolls gently (s3hax 9+:(j67 en+gvvigsxq t$v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of 22 m: 6vn3 t,itwzl/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it verti r9x)mp x4j kt)e4,aap cr,ft6cally upward. With what speed did he throw it, and what he4rrxmjc4e kx),)fa a,6pt9p tight did it reach?    m/s (Round to the nearest integer)    m

An object starts fro b ue1ho2,a6hq mwl58cm rest 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 fro w6ca eh85b2,h1lmqu om t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed ke ew37((oypv(x*v lg c)4ltpof 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 packav(( g e3po k*lpv4t yxl7w)e(cge’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest,r. ;9v8e +m+otib tywq show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2b8q9ovttr e.ym+ i;w +–18 and 2–21.

If air resistance is neglectezkm rd8w xp);2d, show (algebraically) that a ball thrown vertically upward with ar pdx)2zwk 8m; speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed ofbq :t5j9a/hpt ng m1e; 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 Fig. 2–18 (or numgs s9xe: 25h8bab+q ptber of photoflashes p 8 b+h2gqspt9x as5e:ber 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 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). ves2mw(;j;na6glc7im bf/ 2o From what o2js i6c(a ln7vge2;bfm /;w mheight above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it stfwvzh-vj/;2k /6u pjf4;t dh lriking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the clj//6 2 h ;udv vfwhfk4l;jzt-piff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stree st, 4fb 7zycej238iyam 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 it leaves the 483,j7ctybzesfi 2ey nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge/xj/ 7(vldqxa h n fag+4z27i6hfuw8tt,i/wh of a cliff 70.0 m high (F djz6vxuhg / an/,q78ti7aw(42xf w ilt/hhf+ ig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a win u (drj6wmi z8um2v1.odow 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the6rd(i .1vjuuz 2m8mwo 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 veloc:gh xnbq./4 qrj fq,j4ity of a train as a function of time. (a) At what time was r,g:.q /bjh q4jqf4 xnits velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function7 kmin box)9cqp9qr2- sl6hm / of time is plotted i/q 2 s-hcoiklb9m)n7q 96m pxrn Fig. 2–28. What is its instantaneous 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 auh+bo)i*0ucd7r k v4sj- ljv2jtomobile can accelerate approximately as shown in the velocity–t-ho2+l j vs4) dkivr*j 07bujcime graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problebq* xa/(kmvg zt, ,a+pm (Fig. 2–35) when it is in *a kpmabt(,+xzv q,g/
(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 objelzak8 3,xu0z ect traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a fun2fe4bfc 8u4nf pl;b .rction of time is given by Fig. 2–l4f.ufpre 4b;fc2 bn 828.

Figure 2–36 is a positiociv 4p/wj,+2l g 0qfrjn versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the 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? vcf i/ q0,w4 2+jrgplj(g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from ae2e0 2tjkckq kp g:*h- fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before cominqj 2k the:0cpe*kkg-2g 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 what it is on E,s+bvnp7ue m*-t:n.ounc, p, x rz9ewarth. If an object is r7uxnw,psbo-zvm* u,,pt ec+ .:nen9 thrown vertically upward on 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 an over-the-shoulder s ywl 2jsiq99wnc(l)i k-1/ah zeat belt has a good chance of survivin(i1aqiy2kw) sl h9c/z9 jnl-wg 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 h 3k g.nm1neg+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 th1.gn+gke3 mhne 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 i4cj o 8;a )zk.cxqyyt*ts cars for front-end collisions by hauling them up on a crane and dropping them from a certaicx. *zyc q)8aoky ;jt4n height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels 3s ozm2 rx 4.k*dqdfo ;h:h;7agnfgl+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 f(ye:tg*s ,vy if/tp5jf ga f52ront of the train has a speed of 25 m/s when it passes a railway worker who is standinga e5stf tfpfygi2j:(*g/vy5, 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 s xyi- xa09rlkl(8 obr7urface into a deep pool. The person9k rlb7(0x 8y-axlior ’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,5)cuag luw /9jr6um d3 it is necessary to balance the average speed of a train m 9j5ulw3gu)c /rau6dagainst the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings anc0n js(gwp 3c:d 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 actgsj30c n(cpw: ion, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned9 f ,0vog-l86qmgws lrs33g jm so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a g,0m9 s3rofmwjl6s -v g3gq8l 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 spe/lt.uqljwj iw.u f du .5x,2l6ed of 6.0 m/suw jujx6.ulq2fl.tw,/ 5 li. d Just as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roob, 4g*ck:enwal i8a u1f of a high building. A second stone is dropped 1.50 s lua*a4 nb k,:e wl8ic1gater. 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 km/h over the course o3z. v)jfxw2f ff a time trial lasting ten laps. If the first ninwf)z3ffj xv.2e laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as hr8ua jae7vjtpz lury1 30*page,-o(8e moves at 18 km/h . At the bottom, 48la0 p ey8(rv-ja17oug,juaer* p3tz .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 play r:qzf i)c4ar9ing on two trampolines. The first child can bounce up one-and-a-half times higher t:9 4rziaf crq)han the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile travelinma27j)x tut+n g 95 km/h overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the trainnm)tu2tax 7j +’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 of :j0ra0 h*cz 1 ezxhc*m44 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 xz:zar0cje*hmc 1 *h0–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rpo 9sf9/pe/ b.xode 8jest, 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 F rk3w6 + jx /phscc5xsny6*yv-ig. 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 ks/c*6rcxps -ywxv6 n+3hj5 ylights 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, tfvk lo94c 5jf15;ihm passed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up t1 5 k9;fhi m5jo4vclfto 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 fr c-(odxxmsq o ,)vaf-7om the roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time. dx) v xfm c,-(7-ooasq
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The firs-btu8okx1z9 l qpgm .+t 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 stone be ztg9ux.8lmok bq-1 +pthrown 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 worg uxmh;d.az+lkgl2bc4y,;/om272 l7m eok vuld it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 35u,k2 e2d +mlmmyl4ghv2;/l xcr g kb.; o77zoa0 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor1 n1b c9pk4fai.w pfu1 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 burgers are spaced 15 cm apart, what is the b9 kfa.uin cw11pp1f4rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5p8grob:xos; ( times faster than Joe can. How manyg;p8(r:oos xb times 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 ground bell6ra( qqjo ,*pwv 1yz2ow you. You drop a ball from rest and see that it takes jyvr1 zlwq (p2 6,oa*q1.2 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 the ball?    m/s

  Two students are asked to find the height o;:6aeu f.j(b ewn;/ewr m bnw0f a particular building using a barometer. Instead of using the baromete;:/b.e wreajmbe6n un(0 w;w fr as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, gii4)gszq)p2)i k nq4h5v1kn+,h smbA 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 bicycles )gb,4n+5 mh2)1 ikzv4)iqpnihk sgsq 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?