Does a car speedometer measure speed, ve g*3 elg4p*rgelocity, or both?

Can an object have a varying speed if . hmu* ijqpr45np(p-ff5 m r4jits velocity is constant? If yes, give exam-u 44 p 55rn.mj p*hfjiqfpr(mples.

When an object moves with constant velocity, does its average velocity duringj aehv 3ew1:k3g ezl+uc(.d.u any tie .zcj dwgea(l3.+ 1v:hu3ukeme interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossings tfis jfjgy:s 0d,+ c.1yh1+p the finish line to lose the race? Explasscp10tji djf+yg. 1s y:f h+,in.

If one object has a greater speed ,x:zw l5he1kq tdco jp0 f4*+bthan a second object, does the first necessarily have a greater accelerat 14de oc l*0tbzxkw+fhj:p,5qion? Explain, using examples.

Compare the acceleration of a motorcycle that accelerame7dst ,3r4urti ffsw4x)y ,49ma (kd tes from 80km/h to 90km/h with the acceleration of a bicycle th)3,dyx 4,a74 iu(rtr4mmseft 9f wks dat accelerates from rest to 10km/h in the same time.

Can an object have a nov dx1/ho wfg)e/;1h tkuo.;ggrthward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative wheny,fhapvb eb aug5c* y7.jl 170h:4ppj its acceleration is positive? What about vice versa?yppaeb,*a vg0l:.juy5j17h cf 7bp4h

Give an example where both the /ukrmtfuvy(bat i)kc2)2/5 m velocity and acceleration are negative.

Two cars emerge side 5tetg m.6cdn2by side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasonin2. 5tgce t6nmdg.

Can an object be increasing in speetan2 ,zky*xy6.id1 p7d)a1w wi9ayf id as its acceleration decreases? If so, give an example. I9nxywi1ak6 *72ypyfz w1d.ti,id) aaf not, explain.

A baseball player hits a fo mo2g6(6daqjk+stc )nhq50 spul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast wi+ qctas 6)m 06dnqskgpho2(5jll the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is f566si d 3xsul1ouk4phappening to its acceleration due to gravity — doe suuoks643xf1ip65lds it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically prsq06 qr7cc m d ox;la.10ek5upward? How would you estim qxpe;d0qm0ol a1cr5. 6 rsc7kate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant spuxhcf7 :fqh p-7w4ajfwe(32 keed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the enti2:4 7f -uwqfh7w 3h akfpx(cejre trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstp-)klly g4xg4 z,doqo,n o85pration, a 3.0-m-long vertical string 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 the plate. The sounds will not occuog,z5n , xlo4k4 qy)pd8lo-pgr 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 accelerf oyx-o*+ di0zation: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops +-x*i0y zdoo falong the way, a dish resting on a table?

An object that is thrown ver1rbc8tt n:o5g,rb 16bt+nr8lwe+ va htically upward will return to its original position with the same spbvho:bb+8gtwlt +r 8a nr15 cn1ret6 ,eed 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 to the motion.]

Can an object have zero velocity and nzd38stey l/gx nh*tl 5 ; :v;mwyp(8szonzero acceleration at the same time? Give exa znyl;e 8d8:;l5h*(vs zwptys3gt/mxmples.

Can an object have zero acceleration and nonzero veloci7u ;p81t4 8x vv efmfkhvegd2;ty at the same time? Givetved4u g e;x ;vhpf71fmvk288 examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, aowv1p5.lndz48o i*e)m:l dnc , etc. [Hint: First try to duplicate the motion plotted by walkin 5o4*1m:p devczold).n8inlwg or moving your hand.]

Describe in words the motion of,tozp0jw d jsusm 4g iq8+h.(4 the object graphed in Fig. 2–29.

  What must be your car’s um u4,v uw9uic ht4r,5average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it t. 6 y: ,tw gqqszxshzw;xk-53nake to fly 15 km?    h

  If you are driving along a straight road and you look to the si1:y 0q*fq+tje zmno:dde for 2.0 s, how far do you travel during t m0:qnfo1tde qzj*y:+ his inattentive period?    m

  Convert 35 mi/h to h6 .nwluwu8 c fj6,*yhrp0 3uz
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball movesw4sz /mh6iduie)b*:+yfsbe t /rg5,o 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 at 95 km/h for 1yi71 + +lfo1sg*3,wegqmdm ws30 km. It then begins to rain and you slow to 61 wef+1dss oil*,3w ygm+7gqm 5 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 t s:;lv; zv7+qfl g)wfyhe following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially vz:vq)lf ; ;w+ylf 7sgno 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 timexstpr bx-))js4z fb9- of 12.59 x- xp)bf-4sbsztj)r min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away n-w*e5hh sjp/ in 14.0 s. It thph 5w*e-jhs/nen turns abruptly and gallops 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 tras,aos kokq4z 5m4m6k+ cks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will oq64,5sakm4 +omkkzs it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How skc 4dc (bw.j.long will it take the car c4.( dbjws .kcto reach the truck?    s

  An airplane travels 3100 km at a speed of 6)i a9/jf1mdyb xfqx5790 km/h , and then encounters a tailwind that boosts its speed to 990 kqfx/d9i6ja )mb1f 5yx m/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 ms5 y-1i5ffka speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 kmym-i f5sk5af1 /h.    km/h

  A bowling ball traveling with constant speed hits the pins at :oh66qrq0i ,k a 8uziithe end of a bowling lane 16.5 m long. The bowler hears the sound of the ballahkzu ,: oqqr8i6 6i0i 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 accelerates from rest to 95 km/h in 6.2 s+(x:jr,6/two dg v urfeu)2 hu1eqzs,. What is its average acceleration in fgux(r v1/res,2eutd6o) w:z j uhq,+$m/s^2$ ?    $m/s^2$

  A sprinter accelerates frof 6x1 ktyyf /p30gd9kxm rest to 10.0 m/s in 1.35 s. What is her acceleration 1f 9y kyf3/pd0t6kx xg
(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 41bchq7gaj. iqa --l f-g)y( tw8jwdud(d 5hqan acceleration of abou. (qdb--(lh fd8djaywj h atqi1c 5qug4-)wg7 t $1.6 m/s^2$ 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. If it then brak5fsif r(boe5.l gskitg) c1 8rpc2f/ /es and comes to a stop in 4.0 s, wh cg2fr5s ( tfc)o ik/8sbg.fer1/i 5lpat 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 s 08 8a+nomzpxetarts 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 vp+ nemx88o0azelocity 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 s. What was its accelerat*4;n lrhp /,kumke vf8ion? How far did it travel in this tev/ru8fl 4kh;knp, *mime? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distancint+ c15xl0:fb.v9 vstr:w vne of 85 m. What was its acceleration, assumed blrfn. c 0tvvw5s 1+tx::i9nvconstant?    $m/s^2$

  A light plane must reach bhxn,0(7ugfura+ a)n:f jnj2 a speed of 33 m/s for takeoff. How long a runway is needed if the (constantfn7gfu h)ju jr:bnax( 0+ n2a,) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can buf lylqjzgm*3 -x* wt30rst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of thewmzq 3 0yl*t3jflx*-g 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 uniformly from a,.xo( c. pbb kyvx0/sn speed of 12.0 m/s to rest in 6.00 s. How far did.onk(.xxs0/ cyp ,b vb it travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m lonlwik:bytn2,ja3+3; n l u-zqs g on the highway. Assuming a decelernu :y2-,z+ jltw;qksnlbia3 3ation 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. T 4 xxl1tkdri).he 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 ci)1xl t 4xdr.kollisi 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 diskimtxsv*d1h yh085* qtances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an ads yhmkx0 i58h 1tqv**cceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance uy i+fk9psch;p0n 25vof 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 t5d9eeig0ys3driver looks for an opportunity to pass, guessing that his car can accelerate at i5ty3ds0e ge 91.0 $m/s^2$ 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 comple)t wy)da+bx 9.h,yjzhte 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 mhhd) yt.+ywa9xzbj ) ,ust 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/gbghmuj- m5g 7o-o 81th approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maxim7-o mgo5g 8jtmu1g-hb um 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 th,o1-j3eyc u+ lwij3ene top of a cliff. It hits the ground below after 3.25 s. How high is the clj3i y, noluj3ec 1w-+eiff?    m

  If a car rolls gently (wu jkdclr:d8 t*./ g,5uwodq3 eojc6)$v_0\,=\,0$) 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 inzbm7: e teky5/to 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 after throwing2 b;w 9n18+xomelswxz it vertically upward. With what speed did he throw it, and what h28b9 ;mzexlxo+ nwsw 1eight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under thebq4aao v2a3evn7+ .lm,ptrx ) influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of r 7 v2tnxm4abq pov,3.ael+a) time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20vx8g) u 3b.ruvlb:l1r3)ysvof mns./ m/s. At a height of 125 m arm1x :fo3v / g3bb).urlsv s8nuv.y)lbove the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance travei,4xcn m7g :sax-g u8kled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown xsg48u,k7c: x gn-ia mby Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, s)b 7/ ojz-npxwhow (algebraically) that a ball thrown vertically upward-)7j z/nwo bpx 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 speei1/y v73b rsd y4hnnu)d of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each pbh1o:q6 zc+w 4 rdpn dcqx).*hhotoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the a.14bw pcr:o6dqqcxz* h+dhn) pple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel plz1fcuv 5sjb71 *z8xnast a window 2.2 m tall (Fig. 2–32). From what height above the top of tcnb18 1z*u jxfzls 7v5he window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of ij3 mk9zk:jrz 2t striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high2j3z:9r zkkm j is the cliff? H =    m

  Suppose you adjust your garden hose nslm03ttlz,v lna4 cg ++2 p+d m13jkqeozzle for a hard stream of water. You point the nozzle vertically upward at a height ofc l1+3vm +atzkld lt3smp+n,g4eqj02 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 vertically 0p,u ik(o4s ,hykoh14 ,tvwfaupward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig ahvkf 0u,p4 1h4wskyt,(,ooi . 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a ve)pf ;9q2buie lyaw*6a rtical speed of wfe9a6pqi ; bu)y2la*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 trw2b hiz ;bih p7d*67bsain 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) Whb d;*hzhb sii76bpw72 en was the magnitude of the acceleration greatest?

  The position of a rabbit (6e f cco 8sfb ;/*0gactox+k,lr 0isvalong a straight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous vel 0(rvcs*6 lac0g8 /i,;kbfto fsoecx+ocity
(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 automw)w*e0r bjxr 3xhs v+ mxd+c,4u-nn*iobile can accelerate approximately as shown in the velocity–time graph of Fig. 2–33wbcixxwj*e)h rn m,+x0 4s *rduvn-+ 5. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problor .gf*pa jo-/em (Fig. 2–35) when itgjopo -/ *r.fa 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 traveled durubaynot01f nxo r 21f7 ea993uu c32riing
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whp a;vxm2e6oreg d 5)db(6 5 fr2u+nwlpose displacement as a function of time i6rl(p6+dab pe2)vw25don; m xf g 5erus given by Fig. 2–28.

Figure 2–36 is a position versus time graph for tv-pku 5smlt jenwfg8a ol,-;n93s7kx pfq7;, he motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object pm97s ln t,-w p;qvokfu ;pxgak78nfl 5s-,ej3ositive 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 firefighter’s safe 2ddle-5bgqlruna/5n5 ,v*t ety net. The survivor stretches the net 1.0 m before comd5e,/u25 aqd elrl v b-*gn5tning 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 thle j8e6h:oth- e Moon is about one-sixth what it is on Earth. If an object 8h: lo je6eth-is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is propzvp 5* m8d 3e 3bnq9vw)k.dgjzerly constrained by an over-the-shoulder seat belt has a good chance of surviving a car 3 k .3ddngbj)pv*z9vz5eq8w m 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 above the dr8w50twyex*q u5/faroad 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 po85uwyfxt/d r 05a*w eqles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer teste nqn5 vng1m+i(d its cars for front-end collisions by hauling them up on a crane and5+1ngnqn( m vi 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 travelsy;j4x)s/nqd n0aor15 :* 0qrko icf xp 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 restvk9fd5r hi8 5s7adrh4giux ::oan(2:ls wp -t. The 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 startedudwr(a:-: x rg95pfin othlas 84vi57h2 sd:k . 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 divin-g n*ais3s ;uwg board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person whaw3s -ign s;u*ile under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid t2 ztxz2 ahb3p +6led:hoq6ey6ransit 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. To get an idea of t66typzexh2+2ah db6 z 3 l:qoehis 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 n,z )d0p5 krhodiving 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 0do5k)rhnzp,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 planned sog44x yb(oolqse 4uc27 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 Fiqsl g2o co447u4be(xyg. 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 y)6a/;kg 9zsu2*bzc k,af r jstrain traveling at a constant speed of 6.0 m/s Just as an empty box car passes hz9ua6*s, /yb2kjca srgfk);zim, 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 wgjtuuq obv ryo +bxs+a-f1v s 6w39o+ 9)6,gxa high building. A second stone is dropped 1.50 s later. How far apart are the stones whenfu9bosjt xq+,w1vb)+ va6xgw-9g6 yr3su o+o the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must averag film7ac0um y1m w9i(0e 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?(90uwif7ac 0my mlmi1    km/h

  A bicyclist in the Tour de France crests a mountain pass aqk1 (nkbhc 4)x tk:vr-oukc4 3k (shy;s he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What w4 (thc qk3bh1cxs-v:ruoy(k k )k;4kn as 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 bougjmo)hwfz n g(lg/po.,w04 5 skh/i(ince up one-and-a-half times higher than the second child. The initial speed up of the second chil5zn ghf.piog/k h,ig)(s4 wm(0wo /jld 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 1.10n51pckdgz(*i -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 passzg* k(dn1cpi 5 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 bayro*htm,eq6)i7- yq y6 0iinnseball 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 qi6mi h)i7-nte*o0qyyr ,n 6y 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 rest, with an acceleration 9a0(og41 bcqh.gkmdu of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each interseu8ol qqf j, l6q2jh,4erky0a :ction 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. T ,orqyf82qj4u:alh 6q ekl0j ,he 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 -ghc1 y k*9njla speeder traveling at a constant 120 km/h takes off in hot*cygh9 k- 1njl 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 from the roof of a building; 2.00 s after that, psv;45ybqg 4ja second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at t;p5qbg4ysjv 4he 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 first st v3r2mqjuu7-kfn ( es8a v4.krone is thrown with an initial velocity o 2-m.unjsurefr8vqk73kv 4 (af 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be 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-falli9ls: f+(dz insqd4bz+ng 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 resistzqb+s9z df +i:( nlsd4ance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conve.dz y6 k:f;ormyor 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 travelzoy6d . r:;fmk? 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 vwr qz*:/yv 8c.j:8 dxslfs9cb ertically at a speed 1.5 times faster than Joe can. How many wf8z/c8c :db* .xlyvsq r9 :sjtimes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff whi0iy8ph 4xog -hle your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for they0 h84g phoi-x ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a partic jya ex7s)u8*oular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the rojex)o* y8sa7uof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) nr8qhc7u;k c om11)n2.w n sctIs 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 i2mq7 ontcksh)n.; w1crc 18nunstantaneous velocity? (e) Which bicycle has the higher average velocity?