Does a car speedometer mk/qz;/ufz7ap nxuiv1uvk( d r.7 ai9-easure speed, velocity, or both?

Can an object have a varying speels3nrw6 q al9yzf / :ub/7kg9wd if its velocity is constant? If yes, give exa9u3k7/s w nqf r/azybg 6wl:l9mples.

When an object moves with constant velocil1 drb+4 x s/y(9 dqcu,gx):jfyd l;vhty, does its average velocity during any time interval differ from its instantane+uf (ddly:hjcxyx1 /)sr g4d9lb,q;vous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing the xz :c/l ita 2r/iwc9l7mw3z a5finish line to lose thewac/awm7/i9i 3 t:xl rzc52 lz race? Explain.

If one object has a greater speed than a second object, does thn+icet* /b;:/y 3b8vu4 ew kwedrtnh8ry g9c9e first necessarily have a greater acceleration? Explain, using exampww reecntyung+/9rd; be k 8*yb94t :8/hivc 3les.

Compare the acceleratio8ppvjcq 8 *i*jn of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that ac**8pcp8 vq ijjcelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a s6 s c8lipbo8k .:f4fgsouthward acceleration? Explain.

Can the velocity of a.p9)7 /ps*snb cou;wle4(z8 dyegni tn object be negative when its acceleration is positive? What abou;l(o97p ye 4ibt e8nd*g)n .spcszw/ut vice versa?

Give an example wherege;d15lvkya* x(iiv*gi f/7 x both the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling witr5v* ;73h 3nuumhfccx h a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h a33xh 5 nc*ruhfcv;m7 und 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 increapmh4bw a(w4n45 co g-wsing in speed as its acceleration decreases? If so, give an examo nhmwpc5-w4bg 4w(a 4ple. If not, explain.

A baseball player hits a foul ball straight up into t55yb;(9wbznqg jb oi6he air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the cnzbq 5 5(ogybbw6ji;9atcher catches it?

As a freely falling object speeds up, what is happening to its accelerationrww/r5o0r xb mnpw dtp,;h*27 due to gravity — does it o5p20wrt rhb* ,prxn/md 7w;wincrease, decrease, or stay the same?

How would you estimate the maximum height you could zaq, tvo5( o3u3k8aqxns3g2e f x3k1qthrow a ball vertically upward? How would you estimate the maximum speed you could givnv8kzx 13uq3 ksa, 3txeofgq q352ao (e it?

You travel from point1ffzq2;m0huwlm8 (; tw xikx1f wsb:. A to point B in a car moving at a constant speed of Then you travel the same distance from poiw m1is80.bxtwf;; kfw2x:qm z1fhl(u nt B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten6+cjt6s -lkbn47lza t bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at eqtals6j- +4nkt67l cb zual 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: a rock falling ,thxd8f s9 vhcq /d-o*from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish restindxv*tcof qhds89 /h -,g on a table?

An object that is thrown vertically upward will return to its orig9, kyhvfd-ie+inal 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 toyfd-hkvi 9e+ , air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzeroz : veb4y41mq+ vjo4dn acceleration at the same time? Give examplem:qbn 4d4vvzy+1o 4j es.

Can an object have zero acceleration and nonzea 6i t w+,xt 48-5dhjlzkbdvu-2uooo)ro velocity at the same time? Give examples. )-wj+ki ou x,h 6t4ov82tuad-5z lbdo

Describe in words the motion plotted in Fig. 2–28 in terms of v, 5q7e7wo m hy2f b*.beja, etc. [Hint: First try to duplicate the mo72 h5bj *w7foe.eq ybmtion plotted by walking or moving your hand.]

Describe in words the motion of the objec 1r cf)7ipg3vmg4jm;mt graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in m,mrotk(n ,;d471 lqshu;7fwa;ihqo 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take +uhc9y)ujt92(ea l uato fly 15 km?    h

  If you are driving along a s; (l t,omwzh7atraight road and you look to the side for 2.0 s, how far do you travel duringmh;7awzt (,l o this inattentive period?    m

  Convert 35 mi/h to r.tgsg s3 7wu,9 -qiqg y+4gwhez;3nb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr-)g/hp,rtv l rom $x_1$ = 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 1jbo;y(p2lq m-eoz u8 130 km. It then begins to rain and you ;q -b p8oel1jz2yu(mo 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-o8:64fq + if6owuoha: i lhmy9lf-thumb, every five 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 ofh6u9im+a4f8fl6yq ho iwol :: sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarterxidw5+82 rup/a; j dc.v hvzh/-mile track in a total time of 12.5 min. Calculatx //zw25v rvhipa. h8dc+d; jue
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, momnd cjq073x4ld wbb4 (ving 116 m away in 14.0 s. It then turns abruptly andbd7n(q0lc4 x wj4mdb3 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 parallecrerz3ep7*,of. *g hsl tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km 7*zrep c.fr,o* e3h sgapart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling mfw01 wqfy h6/nwwq;z*n .p s,How long will it take*sw; .fzn1qnpw0 6hymwq ,fw/ the car to reach the truck?    s

  An airplane travels 3100 km at a speed ofsnlivu) kwu/uob c(98uo/:9 hz i4c)t 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h foonizcou tk:l/wb))9v9 4c /h ius8uu( r 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 a- h,6nk y+eqe rdleao8px0, dfsd, ;;speed and average velocity of a complete round-trip in which the outgoing 250 km is cny eh o;0,a-fqd;6 ,lke + dexa,rdps8overed 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 constant speed hits the pins dtj+s 1nho0qydhlt + 50e2i*cat 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 release jqtlih nh+0dotd+5c2y10 * esd from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its average acc 5;j*q lbrcq0keleration incql;bqk5j* 0 r $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.gsnjy- 7y7+u+ :qzjxn0 m/s in 1.35 s. What is her acceleration -gujy++nx7q : 7ns jzy
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a p o--)a3bp3 +foc v7 +y8aav;msbsgzwqarticular automobile is capable of an acceleration of about -bmc8v+-z3pfowaqg 7soy ;s3ba )v+ a$1.6 m/s^2$ 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 trav) dh amakqkpanr9.8 8/els 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, wh8 kn maa9hdpq /r).8kaat 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 rest at t =d5r d:cvv,yfn006ro x 0 and moves in a straight line, is given as a function of time rr,cx d6d5fy: 0vno0 vin 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 acceleration? Hg 20nha*,hpizzmp9 z 8ow far did it travel in this time? Assume 8zzg0 iznhm,ap2 hp*9constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a dist/cu45 v7o3pzxh 6q,qmlo)i 36e2g g 9ohzmgfaance of 85 m. What was its acceleration, assumed co66qil5o o,hm2g u49xm/ ez3)pq a ocf3gzgv 7hnstant?    $m/s^2$

  A light plane must reach a speed of 33 m/ss443:1kp zoray 3q ig9ltj 7sg for takeoff. How long a runway is needed if the (constant) accg7tslig33ar4 qs j k4:y1pz9oeleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst oun9z/e 9h :ohu;.qbobs t of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average accelernuoe h.9qzb;so9:bh /ation 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 6.00 s2z20.g 0 fu0 vxhlg-wh1dxwtl. How far did it t220vww xgf-1t00z udxhhg .l lravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. . 3x js6aixpdnv,x ) 3q-gerw6 l)8oseAssuming a deceleration i3-.8w,6r ) 6j3 epgxnoadelq)vs xsxof $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of yvej cn)z nvj5 :du **6ndus5s.z5j* qthe car compresses and the driver comes to rest after traveling 0.80 m. What was the aver)e6c*dq5 .:nznn5v * v *5djus jujzsyage acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speedr4dr bql6 ceia+f:ftm 5cjaqqy6;3 /9 of 95 km/h and human reaction time of 1.0 s, r f5 dmij3byq+efc4r/qlt96aqca: ;6for 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 u99 zvxyamo6al:-j3/a+a u szl /u:ivopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driver)zg:hvu * p ;pxps:rz; looks for an opportunity to pass, guessing that his car can accelerate ;:xvzghus z* p;p):rpat 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 30.0 min. After exacef dbq3 vae rv8m))h 3fg008ogtly 27.0 min, there are still 1100 m to go. The runner must then accelerate at a)f3)0vmbgfqrh do8 08 evg3e 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 w8 2 /qcrnfvupdzn, 74km/h approaches an intersection just as the traffic light turns yellow,p4n q2 vdf/8ruwzc7n . She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. 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 theqx5cn b;pb 5 ;xq9 t8zss(pl*x top of a cliff. It hits the ground below after 3.25 s. How high is the p 9bxq5lxnb;* xtzp(;sc q s58cliff?    m

  If a car rolls gentlyrfp2vh+t*6-rk zd0 /: w :t7tlz)qw.etiqbep ($v_0\,=\,0$) 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 nearl07ie 9wu6gxju y straight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catcheswlf8e1g 74 2cfkdah)yz0up 9u a ball 3.0 s after throwing it vertically upward. With what speed did he throw it, and what height did it rea21a9dk0ycph g4 wlue8ffz 7)uch?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence o sy8km x4j3ddj(xj8v n:vv *m:f gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a functio(nxmxvs:: 4ydjk mv8j 3v*8jdn of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a spec*kp: penj.m/d ) 6,c yl/tddi6ec (cued of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t /)c6:dmjped.,ck *ie/l6cdyc np u t(=__ s

For an object falling freelyd zk8 ) ,cx9rbb(6xhrh from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1c 9,hb( bz dhxk)xr86r, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraicyabju:66ym q0ally) that a ball thrown vertically upward with a spybuym6:qa j60 eed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 1q 2e66qd*zjbi8.0 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 p8oyf b5+3c:ygb2hs7 tjgo;vnhotoflash of the apple in Fig. 2–18 (or number of photoflashes per seg:+3b7o sn;v yfcy2j tbho8g5 cond). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 wa. eny+4g /o *jlfv+jm tall (Fig. 2–32). From what height above the top of the window did the stone e4j vl*++ fngyo aj./wfall?    m

  A rock is dropped from a sea cliff, and the s0)bnz8 s9r( a zwzhzz0ound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H = za)s0zzhz(brzn98 w0    m

  Suppose you adjust yourrgtwd/k js4/4di(6c r garden hose nozzle for 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 verticalk4g(/dr6jdrcs/t w4 i, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed 1:xbsr2v, uwt of 12.0 m/s from the edge of a cliff 70.0 m higtrx v:bw s,u21h (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the4ujri)g .u i5d4cn0ju z+s6 aca7)z bt street with a vertical speed of 13 m/s If the ball was jsdc. cgurn)tuj)zau 65 4 azi 7ib+04thrown 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)oq q a0i4;w9vv At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what pev049a ;qo iwvqriods, 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;y (gmhv5ijda 0g 6gg0 a function of time is plotted 50 gghgid ;(mva6yg0 jin Fig. 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 approximatell+vb:y:)s )rg4uer kd j+/scey as shown in the velocity–time grrer:)gus 4 v+ e)y/ j:sdk+lbcaph 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 carz4b4npra9iek /p0 m( r in the previous Problem (Fig. 2–35) when /z(p9 ak mipr0bn44er it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled duritjwmn au8, ;8zng
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object g2zw,xf6 faqy 4-bm l,whose displacement as a function of time is given by fa xz, ,-yfgl 4w6mbq2Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of a r q9d;v1ecbpp+1ic715sqyi6s zim3hn object along the x axis. Cons7rp1iv qbci6 y5 ;3s hcz9m1qdps1+ei ider 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 questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a f nwl+a 3r9sa.girefighter’s safety net. The survivor stretches the netrg3lsan9a.w+ 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 Eartetw s.gibr3 /ya7n6-th. If an object is thrown vertically upward on the Moon, how many times higher wil/.r76 w -ng3t ieysatbl it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an fg y/ogg7 y93gover-the-shoulder seat belt has a good chance of surviving a car g 9 /o7yfg3ggycollision if 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 on a bridjk0ns1/kl 4f d+nxk hy 8c7k 76oey,vnge, 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 passingef6vh,8dy+sc7ky7on0n/n j4k x 1k kl are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions byod 3kx* wl8d2kwoh8.b hauling them up on a crane and dropping them from a ce8dwo. kh 23lx*w8kb dortain 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 abouzhqmcr:*5b n:wvb, 9rt $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train be)pb ntdxr+j ,. dcedz gu0n*w-3j m .v:nta29rgins uniform acceleration from rest. 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 passes gtxavwz)dmpde nu,rc* .:d.t 2+0j 3 nn9r-bjthe worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board :0mk f5,l yy:xr;o zrx4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surym r,kl::fxxyr0 o5;zface 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 transcf+on .t if q): d+q*+hlm1hqkit 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 time it takes a train to mak+qo* fkc++ lq fmq )thi1d.hn:e 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 stxcy 4)me* cd.graight 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 pelic.*ge 4cxcd)m yan 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 pl k bjzja+u)a,nk f) macmw-.227vg x(qanned 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, w2k (ba gmj+2vam)x z, aj7cufnk) q.-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 constant ye7 li7ty,ys0d*h qc3 speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accele d*y77lqth s,cyyei03rates 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 roouc97rbn uu22ke) pd0 wf of a high building. A second stone is dropped 1.50 s later. How far apart are the stones whenr nde uuk2c207puw)9b the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200:-ipa tkl9,kcu zi5w 8.0 km/h over 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 theki w9 pat:lku85i-,cz last lap?    km/h

  A bicyclist in the Tour de France c 7qbscig 8/ze;rests a mountain pass as he moves at 18 km/h . At the bottom,iqc7 z;b8/esg 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 first child cwcq5+ )i.qe gtan bounce up one-and-a-half times higher than the second child. The i5+c) tqigqwe.nitial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train travelivx m+t+hoyf7*ng in the same direction on a track pv +to* x+7fymharallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite 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 throwx-xe z0hb n:/,o minj9s 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 duringn,oh9z: 0xebn-jx mi/ the throwing motion.    $m/s^2$

  A rocket rises vertically, from3boaoi//txt 21g bc*ya jc1/5; gnujti6c+ kz 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 pattg qt5gj; af)l9;hme/ vern shown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn gree;fhg 9 qte) lv;j/gam5n. 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 b r sx;.1)pchuconstant 120 km/h takes off in hot pursuit. The chr)1bspu.x; police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s aftanumum n pl8r j,,b) ldc- +l0(fcuf:q*j0ar8er that, a second stone is thrown straight down with an initial speedd r nuul- )abjl:+rqp8 f,8(,0ujccnmm*afl0 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 verticac 0c6 . azlhxgw:;e/5eni)ucc lly up at the same time. The first stone is thrown with an initich:6ne)wc ; c iz5.lxg c/eu0aal 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 wo hpia)8g3 dha+uld 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 at 350 m? (In reality, the air resistance will restrict her speed to perhah)ia dahg+p83 ps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send th2. uxu)c; +x;o*oxs g og5yweqe burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in;sougx52 ;* +e wuco g).xyoqx burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times f165iz-xn yabu aster than Joe can. How many times higher will Bill’s ball go thaxban 1-y6ui5zn Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your frie.cetnl;hv+* hnd stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to r hlvc e+n;*.thest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to findlizph;tyopa 7.lqh k (u ;ig(xpm *+37 the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the oitxih;qya u+m gop(l7l zph3p(k;. *7ther, 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 bicyc wz htaari66bhd /.:i1-pu /ryles, 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 bicycl6:zrd/ap6 wba.-iry 1h u/ti he has the higher average velocity?