Does a car speedometer)2hicyuc9 m) irb5 fu+e*x5wp measure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yes, i)r74gpeemx7myou3q sp4f2-u2 p ) wg give examples.ir oppmqw 4g7u7fugpe 3 24m2x)-ye)s

When an object moves with constant velocity, dow w fdduztlgb; ernmj(n5 p39vr+/0-; es its average velocity during any time interval differ from its instantaneo0 b;r mld;ztdw/ng v5-3wnjf er(up 9+us velocity at any instant?

In drag racing, is it possible for the car with thei9xp p ;isl/b. greatest speed crossing the finish line to lose the race? Explxpl.;i9 ip sb/ain.

If one object has a 9 vie7mv7if,,igo rt 7greater speed than a second object, does the first necessarily have a greater acceleration? Explain, using,mi vro9tvgi e fi77,7 examples.

Compare the acceleration of a motorcycle that accelerates from 80ki/: hmx h7sar9jf1lkp*sz 8y5m/h to 90km/h with the accel*hf/5a kxz91 ph8jr7si: slymeration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explain.tdie92; ivyya p xl ;4srf/z 9-rjx.g*

Can the velocity of an object be negative when its acceleration is po:bx / z8cuuh*ssitive? What aboutzs/x8buu h: *c vice versa?

Give an example where both the rwg5ye19 s pa0w :hiw;velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a speed 59b y4 vy9wvr0/ ogjf dh;qp3hof 60km/h and has ahjv9dyp yq54;w309 v/ho gfrbn acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in 9xq8, mkxvhk ,kj/ ma,speed as its acceleration decreases? If so, give an example. If not9/vkxqmh8, kj,mx ak,, explain.

A baseball player hits a foul ball straight up into 9fc7f,g+ojs(q7 .es;d bmz uhthe air. It leaves the bat with a sds q 7h+(uecjosb ff9m g.7;,zpeed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is hapjd nbz i,qb/0 ;qyj(a+pening to its acceleration due to gravity — does it increase, decrease, or st +q/ab0bz d ynjj;q(,iay the same?

How would you estimate the maximum height you could throw a bg b5e dv80cri:)d*apu all vertically upward? How would you estimate the maximum speed yov 8ed5i)pc0a dr:ubg*u could give it?

You travel from point A to point B in a car moving at a constant speed of 5y t/ g my*ba5a9bmrh;z.- kdd Then you travel the same distance from point B to another point C, moving at a constant speed of 95b ady rd-zmk/bt5.am g;yh*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-qwhu q.p iiv--s z5+mc**6jczlong vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time betweenvz q5+zucq-*wh i-i.s p*jmc6 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 accelera/wbr6ygsw( jjx*4se05 nkhk dk2z6r -tion: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting sj 4 / k5zbek6w2ds wn*g0y(6khrxr j-on a table?

An object that is thrown vertically upward will retu0 x3prarl/ r,k3u ypg2rn 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, andk/0r23 rxagr3up, lyp if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zerozdknp9 4h*el; velocity and nonzero acceleration at the same time? Give examples.pdl;k4he9* nz

Can an object have zero acceleration and nonzero velocity at the sxzd-na ho1i 5:ame time? Give 1:zn 5axdoih-examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a 7axkrab9mz 1j/o -s0llfth7f8o s7/ oz;/vyt , etc. [Hint: First try to duplicate the motioy0r1 / la9jlo msv;/ a7-fz 78tho7t bk/szofxn plotted by walking or moving your hand.]

Describe in words the moti)-zz+fl u(u x)p uz,;) thknxg )wak2ywva 6k1on of the object graphed in Fig. 2–29.

  What must be your car’s average speed in b qa1rlqk6ppbr3 p7.. z*lv h0order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How( grvr- cb49u0jq: rdr long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 s2vxf 4onjbvhq 26v :(2lc*rnz , how far do you travel duringqvf b(rjn:2 x*chno4l22zv6v this inattentive period?    m

  Convert 35 mi/h to 1 cv**civ1 ojj7c/k-oqxj ng/
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves 3rcycaw3l :c4 f5 9glafrom $x_1$ = 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 13 4lb vbmqh,-7cy3kdn50 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and nd4b5vy3k,b -qhm7lc 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, everm9c. njps9f*s3rr o.ny 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 at9f on.*sncsm.r j 9pr3 all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile tra)uj)i ja r j*3awuvq;;ck in a total time of 12.5 min. Calculaauq );jr)vawiu 3;*jjte
(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 awx )1273a;k+b7jjrmjagtzca r ay in 14.0 s. It then turns abruptly and gallops +) aj2 7j3amzxtrgrja;c1k7b 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 c4v 3bnio )*np 3axzw(parallel tracks. 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 before they reach each other? (See Fig. 2–33iz( c3 4vb*wn )xanop0).    min

  A car traveling 88 km/h is 110 m behind a trsy9,j gxge6qej*1f s2uck traveling How long will it take the car to jj 2eysfsxg*91e6, qg reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a g00q) ppied1tlt *(8 j3bckgbtailwind that bocjgp0p0t 8g1 ed3)* ( ikbqtblosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average vtc6*i3g .m lfc o2oh,gelocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is coveh. l2,*gt3 mc6ocofig red at 55 km/h.    km/h

  A bowling ball traveling with constant speed lc- j*2strubp3 pg *:lhits 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 c*p3gs: *u- ljrtbl2p of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/hsyou(jiz6;p bcn(3 /7uq s7yi in 6.2 s. What is its average acceleration i u3njpuic(z;7(6yyio7 b sq/sn $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is he7p:3 tz f//h mbixn9yjr acceleration 9xjmfzp7nhi: 3 /yt b/
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automr7s7s z-5m msbobile is capable of an acceleration of about r7 m -7mz5bsss$1.6 m/s^2$ 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 td+g puf7ds3; it then brakes and comes to a stop in 4.0 s, what is its acceleration ft;dg7 +ds3puin $m/s^2$ ? 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 = 0 and moves (pkgs f ppaq cpy :t39(hmp+ jj2bu*47in a straight line, is given as a function of time in the following Table. Estimate (a) its m73yc9k j( sppg+q h j a4ppp(tfub:*2velocity 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 topvdk9 r5x .m/y 25 m/s in 6.0 s. What was its acceleration? How fakr.px 59/dmv yr did it travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Whaxg:so3gn hl.+qjxmz10p:ckkt g +:v 9t was its acceleration, assumed cons1ng:qlx gg.z :h+ct3m jvpskk09:+xo tant?    $m/s^2$

  A light plane must reach a speed ofg.)pb qk5kt 1(s ,jspi 33 m/s for takeoff. How long a runway is needed ifk1s ji bg5k(ptq,.)p s the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can s.zda h29s kjh ;jv9v3burst out 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 acceleration o v2j ka9jsh9dhzv.3;sf 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 ;k:b3g yagnu.in 6.00 s. How far diu3:kgy n b.a;gd it travel in that time?    m

  In coming to a stop, a car leaves3idh*j ximku m:sx4g3sv*( s- skid marks 92 m long on the highway. Assuming a decdiu: 3j -sis( gvk43m*mx*xsh eleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end of the car comprt ,org ,)7zkoutq/y * vna8r(lesses and the driver comes to rest r(kol,* g/ vuoar8)7ynqtz, t 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 distances for a car with as)gl na;we e9.n initial speed of 95 km/h and human reaction timee.e w9) nlas;g 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 tm)vg8q,(u alb he stopping 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 truc6-vkln ;b/ggk1da2ne k going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing v1-kg;dnngbae /k62 lthat 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-sx l eh74uv2ym. q4dt,j xhc66m run in less than 30.0 min. After exactly 27.0 min, hs74qxjdh 6,el 6x. 42vmctuy there are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h ap; 9h+ep wf dq y7s+x6i0j4bq*gyvj))hz,hsgeproaches an intersection just as the traffic light turns yellow. She knows that the yellow li)ybv9qs ,q+de)xi6z4y j s0he+;jpg *f hhg7 wght 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 the top of a cliff. It hits the ground b; hkt,a1k-ynb9k m,euelow after 3.25 s. How high is the cli kt; ae1u-nk hb9m,,ykff?    m

  If a car rolls gently*ll0ria8k ma2 ($v_0\,=\,0$) 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 straigv4visxqx,baa9q + +. xht up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 37flz9;+x*,om /m4utso qjbum .0 s after throwing it vertically upward. With what speed did he throw it, and what 4 qot fbsmu7l,zumjx* +9o;/mheight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gf:71/q c.t)t x muqkwc,ujr1draphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 tc)dkx/f17m ,.:tw c ju1 uqrqs . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At a height of 12ss9xu kq+hup hj -.4nsx 0dx:-5 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 initiald s4:- x.u q0uhxh- jspns9+xk speed equals the helicopter’s.] t =__ s

For an object falling frnp+un0;h z /m1hwj ll(eely from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21l/+hnhw0l1;nmz u( pj .

If air resistance is neglecp5m*wgd1jt, on4fv )tted, show (algebraically) that a ball thrown vertically upward with a spgtjtwm5,np )v 41*fod eed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertic) l0xwdsv5a o3ally upward with a 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 each photoflash of the apple infky*g7 eb2.yz2 j1 f8yb2lpy0, l4omhjyw4u w Fig. 2–18 (or number of photoflashes per second bo. 2llyyygk8,e2*1bzwyf4u4j072m wfjh p y). 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 smlnb4 ptd1nh n8:) ac. ymjcikf)*m6( to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did n4y*apn 6b mhckn1: m8fcd(.tjlm))ithe stone fall?    m

  A rock is dropped from a sea cliff, and the sounkuxgu. -0zan, f8-e eyd of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 mng, k8- 0-.zafuye uex/s , how high is the cliff? H =    m

  Suppose you adjust your g:( x l1btl2ze hk9z/kparden 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 e:91zp l 2ktzl( x/khbthe nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edge of a r/x x9si-i+bfcliff 70.0 m high (Fig. 2–34)9s-/ f +xibixr.
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street wml i-)rzsdr77cqmvlf1*h2 e 9y)2zmxith a vertical speed of 13 m/s If the ball was thrown from the stree f z1 re)mm-m 7x72 hy2sqlrc*vdzi)9lt,
(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.ugjb -wf7oe9m1a snwl* gqj1;u t70a. (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 co*nwqa- sm7 9; jg.711ofjau0bglwe utnstant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straightt4imh,y: nd wgsc cbef21h. ;6n 0wo+z tunnel as a function of time is plotted in Fig. 2–28. Wh,n4t e:. mowhn g c;w1y6bh2+szc 0fidat 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 approxixs et;o g((nt(x c0jk tqf8v(7mately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shift8tq 0(v fso gj(xtex c((n7kt;ing 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 ka uo8bv6sy:4acceleration of the car in the previous Problem (Fig. 2–35) when it is b: a8v oy4us6kin
(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 tra )usn*z2s*uk4 hqcosxw.q 25m veled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. thf o2hux)zc:* graph for the object whose displacement as a function of tihfx) c*:o2u hzme is given by Fig. 2–28.

Figure 2–36 is a position vlr6q fw sp+6avk(hzp8* pt:n; 7/nkyxersus time 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+pzp rq 76/knpa86lhk;ns f v:ty*x(w 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 firefighter’s safet zzfh;vh*n1wlm ;+,kpy net. The survivor stretches the net 1.0;zk+ l 1phh ;zvwmf,*n 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,qvib93 gsreizgz,xv xsd)qo qdz9 2g3 ;9:m/ on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher d:s z9vqm3 ),z rge v3g9g;i/,obzsq q9di2xxwill it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an jpcreqs .-9 smjq) 9f7over-the-shoulder seat belt has a good chance of surviving a car col9fe 9 sj-.m qcprs)7qjlision 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 bridge, 12 m above tq3 bc qwmk.7w)he 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 pa3c) wkw7bmq.qssing 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 by haulinge(pbbi2hl3p 9 them up on a crane and dropping them from a c2p e(blpi b39hertain 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 aro z+f7,f i-jx)eqy6 qbout $10^9\,km$ 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 reb9 tyy7 dow2n6ynmy 20 j8p.uzst. 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 the 2tymjd6yw y bny2 zo.n90p78uworker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 fc cpe io;69(dm above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person whi6;cpo dei( cf9le under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balance the avp+h0o4u :kyyi erage speed of a train against the distance between stopy y:h4ipu ko+0s. 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 and free fall straight down when divinb. y1b9wesn+ tg 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 at the surfacest .b+wyen 19b of the water.    m

  In putting, the force with which a golfe /vw-6sddd,xk r strikes a ball 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 fr6,dksd/ d -wxvom 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 t xo1uuf+t+ mv:9mww.speed of 6.0 m/s Just as an empty box car passesx mwt tv:1ouw.+ mu+9f him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof0rsy7 l uoo:vsif7q0: of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the o v0lf:sq0i7u s:ro y7second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over thse 7j2or0 )pu k-blbp*i s -ca8n-uq8d/c/qx re course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must bj0rrpobu /s-xi/)cul2qq 8enbcspk*8ad -7-e maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a moxgekcbyhl;5 //-ma -6x yy uj(untain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average ay 6/uhxb;5/xyamg( k-eyl j-ccceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce up onur+7 :nv (p;sa8ut phze-and-a-half times higher rz;(u svtph+an u:p78 than 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 overtakes a 1.10-km-long train traae7 p;/i herp-veling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directionsi rap-/;pe7 he? 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 thr5*jsxntcah). e. b)vtrbxvnl *m5v) )) y5 immows 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). Estiv )mexth yvcvmbx ni jba )5).*)).mrn*lt 5s5mate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, fbw7jjfqd + 7kckf,(d9k3 f mz)rom 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. Each intersection has ar:f;(p8s,yscp k wo*l 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 t, s8o :c yf(spk;plrw*he 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 szy)t)c:m ciugv)2 lb- sz2u(ypeeder traveling at a constant 120 km/h takes off iu y tczlg(iy)v2b s2c-:z)mu)n hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a svctb2cu ;u+kv u5 / oeb9b.y:zecond stone is thrown straightuc2; uk e5/tu z.v cb+b:ov9yb down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. autoe*m n/n+j57 )psx The first stone is 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 what initijn5em7o )u*a x +p/stnal 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*xla7vsxd0p6ixc;c5 cl- m8mis1+ le, how long would 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 ripcor+lpcs8xmc 5ivm;cla 1l x 6iedx-7s* 0d? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers througei1bvgp2czt j /.c/c;h a grilling magjcz cpc;2v be/i/t.1 chine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a skbx5 bgtlf6a nm:x7 ,;q i29vipeed 1.5 times faster than Joe can. How many i 69q5n xga,kvix7fb b:2 tml;times 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 th.7: sua yz,pkke 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 in your hand. What is the speed with which youru.,paks:k y7 z friend threw the ball?    m/s

  Two students are asked to find the height of a particgodmsvwws(h5 qab 5y q19m; mtl*40p- ular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How muc5b ;wtqsd5s1pmm m9gvh4*a (- qy olw0h difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A ama86b *mj9ol qbxuj,9nd B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the largerx9b6j * lqjmoum, ab89 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 bicycle has the higher average velocity?