Does a car speedomete 8d1l*r fh/tldr measure speed, velocity, or both?

Can an object have a varying speed if its velocity is cons-isin 1d)sh7o tant? If yes, give exa)h niis-7od1s mples.

When an object moves with constant velocity, does its avev7jtq* err1l/red1ax/p4 mc/ t*ibm7rage velocity during any time interval differ from its instantaneous velocit l1imt*/7/j4rm apr/be rxve7c* q1tdy at any instant?

In drag racing, is it possible for ae;m sk:oy(z28zu ku;the car with the greatest speed crossing the finish liney k(;ze; zoasu2: um8k to lose the race? Explain.

If one object has a greater speed than a ut5at*s f)3cvdj0v(ai: uq ik rt1o-1 second object, does the first necessarily have a greater acceleration? Explaq r3c* u5(o1 fs :1kv-tajait ut)0dviin, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/)nh5l5,1o bj :t0ne7ppl hgk yh to 90km/h with the eo n:t,1g7l 55 h)0pjpb hlknyacceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velo0wwjb 78p0onw1h mo.k city and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleratx;hc02,lui+. jlefu vt q:; odion is positive? What aboucvjq0 2 +.fhi :u; odlx;elt,ut vice versa?

Give an example where both the velocity and acceleration are negative.;d/4smk*y e wg

Two cars emerge side by side from v 2i+ u/04g5virkjnvg 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 thvkn 4j/i2u05ig rvg+ve tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleratimvxfn858 q( wbon decreases? If so, give an example. If not, ex(w fx8n8vb mq5plain.

A baseball player hits a foul ball straight ut4n h 776mwpjh4( )opimd71vyn nr2ibp into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, 72nvtw4747 (6 dmbmyinhn 1op irhp j)how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its acceleration duekv;4*y;p)e ddsu, ikh to gravity — does it increase, decrease, or stay tpihve;y k,d4*;ks)u dhe same?

How would you estimate the maximum height you could throw a ball verticai2sq0 af ;xkqf/cx(9zlly upward? Ho0ck(qqf9 i 2xz fs/ax;w would you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving atkbla 4c(r. b()osk/zx a constant speed of Then you travel the same distance from point B torslc/(ok)a 4k bz.b(x another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts 1 4ir;didkkr8p9b9gt 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 clinkbi18k9 rtd;pd94kgi rs 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 iwl prxt2z-- yc n/))oqs not at constant acceleration: a rock falling from a cliff, an elevator moznrc-o)q-y/lx 2p) w tving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically5b4m(0rho fuc .w /olc 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 rch0om o5l( rbwc/.u4fesult 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 nonzero acd7lgokotvg/5 +3v d7e4mbva )celeration at the same time? Givetol+ m5vd4bd 7g gek7/ v3voa) examples.

Can an object have zero acceleration and nonzero velais, c d75vk/xocity at the same time? Givev sikad5/c7x, examples.

Describe in words the motion plotted in; nk g8dk4eue/an83xcnt ox5/ Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plo 54ece; g88/axxtnko 3u/ ndkntted by walking or moving your hand.]

Describe in words the motion of the object graphed r6urpv,(x(b(j;u 0b nr7ldqy in Fig. 2–29.

  What must be your car’s average speed9g bpaq iv7h,6 2mjukx 09q,co in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does k2y.w omj 5t83k3n*jl l*bdgnbaiz4 0it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for iu *4i p5rcpv buqn.c690v+bp2.0 s, how far do you travel duri0 v+5*c upri ncbi.u49vpbqp6ng this inattentive period?    m

  Convert 35 mi/h to ywx 00 en-vorw:olh84
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves (kr,x2rc*ir h 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 130 km. It then c 23fkrw ,; qu:wyil2obegins to rain and yo:q;2 lyw2o uck3f, iwru 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-th*ojs ( z i7(but5uyl/gumb, every five seconds between a lightning flash and the following thunder gives the distance to 5jitl* b(/gou (us7 yzthe 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 track in a t/l/ 6sk1 .qik /1rtbxhf w)hpootal time of 12.5 min./.k 1i qo6xp1hw rh//sb lkft) 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 in vmst 19+ax,jt 14.0 s. It then turns abruptly and gallops halfway bat 1v9atj+s, mxck in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speed of 95 kdega3mfc z-6ra :m4ha (0d2j ym/h with respect to the ground. If they are initially 8.5 km apart, how long wil(m6fha 40e:ag-ad2jcr yz m3dl it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a .9fm95.bxd x ebgakj )truck traveling How long will it take the car to rede x b.g95a.)9jbfkmxach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a tasfe ulwj -:hrl9+-x9silwind that boosts its speed to 990 km/h for thes9wl-9xruj :h+sle -f 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 a,,auq.e1/pfi- a nfgtkr.bx+nd average velocity of a complete round-trip in which the outgoia/,tar pq i.,feb f1kn+-x.gung 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 km/h.    km/h

  A bowling ball traveling with const6avy)jk ze+2y.u: kg) vb)x mcant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ballj6.c) vyk:2um)+y a bevkgz)x? The speed of sound is 340 m/s.    m/s

  A sports car accelerates 9qt.od-uzd 5tq: u6zsfrom rest to 95 km/h in 6.2 s. What is its average acce 5uut-q qt 9s6dz:oz.dleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates frovu gcv+ 77;uucy/cj 8;dep- yfm rest to 10.0 m/s in 1.35 s. What is her acceleration;f 7;v -gycc7u/juye+ vu p8cd
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleration of abou3m/z *2omnnzyw y,-lpm 25p ab lby,w-*mymnao/nmz5z223 ppt $1.6 m/s^2$ 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 dn-ackxde4z + w 1-13eeao7 tmin 5.0 s. If it then brakes and comes to a stop +- tdx ze1ak-m ad73ecnewo41 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 car, which starts from resalvcb hh8u08;t at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display ea;aulc0 h vb8h8ch 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 accelera4(qn.uo rdtce.hsyt4l c h 2)6 sqr;*htion? How far did it travel in this time? Assume constant acceleration. *c4;nyh qot6(lh r rsqtes.d .uh2c 4)   $m/s^2$    m

  A car slows down from 23 m/s to rest in a distfi )r(nzdg*4dpx5( cnance of 85 m. What was its acceleratiofpdrg n ()x4i*ndz5( cn, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runwayf6oj 5 gd4dept9p0lr3 is needed if the (const 9 perg3tjdfd5l0 64opant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially towfkgzg/ m2-h:p s;l0tp speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of tp gz: ktlgm;h/ws-2f0his 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 from0 lre/n6z6 6(jni0thrladm* c a speed of 12.0 m/s to rest in 6.00 s. How far did it travelh il/l6* 0nr(6jcdzma0et6r n in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the( 2txy7yywfp7 highway. Assuming a deceleratiy2( 7yf tpyw7xon of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car compresses andnt4ypb 2 xtitvqw tdp(r1o9z0e17k4+ the driver comes to rest after travrdxv (42t ope01qy1 t+t9 kib7tw4pz neling 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 distl3gp j54 ytep9zoj7*p ances for a car with an initial speed of 95 km/h and humatloz 5pp4j*7j p3ge y9n 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 distan/j rt(4*i bauvgk.e-uce 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 highway. lu, pa f/7aq+9ohw,yc The car’s driver looks for an opportunity to pass, guessing that his car can a,7,/wu apcoayh+qfl9 ccelerate 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 10,0r t1r-gcg, j24(u;nzsan9g a i00-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acceler( ngj gr 9;rcga2-1,sn4autizate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 458u pph 69)yq rdkx;z8b km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light dqkp8p8y9b); x6uhr zlasts 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 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/l-s, ufinupr6 -/jg b hits the ground below after 3.25 s. Ho,igj-l6fn /rubs /p u-w high is the cliff?    m

  If a car rolls gentle+ au9v p 4axfp1*ebu+y ($v_0\,=\,0$) 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 i s(udhl) b)n722 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.a/)y tg qh5k*w0 s after throwing it vertically upward. With what speed did he throw*5 k)/wygtqha it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw g9qn * m9na hry8bfk,6dc2by5 qraphs of (a) its speed and (b) the distance it 9hd* y qnknrmyfab92q5b6 8c,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 ay 9w9h:09mk(s o emhs0/m 9dlj6llqp,v c- kvv 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 heliqdkylws9 -h mcj,/le v m (l909m6pvk :shov09copter’s.] t =__ s

For an object falling freely from rest, show that the distance tsz ds,j*k,9z bk jdec89v*gv7raveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was e *kk,,*7d jbsv 8zgvjd9sc9zfirst shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is v8nz1:pgei(:.jdrm gneglected, show (algebraically) that a ball thrown vertically upward wiedmpggz( :n18 vr.: ijth 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 slbni + rvf+av h4/7id*bc*a+8(kpnk c peed 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 photofla wmb(bpht ezeu g+(;5,sh of the apple in Fig. 2–18 (or number of p,zu; pgh mbew +e5(bt(hotoflashes 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 ox ;,vl srps7fob/3z )2.2 m tall (Fig. 2–32). From what height above the ,orso) vs3;fxz7 p/bltop of the window did the stone fall?    m

  A rock is dropped from wqodioy9(-2 j a sea cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is th( y9j-o2dioq we cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard streaj,v5l vz)r7n 3/mjflw6 z7ap nm of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it le 7m6l7 z,r)anjv5/wpvzl f3nj aves the nozzle?    m/s

  A stone is thrown vertically upward with ro h-py5w 7u5d2*hui(*3v ik kz u+gxsa speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34). skh+ruy kd 2z-g5 5po3x*vu wh*7ii(u
(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 kr3nfh2/uvj 40ur:sk s-,se qpass upward by a window 28 m above the street with a vertical speed of 13 m/s If thv04skk rhnq-,sj2e: su/urf 3e 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 p e0i+sxr*m;s0v.fm nwhat time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitrxei0*+ 0.pm f msvs;nude of the acceleration greatest?

  The position of a rabbit along a straight tunnel9iufq) m hi*jcz .97wp as a function of time is plotted in Fig. 2–28. What is its instantaneous velocity m 9z p9*qfujch7 iiw).
(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 g 2qz( mquh80ain the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent qzm(u0h28q a gshifting 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 Piykppvh;a*3vtogub,0(p.;ado ) s i, roblem (Fig. 2–35) when it is isdb*p,o.,i v k(phu0a 3agiy p;v ot);n
(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 di(mk od)09g/s) rpoejhstance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose m lkzzbqt ba;9 :(ef*4displacement as a function of time is given by Fig. 2–mb *ea4:;zl 9b tfkq(z28.

Figure 2–36 is a position versus time graph for the motion of an object aloni0wp)2i,nao 9b e:ke tg the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answeei)2twi9, b:ako 0epn r 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 kqv .7 g):1w b3iw*qc. kg2mphywr ;pbfirefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2m.gcwgwk*i7v qw hb;:p)b 1yq p 2kr.3–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what z7u3l djxnv9 m((zt1jkp /kp9it 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 initial vel(pkzt39x9 jpv /muld17znj ( kocity?

  A person who is properly constrained by an over-the-shoulde-;6mgmra2xmj; 6x huwr seat belt has a good chance of surviving a car collision if the deceleration does not exceed about 30 “g’6hx-x6guw r m ;m2;jmas” $(1.0 g\,=\,9.8\,m/s^2)$. 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 above2 j i-00xcusrc the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this coun-j2csrx0u 0 citry. 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 teste3wdoq( z.m e9md its cars for front-end collisions by hauling them up om( emo9q.z3dw n a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth trave)(q;k3z rt spsc6 yqs8ls 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 ac1v2sj i7v 2 tyc4k )z)yikpkvilw8(2l x;7ivxceleration from rest. The front of the train has a speedw vv22)i7k is 27pv;y()xkjy41 8lli tzcivkx 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 worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m abovo8i-21oyb b: o /iamdae the water’s surface into a deep pool. The peria2d-8 bb:1/ooyaim o son’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid tran4 vhed;pmzc/:,xc 399zktz igsit 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 h3z x/tpg4:zcvk9i ; ,zde9cmidea 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 win37j+a17tyagb2 gru tq gs and free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must+y237turqa g7 a1bj gt 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 c d/0msy7 a+r6aqaf;s so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is misfac70/s6; +ysrqda mased. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a/rp*fdd bk)p 9 constant speed of 6.0 m/s Just as an ddkr 9f*p)p b/empty box car passes him, 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 a high building. A second stone is pd-uwbbn139p dropped 1.50 s later. How far apart are the stones whe b1n3- bdpuw9pn the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the courj9z 3(6 i8kru gewuwf1se of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average spfz3w6 urew91 i(kuj8geed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 18 k5. siv0ma hls+3:rxr ym/h . At the bottom, 4.0 km farther, his speed is 75 km/h . Wha3y rasmx .l:+siv5 0rht was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. T8kb m7v18z8; k*d wvp e(c/tn py9sphuhe first child can bounce up one-and-a-half times higher than the second child. The initial speed up of te88bdupkp918*cs(tp n;vwk / zv my7hhe 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 travelb;egmq558t2ejf,e :rv6hiaaz5s ul5 ing 95 km/h overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveet:5e uei5 mz52 jvaa;bl6sg5rh,fq8ling 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 o qd87/nca47elo2/sf pdwjpy. l ;gyo)f 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it e p7w sg47.a2jfol ;/)o8pqd/cy ldn yis 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 a7sewvw m8a5 kheo j5*rv-(o+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 inm:0cl,uya nxn wu7l -: 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 int:y -cl0 7muwxunn:a ,lersection, 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 atim1*: ;wpxf: gaj8 zxr a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant accel 1:f 8;a*xixrmwgzpj: eration.
(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; gbk5+yoks0mtm7 6kf0)m; b d e2.00 s after that, a second stone is thrown straight down with an initial speed of mdfb00gsm +ytkbom; k7e6) 5k 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 s7hlpzc80xl d*g3m4l vertically up at the same time. The first stone is thrown with an inil3m l8*h lxg7scp4d0z tial velocity of 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 w9*jtsl::dra3tv (hu0l zkq/t ould it take a free-falling 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 tujt :*ral30z q(:k9s ht l/dvat 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 buna mkb2y1gjd+-x5y u2f 83 wnvrgers 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 spac-bgmj d+nky2 2153yvwu fna8xed 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball verticallyl9ypc a2hi0m. at a speed 1.5 times faster than Joe can. How many times higher will Bill’s2cim.ya h9lp0 ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a clifmt.liyj/ xks d +(/0tyw:p (qff while 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. Y /kwfpti. (qy s/0l:j(ty+dxmour 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 heig idtyl7bp25/i ht of 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 droplp5b 7i /tdiy2 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) Is-)/,2nsjkqx;btso9vkm 8 qkz there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) vz k9 jkmo;8, nq -b/k2xss)qtWhich bicycle has the higher average velocity?