Does a car speedometer mge4ml yqs h+ tjzx(knfiu (.2w4.o*c4 easure speed, velocity, or both?

Can an object have a varying speed if its velocity dnacla bx zxaky() :u 2/7de3)is constant? If yes, give examp ad(x :nd)/ycekul72bax3 z)a les.

When an object moves with consta wycixx9 h3ay f.6id7j3 i29gdnt velocity, does its average velocity during any ci7wfjxh ag6d9 9y id.y3 xi23time interval differ from its instantaneous velocity at any instant?

In drag racing, is itya, mul;.o ;3rap /hh(yrbn)m possible for the car with the greatest speed crossing the finish line to lose (aa3y.)/,;n;ymm hlpurohr bthe race? Explain.

If one object has a greater speed than a second object, does the first necessari;kffiy;pr+ nldh- o7h,c-)oely have a greater acceleration? Explain, us7r;+eody poh-; fh - ki)fnc,ling examples.

Compare the acceleration of a motorcycle that accelxap6v ;lc*rx+y q*n5 verates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10kmvp+rn * 5clyxxv6a* ;q/h in the same time.

Can an object have a northward velo4t py.z1i(db xcity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive?c i ebn6rx ,*wmm6ulw siamuu5;o0404 What about ue 56ulbi;w o*m6 0n xm4,4ricwsm0uavice versa?

Give an example where both the velocity and ac uoy7 g2uj2x wbf :b2,f:;o mrfo.lpg;celeration are negative.

Two cars emerge side by side from ;o.a poa(e y4sa tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an accelerations( .a yo4o;eap 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 speed as 90 rrv50x3a5edor sfvs7 c/ilits acceleration decreases? If so, give an example. Ifv5 lri/ 30dvs9xer 7osc5r0af not, explain.

A baseball player hits a foul ball straigh+dlt,l*i)kto r llf831b1f m ft up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance,3 idl8tlo1fl t +)1rfmklf*b, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to itc- e 4l8zjh*res acceleration due to gravity — does it increase, decrease, or stay the*8jz4clr he-e same?

How would you estimate the maximum height yo b +de2+a3r7mqt0 ;,xoasqy5g)c y pnmu could throw a ball vertically upward? How would you estimate the maximum s,yd)cma g 2q on3yrpe+m;t qa+s x05b7peed you could give it?

You travel from point A to pkg.:bfm a3 7zroint B 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 s.b:7 z3rgka mfpeed 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 wite:o0y r t*7lsth ten bolts tied to it at equal intervals is dropped tol* e0:srty7from 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: a rock mdtet zq/;; zls;9(effalling from a cliff, an elevator moving from the second floor to the fifth flmlz ed9tf;/q;; (estz oor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwarvglb15mntfbf lnl:z/b3h1wdqj7o;( o; +8b rd will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this rnwl83nb/;f; oo lqg:b15l +hf 1d7 mjr(btzvbesult be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocitwxwge+;)xv,s *x+2 /v4rinrn;r i9y4wapd at y and nonzero acceleration at the same time? Give ee,9a;4 t;rpxi4xvnir +2 v s*xd rna/)y+wgw wxamples.

Can an object have zero acceleration and nonzero velocity atdy5p 9m9fzv k+ the same time? Give ezfmv5 9 +dkp9yxamples.

Describe in words the motion plottedh /-gkm*4p rcam/,g ge in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving youm/ram-gekg,4 ph g*/cr hand.]

Describe in words the motion of the obje/7mg f6icgr(oct graphed in Fig. 2–29.

  What must be your car’s averauk la9e537mkrge speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it 8 ;kp.qm5vqy7ay 4tubtake to fly 15 km?    h

  If you are driving alorumq 7q6v,c4s ng a straight road and you look to the side for 2.0 s, how far do you tr,umqrscq6 v 47avel during this inattentive period?    m

  Convert 35 mi/h to zum r4alp-i4 qyt0i.*1jml l+ :tdl-h
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from 6hog7 c y)k4qkv7r 5fqeb9 i;m (-wadd$x_1$ = 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/bp wyyv- :zt7b :w17vyh for 130 km. It then begins to rain and yob1vwt7y wzyb-7:yp :v u slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a d97rps)smh a99-j6 *d ukd1e tk5uex llightning 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 ) d 1du5xdrs*9se jlh-6 9 ekpaktu9m7all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete d0vzeys m8 4 mh*sh9hc 1ku.6rhy/*kolaps around a quarter-mile track in a total time of 12.5 min. Calculate v9e ok* hsmzku6ds8cm* .h4h01yr/hy
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away 2-8h l,jmatu v)par9pin 14.0 j vp2 )h malpr-aut89,s. It then turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each jtmdda,50v- axcr3h *has a speed of 95 km/h wdrc,adhmavx3t - j* 05ith respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck tra+lw z8busg l4q1di4.x veling How long will it take the carg1+sllwd.8 z4 iqbxu4 to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encoun-8yccaer96 fwd; 6opn ters a tailwind that boosts its sp8y6oef9n-cw prda 6c; eed 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 aver8tefm g ud77g(age velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/hu7fe8dmgt( 7 g 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 conr1bjo9nq ;6j dfez k7(stant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after bo;jn7k 1z(d6q9f jrethe ball is released 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 /-p*vqy e) t bb.ee a:xvmsa h+wa720bits average accelera x)2:aaebqyve+ 7-ps h.0w * bvmb/etation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s i-dqhre(fz(gpy)1 7r nn 1.35 s. What is her accelerationr n-1zfrdy q)h(g(7ep
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular x+ kxdvms 9di :h-9spb lv)z7(automobile is capable of an acceleration of abou + svzl:k9 imp )xvdh(97s-xdbt $1.6 m/s^2$ 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 ( i,.nk/zj 7ul4dldd9t.a pqfa (y5zpconstant speed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what jutd9.qkdnzl(z5ppfd 7a.ia/l ,y4 ( 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, 4i lc6,8o0 vyrc;tk66/-aqdni(hxu2 zhjediwhich starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Tablj,dtaiv u6qk/i2h(yo-08r6dl4;exn hc iz 6ce and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What was its acceleration? Hogg ive5g8ej6m6iv. :gg 3ufifh; a(xk5-r6 imw far did it travel in this time? As 36i g gvi(m86g 6xf;imeh-gefa5j5.rvu:igk sume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to restk 5, ls--miqwbs(.oob5zr n j9 in a distance of 85 m. What was its acceleration, as.qbb -i,5sz5ws9njrm k( oo- lsumed constant?    $m/s^2$

  A light plane must reach a speed )nhp(f-euslk- krz u6(7dpb* of 33 m/s for takeoff. How long a runway is need* 67lfbukz -dh s-pe(npr(k )ued if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprintea/ sv*u;kx:re r can burst 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 of this sprinter, and how ls;au: */rxvekong does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly frowfjnw.id,oa *v kih/9 n:y; l-m a speed of 12.0 m/s to rest in 6.00 s. How far did it trav vj;fwaik/*:y. ldi9wnh ,n- oel in that time?    m

  In coming to a stop, a car leaves /2wv96r1s xy fdvln z7z;/cd +6swyraskid marks 92 m long on the highway. Assuming ad9sw6yn2x1wc/r z a +sy vl/rzvfd6; 7 deceleration 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 conts.) -mx j5jnwen e+l/z- 2rampresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the d +z-l w/nms.2ex ternjna)j- 5river 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 a8kwi r7n-iry9 car with an initial speed of 95 km/h and human reaction tim7 9iyirwkn8 -re 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 he ;1)c(ihnfd a,(jkothe 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 truck going 25 m/s on the highwuk3q w0 pelc(;ay. The car’s driver looks for an opportunity to paulqk w;0c ep3(ss, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After exac5 5k4mp ick9wjtly 27.0 min, there are still 1100 m to go. The4p5c5kj9 k wmi 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 a3 1 z9jp(ijexat 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the ia9 e1jjxz p(3yellow 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 the top of a cliff. It hits the ground belobek :pg , 1oa,v0yc3xv+ocx.pw after 3.25 s. How high is the cliff v0p e, xykgvpa,x c1:b3+c.oo?    m

  If a car rolls gentl jalh n8*f(rnqo s5y ,ahme(n+:x1 kn7hbg/ g,y ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straix3vxke 97bm 5/npf g(i -e+rreght 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 3.0 s afte:a.sliy) q+ kb. 1dusu 0s2ftqr throwing it vertically upward. With what speed did he throw it, and what height dis bkq +iyqs)ua sdt0.ul 2:f1.d it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. qm8g u 2om tndcb/hj6m/)b0n1Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore a1q)2c0tb6d u8/ jn /gbmhmnm oir resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At ar8gh8to hk ad)lv2/. u(du5r 4erm oy4 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: Trv4ol(u 5 edmdhyh42u rkrt8.8 o)a /ghe package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from gne8az chi: zsq*(h *;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 byn*sz;i q:8 ahe *h(gzc Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglep:44(cvk1 mes ezuk ;vcted, show (algebraically) that a ball thrown vertically upwarduk ;1 (emzc4 ksevvp:4 with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically up,wqhkr)d +vc(w3ht 2 pward 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 in Fig-i9vpii h3qk 2 s ;vxkkc*u 3w0q0cts/. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ox0u/sqwkkc*9;3q- 20v i vspic thk3 ines at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to tra+ vlzm/7t(xmq np9ih8vel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window ditvpm 8+9xhm(lqz7in /d the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the h v(+ec9we63s/q p(bu) lzdnbocean is heard 3.2 s lath9 (e(q)d ew3bslp bu/z +nv6cer. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzl *j,hk)dzgrh4vs)k2 lg wml d8rua3 7/e 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 a3 4hsr/k) *g7d)zdm g,lh jlvwrk8au2way 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 edibdngb8-ug 60lx em:+kcr 2a*ge of a cliffla2c8d -gkm b:b6e0ug i+*xnr 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 pass upward by a window 28 m above t6pkxg i)--ubdp l;t/ezic h5+he street with a vertical speed of 13 m/s If the ball wa/-iplgz kbc5h;p-xi u) e+ 6tds thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a) At what tiw(,obopc1ae 4me was its velocity greatest? (b) During whap ,o1(bwo4ecat periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a funct+0jeke.8,z n(6ee0djfxd e*)bcxg ahion of time is plotted in Fig. 2–28. What is its instantaneouj xfnh)d( e860eaxjdkbe0 .ge,ce+z*s 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 accso (nc7+fh 2g,hdygo1zz6 / (c*uo ikkhcv 6*pelerate approximately as shown in the velocity–time graph of Fig. 2 yfh(c6 c u*hgs1h7 o*/z no 62z,dg+(kovipkc–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 accet wd76s-wd 7td)hz hq6leration of the car in the previous Problem (Fig. 2–35) whenw7zdd6 h th6 d-qs)tw7 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, estimateoitmgy (o c vs8p;fz (2y4a.l7 the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t g lk6d5 z*umr(,ncc(n wkn+92bua:vq yraph for the object whose displacement as a function of time is given by9+vq z( 6a,uc 5n(wcybk2ku*mnlrd:n Fig. 2–28.

Figure 2–36 is a position versus tia(1 .uu p6kheame 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 accelerae(h1uku. 6apation 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 *ttn c)( a4+ fltb8cfya fourth-story window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before cofabfc +)t t yt8c(*4nlming 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 one81f 6hz g/2mqsb*et7f cz:akv-sixth what it is on Earth. If an object is thrown vertically upward on the Mgc8b*efv6 /1km : hzsq2za7f toon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an odpsdkb m o391ktr p gtk205*s.ver-the-shoulder seat belt has a good chance of surviving a car *td5 pk.kts 2mro 3g0p9bkds1collision 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 them0bw zsx;vz3w 9*su- ynf,5st 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 tezs;wst- bf,yw 0 sm5u*nvx3 9zlephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested yzsl3 w-iiyzw(w 5l8(.aonc/ its cars for front-end collisions by hauling them up on a crane and dropping them nyzacy5o(i3l.wlz-sw i 8/( wfrom a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels abouh4eoi- c 8,8 5toqr5wls ,anskwurz1:t $10^9\,km$ 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 accelerati(s- xu jf*)r y(.yb 6goqjtckc3 9 e3hibve84uon from rest. The front of the train has a speed t8uec *yoj-cq(x4s (3ibhkvu)b.96yf rg e j3 of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a dtzqm4. 0xao(fiving board 4.0 m above the water’s surface into a deep pool. oz0 q (t.af4xmThe person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit systv5 rdfj0i3)ghem, 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 5ih0d3 )gvfrjmake 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 an9;fen6 fkpyu;h5xpu+h j+2x nd free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot nxj+y6uh n ufp+;f h5p9xek2 ;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 surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned hvxr3xz e(,x/y2i;5nnwv s *pso that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missenp, sx yv/xzx;whnr2iev5(3*d. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling azrm ;z.s o7qipg9y r9 b/k(/jdt a constant speed of 6.0 m/s Just as an e(zrzo9ygmbj/9/k q .irps7 d; mpty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a zqu m)vmx/2xe )i(:gw high building. A second stone is dropped 1.50 s later. How far apart are the stonew vuq i2zxmxm():)g /es when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must a3 o:cnbevsvg 6i1be r5/59ra-h5epv iverage 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . whr :vn5-/hibrc5g s5aie3b1 p vee6 9voat 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 18 km(u5yefcvcs px.4+tr)/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average accelereu tv.x+cp5f4)s ( cryation (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce p q-1aid;aw9i up one-ap9 iwai-a;d q1nd-a-half times higher 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 adje a zz,, (u4q4bga3 ,flhb)t 1.10-km-long train traveling in the same direction on a track parallel ta3ju ,g(4 lb4hfb qe ,)dzaz,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 throws a baseball with a speed of 44 m/s In throwingu,6t mn8 cuc3 hh(xhsyuus,t v-i. 9+u 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 du-3n,u.hhu uut+,s i9 cv(t8ush yxmc6 ring the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerah1igip31+- fgp em*(nd wb3vakk d o-:tion 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 i xgic uc*5hnh3nve): sc- r1z6ntersection 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 grer *e6s)u3h c1c-zvxh5ing:cn en. 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 t0 i nhn63ze6mspeeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a imh6tz n06 n3econstant 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 thq4+ d l5zem0vbh*zgs)at, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones+q5v4dz lmg )z*0hbes 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 . zptve9kvb5ph.;o eo8pq * +nthe same time. 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 afterqz p9e*. h.p5pvon8ov+ ektb; 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 would it take a free-falling parachut.o1 ukm4s-a5uy kgwv9-d5cs vist to fall from a plane mg- -55ay swv9k. vsou4dc1ukat 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 perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belzyhdy5i) h)0f t to send the burgers through a grilling machine. If the grilling macd5h0f ihy))y zhine 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 speed 1.5 times faster t.vyf7+ir pnc23kbe q(han Joe can. How many times higher will Bill’s ball .v7f 3ircbpqn2ky( +ego than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff w4kb kyhu)wptt 65v3y.v. t5z fhile your friend stands on the ground below you. You drop a ball from rest andv . .5 f)6up5t kht4wtkv3yzyb 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 your friend threw the ball?    m/s

  Two students are asked to find the height of a particular buildinj v0o: ;6gclm;x+awmpg 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 sto6l0w ; a j+x;:gmvpcmudent reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a)rc(mpc1 ,fz ;ioy*: r rlni44r Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the1cm(yiil rrr;p nfz,r44o* c: 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 bicycle has the higher average velocity?