Does a car speedometer measure speed, ve:-gc6ve q1spg-v6cvs t sh t*-;qh+cqlocity, or both?

Can an object have a varying speed if its velocity is c05yf-kw, gepzldtd l6g/u5w ;onstant? If yes, give exampldle6fp/;0ywz gt g k-ul5d,w5es.

When an object moves with constant velocity, d-1g6jm43 q qvyhv 3nvxoes its average velocity during any time interval differ from its instantaneous velocityjmqxv3y4 3vng-h qv61 at any instant?

In drag racing, is itxiex,m q97i/f.w 6m-o hb zoo; possible for the car with the greatest speed crossing the finish line to lose the race? Ex mz9 fbii,xoe-/m7qxho6; o .wplain.

If one object has a greater speed than a second object, dn7md,*ilgsc1 ;p fki)yo7-gm oes the first necessarily have a greater acceleration? Explain, using examplesmn;l-1 i*,7idfo p)yggm sk7 c.

Compare the acceleration of a u1b0b li:.u a -8f;hyn4ekoqcmotorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that acce1blnikf:yu- e4ch. o0qu8ab;lerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explac ) 77* +p*vvmguc:kvn/kk(u .mfy ioxin.

Can the velocity of an object be negative when its az6zo +rzjr9calz c 9; q*zu;l.cceleration is positive? What aboutz c* jz9.9ar qouzlr;6z;+l cz vice versa?

Give an example where both the velocity and acceler oggz*+ffjdlaex4 n(a,w74 6 vation are negative.

Two cars emerge side by kmt(zs-,h b fkt/(o3d26 c ovtside from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Expla (tmoos,kb/ 2 h(tvcd3zk-f6tin your reasoning.

Can an object be increasing in speed as a68 ls 3f4j0mqxsgi p*its acceleration decreases? If so, give an 3i jxssfl4 g0amq*6 p8example. If not, explain.

A baseball player hits a foul ball strai/h9rm n(irzo8ght up into the air. It leaves the bat with a speed of 120km/h . In the am/9i ( n8zrohrbsence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its accelern ,z .g+dvju(90 ru,olgcmt b:b5ad o,ct01nwation due to gravity — does it increase, dd1gu,(. ,:n5 z tto,glrmn cwad90v+bu0cjboecrease, or stay the same?

How would you estimate the maximuml:h vc+j; 5yox height you could throw a ball vertically upward? How would you 5c olyxhv:+;jestimate the maximum speed you could give it?

You travel from point A to point B in 46bi)h c7jxn sa car moving at a constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or i j cnx)sb647hwhy not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolsx1r/(co m gi;ts 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 /s(i rc;gomx1the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant accelerezs kln l,b e3/izf9 7.h+pg7iation: a rock falling from a cliff, an elevator moving frfn e /b9+gl z37h .klspiie,z7om 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 will r26h dxkgy6y7bid1:ae eturn to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]217x : yd6ya 6kbgdeih

Can an object have zero velocity and nonzero acceleration at the same timv0.jn(a ynm(ms:6 t jke? Give examples.(6mmnja( v jktn0 ys:.

Can an object have zero accelerati 4nme 7561phwls b)jcion and nonzero velocity at the same time? Give exam 146 hncjp5wsl 7bim)eples.

Describe in words the motion plotted in Fig. 2–28 in terms ssn )08,xq8z ; miotwq *mfen;of v, a, etc. [Hint: First try to duplicate the motion plotted by wizs;qqe*8f s m xm;8nn,0wt)oalking or moving your hand.]

Describe in words the motion of the object graphe u0qx98oh gctb)t2 ji5d in Fig. 2–29.

  What must be your car’s average speedhpymi-e86, ckc. *kyzmk4 * od in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does 8pg*,+h jo-ktkem8ram7p0c q it take to fly 15 km?    h

  If you are driving along a straight road andj;omq. c6 hf:shl j+pu3:j x5v you look to the side for 2.0 s, how far do youf:lo hqs.: pjh5muxc3j +v6j; travel during this inattentive period?    m

  Convert 35 mi/h to 9j3-qzi kk.r:o db4a0eo:bha
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fw qi.g,1up;mio g.q;prom $x_1$ = 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 jvl-0elb;32rx d3hrcdolk66130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 holerbo-v06x rdjh l63ck3l2;d urs 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 fivekdga,sy7f-. 7yz (uia+pabu tb .n /*b seconds between a lightning flash and the following thunder 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. b7*zs-np7di.ay kb+ ,g.uytab u af(/   m/s

  A person jogs eight complete laps around a quartec5+iuy3h q 4gqr-mile track in a total time of 12.5 min. Calcuhuy35iqq gc4+ late
(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 aw w6b 0xauv4me83(tk ayay in 14.0 s. wkvm uate30y x84ba6(It then turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel t5(irg aqium 2+racks. Each 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 beu2 +r5 imagi(qfore they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a trlzd)sea r:; -ov d:yq(m.uo u;uck traveling How long will it take the car to reach the t:u.sov( q mey)-d;d r:aul;zo ruck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encb klo81skc7 7,f :efqkw hme).ounters a tailwind that boosts its speed to 990 km/h for the next .wk ,s7kho8km17 e qff)blc:e 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round, jwi,hjgd 1/cfi4x y+-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-houj1hi+dw4x fy,/gi, cj r lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant sp9+/aert2gq hualu,h 5eed 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 ball?59t,r2uga +queh la/ h The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h + suldky, 5ffceud kcz1 )6ca389+,m rc+zbmlin 6.2 s. What is its average acceleration k6al8d,3 c1+9cmf+d l,uckz5r +mbue)fs c y zin $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acc6dm g vcm1svi9he/1ul :u8o9o eleration /ooe9m1ic:1 muud9h g v68slv
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobo942:ld wc)wgpm,u4nfximm5 ,gpz :oile is capable of an acceleration of about 2,u4f):plgw:iowmc z g,m 4x 5o9mpdn$1.6 m/s^2$ 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 brarjs(xlaty q+j 964hj4vp1agg54 6 bewkes and comes to a stop in 4.0 s, what is its acceleration i w 6+pbe4jxyv4a5t1j9q ( a4sjhgr6gln $m/s^2$ ? 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 res4 -vf qw)y97/5 tgyugdikjp;nt 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) -yyg;7/kfu)v 5gj4itdqwp9 nits acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleratioe14rwm2 9 nwyxkhy2j;wb v: m;n? How far did it travel in this time? Assume constant accelerahw:v;nmr1 bm2w; 4xywje29yk tion.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distubkd h,m: 0 bk.0jrw)cance of 85 m. What was its acceleration,k0 wdbk)b j,hrmu.0c: assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runwa 8a;kkr5vrj:q:qa 4hny is needed if the (constant) accelernqr8r: :kkaq v 54hja;ation is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speedx2d,aowy2qu yom v/8 -3os ub0u *ele5 (of about 11.5 m/s) in the first 15.0 m of the race. What is the avweb l a-5o 2xuvo, 3u soyq*e820y/umderage 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 m/s to rest in zzx/0- yrx)t x6.00 s. How far did it travel in that/x) rxz0yxz-t time?    m

  In coming to a stop, a car leaves skid mar + ghjz4eajo/0ks 92 m long on the highway. Assuming a dec g+zjh04ae/ ojeleration 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 oif--)k5:c/qsjgun 5yopm 6 emf the car compresses and the driver comes to rjy kf )-mnpgs -qm5: uco/i6e5est 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 distancesn71 )js5xagj 4so d;sb for a car with an initial speed of 95 km/h and human r ;sgs1aoj b7jn d5)x4seaction 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 st dapu(;u5)wpb6 dl(f uopping 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 truc37oo4 )aj w qo2hkl)ox/,epkmk going 25 m/s on the highway. The car’s driver looks for an opportunity tpeqko 7 o ljh/42xa m)wo,ko)3o pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than/ut+ nn7ku mba1 y9oy7 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must theny yubtn+mu9/n oka717 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 intersection just as 4so1u f3bp e jv+fo/0bau*/ubthe traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turnin3/b4uu*+j 1bfps bo feou/va0g 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 hits the grqw*ayft96 e9)fhabvp1 o 26lsound below after 3.25 s. How high is the co 1h* fl)fast9y6pbv a62e9q wliff?    m

  If a car rolls gently (lo nh(6fs4wif5 a+k7v $v_0\,=\,0$) 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 2+qhw a x37 xw3whw(rc52 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 it8a/rsumi2ho/ u-zxz)v 8/5jb2rbh ah vertically upward. With what speed did he throw it, and what h/82 r2/a)vx8zazu/5i m ohb- hhbjs ureight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest cag;-n8zf1 i 3k xo/(:bsenjz and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallenzzci (g8a; n bse3xnk- j1/:fo, 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 hezmu f3x m+0xi6ex/up0ight 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:0x6i/3+0xzuem ump f x The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from res e6jv3 hlg b(5xzrgf. lpd53o.t, show that the distance traveled during each successive second incjzf 5 3hgp3(eg5xlo6 ld..vb rreases 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 (algebraically) that a ball thrown vemdp:azz sb.8grr k3 ;)rtical:z.;3mb )8aps rkzgrd ly upward 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 w i3qnn:n r:7cspeed 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 photoflash of the apple in Fig. 2–18 (or number opkbdx a eun9+oog. h kw:.y,+oev0s-6f photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at thvs gud-h 0,6n9oba.o.y: k oxee+kp+w e top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a winc9yo;)mo qykveg1 o*awjq:h x54( w-jdow 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fall?w- yqox*amcjvqoy;koh) 1gje:45 9w (    m

  A rock is dropped from a sea cliff, and the sound of 2 vm v lphn/+yg:o1ro*it striking the ocean is heard 3.2 s + loh yg1 pvovm/:*rn2later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for ucr5arpd l q6c770uwc*c +e9d a hard stream 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 wate9p w6u dc+5*drq7 rc0u7ca celr 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 fryx/o3 fowl ,-com the edge of a cliff 70.0 m high ( x3oow l-yf/,cFig. 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 pas6 pbz7bfte:aos1 dk3q6 .fw ,ms upward by a window 28 m above the street with a vertical speed of 13 m/s If thpwb ta6,m z. 6d :foe7b3skq1fe 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;aeom*all(v1:t5cyk 2v y k .e a train as a function of time. (a) At what time was ;v1 y(*ocl v25ktk.lea:m ayeits 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 magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function c.b:)zpvw ) q .dplb0o 8rt1fmof time is plotted in Fq.r.z vw)lpm:c t bpb81of) d0ig. 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 can accelerate approximately as jtm-136 l7qw lsy, abxshown in the velocity–time gralq7am y31,bt js6 lxw-ph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in th;q*u 1jobv k*ve previous Problem (Fig. 2–35) wvv*b ;kj1*qou hen 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 thjt8fp)b tosc1dz8kn4f 6xo;6 e distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the :rbl17kc9w jcobject whose displacement as a function of time is given byc:1kj7r9l b wc Fig. 2–28.

Figure 2–36 is a position versus ti+nlhv +a m m x*zc47dmb1cmd*,me graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (cbm7x,cdd+mc1ln+am m*hv * 4z) 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-stoy51-hgd/e z hyi apj95ry window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before comi15hza- gde / 9yyihjp5ng 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 thetv,xppwqpkuj77nx:ml ( ) 5c ; Moon is about one-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 initial veloci pk(wmv;)p ,xql 7juxct:57pnty?

  A person who is properly constrained by an over-the-shoulder seat b+,n 3v(et: hcakw ln-sq7nlz,elt has a good chance of surviving a car collision if the deceleration does not exceed a,w:sn-na +clnl qk(37eht,zvbout 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 t9r3 .a3,q;h hglthgs whe road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto thq g,h9shat.r l w3;g3he truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for 1 tejt,lt m-tbc+ z94-bp,po +enuo t3front-end collisions by hauling them up on a crane and dro-t+nptt3oe9,l -4p ojett u1bb, + zcmpping 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 abmj c )ty +a9/:o8hycs8pl d cfbi/;;v4shw pc,out $10^9\,km$ 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 f::(ryfuje) qrest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it q )f:u( fj:ryepasses the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m a6mhx9 5w2rgus a/b5fc bove the water’s surface into a deep pool. The person’s downward motion stops 2.5 xws5chg6/ muf b92ra0 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 rap ,7cl6csfa le29p7 ojz) inm+wid transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the t9cecl )nm7osfj 6azp+2, wi7 lime 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 fish. Supo*+v0 k 5hni29+ slckwm+o)bo rhbf*cpose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the* lv )ko0s9rk+++h fcch* b5ob wi2nmo surface of the water.    m

  In putting, the force with which a golfez;qqm;tgdlqs )s7qb* q .cm82r strikes a ball is planned so that the ball will stop withc.;b;dsm 2qqq 8)lq7mt*gsz q in some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train travelinq d)ghz)1.. xgh(x ue lx-xda(g at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accelerate.h duzq .xhxx(e))1l-ag dxg(s 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. Aheajj;- vx)58foe oe/ second stone is dropped 1v;e o h faex5jo-/e)8j.50 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h o s uyofwc7x;191:vt jover the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?ytfoj 1o; vs :x7c9w1u    km/h

  A bicyclist in the Tour de France crests a mountain pass as he u7 dxwo-t:7lt1ef p w9moves at 18 km/h . At the bottomou 1w -xp:9 lt77wetdf, 4.0 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 fir l -y75k;virnzk) c)anst child can bounce up one-and-a-half times higher thak7vnk )5 ;)rl-n izycan the second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtak;xwwb4h l1y xzivi34 3es 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 4vwhxbxw13izi4l y3 ;, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the ba-*q : nqli-bcbseball, 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. b -i :bq-qln*c2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertiwgo xc737 aqnp-6h ox2cally, 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 pattern shown in Fig. 2–42. E tm /(e6m*x)d ezk xg*w9fhja:ach 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 ligz x*e(ex)mfgh6w: t9jda/k m*hts 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 avc m l4hps4 5c:ve)hd.j1l q9n constant 120 km/h takes off in hot pursuit. The police officer catches up to the speejs4 45 vchq:n)m19c .hvlpde lder 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 second si 2lw km .ud,jxe/4.kzcnwy: +tone is thrown straight down with an init 4k+. ,kdx:2u./wzmjeiclnw yial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone w3+ 7iif7 / bgm0dlyvais thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With ig lw+yvb073 md7a/fi 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 fres7a9(8qn+vwn v 6sq (a cfxz/ke-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull hsk96cvqzn(n8 7qa+af/s( xw ver 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 con li311wwla3qx3hk r 2j *9drwrveyor 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 23kl1xd3* hj3r w 1lirw rw9aqcook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball ver8,*nrei88 /:y(dfxalkkiz zl tically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go tz* :8,kiy(eidllznr f88 xk/ahan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on t3 -yvqhoud/+6 qf/kjvhe 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 it just comes to rest i-/jhkfvyv o6qqu3+ d /n your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building us)2i: zq0qc/ oqw:le yting a barometer. Instead of using the barometer as an altitude-measuring device, they tq lqy:q2 )oz 0t:/ecwiake it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference 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 bicycrjev :r;;3vu eles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicyclveu;jr: r v3e;e has the higher average velocity?