Does a car speedometer measure swpruvl)d/+y2ye5 4(zg;mx2td 9inl u peed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yesin av b (x00u0+s/nvny, give examn x00(/nnuv0+ y bavsiples.

When an object moves with constant velocity, doa v0 +l;n,r og7 zuad3lnpe2.r cx*g1ees its average velocity during any time interval di10*ncg3v dp. n,eoxaalr+2z; ue7rlg ffer from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the zywmos4ylxb5 7(-ao 1greatest speed crossing the finish line to lox7bay-oo(sy wl m 514zse the race? Explain.

If one object has a greater speed than a second object, does the fi4sr;d aec6wnt;js ec7:.6bwx rst necessarily have a greater acceleration? Explain, using dbw; n srxwj 6tce4:c67e;.saexamples.

Compare the acceleration of a motorcycle thlu i0 5c. n8bs7kfpe;rjn41cbat accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the same time.8 ;s4. jpcun5kcf1r nleb 0bi7

Can an object have a )9xfr sa4 *dveh 8qrz3northward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positived rgik8xx :5qd.e)9rnp 6u(jsx2ujq7? Whatxskx 9r :eqr 6xn.jgq jdi p27u8(d5u) about vice versa?

Give an example where bothehhwgg7 v7 fg w6+:y,l the velocity and acceleration are negative.

Two cars emerge side by side from a tunne3rz; +q7 g2 mk:na k6jwitxaj,l. 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 otn2kjtq gwjzk7, +a;3:rxa6mi her as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in spefspca// i zqbk,71c o1db 2h1wed as its acceleration decreases? If so, give an example. I1d7caf, 1 s iwbzo1kbp/c/ hq2f not, explain.

A baseball player hits qp7e,hk,j 4zbfi/an* 9-qpzk a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air9zb/*q, epi aj7, k fnq-4pkhz 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 alk c47 .8t.hm:cv1 se2ihcvqycceleration due vcsvechtk2: .7hym84 q ic.1l to gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you m, lc0w kmfbe97fxxk+m3 1nq9could throw a ball vertically upward? How would you estimate the maximum sf09 xl be9q mk,x+nm kw1f73mcpeed you could give it?

You travel from point A to point B in a car movkibjb: ; 4,li+4 to+y dc;lowjing at a constant speed of Then you travel the same distance from point B to another point C, moving at a+o ,loiwj;:4i cj;yb4td k +bl 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 r b/g9w bw;ka0with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hakb09wr aw/ ;bgll. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motionbjzq4, b)w5 les is not at constant acceleration: a rock falling from a cliff, an elevator moving from the second flzq4 ljbw 5,e)boor 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 positior.i2-urayahkr5 fs02xm m9-lh/ u/jcn with the same speed as it had initially if air resistancak5 s2fu-.rh2a 0/ m mrcuihjyr-x /9le 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 dr r/sdznp r q/*3rdw0j8y43),jpm crand nonzero acceleration at the same time? Give exa3pdd/, 4 r8q 0wpcrdr*jnrymsj 3/r)zmples.

Can an object have zero acceleration and nonzem p;qjgxrr8e:v8to6mm/ .2hpfdv2:l ro velocity at the same time? Give examrvr8 dfqtpp:26em8 xm/h 2 jv:;o. lmgples.

Describe in words the 11owqnr- s4kt3wmka z r3 e3l3motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion p 1-rkw34zml133werqt 3nko salotted by walking or moving your hand.]

Describe in words the motion p(cnsr1u( zff0qx6f/ ) 4ftumof the object graphed in Fig. 2–29.

  What must be your car’s ju(/a6eih4x5:wlvi h 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 tajiwik4yqkzvht, 7s 5umr)+);ts9vp, q i 7+mzke to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 l:q4t eg- uv)7r oqevzw*x0p3s, how far do you travel during this inattentive pxte*73 q v v:-wel)r4uoz 0gpqeriod?    m

  Convert 35 mi/h to vrs:)yerka:o m30s3x
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves af s l3+*w4nmi7*jlhj from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily atigw i/()m1qdrw) :xjo 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes. )(x1wgq woiij)/:rmd
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thurnpa, po y2ldmj;.gsw11l34p mb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arriv1pynar jw4 3g.o ,l1p2 slpd;mes 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 in a total time wu941j6ft4 g adh:li,:e8xx tiau if5of 12.tel g:i5u4 8 9,f4 1: ajxahiwxfdi6ut5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away f2u1gp yhkh7,erom its trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops half7p h1ygu2 e,hkway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has acd)e,n-5jrf u 4s6u tu speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it beuec6ndfs4u5,- )ur t j 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 wilomd5p:(4w23 kjjjq-lipa8 bj l it take the car to reach thep jl8 bj w2aimk-4j: oqdj3p(5 truck?    s

  An airplane travels 3100 km at a speed j8cg1kc 5q,bvqu9d7jof 790 km/h , and then encounters a tailwind that boosts its spee9jj8c udgk71bc5 ,qvqd to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a completea:n) k :7uba-kk j1six round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch s:b7knk-xaau)kj 1i: break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at tqjmg0*1smjg b 0 t5ss5he end of a bowling lane 16.5 m long. The g*t0jbmg55 ss1sqmj0 bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car acceleratesacx 9sq3x+,r j7wne( *ipo3md from rest to 95 km/h in 6.2 s. What is its average accelerriqmj 3eax7 pd,(3c9 *now x+sation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her accelen-aqd59zcs5nyx:pvd:. q ww m.ni*n+ration *+p5dy.aq:qd-w5n .n x :i9svmncn wz
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automob k2iv zz5hvi17ile is capable of an acceleration of about zv7hi v51iz2 k$1.6 m/s^2$ 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 vnmf6 .shl gnr/) .ge(at constant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s,.(s f hngm/ vgl.ne)6r 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 rest at t = hl+)* 99c uhdpdu:jvh lvk(f rl4y 0y.0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function oud0 lvh4 kr:.(hy*cp)fuy ldl +vh9 9jf time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acco yerz8kdmmp)jlts iw ;m2v+j*0;: /yeleration? How ; ewml2m;ovp)r8jtk/i ysjm*zy0:+d far did it travel in 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 i 5k-zcnh7.dv1i y 3avmts acceleration, assumed constant?a7ik1-z5vvh3m nyd c .    $m/s^2$

  A light plane must reach l y/0eg h6)ne nds0ufnom; ;l-a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) accelera0; fnn/s6; omh0 dyne) guel-ltion is $3.0 m/s^2$ ?    m

  A world-class sprinter catchyt )21 :+vl,dmenzn 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 ave),lym ct2:d+e1 t nvhzrage acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly; kto xegg)9w6 from a speed of 12.0 m/s to rest in 6.00 s. How far did it ttewx kg6o;) 9gravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assumld29h :1b hsfbing a ds 1:hbf2hb l9deceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikespmk;,yx 2. fx12s mnxmsqyc 18 a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express ty,n8ky2cx . 1 p xsm2m1m;xqfshe 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 :t( 1u*cgfzjk speed of 95 km/h and human reaction time of 1.0 s, for an acc z1cug t*jkf(:eleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the strn gzh6va dta*)5+ dvk16 vpa3md2 hs5opping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver looks fo3x7jf+ * c4m0qdhnc x/u ofz,hr an ofd3 /juc oxf7zm* qch+nx0h4,pportunity 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 the 10,000-m run 2 3; saox4 knp7x)rj 0n)nqgupin less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner mustp pnn;a2sr7gqx uojnk 43x0 )) then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her careh4br- v.vy- b at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the y4hvr-yb-ev b. ellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a clifyvkz 0p thg 84yqe)-;n :mx v9cihm(y6f. It hits the ground below after 3.25 xv0 6hvc(9y zy)mi:yhg-pmqenkt; 48s. How high is the cliff?    m

  If a car rolls gently (gdwx9+i 1mu :q$v_0\,=\,0$) 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 nearly3b/3i)z) 1rdgdqroec v g) zq.nk8l8f straight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s afxftd3k nc)4m, ter throwing it vertically upward. With what speed did he throw it, and what height did it reach?x3)ct 4dknm ,f    m/s (Round to the nearest integer)    m

An object starts from rest and falls xh0dhwq07udyu6o/* u under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a f do0u/hwqhyxu *6u07 dunction 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 heiu ,y n3k2fc,wgght 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 equalsygu2cwf nk,,3 the helicopter’s.] t =__ s

For an object falling freely from rest, show that the dist1x im )vtj /8h/s0 zvr6akfr6oance traveled during each successive second incr)ko1 0/t r6vh j siv8z6rm/faxeases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (av4z zfxswc 3am+ky3+ 7lgebraically) that a ball thrown vertically upward with a spza373w fs c+zkx+v4ymeed $v_0$ 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 of 18.0 m/s 0s +ov.fm 8czz
(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 Fjj(:nj0z3 y,m vwn5nuig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the:j,uwj nvnm(yz 5n03j 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). Fro0 p7,ijiag0j(4fdj(pfx ri:um what height above the to7 uf (4:xg,ia0ijjp0 d(jr ifpp of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and thz/ a0;s9; hyef3rgmt ye sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/sgr ye0;a9 ;t mhz/fy3s , how high is the cliff? H =    m

  Suppose you adjust your garden hod y;al 9is xx+1bpx1e-se nozzle for a hard stream of water. You point the nozzle vertically upward at axdp+x eyb-9 ;sxia1l1 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 vertizd t:j0r(pp+ w/i-+wwwxe i ges07ms vc1v2 c,cally upward with a speed of 12.0 m/s from the edge of a cliff 70.0 me+igrvp2cx,:vwjwp/z swi-e(m+wd st 1700 c high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upwas.qml 5zfw 5 xc:u(0 om3wzut,rd by a window 28 m above the street with a vertiz5:o(mu x5m.ltf0u zw3ws c q,cal speed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) At(c.mr -gz+nsg what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what cs+mgg ( z.-nrperiods, 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 fm;i5bs 8l-g vis plotted in Fig. 2–28. What is its instam8v sflg;i- 5bntaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in the 0c gu/:koc9bana z+vx81yo(tvelocity–time graph of Fig. 2–35. (The short flat spots in toz1:9c+ tunaavyg0kc/b8 o(xhe 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 averageywileo*;: 6k)j6r a--zpdzbu acceleration of the car in the previous Problem (Fig. 2–35) when dek - uzr: 6-ly; 6pj*o)bwaziit 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 og*.uao hve* 2object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the wug9-rl a;ev:k2 (ubpobject whose displacement as a function of time is given by Fig. 2–28. ruvl; eup9g:bak 2( -w

Figure 2–36 is a position versus time graph for the zzyy1:9x h5a)x3l l hmmotion of an object along the x axis. Consider the time interval from A to B. (a) Is the object:zh a1xyx l3mz9l 5y)h moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefightvas77+u *vk+,msm s tper’s safety net. The survivor stsk*ss +,vu mma 7+tv7pretches 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 M9,hr7um;jh x g+xi6 vioon is about one-sixth what it is on Earth. If an object is thrh;j u9 i,i76gv+xrmx hown 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 constra7k0la b2zmxi60q 49 m7zynxj yined by an over-the-shoulder seat belt has a good chance of0x047z 7bxl2nyjymaz 9 q imk6 surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridgezdofbj )kheo 504;s;m, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto thee; ) 0dbfsojm z5;ok4h truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturtpagou )eh cjx * jxu+qbch5w 96;o8)*er tested its cars for front-end collisions by hauling them up on a crane and dropp wgx ju *co*b8htje95hxq cp;o)6 u+a)ing 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 travelob +ql4 krot+0s 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. Th)czq0c z w/zqo,0ohl9e front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will becqz/oqw, )zhc 090lzo 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 suk87s)tz:p2n fi;udl ppk.xy7 rface into a deep pool. The person’s downward motion stops 2.0 m belk:fpd xl)kp pz82yuin7 s. ;7tow 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 balance the avuzqyba2 w y1r wq e4q8dm;x.,3erage speed of a train against the distance between stops. T4 wz2;e1aw8y3d b,m qrqyu.qx he 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 and free fall straight down when s9mj7 criqy 9meg05vq am7d5jc 2x6p2diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot i5mjcg pmjr9qm9q77d526 20axvc ys echange its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with whi2irla o;n/a yy2m5o /2jx;h r7wsqtf ltb05y+ch 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 difficult than from a downhill lie. To see why, assume that on a particular green the ball decbls7 ai l5;;y t2wq2+o yj nxy2tarhr0/5/omfelerates 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 tr:pb/:q1jsog - isyb0ga0hdh ;ain traveling at a constant speed of 6.0 m/s Just as an empty box car passes p1:y hah :0 ;0sgoji/sq- gbbdhim, 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 roof of a high building. A sec .nx5xfwr:0eme t q6h9ond stone is dropped 1.50 s later. How far apart are the stones when the second one h5nemx6.h:tqrwxf9 e 0as 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 trialp:l(m)a5jf, stkmy y. lasting ten laps. If the first nine laps were do(sa5,.m kpyy)fmtl j:ne at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France cr3wm -8n1a rlxxh. ) 2esac4mgjests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his ave)lx3 n4erc2a8mmwgjha .s1 - xrage acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child q), :lyus szeg oloq- (i7g8u*b ob1z9can bounce up one-an obyblg:7zu)oes q-s *go,8z1( qu 9ild-a-half times higher than 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 traveling 95 km/h overtakes a 1.10-km-long train ts )miyfzy 5-,braveling in the same direcib5 ,msf y-)zytion 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 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 base1s)0cwj:qw( kn h(-ktckxxr0 ball 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 tk t kc0k1w)j(0nxw-r xsh(q:co 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, f/ oj+x .efjn;drom rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in 2 zw,bvdc1bj b ;*qf/a6kez.cw,j7diFig. 2–42. Each intersection has a traffic signal, and the bd *vwka2 / wb;dc6qze.1zibjjf,c ,7speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights 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 speed m-(wwfzmg0 x7a0vfkb (f2gt*3b eyo 8er traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speed0tg0 f8fk*7bxw2g 3boy e m(z(f- wamver in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second stonla9z w-i7m vt z );ol)pzj(us4e is thrown straight down with an initial speed of 25.0 m/s and the two stones land at t z lwv zj4(m)as;z-97lo)t iuphe 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 zyz5 ;;*ot mvnup at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a;o5m tvzzn;y* 12th-floor balcony of a building 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 airae-9r2u gs s5dm (n.ly resistance, how long 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 wasnylg (m e5-d s.u29rill restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers thr;zh+,yki 2;qeamd 4ipz+cn, vough a grilling machine. If the grilling machine is 1.1 m hmkdy+n;, 4cvqz,i ei+2a ;zp 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 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 Joe can.hpfezs1x9 ql w8a* 7(3th x38uzf 9chx How maq89za(uz9selc xwtfp13h *xf7xh8 3 h ny 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 frien3s bon;kib.q i(i/qhm6s+t3td stands on the ground below you. You drop a ball from rest a t6kbh mb q/no3t (i+qi3iss.;nd see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of4*ope g)eun/ -o(ayz9 xxp,ku a particular building using a barometer. Instead of using the barometer as an altitudeo zaeopn,-uy*e9 4xp)g u(kx/-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 graphbng d sssnb1(:8xe94k6gzlk 3 for two bicycles, A and B. (a) Is there any instant kbn9 6gs4kb xe:lds8 (s13z gnat 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 other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?