Does a car speedometeractb 8wd4o v1b5c0cu,f8zo s : measure speed, velocity, or both?

Can an object have a varying speed if its velocity is constan ebl9nuib x:j.ji wp( 0l(4+ddt? If yes, give examples.jwd bi 40+d(9j.(ubpnli :lx e

When an object moves wi1/c+7 abeg a40; /mlkxqjgk urth constant velocity, does its average velocity during any time interval differ frb/jg k0; 14x+aarkegqulm7 c/om its instantaneous velocity at any instant?

In drag racing, is it possible for the car wi w 12/ hq/) ;rflnupupmirq8/1mnmg-rth the greatest speed crossing the finish line to lose the race? Expla umu r21 n nil;gf/r//-w)18mmqrph qpin.

If one object has a greater speed than a second object, does the first nec q(ht +mp.jt/p *u8cjl4 2ixxcessarily have a greater acceleration?mx8uhc.*jp2tqt cxpj( 4 +i/l Explain, using examples.

Compare the acceleration of a motozpd dbi3cft47 c 8kc33rcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in thezcf 8bc74d3 p33itdck same time.

Can an object have a northward velocity and a southward acceleration? Explai+-d l :p vpns- ;tnwgd.sif6(wn.

Can the velocity of an object /h4zjha(hj - lbe negative when its acceleration is positive? What ab hj-l /z4hhaj(out vice versa?

Give an example where both the velocity and accelern.dvr/b 7, zh9,pwipd ation are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with an0 3s0xj a8hbw speed of 60km/h and has an acce003xhna bwjs8 leration 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;tfnxz4 (5g4d3hl gwf in speed as its acceleration decreases? If so, give 4 (dfgfz3nwxl 4t;h5g an example. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the /)qwn7.*rn octvg o- pbat with a speed of 120km/h . In the absence of ai/ p.-gno7 ortn)q*c vwr resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is om6 5w*rdjhr).wf :1en,ppa c happening to its acceleration due to gravity — does it increase:61wp* fr ,oen.cmphjr)a 5 wd, decrease, or stay the same?

How would you estimate the maximum h 1qc u0,u;ykfy/fftp 1o* uq6oeight you could throw a ball vertically upward? How would you estimate the maximum speed ytyup* fo/qq; f6y110cuuko f ,ou could give it?

You travel from point A to point Ba uxmn, g*w y-rb+jqegbl+ *(9 in a 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-em9nr+u,+bg*a (x glj y*wbq why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts tied t1j2br .vwrf7r o it at equal intervals is droj. w1r7bf2rrvpped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration y29bklq5bpz *: a rock falling from a cliff, an elevator moving from the secondb* p59q2yzlkb floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original posiu/ 6xxqgs0z )b7b 2nd8(nlonstion 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 d 0xns ln2(b zn )s76bguq8/oxto the motion.]

Can an object have zero velocity and nonzero acceleration aq,h7 bd g2 juwpif8 -qpkhf7-3t the same time? Give e pd7gh2-hbui3k f,qwq8-p 7 jfxamples.

Can an object have zero accelera4 ac3qui kaw(mz0/dt /tion and nonzero velocity at the same time? Givecata d/4w k3mqi (/zu0 examples.

Describe in words the motion plotted in Fig. 2–2fa6;:9 )rd1ysug x8fy)7q ,bt bqlxl-rvot9i 8 in terms of v, a, etc. [Hint: First try to duplicate the motion pbyoq;ty :17rts99) x r6, 8xf)bqdllfa i-vuglotted by walking or moving your hand.]

Describe in words the motion of the object graphed :lb ee59lm(/-e9v kyn1.y vyizb x3d)fxkij(in Fig. 2–29.

  What must be your car’s average speed in order ,7:v7nefd.o r eelh w,to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does iumrmq:**kum/.n o aw/ t take to fly 15 km?    h

  If you are driving along a straight ka ,fgb2h 5hxbid*fxm e +ta5:r8e)6broad and you look to the side for 2.0 s, how far do you travel during this ina)fa5e*58 eh ix dhfbbt:x gkb+r6,2m attentive period?    m

  Convert 35 mi/h to 5cbnosmj-t)*ljg 75 w
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves exfo 7pw+.v5t2*atepfrom $x_1$ = 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 steaxlm;38 /(iz, :y jpew z5okfuvdily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You ar:j;,zxyiz58/( fv plw3kum o erive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning x+te 1g6z19eysh8oect i +hvk1yy+2 fflash and the following thunder gives the distance to the flash in miles. Assuti 6gx12eheoz+1 sv8cf+e kythy9y+1ming 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 total ti gq7ej 8uqmscrp*+ k2 o6qyh:(me of 12.5 min. Calculate sj6qq7o + 8*ym:e2 ( qpcuhgrk
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a0 3h6( l a3kjmcahzc-z straight line, moving 116 m away in 14.0 s. It lam30czzcjhh ( ka3-6then 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 o3.7pg:jlqqe hjq /f0 aqy b-j r4c)pa4ther on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km aq-jpjj44c:p q)07ay.3q fagq blhr/epart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m be nyt k0q*x4 +ub(0qkpk ;chw-xhind a truck traveling How long will it take the car to reach the truckw k*(tnp4 x0cbuyqh 0k+-;xqk?    s

  An airplane travels 3100 km at a speed of 790 km/h , and e / q8e08rmt. hazz(q4e*lvfvb4z4bn then encounters a tailwind that boosts its speed to 99v8hbeq4flnm e.z8q /tz (4ez *a0r4bv 0 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 velocity ofvmvi3 e 8l.lc6r t)zt7 a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed b ) l7vzttliem6.3rc 8vy 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 the pins at the end 4p oegx5,w3m.mael-/x i/;zzzij.sau ,w 8zq 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? The m ,lz-x8 a5z,sq o.wz3e gx eam4iiu.jp//zw;speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is it6 zrmwhzoh y het0*62*s average acceleratiot6h * eyhzm*wr h60oz2n in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleq;eu+ upd uryhprsjb;b -:q2/x8-ya5 ration u+;e5qhb/-x 8:- d;2prusr ayy ubjqp
(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 vvi)4.l6rt ww7+i uubc+;zufat w7m0an acceleration of abou0t+iz f. b)4mvwair+wul77wtv; c 6uu t $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 sf 6logr is 09sq/-pj:u. If it then brakes and comes to a stop in 4.0 s, what is its acceleratps isgr/6 lf:9qju0-oion 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 ca8g(34 la4o,dl(u(bumfiko anr, which starts from rest at t = 0 and moves in a straight line, is given as a funct(kbuo(n3f, 4agll a4u(8o midion of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleratiexxzinsqxupz4/n6* :y7( v r ;on? How far did it travel in this time? Assume constant accelerar z6ux*x : (4znvp/ ;iqesx7yntion.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 rzu kjr8 ai d89(0rx0s1d byz0m. What was its acceleration, assumed0z jd u( z18d8byxr0ra9sk0r i constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is 5uu8b fz7,kh: .jgqgnae; b1t. w9nltneeded if the (constant) acceleratibu : 7.5lgeaw,9bgf j8n1.tktuqz h; non is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of th4kiqr dml0, 2ye blocks to essentially top speed (of about 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 reac0 rdiyqkm,24lh that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.fxmvq *()h49kk pez:,wh:evtjtl v8+0 m/s to rest in 6.00 s. How far did 4 mve*qkvjh :f9(et ,k pv)z+8t:xwlhit travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. A3xa; d165ksmaku6z,ikr ou;z)t6zc tc,s r; fssuming a deceleration of ;1r6uus3oac6fsx; k,i6t 5z)dkmatrzzk , ;c$7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The fron-3w9b eg(znxw t end of the car compresses and the driver comes to rest after traveling 0.n (bzgw93xw- e80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an inijv) qkvp5b5 k(tial speed of 95 km/h and human reaction time of 1.0 s, for an accelerkqkvb5)p5 v (jation
(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 c6e))ago2a 6exx. gmy3oe2mrqar 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 t.x7r s:ra k+0iow. bhkhe highway. The car’s driver looks for an opportunikwks: ohr.+b ai.x 0r7ty to 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,vu 7u/re9o l6/80gnuul st9ij000-m run in less than 30.0 min. After exactly 27.0 min, there are st/ue9ur 7vl i onug9/lt6jus80ill 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 cartbxdezjpj3r9v. u 418 at 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 shou ju8te9pd r3bv14zj.x ld 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 th ,bdfnze,fuo2 7)0:zqobda4t,7f mwwe ground below after 3.25 s. How high is the cliff,fbob0mo),qn: 4d7 de zfw2 af7,ztwu?    m

  If a car rolls gently ( ot: t3y4lm+4)qvrx tw7jycq5l -m sf7$v_0\,=\,0$) 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 intfg nbz2c9-u.s o 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 verrj e )/www,/tttically upward. With what speed did he throw it, and wh )/w rtw,tew/jat 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 g7+8ygtiresa+c)lozs ,5 o kr*raphs of (a) its speed and (b) the distance it has fallen,o*+ cr e ias)zg,y7srk5 olt+8 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 5.2 ym7:m9znac2m w6f*(*w dwaxl 0 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 equalszm *2d (7mclanm: a9xf*w ww6y the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled during ee/--cku. /umcz h5wnwach successive second increases in the ratio of successive o wme--ukc u. 5n/hzcw/dd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (alg4b+-9,9) k)kme vlhffnbr1+ mvqufmv ebraically) that a ball thrown vertically upward with a spemmnv- k)lv eq9, bu frf)mvk9+ 14b+hfed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with am+f(rj6-,/p ,g6nnd za. )p iitlzxlu speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between e-)ppv90zzf,1okz zuge 9a0 bbmu c*,uach photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the * pg z9uobv90zkmpuz )e1z0b ,-c, afuapple 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 takesjd cy:ozg *;9m+h2 cwy 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fa;c:yw+9dmz y*j cg oh2ll?    m

  A rock is dropped from a sea cliff, and the sound of it striking ta:uughln raa4 0 0(td5vj7xp: he ocean is heard 3.2 s later. If the speed of sound isjga04d (70au5anuvr: tp:hlx 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard /skn,;6 l.a vudhsy :zstream of water. You point the nozzle vertically upward at a height of 1;ssh l yz 6un:v,dk/a..5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upw uw9g34;q tcsk-jzrl ;t:p:h owor +u8ard with a speed of 12.0 m/s from the edge of a clifcu3:;krw;o h+s4lw-j8z uptt9q :o gr f 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to bs/8c c2 h5, ki- wwsk(qqb4wfpass upward by a window 28 m above the street with a vertical speed of b/ wh w-k8bq24 cck 5sqswi,(f13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows th +l;jzu/5ph roe velocity of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of jp5u h;r +zlo/the acceleration greatest?

  The position of a rabbit along a stra s5f 0x7qi;u5ov9dihiight tunnel as a function of time is plotted in Fig. 2–28. What is its insi5;diifx950 u qosvh 7tantaneous 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 velocianyib6 a1 u6h9ty–time graph of Fig. 2–35. (The short flat spots in the curve represent shy ba61u 9anih6ifting 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 accele- ; 9zmv/a ,aghiom9gqration of the car in the previous Problem (Fig. 2–35) when g 9h movi-a9 /,amg;qzit is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled durin: pgde/ x5-i0aobw:lb6v s.vf g
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functdae,*jyn l)g-e zh9/z9cfr4 avf7 j 1vion of time is given ev9/a n c- dfry4je,zv* ) h91gj7aflzby Fig. 2–28.

Figure 2–36 is a position versus ti8 6l9ycp fm),nwd g0isme 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? (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 queg,ly8n9 wd6 0)imcsfpstions for the time interval from C to D.

  A person jumps from a fourth-sto;f mpv1 yq)zei-f*. fhry window 15.0 m above a firefighter’s safety net. The survivor stretches the nh. yz; 1fq-ffe *v)impet 1.0 m before coming 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 one-sixth what it is on Ea by32co*a1tev 6ky/klrth. I1evy6*a b/kol k y3c2tf 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 velocity?

  A person who is properlym6y7x a oqb- ,6a3wfjq constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision jo-3bwfx , 6mq6yaa7 qif the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing-entc b6z 3 (3v1: mykiad,bat on a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the 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 poltiad3ab,1 v(-3nt bkzmcye 6: es 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 fyydhlhr tai3 qw0; hl-*t),p2fa0nt9 or front-end collisions by hauling them upnw 0da;iyq,yltlhh pht-3 92* f0a)tr on 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 traf -oot(y,2 jc/nb7kokvels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest. Th8wll:ofz uy6 f57vw- ze 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 st6ulfvw7lzy:wf zo-5 8arted. 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 above the water’s 3 i;.7: ma qmgio1/bp wsmou3esurface into a deep pool. The person’s downward motionm;e3 m3o g7s:w .b iiumo1qa/p 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 ra4n d-pf pc0 lp8wao pc(l06f- lwj.d)dpid transit system, it is necessary to balance the average speed of a train agad-00oj(pn48all d-fp6cpwwdc) p.lf inst 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 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 amoxb yfmxml, o 01;c.i 33mn;jnd 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 it spot the pelican to escape? Assume the fish is i13;,m b0x lnfoc xo;mmj3.myat the surface of the water.    m

  In putting, the force with which a golfer strikes a bue/shzn,cn zs83r8pu5 )6vlrall is planned 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 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 baz r8 ) ne36hus8vc,rpzl /us5nll 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 aqqv9c8b*8 rg j:by5s nt a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rej b*:8 n59bry qsqvgc8st 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. a60q1 mpmmb4 d: 7dqhh4hcx3y A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reacd:q m1mhdhac 7 44hp6 q3ybmx0hed a speed of 12.0 m/s ?    m

  A race car driver must average 02,suv:kb.m8xpj+plec1k k q 200.0 km/h over the course of a time trial lasting ten laps. If the .lq x kpucb2,8 k0mkpe1v:+sj first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at 1r3lvlz 5 5y1m6 ajoy-q t/e,j16 ifpuf8 km/h . At the bottom, 4.0 km farzfvra3l6m6j5qo 1 1i,ltpu/y-j ye5fther, 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 trai -al*t5we ,qtd 9t2azmpolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chi*e za5wd2l t9tt i,a-qld is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-)yp nvf6 5,:vzbuz n6rlong train traveling in the same direction on a track parallel to the road. If the nzzu y:n5p66f, v)rb vtrain’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 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 thropi u4+ fgvzrf5lmgmn wii;v(9epf* , f..4ue2ws a baseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwin9g4ev ng*ile5f;fur (p,w uvi m2 4+zf. pmf.ig motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accel9bp2nf)c h qp-eration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each interse:tg .j w,*s/ goiisy3cvjmz ; lg(a5z;ction has a traffic signal, and the speed limit is 53.o;: l;/*sgmizvz ,ciatjjgwygs 5(0 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. 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 122x1jc 8c+w5hs+kp x vm0 km/h takes off in hot pursuit. The police officv xc 128+hjkcx sp+m5wer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a xpl tl)mz nyi) eu,47s. +ebk9second stone is thrown straight down with an initial speed of 25.0 m/s and the two sx4e7n.sp uzlli9e,)tym + )kb tones 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 ssb./38 -wfig 2mrrqa2c h-3rccsh en v 7-xqc(tone is thrown with an initial velocity of 11.0 hs -cbisqwrrch-nafg83e 2/m 3 c c7-2x(rq v.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 w0wy 3* zby4*kav xzn/ uaqhv9,ould it take a free-falling parachutist to fall from a plane at 3200 m to an altitu/a nh*,buvayv*3x k4z9ywq z0de of 350 m, 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 coeprmc:d+ ,rv4 nveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger prod+p:emc rr v,4duction (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a -(68p h)s7bn7 a afrmdjtq5ee3k n)smspeed 1.5 times faster than Joe can. How many t3h-(a sa7qnn m ftdse6be)j5) 7k8rmpimes higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground 746b oa 8nkcz jy3v+u .0oyxowbelow you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the grouvo. w3a+u4x8c 067yoyjb kn zond below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particu(5un o nfkk: y y3x)1i1+rlclflar 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) f3xrf:ui5 (ck nly+1yokl1n 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. timf3m,/zn1tpi+ k fhor 0e 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 bicycle has the highest instantaneous velocity? (e) Which bicycl+n itk, mo1zhr/ 30pffe has the higher average velocity?