Does a car speedometer measure speed, velocitc17 qasmi 4v4wy, or both?

Can an object have a varyinga r/upaozk1dzge5 +f -ohav nf0*4z9: speed if its velocity is constant? If yes, give exampleo*z/az5v koad:f- 0ef+z 9n4a rup1 ghs.

When an object moves with constant velocity, does its average velocity during 4q5 j iuxmq:e0f9 ixv-any time f0:9-qjq iiv m4eu5 xxinterval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car wi +h j,bam5oc;r+7gp rath the greatest speed crossing the finish line to lose the race? Explc7p r+,ajoh;rmag +5bain.

If one object has a greag;r.2m8p8iub8 0 xhvnpe 8 ztxter speed than a second object, does the first necessarily have a greater acc ti8x08vnzup 8.x remp2hb;g8eleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90km/(7 3)ts m7 dkwyy3t;-xjtlk3vh2ybp gh with the acceleration of a bicycle that accelerates from rest to 10km/h in the samev y t;23t hdgtlmkp3-y( )77b3xkjsyw time.

Can an object have a nqz1p +yhfqo)sw, lmga-m7e2,9 nu6 j northward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when ak.)r3)oytfn its acceleration is positive? What abo)nakr.yt fo) 3ut vice versa?

Give an example where both the velocityax(1 /ars:d8esgnr 9;r t8we w and acceleration are negative.

Two cars emerge side by side from a tunne**i z;e:* zwo(9nv (g)d rp-wwph dvzkl. Car A is traveling with a speed of 60kzw vk*r hp *d;wzz)opvw:*(e-9 ngdi( m/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 reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, g +kknmt(x7jmb3a:jh c9k1.e aive an example. If no cmxmj. k3kh9:e aktb +(71najt, explain.

A baseball player hits2em4 5s9akx a a*nuv2i a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the 2 e9aas va24nux*mi5 kcatcher catches it?

As a freely falling objec aa2o n gwn.w6r.:gkn7t s wni(we9 r4z8wc-t,t speeds up, what is happening to its acceleration due to kt6znanrnngt .we49-iwa.,s2wrw7o :8gc w(gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum hen 9rs(fz,wz;yuq2+ht ight you could throw a ball vertically upward? How would you estimate the maximum speed you could givft,quz2 n;9rshwy +z (e it?

You travel from point A to point B in a car moving at a constant speed of Thwt 1ixg 8ogoh kwab3( z)41uj7en you travel thk7j13othw1wuag(igxbz8o4) e same distance from 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 3jacggy7 f:-o x0x*6e ec l68 i*32u qltdj1tlh.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 occur at equal time intervals. Why? Will the time between clinks increase or decrease neatljeli d:-y eq2ufxc67c ogxl t*18*h36j0agr the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock falling frgm-npgy0 9s4w, yvt/3 1ergiv om a cliff, an elevator moving from the second floor to the f /pigyw9rt3mg-14ns 0vygev ,ifth floor making stops along the way, a dish resting on a table?

An object that is thronhs238s a2frp- 6e 8peyt(t j .k:fvc-+xm sqxwn 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:vthx28sxn3kp-r scm- 2a . 6ef+feysp jt8(q a direction opposite to the motion.]

Can an object have zero v jq6r-9 fsad1lbbo47c elocity and nonzero acceleration at the same time? Giveq164codsf9jrb abl- 7 examples.

Can an object have zero acceleration and nonzero velocity at the same tim/zknc9whyw 29e? Give examplesckw wy /99zn2h.

Describe in words the motion plotxp58 8)ueklved*-i tf ted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving yourk)peet 8uf-*l5 8x vid hand.]

Describe in words the motion of the object uh,x(+i-whs u 0 3j2mgn wwl1xgraphed in Fig. 2–29.

  What must be your car’s 5 qfrp7t kxm(r85jq)zaverage speed 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 fl,o1 jamqhj-s /1rxvf;y 15 km?    h

  If you are driving along a straight road and you ldxr jyveeh8+9phw 3 0-1txp9 jook to the side for 2.0 s, how far do you travel during this ina+xjx e39pjte0pyv1 89wrd -hh ttentive period?    m

  Convert 35 mi/h to ; rg,h rejcb; ws+s275g1chql
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fpha00vr0jj1t q v;pkv/ t 9*kx (,whs9ak)zcqrom $x_1$ = 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 th;;;hlf y zmt5aen begins to rain and you slow to 65 km/h You arrive ho5h;fm; ty;zl ame 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 betweu9ufyb p(1b2 ah-g4zn en a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of lightnzu9a2pfbybg-1( h u 4 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 aryfro))qfyjv b 9)q5x(ound a quarter-mile track in a total time ofb qv9yf)x )jr5)qfy( o 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in afs (tw r)u4wh,z 7vxlmy4h/k 0 straight line, moving 116 m away in 14.0 s. It then turns abruptly a/7)tk(v,h r w yh m0z4x4wfslund 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 othevnn (msjtkxc;56de*b8n4y1 jr on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how mnxtnd( b;knj*s84v 5 ecy16jlong will 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 Hoevbjlzx7 )75 edu4iw8h h w*b8w long will it takvhjelxb z 45ie )db *8u7h8w7we the car to reach the truck?    s

  An airplane travels 3100 km at a speed of ga(,7m,ct8*cw6vqh2.h fp e0pdgfw 7 qyexj5790 km/h , and then encounters a tailwind that boosts its speed to0cwgc*d 77q et, p2qf. fxh6,( phmvyg5ewaj8 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 velociha10, wwnhmm ,ty of a complete round-trip in which the outgoing 250 km is covered at w,h 1hamwm0,n95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits - 58mib4iy(p-s0atyb6ee xpy the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2t8a i0pmbpsey -4 e(xy-5yb6 i.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 frg3iam l: k7x q):h+gvjluv. c8om rest to 95 km/h in 6.2 s. What is its average accelg+lk .vgqm: cv8lh:7ux3a ji)eration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What iss beurx949k o2qib7wy8rj+j0 her accelerationbb rw7u ky xsjq+8i0j2o 99e4r
(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 d o*co816 wlm5vzf3+il-ju.noh b 2gyan acceleration of about +inj-bl2ohf * oz83 mo v56wul1y.dgc$1.6 m/s^2$ 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 b.yn8dc r:ed 1u nlz+puwi)x)0rakes and comes to a stop in 4.0y . rn:1dep0d)+wuzux 8n) cil s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from resv8d,raz8 at g4ilg-;/vdxlg l wb)4.qt at t = 0 and moves in a straight line, is given as a function of time in the follow ;d, db8w4g aztlq.vlr-g/)i va84gxling 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 s. W2v(ym 9du gtizd9p02g-)xlyn hat was its acceleration? How far did it travel in this time? Assume constant acceleration. ivzu9xpdgm(-g)9 0ny2 2dlty    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. m)e2qx xw 2ln4glm *p:What was its acceleratiolpl*n e: xmg4mxw2q )2n, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for take+ fl u6m0eka:tn (b4ugoff. How long a runway is needed if the (constant) accela tf+ubg:m(l e6k4u0neration is $3.0 m/s^2$ ?    m

  A world-class sprinte9ob 8 n) phe7resd/8 th7.ojikr can burst out of the blocks to essentially top speed (of aboutt8 h)j.se nk ph b7o/79de8ior 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 that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of *-veoasx4 mz +12.0 m/s to rest in 6.00 s. How far did it travel in th 4va+zm xe*so-at time?    m

  In coming to a stop, a car leaves skid marks 92 m*g*)rmm/sa :m es/xuh long on the highway. Assuming ag/:a* u rxmm/hsms*)e deceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h b *2c7 rq(bgz-ap 9lqmstrikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the ans*b29qbp(r - ac7 lqmgzwer 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 and87tcepf;vn* nz qte,2 het *t7qz8e n2pn;v, cfuman reaction 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 car 0r6p fcm + z;ewlc8f0sis $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver looks f x*(o0wwaniw 8wmk*5lor an opportunity to pass, guem0 (*wkinlwa 85owx w*ssing 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 than5fla 4o:+qim a,gi n96uppo2 p 30.0 min. After exactly 27.0 min, therefoia: 24 p9numa6qlo ,5pg ip+ are still 1100 m to go. The runner 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 airl*a9*gkcw 5( jfm9dn-x 6ist 45 km/h 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 spex-wsf5 *dnig9ik6aclr*9 j( m ed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the hl 3/zl .aye.lnux;x;i9)z xlground below after 3.25 s. How he. ;a).x uih/9;zx3zxlnlyll igh is the cliff?    m

  If a car rolls gently u-g(4 nycyp y7($v_0\,=\,0$) 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 nea; lx 1vfzvby0yi -7u/frly straight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertically upward. Wuq8pv,,dsx5c z, fqo,m m2t pm )eo2-kith what speed did he throw it, and what height did it reac)ox m82,eqkcdqv2, ,up ,fmoms5tz-ph?    m/s (Round to the nearest integer)    m

An object starts from rest and m*k1f3;l zvk2oc snv d88jaa(falls 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 airk1*j3 mfovazl88da(s;v2c kn resistance.

A helicopter is ascending vertically with a speed r zp/sb )vnjj1j(:iz;of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] tv z j(r;ns):1p/ zjjbi =__ s

For an object falling freely from ncu(a1nuo zyr26eg 7* rest, show that the distance traveled during each successive second increases in the ratio of successive odd integerscu1o7zeg6(*ra 2n yu n (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglp v9( ,lwfiuotnv3 l;9ected, show (algebraically) that a ball thrown vertically upwalf twpl(v ;u3,9 ovn9ird 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 of 18.0 m/s via1f0fvx7/c 0 l,;owq4: hplujs7 qi
(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 ofx ,/b *,pa)ycpzz)m zl the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hinz/blymx ),p)z ,*pz cat: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0. xl-ao4kdw;j 77/s0v oqvjm9a28 s to travel past a window 2.2 m tall (Fig. 2–32). From what hei4j/ o kd-vxs lvq90;j7a7mow aght above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of z4b+mlwax / :fsq1 c5tit striking the ocean is heard 3sz/qbalt+5c mx1 4w:f.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for i/alz l/ fif+d0tj* -aa hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the grounai0/f j-iltdlz a/*+f d (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 l3c j).pe1brgsb5m) jooz8x s4v k 1+oof 12.0 m/s from the edge of a cliff 70.081bo+3brc .)s4 oxe5vzj)js 1 kpogm l 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 2cmo9 r/tfek-+ arwh+with a vertical speed of 13 m/s If the ball was throre2/ k-fcoth+w mar +9wn 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. ,ld y4:uysc 0y(a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if al,d4syyu y 0c:ny, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a fue. i:a7b*dnj1ol /i hqnction of time is plotted in Fig. 2–28. What is its insj qb7/: .1niho ila*detantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as shown in the velw -0kjh8eu7 ) 6kpqzzeocity–time graph of Fig. 2–35. (The short flat spotze z-7qjw0)ueh86k k ps 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 car7bs 40mz- idhl2ry 6ya in the previous Problem (Fig. 2–35) when it is inlby- 0z74am6 drsi2h y
(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 distanceeacyxb/97 dqs4 d 5j2g the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objeru 4n/ilpvd-1 ct whose displacement as a function of time is given by Fig. 2–28dnrl4/ pu-vi 1.

Figure 2–36 is a position versus time graph for the motjfsk3 5rgj6w)9c)ke o:cwrf )ion of an object along the x axis. Consider the time interval from A to B. (a)ejj:3c96fkrf w )kw)rs)co5 g 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 interval from C to D.

  A person jumps from a fourth-story window2jygm n y54e,h;zi/w5kj9 arg 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before comin95kyj i g4zy;g 2whnmera,5j /g to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about o8pelsxn+91. bwvk( e/ufkt m ;ne-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initi1e.v f+89nx/wksu ; met( plkbal velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a go )zyp scy6(y:god chance of surviving a car collision if the deceleration does not exceyp6(): ys yczged 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 road below, andkap*ef p i 4f,mqx:o7; 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 qa,popf k4: em;x*if 71.5 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 fortzc) j8yf j7l0 front-end collisions by hauling them up on a crane and dropping tc 0zy78jljf )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 travels about +/kijt+cz dq7r 9q1lo$10^9\,km$ 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 fro2g 1kwv4unyq0 8;f 4lf(kkh/c3qk jdym rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 14 80 k nd(u1;yj/cqkk32glfk hwfvqy480 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving boa jhukwud t7,;8rd 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 uk;udj8 ,w7thdeceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapo(x 0 * 4opwg uxjez05tf1jt7yid 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 p*tzgtoxj0u71x 4 w yofj0e(5average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when divibp/g/ 8ik tiszoohq ))(-zx( wng for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once comk g pw/zb -o z)(/)ixhi(o8tqsmitted. 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 planned syq.zl d9r9:;9 jajft4fb:dpho that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, asshlqr.9 ftdz j9db9 :fa; j:4pyume 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 traveliqac3e8:j n5m 4ho4fxjo*1k fk ng at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts ej1hk8cq:o*f34fa 4mx5n ok jfrom 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 roou+)x j t )odyo45x7bwh)om-fg f of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when t ob)x7x-o4+m )hyjdgto5) ufwhe second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a timi)7 b-u4ctopte trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for tt)ti-4cpub 7 ohe last lap?    km/h

  A bicyclist in the Toyv)dfog82fvxe32kp m v)y *l*ur de France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.m ofy vgv2ek8 ) f2v*x*pl)3yd0 km farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first childc/wn2,txxl6s.8.jm 7hsrownwjny 7 , can bounce up one-and-a-half times higher than the second childnx,,cw hsor2.x8 n 7l6w7j y/ wsnmt.j. 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-ko3 5/4tf dyfnkm-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite dirdtofkn3y5/ f4 ections? 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/e,ble2eg8.1bxv 9 hgj s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 8 xg9h2, b bevjele.1g3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertic *kx6* ytzzqhb9ns z04ally, from rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street p.xs v h)i g6ms,leonw (/:htgjn6q0 a3attern shown in 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 naso6v 6 t e (w:)njgg .lm03hqx,i/shlights 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 tav1a z bs.d+*fbkes off in hot pursui1 .*ab +dvszfbt. 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 .k0j wdel:ss: after that, a second stone is thrown straig s. ls:0k:ewjdht down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vert; txh ;hky(z9 0g)s:qktn2xkq+b;jd vically up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balco2 jxqxk s0v9+z; ;): h;dnbkghytqkt(ny 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 woulb1 f2kvtu ;3r pf*aou0d it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 mu0f *vk2u;3rtp1a bof, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a grilii/o +u51vi99fgw zz n2wn)gwling 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/mizw/ 1 w9u)gvz+n259ifwign o in)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1. j.a8hrm e)u/ki t7yh55 times faster than Joe can. How many times higher will Bili7 e8k)h/ .tjy 5arumhl’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top od 1xhy6lh 3x ;hcsq,.mgnn/.rf a cliff while your friend stands on the ground below you. You drop a ball from rest and sey.;3h6d/cq.mg ln1xhhx,n r s e that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height ofius5b2q67 fmy*ayg6 i a particular 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 diffe6yuy m*7gqsb ii6f5a 2rence does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the pu.f*d .(l3d 9 xtktwgf;ayb98 tk2 sbcosition vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which b 8bg9d .a(.ft;tl92 fsc xkt3*yudwkbicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?