Does a car speedometer measure speed, velocity, or b9lef qsw;sd jmb dn-*u 0+(7n m-tja1noth?

Can an object have a varying speed if i)s0wofh9/ bs mts velocity is constant? If yes, give examples/9sm0 b) fswoh.

When an object moves with constant velocity, does its average vel/c,rbjcoesd9n : .d 1bocity during any time ./cn edjo9:rsb b 1,dcinterval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the grrzgv -u ord e3f8b-x+.eatest speed crossing the finz+ vb8.-uefd3 g-oxrr ish line to lose the race? Explain.

If one object has a greatern6 4+vap h)rx)jhrg,odb 00 zd speed than a second object, does the first necessarily have ah6 bda4n ro)d,+jzp )0g0vhrx greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90 1i, ebug:-nojiu+tm6 km/h witm6 beii,o-g:uj ut1+nh the acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Expla2 ,hln 1oug*oiin.

Can the velocity of an object be negative when its acceleration ik0sv:xqciswu4q,4,apgyw0 z 4 j3n wj(*i f h+s positive? What about via ugfx0+vws: *y3 jwij04,nhcsw4k ,pq4z iq(ce versa?

Give an example where both the velocity and * df 5bo3*yqymacceleration are negative.

Two cars emerge side by side from a tunnel. Car A is trave kn 2s7( jr6epdgnua6;c 2f9v7 ggxyh1ling with a speed of 60km/h and has an acceleration of 40km/h/min . Crndvfh6gg cyg9p7s 7euaj 1n kx26;2( ar B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? I*yd-rmrb6g6r )g bdq02vxa +j f so, give an example. If not, explajv2+r 6*-gg m0b6)d qdyrrxb ain.

A baseball player hi lko;k fj8*bs3ts a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of * jk 8kf3b;lsoair resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its tuzb ,c v8 in*okv/+)wacceleration due to gravity — doeszi )+nub,ov/*ct8w vk it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball verticalgv ha.tzmq)28wa 3 qsm r1t3poxj6aovd70g-6 ly upward? How would ogvrx7ohqzmjqv a ag6 mdp3-a1.2 8tt 3)6w0s you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed85,pa.ey on6hvx x4ke, 3cy1qzr p- yq of Then you t8q16excop3x5 p-4q rz yvke,,yhya n. ravel 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 ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with tuiq 0shx r2z27en 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 equaszq ri0x27hu2 l 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 aa2bc -2itttzzqf 4tx zvinj/) );,m 9is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on aaqb,t2)t fvct -zmt ;iz4a) ni/x9jz2 table?

An object that is thrown vertic:fh93 w)h)re gvn ;y ;* whbp+baug.vlally upward will return to its original position with the same speed as it;*3ra w)b+ v.n:gwp 9euyhgh)h;fb v l 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 the motion.]

Can an object have zero velocity and nonze5eb nz5 yf2ej+ro acceleration at the same time? Give e5zejnf +2 5yebxamples.

Can an object have zero acceleration and nonzero velocity at theryd2co.z ubsgz.f(4vz5b*es (7 ;k z l same time? Give exzb(zv 5(fg4yzd7 k *sz;u..eb ro s2lcamples.

Describe in words the motion plotted inc+6i8x v dp qs3eu7nq1 Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplxpn6 s3v18+deqq7c iu icate the motion plotted by walking or moving your hand.]

Describe in words the*ccltz: 9u9 g a,xqq-i motion of the object graphed in Fig. 2–29.

  What must be your carpo6p y15i2d0;iczqtn rv:6z r ’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it tab5ctx m: h wi*a5ld9i-ke to fly 15 km?    h

  If you are driving along a straightyu)f6 sh1 wp bl zi2--x61doqw road and you look to the side for 2.0 s, how far do you travel during this inattentivyx6wf-bh -qu1 p dzso6)i21lwe period?    m

  Convert 35 mi/h to 9p9+9av ( e dzi(vgdg cqtrw..
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves eng,ik2ruy v7ph 4 f:;from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving homejmabd5f04ry * a avh)2 from school steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 k a a 05)2fbvjdm4ayr*hm/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 se 7vp;k +8kdgnjconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the + nkdjg;p8kv7speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile z:e gc3zwu 4p+jtn*v +track in a total time of 12.5 min. Calculate z tpe:3n+4z j*cv+guw
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer1mmchmi 2bwd6. n+ yt: in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway 1 wcmbdmm+ 6:yn.i2htback in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speed o,b:rp0 vd.jc vf 95 km/h with respe. ,0pvrb:vdjcct 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 traveling How long will it taqym19 x*g9mdh ke the car to reach the truc9q*1 xmhg d9ymk?    s

  An airplane travels 310k/pju 7z;v ,pe0 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed tov;jk u/pez7p, 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed an: bt5rg,* 2/pzefcc 0tul dfu9d average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunc ctze0u2pf u:l*cd b9,/r5tfgh break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hit;,+ ayp/fze/i7 iqcba s 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 hands. What is the speed of the ball? The speed of sound is 340 m/ 7pca+/bafi,;y/ei qzs.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What rx1,kromsdor5cz17p*w c*d0 is its average accelerato7r cr1,d p1wm5z* r*s0koxdc ion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. enk7 e nsk hi4y(8-0zwWhat is her acceleration 7i 0z8k(ehne-y4kns w
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a ppt ,2;mpj :bgb50-usrlm ib :larticular automobile is capable of an acceleration of about 5m ij,: p bb2bt;lr-gp:l0smu$1.6 m/s^2$ 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 c i-ohsbr73bce,c5:gw sz6 wdd/+x g( bonstant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0brs:hdswx5d e- w+o6z7g 3g/,cicbb( s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from ry2p x jj/1 0mxx pd rs,e3+vj)usn+5vaest at t = 0 and moves in a straigh+ p2vvjy)5jar3/ xusn+pmd s 1 xe,j0xt line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m54sndkwvlp) z x(l k9m a-9k)f/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceleration.-9szk)9xw4vka5k( lpld nf) m    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dista2l jl-;6g dalk-5lteo nce of 85 m. What was its accelerationtl;jade2l-o lkl6g-5 , assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/shkp/(hwe m hkp5x 06uupxl 40m0, 1nbz for takeoff. How long a runway is needed if the (constant) acceleratuk mh4 pw6u em0bpz0hh,lk 1n50/p(xxion is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed (ot/c1*y6mlrybl:b+el dv o)e36 xs9sof about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinyy:* s3lv+ dob l6sxm9ot/e) br1el6cter, 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 12.0 m/s to rest in 6.00 sw3en1cnnc4n ;ztt1 * x. How far did it travel in tha cennt1t; n1nx* z3wc4t time?    m

  In coming to a stop, a car leaves skid marks 92 m lfu a4av.ugp2)m i5suk00)lgzong on the highway. Assuming a decelema4lfak5s0 vg)0 g 2i)uupu .zration 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 cto l3fggf a;2bl-pf; 9ompresses and the driver comes to rest after traveling 0.80 m. What was the average accele 3lpf-f;2g b agflt;o9ration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 k0h.3verl :a9tan gvk/r .q ch*m/h and human reaction time n:rvl.gtvc /ha0.k9 ehrq *3aof 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 distance n.qfb+bfn(v6 i,ge3io 9: h vdof a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver looks2r tz6q7+f zxs for an opportunity to pass, guessing that his car can accelera2+rs67ft q zzxte 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. Aftw0hst(u+k4hp z s0 m8ker exactly 27.0 min, therks 0( phtmu +40hkw8zse are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection ju7)4.3vctsy nf swm *itst 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 lights t3*. wmy7cifsvtn)4 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 cli7cxdl zxyshbk(z(+9 6ff. It hits the ground below after 3.25 s. How high iszx +k6y( lcds7hx(b 9z the cliff?    m

  If a car rolls gently g;i9 c, u w a(+vdxg+wpk.z zb:0pxii(($v_0\,=\,0$) 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 m8dkgpv 0 ipcqzx 4 */rfy7:j0p/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 0,q:,y bqowj eg/g f7c1skb h*it vertically upward. With what speed did he throw it, and /c,fk0 bhjggq*,b ye q:1sw o7what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gsdyk/cp3 ic 5.8 un6cpraphs of (a) its speed and (b) the distance it has fallen, as 8c dcpnsp yk i3c6/.5ua function 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 heinl/ot 8jm- i ze:q-vapo8ca/1ght of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals t pz-8ona-e/o al:mtvc1qi j/8he helicopter’s.] t =__ s

For an object falling freely from rest, show that m;py/52,fawu r* 7ne dx+panvthe distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first sfa ,nm2wx +7u pe;r*vayd5n/phown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglect wr,;s 8dsb:nb:q n/i izilj0*ed, show (algebraically) that a ball thrown vertically upward wi,iwl 8r ;0sniis/* z:dj:nbqb th 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 a /8pwsuc g g/8r8/aggspeed 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 Fig. 2–18 (oj7ugd qjn1a1dc*u4 0kr number of photoflashes per second). Assume the apple is about 10 cm iudng*1j 1 7qcakdu0j4 n 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 ai47*18 ypvlzzm,: scjjm k.za window 2.2 m tall (Fig. 2–32). Fro 8pyjzaiclz71zvjk:sm,*m4 .m what height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the (;mqw bt0pvaz/e4gj*j ,jth .ocean is heard 3.2 s later. If ,wa 4ze/*h0j mqbj.v (pt;gtjthe speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You po,lb.rz.zvhx().hb1 0d a pofgint the nozzle vertically upward at f,b.ha0lvd .pz. 1z)x o hrg(ba 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 nozzle?    m/s

  A stone is thrown verticallzqs bpix+1e(/n q)ljena nw6s9s*j x /)y:zz4 y upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34). ez n p)jqlswq://x +b(zna41exy )*nssi6 jz9
(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 sls t+mnb (n):otreet with a vertical speed of 13 m/s If the balonb(m+t :) snll was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a funcpnh glew :4c )1n;mi.ution of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity conste.nh n) c;im4p1g wu:lant? (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 function of time is pu +rx3t r5-m3dfqc(zd lotted in Fig. 2–28. What is its instantaneousr5q df-u x(czt3drm3+ 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 automo d;xaj3qwv5 6tbile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (j56vw 3tqxd;a 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 Probcfw,rr-,yje2 4 y9uh*dsp +os lem (Fig. 2–35) when it is in ,*sp2h+ywsfc ,yj-9d 4 eorru
(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 theo 0 rn1wy+r,mxb4:xmw distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. +x ;7ja*nkp7zz we+ d,db :pxrt graph for the object whose displacement as a function of time is given by Fig. 2–;x,d++ zzn:k bpxd*jpe7w7ar 28.

Figure 2–36 is a position versus time graph for the motion of an objecn. (nf; tigkhdhs3o- (t 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? (fkfh din.(o-t gn;(hs3 ) 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 l r)q,avzan, 8ug oblf.d +7,dm above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to re8d r,d.+vfaanqbo 7lzl g),, ust, 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-s9dgiy74 fr6m oixth what it is on Earth. If an o9frym4d 7i6g 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?

  A person who is properly constrained bzrvs7 2i gz)6uy an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not exceed abz)z7vi6 2gurs out 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,:kbv 9itr daw p7rzo/0a: -y1h and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck shyairv:prdab/-z w1k0t7ho 9: ould 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 itmnb mq8.6e fqhi;c9ysj9: 4aos cars for front-end collisions by hauling them up on a crane and dropping them from a certain heiga:je yqfc;4 . s69b9hio 8nqmmht.
(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 Earthssd m3r1 cy/s9 travels 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 the train 22oy9mopdl /xl+) b nuhas a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it pas )md2oylo2 pu/nl x9+bses the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divij(4gc:wo+kho ng board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of th4gwo(k o+jc :he 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 nebht ssk h- ij5.4gx:nuor8a/ .cessary 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 getuh -/5:gbri.s ah s4.t8konxj an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fa q :u4wso.(olqll 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 mustols( oqq4:.w u it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golferu)p7u x nsghoyms7mu,qixa gvz9 s8f96 5:n66 strikes a ball is planned so that the ball will stov: ahsq9m6izus7mo 9u sn) gx76fg x8u5ny6 p,p 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 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 spee27h4r b;c iquld of 6.0 m/s Just as an empty box car passes him, the fugitive start2l4ri chq7 u;bs 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 high building. qv.cr66on zo :tfu th/-;rvw.A second stone is dropped 1.50 s later. How v v/ hrnrf oq.;uwt-ocz:.t66far 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/h58c6)ikztqr k5,d+ l8zdsdtt over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last,t )d ckl tt5s6dr 885+qkzzdi lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 km/h9h6nu5y 6:n ypc*cfl m . At the bottom, 4.0 km farther, his speed is 75 y 6p9c6n:numfl cyh*5 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two tramp t+n9nbppqma2 -56 c,:tzwtkl olines. The first child can bounce up one-and-a-half times higher than tp bw:6t5n9+,nqzlm-atcp t2 khe second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 kmze2dljoy 2gr 3ocdal;j 8i8mc t7t .8//h overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed ijtrdyig ;/jt3lo7ze8cmoc 88.2a2d l s 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 b(95 bhgzhpm,m aseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the pointh, zhm5 bp9(mg where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with anu0(je5to- g ep acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42rf;g/ly+h5e 8swaewp 0x.+qb.x . o rm. 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 lighte. mph.rfxr+5a0 wx.g+o /b ye;q8sw ls turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling ,*)jqkeb7xe7a3y u keat a constant 120 km/h takes ofb7ka,ee7y3ej )qux k*f in 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 f 8qm2wgnjk o8eklj8vhryi305jih9m**aw7, a rom the roof of a building; 2.00 s after that, a second stone is thrown3qn *m w vh87ail5y2ejkh9,8rig mwj*0j8ao k straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the st- 3*x)ypc a/h.fa oqybem ;v7ame time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building ando-7;qty ym xa.behvap)* fc3/ 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 lon -:-lkduf 4psx/ kyke2g 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 wsypxlked24:- k/ -f ukill restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burge3 nilbpc/na8 qdba:ao5 u a+0+rs 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 trqb:/oaaa+lc+nb 8i a nup5 30davel? 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 ball vertically at a speed 1.5 times faster than J2x9k: t bv3khhqxclmdh p)i9x e9-1c;oe can. How many times higher will Bill’s ball go t k xxb3h1t9)e hmclxkp-2dcvqi ;99: hhan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground below yhwr yl k-f1fh*1r0 lj-ou. You drop a ball from rest and see tha - 1frhr1wlf-ylj*kh0t 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 the ball?    m/s

  Two students are asked to find the height of a particular buildy9i7gapuc m2y9 :vt/c ing 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 9 pc7c 9tai:yg/ umv2ys make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B.c2t5( ri7xkgt (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 passing each other? Which bicycle is passing the othtkc2 x5t7 ri(ger? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?