Does a car speedometw9m bnr g0o/km 8.utg1er measure speed, velocity, or both?

Can an object have a varyo1/wrs f;rp-w ing speed if its velocity is constant? If yes, give exampwws;1f p /rro-les.

When an object moves with constant velocity, does its average velocity durv u,7 6idjtlu2ing any timut67l2 u,vjid e interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for v nr1c)x:bfgmk9 ,p ,-b2ushrthe car with the greatest speed crossing the finish linp-mfsbnk,bx9urv2:,r h cg1) e to lose the race? Explain.

If one object has a greaj6iwm dlk 2 xj:se6+o2ter speed than a second object, does the first necessarily have a greater accej+ wel266dkm o 2:xsjileration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80k83-5a ok0jz nuum(/q n ;urqmom/h to 90km/h with the acceleration of a bicycle that 0m-qzunu3jo;noqa/(r k8mu5 accelerates from rest to 10km/h in the same time.

Can an object have ao n2fl3 gay*;u northward velocity and a southward acceleration? Explain.

Can the velocity of anevatt;m zna1 a jg6v4n u9+oew 8.x .b-tm:jj) object be negative when its acceleration is positive? What about vice versam):eg .aj8jt .vxuv9nj-tme+ w4 b61azot;na?

Give an example where both the velocity and acceleration are negative.qs,;;ut ,xftif 6mk w/

Two cars emerge side by side from a tunnel. Car A is traveling with a speed o+)qtje wm );vy ko28d1ca9xsydzh2z)f 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 z2 d))19etz)c dsyo2am;vqx h kw8yj+ 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, gfjovd1)ajv nld-.4-bive an example. If not, expnv14-) odfjj a .dv-lblain.

A baseball player hits a foul ballun o)v - d8oa3fx-yn4p.c5pjn straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast w)nuvpjpn- 85-na.4 fox 3ydco ill the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happe2g fltqc8z y)hrq491 qning to its acceleration due to gravity — do1rq4l 28qgzh ct)9fq yes it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically upw1w.i-9/f5e (o prpwe/qbji zward? pqo95j/rwwzb 1 f/e i(pi.we-How would you estimate the maximum speed you could give it?

You travel from point A to point B in a card8iqwg:l+:grass ., t moving at a constant speed of Then you travel the same distance from.qtssl:gai rw8d+, g: 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 wit.r ;gbep+df8 rh ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. dfb +er ;prg8.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 motions is not at cons ckr:-auc,d(u ,l i7fm2fr/tptant acceleration: a rock falling from a cliff, an elevator movingripc,a 2k-f utu/( c7fl,m rd: from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thr9;8c5pn xwr fwha)l g8own vertically upward will return to its original position with the same speed as it 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 8 h;wnlg5x)w9r 8acpf to the motion.]

Can an object have zero velocity and nm00rcs- 9g2 )ff;slbx38qungj jhnd 4onzero acceleration at the same time? Give en)qs-fx9gh3;mdjbj l c84rs 0fg u02n xamples.

Can an object have zero accegf but3 7gf152mjo7 zqleration and nonzero velocity at the same time? Give examples.jof1 72q5tf bgu7 mg3z

Describe in words the motion plotted in Fig. 2–28 in terms of vyi ,w*l , .y;yic9jjvp, a, etc. [Hint: First try to duplicate the motion plotted by*yi ypyj l,j; v.9c,wi walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. cl* x+yx 9.lyd2–29.

  What must be your car’s average speed*fk :myk4k0t n in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km? bfn(:sa q k/9os6ni4z    h

  If you are driving along a strazuozh21 vvm85v1;kxc gt8- xtt j4jp5ight road and you look to the side for 2.0 s, h25zjhzv-4tkjmt v cx8uoxt581vg;p1ow far do you travel during this inattentive period?    m

  Convert 35 mi/h to 3vi6 (fhrc ( 5sxb0equk:;edz
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fo.uka,yyn h (j( 19szqzxyj( 2rom $x_1$ = 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 at 95 km/h for 130 km. It then bscto4bd8xvcp * ta-0s 7r9*p begins to rain and you slow to cx8s7d4sbop*0 -vcb9r tt pa* 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 flash and )2l24 n yyw duft;,dsm 0htd7athe following thunder gives the distance to the flash in miles. Assuming that the flash of light d 4t0 mw2d7y u2hynt ,af)d;slarrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete lap9i34eb ynyw td*i vl8:s around a quarter-mile track in a total time of 12.5 min. Calwyivnbd4*eyt9 l:83 iculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traini5 jibr3g h6*i+hqnn)er in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gal qi n3n6 b*hirg)ji+h5lops 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 5je52 h;y6j zq )jomsl95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before t h); 5oyjl2j em6sqz5jhey reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How dz uiq :rzl 3w9*xuk)4long will it take the car to re 9)dz r4lwx3:kiuuq* zach the truck?    s

  An airplane travels 3100 km abj2b g1w).r3 uhc/q/isum5 yz t a speed of 790 km/h , and then encounters a tailwind that boosts its speeduyqbuszmg r j/i3cwh 25b /.1) 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 complete rou. 2ti6 wxidlo9nd-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is cx9 tiow2ild.6 overed at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits th8mqf+;p)ijoyp z/ed0py3t uq f+9.yp e 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 dq.tpmoyq9pp; y+ fjz8u i+ p3)/e0 yfreleased from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in7n(bc ft i.4aq 6.2 s. What is its average accelerata(q .t7ic4b nfion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from r8 cld*3kcwcb*9s 9 1kz8ug 7dw7gw9b1iju wzl est to 10.0 m/s in 1.35 s. What is her acceleration b sg lj uzk98bud9wi3wc9**1c1c7w7glkwz8d
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is b2id6dz cjj/io y-+ y)capable of an acceleration of about jj2i+ b)6odzy ci-/dy$1.6 m/s^2$ 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 f/boyk.a5wvpc (w1x a+8rj7ndv e,0 q constant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what ixra.opyn8 ,bf5017v/v j +we( wdkacqs 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 a4o(38xdj ehc te7y(z qt t = 0 and moves in a straight line, is gijyztd ( 43h8(xo7eqecven 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 m/s to 25 m/s in 6.0 k.:7irp+3wok er 1pg myr.xmcrq:q3he 3m)2ss. What was its acceleration? How far did it travel in qeq3 3mprc.rkre17. gsyomrp 3hi+2 m):xw :kthis 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 wad2x5ixmt k x,)s its acceleration, assumed constant? 2)mtixk5 x,xd    $m/s^2$

  A light plane must reach a speed of 33 m/s for t,so *x c/saw-o*jmoc 5ke o+c0akeoff. How long a runway is needed if the (constant) accelerm sx*a5c/oo*cjs-+e ,cw0 okoation is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially t9 h:qadsm. c k/qpv6 +ggig,)gop speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach ,gg/ms i9:6).+dvq p gc hkgaqthat speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s r2gtf 65+4zci0bi grvto rest in 6.00 s. How far did it travel ini2grzg0+64b 5i ftcr v that time?    m

  In coming to a stop, a car leaves skid marks 92 m,p/wc )yu lr/k long on the highway. Assuming a dew)cku/l/p y,rceleration 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 fron* kommwg79(n:d xs id4t 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 7wm(n xdmd94oik g: *scollisi 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 km/huaxv ct)jhb0.xsw +cb2d7() v and human re j.sxvub ccx0v7had2b)t (+)waction 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 of a mu, a;asg1s0mcar 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*s7vmbc eh44s car’s driver looks for an ophss4bc4v *m7eportunity 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 com0o be7;;l /qgqga i0s2n llo1mplete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acceleraiolq7beg2ma o 10n0 gsql;l/ ;te 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 intedik o g)*7mkv2rsection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersectvk o )72id*mkgion 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 cliffk7ju45eecvp8d:e0f b; av6 r v. It hits the ground below after 3.25 s. How high is thvj7ed05:v6ep vaeur4k8f ;bc e cliff?    m

  If a car rolls gently ( k)9ij ypfv2,u7m+dpc$v_0\,=\,0$) 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 :, * 3j0fuujag kqsskib 9d1/othe air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upwj3ko.+pk+6uk1aw, mppfif fg 1,.yfd ard. With what speed did he throw it, and what heig+a wo.31 ,p.ukiymk df,f1 k+ppf6j fght did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and fa9frs +3q 12di3jdpk:v:ar ozdlls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.1r d 2i3:kzj+sp3 f d9:oravdq

A helicopter is ascending vero1ohx0xhr7g,m (y0 j 0w5rrlm tically with a speed of 5.20 m/s. At a height of 125 m above the Ear,r05gj0w1 h m (0olrorhxy7m xth, 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 the helicopter’s.] t =__ s

For an object falling freely gp+)k bcuk54 jfrom rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This wagp+4 k ujck)b5s first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown vertic 9r.u, nj7fch.iv ysv:sac)5df8+ xinally a n5.x8f,d9r n s+jvh:is fuiyc.c7 )vupward 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 upward with a speed of8u ;k h tq5,zquhgik-* 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 z8chl lc6o1ltf qs3*mt1.xm;in Fig. 2–18 (or number of photoflashes per second). Assume the apple ix ml 3tq11;*l6mcz.fcl hs8o ts about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel pasdnlh jthxh nv. nky.5wd6 4p77ww1 30yt a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fa 7dh. 4x y0n56.ywdkvhwwl3ptnn h 1j7ll?    m

  A rock is dropped from a sea cliff, and t t;ey6rj 4tyk amr jp;,d-yh95he sound of it striking the ocean is heard 3.2 s later6rt,pedyrah5k y;tjj9 my;4 - . If the 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:fht3k30uk6ih1qy x mak;l j * point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water;0kmk3x63aiju*htq :1 k yhf l speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a a6vjyn63zb2y-ngp omf)a -4w speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–3m a y-wp-6bo4gvzj3 an )f2n6y4).
(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 vertp19u; 4dy jfytical speed of 13 m/s If the ball was thro 19 ;ftpduyy4jwn 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 fkq4q8(e2avb gunction of time. (a) At what time was its velocity greatest? (b) During what peqqagb84(v k 2eriods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plottocxdq9 ou -t).ed in Fig. 2–28. What is its instantaneoutcux.9d -qoo) s 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 i q:1spo)ji3h nn the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the ji1o p)qh: 3sngears.)
(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 Problem (F4fb(uq lvk3w4y/ saf :av *ps*ig. 2–35)v 44a/:ayfq*u ksslv( wb3f*p when it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object travemn;n)m le5.x lled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t gr0uecl24) icayaph for the object whose displacement as a function of time is given by Fig. 2–28402yilacc)eu .

Figure 2–36 is a position versus time graph for the motion ofz4;7 n:wsfw .did bxr/ an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time intz d7xdw;rsf. :bn4i/werval from C to D.

  A person jumps from a fourth-story window 1 isjr.*zm9h z75.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig.s.7hrz9 m*z ij 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 due6a xskfc0/g: i to gravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times hi a6kxsc0:g i/fgher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder sea2sa2/uh23y d le*g npct belt has a good chance of surviving aps3 ygn da 2/2l2c*uhe 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 bridge, 12 m wzd0cjr09 mw1 :eo i w9h7wlx8above 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 hec0j: ohd0m9w79 wlreiw81x zw 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 f:rjl/ewt4-n t or front-end collisions by hauling them up on a cranen/e t 4:lwjr-t and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth tr;/x5w 8wekczppn ;sdx)mk.5c avels 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 tdq-eod c6cd/fl 5z44the 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. flzc-t 4de/dd546o qcWhat will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above :7jq g8l l9z;e7yom ecthe water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration oq7llz yme87o: e9 c;gjf the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a ram) t- y u9wu 0.r,fblv0df)naypid transit system, it is necessary 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. Tob- fu)y9, y0drwfman0ulv .)t 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 straightee1 42vq/q3x ag9uk7rxv4 jkcao r14n 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 must it spot the pelican to escape? Assume the fish is at the 7xv o1e 9ca4gq/1 exkr4k 2nuv3 a4qrjsurface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so thatx7 lh:du 0ga2 c) elddxio2d/3 the ball will stop3e c)oddld2: l0xuga/2i hxd7 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 speelvha eirl v/ ki5v)z.l:*3 .xwd of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and acceler*k3 hlwvv.l:l.)z vxia/ er5 iates 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. tpzk kcba+ 9* oy22k0tA second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a spee0+ 2kc2kpt azb kyo9*td of 12.0 m/s ?    m

  A race car driver must average 200.0 km/k qn+*6 g2jehoh over the course of a time trial lasting ten onq*j62gk h+elaps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France cres u.(khrcylj+qrg*5zi g g3. :nts 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 average acceleration c5gg:*q n+iyg(h .jrk 3zu.rl(in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing obqyq)w8)4qxz2odl5 hn two trampolines. The first child can bounce up one-and-a-half tim)8)hq olwz45qxqbd y2 es 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 traveling in g1+8jv(ks i*v kpcvo (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 travelij+k1pvvgk(8s *icv o(ng 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 ba)u(m3ed*g4nq1x5zr jvljf u* seball 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 point where it is rmlu( *jjdf5egn*3)u zx 14vrqeleased (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleratbp4 ;z)3 tiayzion 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 inq - :+ywhu*iptkh0 fg- Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lightgyu t +h:q*hw0p if-k-s 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 spee2;py 1ppul2yi der traveling at a constant 120 km/h takes offp12; yiplyp2 u 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(c ;kj v(p3q g;qlxt0arom the roof of a building; 2.00 s after that, a second stone is thrown straight down with an initi;pk( 3x q; qct0(gajvlal 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 same time. The firsp,p4l gr4,wmvt stone is thrown with an initial velocity of 11.0 m/s from a r,p m4 vl,p4gw12th-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 parachuxnii,93sx.v :qf jyn6/ar) dc7f m.mptist 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 3r yq /9apf.cvj,f i)6m.nnx3m sx d:i750 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burfkiy:5v yoekb3;ejs4+hc+ p .gers through a grillin.k3y fej pyciv;+:4+os h bek5g machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the 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 . i+h hah2f t:dl1z(uuthan Joe can. How many times higher will Bill’s ball go than h1f:uathldi 2(h+ .u zJoe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your fr * 0kc-tlgll.viend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hitlv-lg lk. 0c*t 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 particulryqh// dok(o 3ar building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference doeskhq/y dr3o /(o the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time gc or5k/ a4d7icraph 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 instantaneous velocka 4ric5/ dco7ity? (e) Which bicycle has the higher average velocity?