Does a car speedometer measure speed, velocity, or bothfcx dea9i 3: +vip28y+ok. xku?

Can an object have a varying spee,z fjd.l94e0os8 bbomdlz hn((sg3l4d if its velocity is constant? If yes, give exab 9s4.(40 (zlm,dodb sgh olfj3nz e8lmples.

When an object moves with constant velocity, does1f- niaz zbx1wx t/28t its average velocity during any time interval differ from its instantaneo zifbn211/t-zx at8xwus velocity at any instant?

In drag racing, is it possible for the car with the greatest speed cri5aih-vs) loc6 wdb,u2a9qr8ossing the finish line to lbd2sr , vqilaw oh8-9 6)ci5uaose the race? Explain.

If one object has a greater speed than a second object, does the firstb a3-l d* uzkd+jjaea.x/. +j23njv) e2lzjdx necessarily have a greater acceleration? Explain, using ej+/ax zlb. jea3nj).x-3dvk*ej+ dd 2z2a lujxamples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 9l(kb* bxq -r)hy +f(st1b+b8uo m8oqe0km/h with the acceleration of a bicyc+ bsmrq 1fh8k+ylo)e t*( x(bbub8q-ole that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explcf0xp)almk g (.q)mn) 53cxs main.

Can the velocity of an object be negative when its acceleration is positive? W*5qlxxa9 fsnmb 8.dj ;hat about vic98 .qslxb f n;5jdx*ame versa?

Give an example where aw; p 2s h(r9ujy4yu;fboth the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling wip d+w(i;qn7oqk anr 34v (as1yth a speed of 60km/h and has an acceleration of 40km/h/min odq(q(yi 7 ;vaa pk3r4+1s nwn. 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 the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, giv3glwuj1:o- ow0c49r4ztoh k8 kwq:ue e an example. If not4:z9uwr43ow8tok qhw1 egl-c0 :oukj, explain.

A baseball player hits a foul:rsf egn8ry42fdz + -m ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ballmg8zsr:-dnfy42re f + be traveling when the catcher catches it?

As a freely falling object speeds up, wus8*kq gr2 7yfhat is happening to its acceleration due to gravity — does it increase, decrease, or stky2r*8 7uf qgsay the same?

How would you estimate the jq;;.hu iyodil8 bz.0maximum height you could throw a ball vertically upward? How would you estimate the maybj zd ;;.qh0io u.8ilximum speed you could give it?

You travel from point A to point B in ac- zs-v:/1bbemb9 pbi j1wu4z 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 cvji-z94bw bu1e:p/1 mbzs -b90km/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 stringwicuoh52y () q with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits wy i(hoq25cu) the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock 1fx c kukl4:x-falling from a cliff, an elevator moving from thxcx 1 l:u4-kfke 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 position d7dgu4mkqu/0- m tr ;cwith the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be alt-; m0dqtdrumcg 74uk/ered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acces 5vaeo+pqv; /leration at the same time? Giveaeqv;v5s+op/ examples.

Can an object have zero acceleratiz f6) ch9vn7kpon and nonzero velocity at the same time? Give ep fh7n)cz kv69xamples.

Describe in words the motion plotted in F y+gnor +5w2zyig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the mogzywr 2n5o+y+tion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29. dk9q/f;g d2cfo(j;tz f8/sfv z3hh8 b

  What must be your car’s average sh/x02x5q2s g 2w /n otzp c6zo:dhzuc-peed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long)gstz2/.7ttxlb q8zb does it take to fly 15 km?    h

  If you are driving along a straight road and yo// *0ppsclnssu look to the side for 2.0 s, how far s0sn/*lc /pspdo you travel during this inattentive period?    m

  Convert 35 mi/h to 2s0ts 95l6(mtkbrzvhs tfwdyg1t 7 11
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frlqj/ zgja7e(; om $x_1$ = 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 frc n+9+rl pb0veom school steadily at 95 km/h for 130 km. It then begins to r0lvcnb++rp e9ain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flas+svlj7 ;5+s0qmuvy8 0p king sh and the following thunder gives the distance to the flash in yj80 q su7s5gvls;vkpn0m++imiles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a total ti-pgev;rj5:k wu ) mp1fme of 12.5 min. Cal- mp rj1kf:p;ew)5ugvculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer i/vc+jd5 66y4hfk 0npqi uzpz;n a straight line, moving 116 m away in 14.0 s. It then turns abruptly and g 5v h0; p6ijkfdn6+ uyzcq/4pzallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speed of 9l*8f6)mmz l9lx ob:bv 5 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each othelxlzv l 6f)mo89mb: b*r? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling Howo 4h.m2pa-e9 ,hywa4hq*a zbt long will it take the car to reach t mb4ha-t4e ,*q2h zy. aphoa9whe truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tailw9s uh htta,5l;ind that boosts its speed t l;s5t,a 9uhhto 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 awyp-3/ le9 cy 23z qe7o snn3wtzv)gk3verage velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return -)w3z en2y79 oncplqt 33wvkz/s3gey250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins , 8fae41jeeos 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 speefse 1 ej8o,e4ad of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 shqm tc.hau,i2(kxa 1(s0zv, k. What is its average acceleration in. 0 sqk,kh1aai,t2chmx(v(uz $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from ret: vzqjy-)i3sg )d(zmx t:+u mst to 10.0 m/s in 1.35 s. What is her accelerationj x:ygt-)i+vu m)z m3zs(: qdt
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleration of abo3 o vu,0*+;t7g npdp2znitazp ut n ,z0pat7 ptgzou*in;23+pdv $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If1)nm, tc8x yyc it then brakes and comes to a stop i1t nmy8c,x cy)n 4.0 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, wh h-qu*cgiww 5xi y(01 elaq-nyb5(m6t ich starts from rest at t = 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 accelery6nt0 u5qy-5cl-mbegq(ia iw1xhw( *ation as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 g * no6l m la*1(16rjre7rm djjx5a,apm/s in 6.0 s. What was its acceleration? How far did it travel in thiam rj ,1la6gdpjomr* j7x16a5(*n lres time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s0x9jl mu :dv7n to rest in a distance of 85 m. What was its acceleration, xu:mn7v0d l j9assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. Hw dzucst29c6(i: 9tiaow long a runway is needed if the (constant) acce9zudtiw cc:a( it9 s62leration is $3.0 m/s^2$ ?    m

  A world-class sprinter casafvk ogu , .+v, 6i1enk4x0rbn burst out of the blocks to essentially top speed (of about 11.5 m/s) in the f g.kbs, ,vnv k1+ur6a0ei4foxirst 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformlq5b5w/7o6 sn uzcq)ofy from a speed of 12.0 m/s to rest in 6.00 s. How far did it cu5 w7qbs)fo/6 n5qzo travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. A 7c-1 zb/zeasqssuming a decea/7 -zc1qb szeleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/hnqw*b: 9bu lt,rxxc)9 strikes 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 the answer in terms of “g’s,” where 1.00 g = 9.8 qnu99bc,x*w tb:rl )x$m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 ( *tw6elm a5jl:/xc xgrl).hi.bq a2dkm/h and human rea.hq)eixgj5ll d r*m: b/2alt6x. awc( ction time of 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance o g4yvk.4aaan:1 yq*mv35i,0ydq bjku f 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. ,r 5uhif7qg5p The car’s driver looks for an opportunity to pass, guessing that his car can accelerate r5f5 ui7 ,hpgqat 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 mi,s5e6t91 9z wnac:l x is3ifqr*ecn2pn. After exactly 27.0 min, there are still 1100 m to go. The rip 6n tc, ilcn3xz9ss:free591qwa2*unner 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 interh qcpu6f e(u3 kwt ;m7:8txhp9section 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 intersec3uu(qptkm eh7f ; 6t xhpw89c:tion 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 oni 2dd:s ;3(x m 7:dnaore9oy7 zcg7tof a cliff. It hits the ground below after 3.25 s. How high is the cliffsr ta d9ooxg;m y::7 zcino2n7d e73(d?    m

  If a car rolls gently8sb zjnz p..12gwktd8 ($v_0\,=\,0$) 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 0-lx 3t ynn7joi9lpu ,w3a wx5straight 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 3.0jfi *js t ,cc:m2y wa6;:dd5u)uoj (mx s after throwing it vertically upward. With what mudc ji : ycxjjdf6 5,(t;:uwo)*2sm aspeed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Drawu6,kiaj or 686v zv5lmfh ;,cqiy88 kg graphs of (a) its speed and (b) the distance it has fallen,o,iv6ur lcikv5k ;gza 8 jm8q68yfh, 6 as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending verticall ceq4wxm lo*l6(sw )pz)fz:g, y with a speed of 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 packmelxfzl6, gs4w)zc*p :(w )qoage’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely fro0yzjr,:5 +b,ptszfq vm rest, show that the distance traveled during each successive second increases in the ratio of successive o fzb,r0+5,qsyvzpt j:dd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (abz8.b* bpei )(u 4wwenuj+q* hlgebraically) that a ball thrown vertically upw*z beuj ienp.wub4w+)* b8q(hard with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically u8qei b.x*yk+(l o;yp q.fb u,dpward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between to: gx8rda v3 8j42:m9hqo aeowl8 h/reach photoflash of the apple in Fig. 2–18 (or number of photoflashq a8 w/4mg8er:3t8la o2:ho vjx do9hres per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takeul ,u0ngn x(d0s 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did u( 00u,ndxgnl the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is heh in-) 1sqpsskme0 x7oj i7km(q q6;5eard 3.2 s later. Ixjioh (iqe )7q1sm msne67kq 0 s5kp-;f the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozq 3b mv3:h*k-h0chxl czle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you qu:3vl h0xh-qcmcb* 3 hkickly 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 vertically upward with a 8 v , maxru+bxu)w:g5rspeed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–ba)gw+u,xuvx5 rmr 8:34).
(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 window 28 m above the street with a ver m,rxmh0..onf v fd/b4tical speed of 13 m/fvd 0rf ,.h/b m4mnxo.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 ofec 31ie8yl b7q a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of tieb 7e8qy1c3lhe acceleration greatest?

  The position of a rabbit along a straigholk 0pz+go lw-i2 d3l2t tunnel as a function of time is plotted in Fig. 2–28. What3odkwllo 2z+i0 -l p2g 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 automobile can accelerate appr8po.y ryp.v l0py k6.v5dz) gkc-od 4foximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots iyz5od8. drk6 4pfpg. py ycv0-).lo vkn 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 0ogc2nu ;2 hfoin the previous Problem (Fig. 2–35) whe0u22;fh n coogn it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the q2cd*dkm )qm0 object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the zm7 (j skmzyu an6/3t6*(x1t:yos i rdobject whose displacement as a function of time is gy iu*r mz d1 3tsy6zom6t n(7jk/axs:(iven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an obj -qs9kj zzz(td 9i7;r+nq1zfyect 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 slozr +-iq9 1n;z( kzjtz9qfs y7dwing 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 windaeoe8xn34dok( , b s,qow 15.0 m above a firefighter’s safety net. The survivor stretc(k, a4qe38o ed xbs,nohes the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what ixggh7 fpd d;7hz m1rpuunla, yy1*;11t is on Earth. If an object i1 h gdlhu7f n, x yzgy;;aud*pr11pm17s 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 prope4pn 85wqi 6+1ry3w y rcaw)kkarly constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the da )y5r8nkkyc1rww iqa6 w34 +peceleration 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 b++apr mt;de sjsa+6/ jridge, 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 trua++srm;a6sp +ej t j/dck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions byxa6cft2rqyh(;i 0h- f hauling them up on a crane and dropping them from a certain height.i 6ah2;c (ht0 ryq-xff
(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 Earthp8 m :yj,ii,wy 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 traipc*7xsnei isg cb b 1)t17xx26n has a speed of 25 m/s when it passes a railway worker who is standing 180 m fro1 12cix*e6s7 isbnpgt7 )bxcxm 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 boar g bnp*g+.3jfcfn z8.wd 4.0 m above the water’s surface into a deep pool. The person’s downward mof jg3 w.pg+fb.z8ncn* tion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the average2z l-6ae q(o,kba p.bn speed of a train against the distance between stops. The more stopon6 z ql-,ae2p abkb(.s 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 fri p 9.ecimx7e-ee 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 .9mep-i cx 7eitakes 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 which a golfer strikes a ball is p.a: :w9w 07s siewdcl;1 cocbllanned 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. Acei;d17lcwl0w b9 a:c :sswo.ccomplishing 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 tc9yma 7a w5km *uqf:9zrain traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelerate yu:zca9k fm5w*a9m q7s 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 *0vfi+m,a ; x(svqvu na buu00of a high building. A second stone is dropped 1.50 s later. How far apart are the stones whs a n aqxuuv, 0+if;*(vu0m0vben the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial gw9 ug*u/,dhcmsu b:kl0.s7o lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed mus,kbd .h: sgcwgl0m s7u9u *uo/t be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests 9i- rajy- brssij81pi k-ro+7a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farth+ rs9brkypa -soij-ji-8ir71 er, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce up oneo53uen+zeu mtk-c 5n8-and-a-half timese z-+ okenu8cm553 tnu 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 br7etp m8eu1r1ks y(:km/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 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 op: t8 sbrk( u1yp1erm7eposite 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 baseb5cea)1+ nn/aak o-wn qall with a speed of 44 m/s In throwing the baseball, the n-kao a1+ce qn5)/ anwpitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from res ia rr:xor:dc39+m.0c rch; fkt, 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 zyd yb8(4/vsfan m jq,l/-lc pu+:(vashown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you arenjl / amal((f /u ,ypz+4qv8dbv-:csy 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 cxzg6*mh7lg9f:f(m8)v ;qju qi m s0qspeeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 7 i:j)zq7ch06vm gmgqs*f(x q8mu9f;l50 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;u9qw:p94l qr hl8.l/o/z dtvx 2.00 s after that, a second stone is thrownlq9. lx9 r/dlput/zho q w:v84 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 the0dz vt; p01l*k: fnmks same time. The first stone is thrown with an initial velocity of 11.0 m/s fro0ms 0nfp* :;kl k1tdvzm a 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 air resistance, how long would it take a free-falling parachutu0x3c8 01jnoo lx:maw.u1hmqist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would:m0ulq3mh.au xoc 1w 8n xoj01 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 ql 7dc+ m ntf23;02x 9 ki2eidurigw3qconveyor 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 th u rq;x3kc2q 9d3i0n tl2m d7wf+2igiee rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertica rm-wyt ebws4,q0+j)e lly at a speed 1.5 times faster than Joe can. How many times higher will Bill’s t+w -jym4e)ws br0,eqball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your cm:yr 2h0zr2 m76 fu2b nd lm/sxv8:4:twgrwofriend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throl m6:r:: 2uyw7 sngw0z/4 rvmr8c bt2xmh2fodws 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 building 2.-jt5p hlf ekusing a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building k-t .p h2fl5jeand 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 the89-md1i r rrpv position vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantanvmi rpr9r d1-8eous velocity? (e) Which bicycle has the higher average velocity?