Does a car speedometer measure speed, velocity, or bogg y*(n nfj7d-th?

Can an object have a varying speed if its velocity is constant? If y d;)xv 16celndes, give examplx6d)v nd;1leces.

When an object moves with constant velocity, does its average velocityh:ki+;c7ekyd)- xn xo during any time interval differ from its instantaneohk :7oecid ;x-y)k x+nus velocity at any instant?

In drag racing, is it possibl a7 i-cdjc(x c1)-euuqe for the car with the greatest speed crossing the finish line to lose the race?(ixud a)7q-cj-e1c c u Explain.

If one object has a greater speed than a second object, dvzbmxq i1 / oeq4 6sze+mg/19jk.c8zkoes the first necessarilqx k+. 41mvcqgkzzes 9e8/jo6i/1 bzm y have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that acceleratesbsgu c2s6+loa7x4rbix+t a(3xoo0 6y from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest oy6x++032tuxab 47 6gcsliorxo s(ab to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explain.v*i 1q 5ztnomkfg25(q

Can the velocity of an object be negative when its acceleration is paq9 o9tn viep1e82z-l2kr e /bositive? What ar aoetznq9pb 9ke-21i28le / vbout vice versa?

Give an example where both the velocity anjws z, k:s8n7ld acceleration are negative.

Two cars emerge side by side from a tunnel. C/vb f f z;dn64aqpr)7i+9xbtnar A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a tn9 4vdi pxqbfbf7 ;)z6+nra/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 decreasdg we1s+d- umg 2tz1hr(li- ,fes? If so, give an example. If not, exu+h -1mze-lifds gdrw t,1(2gplain.

A baseball player hits a fvzy bezt5-p.m kj x94gj-(bf;oul ball straight up into the air. It leaves the bat with a speed of 120km/h .t. jg 45ze(mjb-y; fp-vxbk z9 In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happp-tny g 0*dqq43g0 ipiening to its acceleration due to gravity — does it increase, decrease, or stay the it q 0dnpq*pg40iy -g3same?

How would you estimate the maximum height you could throwp/nw9g ))vamx.j s1 ca a ball vertically upward? How would yonx9 )cav m wp.)/1sjgau estimate the maximum speed you could give it?

You travel from point A to point B i)gaa(mnf/* dzn a car moving at a constant speed of Then you travel the same distance from aamnf)/ zg(d*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-longj pfvlp6kz-:j.e. y*crv an/) 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 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 interjp:lz- a)pev. cn .y*vkf/rj 6vals?

Which one of these motions is not at constant acceleration: a rock fallingc6p* aam6.ee g 8kip*v from a cliff, an elevator moving fromv pp *8gma6aei. k6ce* the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward willuo8 mzxj uo nb(z0d0;. return to its original position with the same speed as it had initially if air resistance is negligible. If ozn.m dj( box0u08u; zair 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 nonzejm+y 3c zfeu-/*zj9j qro acceleration at the same time? Give examplecy+* /je z9u3- zmjjfqs.

Can an object have zero acceleration and nonzero velocity at the s7e 22 vw54mxfrxnj5w wm7jn* kame time? Give examplesrmxw5e n*v27wkw7jm5 xf4n 2j.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, ety :2sh6 2mzz,:vh9vcvcz e/.esm hn3bc. [Hint: Firs9bv ze,6.vc vz 2c3yzms /2s:h hnme:ht try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2g/zuid 4m+i:c –29.

  What must be your car’s average speed i4nb6iyp 4n b5rn order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does1dfpn ngp v,(9 it take to fly 15 km?    h

  If you are driving along a straigu:a4r bu6 p;sxht road and you look to the side for 2.0 s, how far do you travel x; u6usrp:4a bduring this inattentive period?    m

  Convert 35 mi/h to t eq3 7gceu twavtt+x2fs6 962gdz(d:
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from u5f)ryy 0 qn glliq;/9 q2v6ym$x_1$ = 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 stuiy p2p evobe/7( +3eyeadily at 95 km/h for 130 km. It then begins to rain and yopbu ee i+y/oe3v( 72pyu 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 seconds2xlt3.0qf q.c5t abbb between a lightning flash and the following thuf2taxql 0bqc53. bb.tnder gives the distance to the flash in miles. 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 tr,zi5t(hudz o+b 86 lrgack in a total time of 12.5 min. Calcularugz o l5tdhz,8+(i6 bte
(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 ue l;npbyla*j 1rb1- nktq1,; m away in 14.0 s. It then turns abruptly ,- 1*rynl1 ;lpuj 1enb;tb aqkand 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 tracks. Eacbyxp8u(b1:;8n-,ekndn g a8ulx v uo)h has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be ;pagodu :1ny- ),uk v 88lbnxex (bun8before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m beh rze9m+jh rt(7ind a truck traveling How long will it take the cejtz+m(r hr 79ar to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters as0//mfdym9o)dp as. ft79ffm tailwind that boosts its speed to 990 km9s maotf 0)7ys/ffdp 9m/f.md/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 averags71mgk gdo )9he 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)7 msg 9h1kodg km/h.    km/h

  A bowling ball traveling with constant sp2xjgqzb;o) (uo,p bo,eed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hi,(oxo,2)z;bj bp guqotting 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 4z2 gj5/jfs zqs. What is its average acceleraj25/gszzjfq4 tion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s inqy+4kep2 vo 0h 1.35 s. What is her acceleration q0+kp2hy4ev o
(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 accelerati,g+b0azm mr efb.bqw +t;(, kdon of aboute(,b0 qt . kadfw+mrz,mb;g b+ $1.6 m/s^2$ 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 1)ix 5c)l,xaoy 10 m in 5.0 s. If it then brakes and comeol )),5i xaxycs to a stop in 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 carn-+bthy79zi) 4cgd qmxscb 15, which starts from rest at t = 0 and moves in a straight line, is given as a f 7h- t4dqm1bbzc igs+ny) 5xc9unction 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 ik0 z,+dfjs8y*ujc i8ln 6.0 s. What was its acceleration? How far did it travelcsi l+8k,8 j jyz0fud* in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to restn m01 r9.iwti;jriq(c in a distance of 85 m. What was its acceleration, assumed constant?i (t0 jw rc.q;r9iinm1    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How 1n c,6nakl6vs2he vk0 long a runway is needed if the (constant) accelera,el2 6chka v0vkn6 1sntion is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst ouuurcr/wm-vjbp6 vps7 (x2n3, t of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 nrvjx/-73 crp(v2u,bms u p6 wm 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 uniformly from a speed of 12.0 a+oznf (1f*j3ot6o,qnbuz 71tva z s(m/s to rest in 6.00 s. How far did it travel in that t1a +*os76,z1ufo(qa(f ztt nz3njbovime?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highwa+;z( on2:omvjhw2* fezpgtj ;y. Assuming gw2:fo epv to;z(hz2nj*m j;+a deceleration 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. 3sd 0 d1b 9k-dkzdywv*i 1g.yfThe front end of the car compresses and the driver comesdwdg0v1.kdb-3fi*1zk 9d yys 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 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 km/h and x,1q ik-f:/+x qhhd6. xce8ebzhw b,l human reaction time of 1.0 s, for an q+1xhh qlbk f/8ze-x,,ixh. ewb6 dc:acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation f; vj6 kqj+xtj0or the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the hi2,a4kn+ ns9 heph *xt0: zffurghway. The car’s driver looks for an opportunity to pauh*n0psf+er2ktx: a 9n4zh ,fss, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less thang.nfcs+ qq 4 w;gl1y*)w*nvu l 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner fwu)nysg4 lnvq+*1qc.* g;l w 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 intii3zcu 3;cxf4 ersection 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. Hec fu4 3xi3z;icr 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 cliff. It hits the ground)3zfi.r7aa;kk9 (huc5 ,sm7 wc tqfqn below after 3.25 s. ,q;z)3at ( hk.u75 nifqs c9ck7m fawrHow high is the cliff?    m

  If a car rolls gentl/c;b8rs(a cl8e ac5 hi70hdb oy ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the air with a speed of 2hspz z4d/r( s+g*:p yc2 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 upw5lat+z f,l z(f pa ;7q6lwi3pteo4f ,gard. With what speed did he throw zga47elo( ,izp ,;lflf w6ptqt+f a53it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and fal/ywf)bu - 6ptq zput43ls under the influence of gravity. Draw graphs of (a) its spee /4bq uz-3pu)wf t6pytd and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a hep zsyfwhph5 ,qfkw:h me:45k*.ezf1 9ight of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ ::5z, wyzkhqe4 whpf5h. sefk 1p9mf* s

For an object falling freely fr.cyfk 4 efi1-uu) h/huom rest, show that the distance traveled during each successivk/)u1 hiuh yfuf.4c- ee second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebra+ow3-)zjj ita9 ,iwync: bb,escl0n6 ically) that a ball thrown vertically upwa+0b js -zni)enw6i,9c,c3j owy:b t lard 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 ved1ta(eay;fm 877 tj udrtically upward 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 each photn:(y0)bs6 vqu i 6+6gexew tbmoflash of the apple in Fig. 2–18 (or number of photoe:(t06+b bq66gnsemwi x u )yvflashes 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 takes 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). Fr q:/8d, htdt3u3znkck51ftg m om what heightgn833ktfq dt1m :c, 5k/hduzt above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikingh 6c9 )hsfd7vu or)r l*hgg15i the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how 6*sh9 gfohdc))ir 7 5rughv1l high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You po fn) ubdyg:(z/-k3kn nint the nozzle vertically upward at a height of 13 gknf y/dz)kn-bnu: (.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 upward with a speed of 12.0 m/s from the k745a6tbuy+c z ve.ds edge of a cliff 7c.bz6v5u d+4 t7seaky0.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a vertq4ss hc c;i/go58p,u oical sp sc8q,oohs4pc 5;/igu eed of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) At wha shp5h,15 baqqt 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 hh, 5sqqb 5a1pwas the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a* 9g,7es byi5-oqah /xsr)agn function of time is plotted in Fn-s, * y/ahor xiea75gb)9 sqgig. 2–28. What 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 9r*safmpm98x can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiftixsp8 rmma*9f 9ng 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 Problem (Fig. 2–3f+zg3 iufnt (z-c4/ y;po8odr5) whc+(-iopyzd tro3/ fu ng4;z f8en 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 8 u,z63fua-fmyh5u* ba7 mnf xdr4 lp; 4x.ltddistance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function of sxir,- 6cj 7ag 5 vt8dyiv1ty5time is s 6grvta8 yd,75yix j5i 1c-tvgiven by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object along th:e+)om7we d 1pow zwv7p4+9aczr u5 qee 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 objeqm:v5r7w u4w7z+eo+)p1 9p eo cazwdect 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 firef, ,rmgp w,a0wvighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–37. ,m ,0g pwvaw,r
(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 it ism ftehs04dd az567p 7h on Earth. If 7f dhm tp764d szh05eaan object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constr kv6e l*wwn;/yained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the decelerat;*nkvwwl ye/6ion 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, 17i 2cx 02iopqj2 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 teleph7coij 0q2 xpi2one poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by8a(,ydu(gfuxma+ q2 n hauling them up on a crane and dropping tma8f2y( +a,gx(dn uquhem 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 tr8*udmqm/md,a4c 6u gf 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 -ud u4;4q iceqof the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the woq; q iuu44d-cerker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface z(/r-vc*8w dysj3kpw 6nk+m winto a deep pool. The person’s downward motion stops 2.0 m below the surf(jr3v8w /+ n zpdwkckw-y6 *smace 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 necespn/nd 9 tf)*us9j 8lhpsary 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.*hlu9p 89ts dfjnp /n) To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fiac43i.. n zlc 5gtp+ekhax.z 4sh. Suppose a pelican starts its dive from a hei44 i+kn5 l cex.g.hct3. pzazaght 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 surface of the water.    m

  In putting, the force with which a golfer strikes a ball is pl8pnoe.kkj*rt 5.a-l r anned so that the ball8.erkp*a 5rn-.kloj t will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball 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 aa ucv2vx98vn ujp:l6g) 0m1 gc freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and avv 0pm 2g) :lguc8vu9nac1x j6ccelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A secop7ysbr9y7; 0vfd(xqiz7 h gd /nd stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s7(g;zfbhpqxvy r/ds d i07y9 7 ?    m

  A race car driver must avz yr0ru6,wydqw.7g xr9uw5n bt4 n/d1 erage 200.0 km/h over the course of a time trial lasting ten laps. If the fir0t 96,nwy g rywwq.xu/ zr5n7rd b14udst 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 6j8-wb ;r kzpfde France crests 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 acceleratjpb6k fwz8- ;rion (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can 4zu ,m(n(xs qsbounce up one-and-a-half times higher than the second chiluz n4x(qsm ,(sd. 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 travxy 3jaq g; glxxb4l mn.9:bb,:m3-jngeling 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 ;m4bg93. ,l jjgm:-: qanb y xbgnlxx3have 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 baseball with a speed of 44 m/s In throwin5 gbg;okxcvj5v/ :1*fi 6l xzjg 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 released (Fig. 2–41). Estimat v/bifx5:jl;x 1 v 5okg6*jgzce the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an udhei27 bugz*hq k 64vimor6*e5+ 6g xacceleration 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. Ef8 rj1, :* dyc. ldwpew.:lpumach 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 :ycldrmljpww e. 8d.ufp,*:1, 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 speeder traveling at a constant 120 km/h tak(9tau q 8( b4ykb/ 6+errn3rqcqty 0wwes ofyntay r4bq+ kqc( trwq(u3/ 09eb6 8rwf 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 from the roof of a building; 2.00 s after that, a secondbjq1 ,1 2ia,z cqo.njr stone is thrown straight down with an initialj1.i,j 1n zqo 2a,qrcb 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 timew e4rtj a78 f*e/iew6r. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits thei /a46wrf8e7 jetw*er 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-falll( is(zve*)cwvp,. iy ing 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 reali e.wp(zcl*v y s(v,ii)ty, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restauran58cy/a qv0j+l xbuu y2t uses a conveyor 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 the rate of burger production (i xqcvyy80aj2ul 5 /bu+n burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe can. Ho 2 271jkkvecnrw many times higher will Bill’s ball go th c71vj22nkerkan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while z9 wr+ql( ka xm9 aui/viq4o:;your friend 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 throws it up to you, such that it9ri9: i(4 avuz/lawk qq;+xom 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 rwfz ct. y1i(aiif*jo3(j2w )the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of jac )f(z(i*ow 13wr2.jifi yt 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 bicyclr67fd,kg t)mxes, 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 othr m,gkdtx6f)7er? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?