Does a car speedometer measure speq ;cg1 csf-xo-ahb6u4/b3bj qed, velocity, or both?

Can an object have a varying speed if its velocity is constant? Iuq5l om9y9t ;mf yes, give examples.;y9q lotu m5m9

When an object moves with constant veloci9 k (t.1pgkzhbty, does its average velocity during any time interval differ from its ingtb(9.kpz k1 hstantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing t(o rq5qq3)k /t ktt4w -tkx+ylhe finish line to lose the racqq)twy(k5to - x krqk34 lt+/te? Explain.

If one object has a greater speed than a second object, does the finsrcr z548fw(;z *o7 x(yv85 l1gztcfe*aa wqrst necessarily have a greater acceleration? Explain, using extervf(c(a4fsz 8 w z**y7onz5r85cl x;gqa1 w amples.

Compare the acceleration of a motorcycle that accelerates fromy65xh1n* ttjg0 gevk; 80km/h to 90km/h with the acceleration of a bicycle that accelet*;g16 0ejkv g ht5xnyrates from rest to 10km/h in the same time.

Can an object have a northwar+j+ltw0lsx, k d velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wcj5hegg072mlm; nc/cxtk-xt(x0 t h / ,t0yqqhat about vic mx2t hjxctmh/gknq7e;t,qlt0y05-(c / cxg0 e versa?

Give an example where both the velocity and acceleratbl,2 0:6w yj2uukwoozion are negative.

Two cars emerge side by side from a n cc d4(zpobn0*2g,jo tunnel. Car A is traveling with a speed of 60km/h and has annzno(o*2p4 0cdbgc ,j 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 speed as its acceleration decreases? If sohv gj k*db lp4y*:(+ y/0q d30ueeiwlo, give an exayedilq4k300 v u bowjlpgye/*d:+( h*mple. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the babni-.q pg.e/m cxr a39t with a speed of 120km/h . In /9. aqnpie3bcxrg -m. 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 happening to its :nv gpmhb5bm7 1y+hr9u r 0jeyd o;s)-acceleration due to gravity — does it invjhb 9umde)+sygory75m;0 r-h p nb :1crease, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertqztxrb oeajr3g4y+ 8a/fck pr*03p8;ically upward? How would you estimate the maximu40p3ory / r8xzcaqj;8rfe p+bk*ta3g m speed you could give it?

You travel from poin1kjol+ygr z) ys/ aj75t A to point 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 speed of 90km/h . Is your average speed for the y 7rj+ja)1g/5lzyoks 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 ten bx 40t 9d/jbautdji 2:rolts 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 between clinks increase or decrease near the end of the fall? How could t9aj40:2x idtrjt/budhe bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a r;tlef-x:z t3l ock falling from a cliff, an elevator moving from the second floor to the fifth floor making stttx:3z; -lelfops along the way, a dish resting on a table?

An object that is thrown vertically g9oytuwg :5s;ta-w- w upward 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 result be altered, and if so, how? [Hint:y9 awwoutg t;gws-:5 - The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero vee07owul-4( +eors q2f3 up qdmlocity and nonzero acceleration at the same time? Give exam oew(u2 spfdl 7-m4u0 q3or+qeples.

Can an object have zero acceleration and nolmq ,+wxn;h *enzero velocity at the same time? Give exnewx+ml,q *; hamples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [vvoxw;0/w q(dHint: First try to duplicate the motion plotted by walking or moving yoq w;x/0(vdwov ur hand.]

Describe in words the motion of the object graphed in Fig. 2–29 jpcukx oo+01u-q) m(k.

  What must be your car’s average speed in order to travel 235 kmbeoe(cb gv 44. in 3.25 h?    km/h

  A bird can fly 25 km/h0(d ;zf flya;hsa(n*i How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for tl z9xl6m tm+,2.0 s, how far do you l+zm t 6t,9lxmtravel during this inattentive period?    m

  Convert 35 mi/h to t+:v7-w3 br ui9kun rn
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fr 750m* 7pet1 vuymh8.tfocpbmom $x_1$ = 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 stead6-knv9 thbi)r+ u+ m1grl/tisily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after drivini u- r)l/9rkishn++gvb6t 1t mg 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 seco0zxci0 79t;zvwgd2 ot nds 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, esg t; o27dwtxc9zv00iztimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps aro9:/ q2thto*r 1 fxzmsxund a quarter-mile track in a total time ofsotf92x: tx z q1r/m*h 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straighac 22ed pvia ,/ipqd;mo ;,q1nt line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back iv 2po naq2/dpmie,iq cad;1,;n 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 t7fm9:mxsib217 h j rfzracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how longi9zx21smbr:7 mf hjf7 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 How 4y6 s qxgjj0ocxbj+qi:orl6, lm w);;long will it take thowxisy,bojr;j+l q6;lx:)g j6c mq0 4e car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encx jd5;vzmh)q4 otce05 di, nz6ounters a tailwind that boosts ihdez4 v0nc) m6o x55t ;jzqi,dts 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 velocity of a complete rjevn*a5z3 - b9nnhbzvu0u2 2v ound-trip in which the outgvv z503nba*eh2v- 2zjunnub 9 oing 250 km is covered 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 at the end of a bow9dgz i 1rk54 n 54unza 8blwv5-xaftk6ling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 sl8 d55rfx1g94wzau 4k znbia - nk6vt5 after the 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 fromb( b2e kboc2x. rest to 95 km/h in 6.2 s. What is its average acceleration inceb.kbbx2 o 2( $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 mc8fvan ur)zc3k*d;8sm 9gp5dj-i m 3 z/s in 1.35 s. What is her acceleration 3)d dz mg 3mr*ifjscpck-n;vz85a9 8u
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an accelerzf-*zgccphkuj* 9 q-v lt6u 0;ation of about t0zc*fjch kl-zu9u; pv-gq* 6$1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If it then bl,ee p*:2j ikkrakes and comes to a stop in 4.0 s, what is its acc*ikl:2kpje e,eleration 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 rac;cf w-9 mpsw- trnbbw*. :tn8ling car, which 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 fup;lb-*cm.bfwwn-t9 tsw : rn8nction of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to f,t13jcpch 9ts/lxs+ 25 m/s in 6.0 s. What was its acceleration? How far did sc/h3f+l, ctpts x1j9 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. What was its a m(c 6j3 zvobp8gc7:cacceleration, assu a moc7pv8z 6gjc(c3:bmed constant?    $m/s^2$

  A light plane must reach a speed of;kj7 gllv u7/y;2n8ig k w;+ys*potid 33 m/s for takeoff. How long a runway is needed if the (constant) acceleratiw ip d ;vyos+n/g2j*yk l87kgtu7;l; ion is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top sf/wt/q rx 39 ehjva5,jpeed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take5w/ jxveja r3/f,q9t h her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly fromoa ( ,7utb7v ka wka5ad(qe,*w a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in tha kw buakd(q, (w5eao7a7* t,vat time?    m

  In coming to a stop, a car leaves skidw r: e8uo9i/4jk z16xznfr jm/ marks 92 m long on the highway. Assuming a decelj/o wnxu/rf1e9m 8zj6kz:i 4r eration 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 compresses af lrt;1rn1e5 iatvuvl0 mp 7i-;r )fp;nd the driver comes to rest after traveling 0.80 1ltfru7afvpr1 - nvr;5tp;); 0m iilem. 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 m( /ui cdf 0l)a/7t.kxh 4tdpmfor a car with an initial speed of 95 km/h and human reaction time dtf ik)(t0hm7./dmpu lcx/ 4aof 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stoppin68rys; emc7rr*h9xnsg* no- fq n0 )crg 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 looks fojykuhdt ljtbf9 ,q; (2jk(a :i1/vn(vbe(+ ejr an opportunity to pass, gues9lji ,d(k ajj/bq1evkyn f: ub+ (t;2th( (ejvsing 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 exapw,ozdy8wf y 8) o/r7wctly 27.0 min, there ar w)w ,rop7z8dfwy/ o8ye 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 approaches an intersecti ew4hle 2 ns1cfb/o+u-on just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection beflc be1+ -ufse4w/ hno2ore 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 below .8vwx:vhvvh2y6 zw*-v cq9hj after 3.25 s. How high is the clxv vj*:h8wvzqv-yh26w.9h c viff?    m

  If a car rolls gently : 8hn:yzl;0fk v l-exd($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

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

  A baseball is hit nearly straight up into the air with a speed of 22 m/s3, ul- v9apb iy nbqxd4+s25tn
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s dggo3l,b 0h-b after throwing it vertically upward. With what speed did he throw it, and what heig b glho0-d,b3ght did it reach?    m/s (Round to the nearest integer)    m

An object starts from resxv6m/ge addb8p1z(x 3 t and falls under the influence of gravity. Draw 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 air resd(p xa 3xd/b1v86 mzgeistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At atj xgn;3yzv 8o/d8lm. 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 v;8/g md lj.8tynxzo3speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show tgv(g8:yz r5e.c pc.pk l;*8vm iumva2hat the distance traveled during each successive second increases in the ratio of successiveivugpa.c8 ycm.*e:rp;gl(k 5zv8 v2 m odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a / m9fys*t.jhp:onbr 7p +gu j4ball thrown vertically upward withh:ypoju.* mg p+jf b/nst47r9 a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verticnr 8(zpm9spq x5t.8t uw.brmg 7 eq*j(ally 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 in Fig. 2–18 (o 0v5f1i7q 0vvce dz uf,wsbq34kb)gy5r number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but 531ebcquiy0fk b7 5fq0vv dsw g)zv,4not 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 m tall ma7rsgs8, *2j j+evof(Fig. 2–32). From what height above the top of the windomgre2+fsosa7* v8 jj,w did the stone fall?    m

  A rock is dropped from a sea cliff, and the v7()q.wv;,,ttn l hy p0fo3y 8mxitwp sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how8xw,f) nm7tt0wv t,py;l o 3.(hv qipy high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. bs b.fj:abua4k:v wcz1-z + g*You point the f:wbzskc b4au vbj*+-.:1az gnozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the 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 up ms)qj2slfd8y4*dn4d)b(d b 8 3lzbqr ward with a speed of 12.0 m/s from the edge of a cliff 70.0 m hb*ydz)4lsq ) r dbljm42n dd 8q8(3sbfigh (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 the j/6ofcsg) )5 voqhyr3street with a vertical speed of 13 m/s If theh53sqojc)r6fo /)yvg ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velogxm1i lrd9 y)n8wh 5)xcity of a train as a function of time. (a) At what time was its velocity greatest 1 wxyigm 85lrhd)9n)x? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a funct :)c n)vaveq4 yw;q,gfion of time is plotted in Fig. 2–28. What is its instantav;e )wn :acqv4q,)yfgneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

  In Fig. 2–28,
(a) during what time periods, if any, is the velocity constant? t =    s to t $\approx$    s
(b) At what time is the velocity greatest? t =    s
(c) At what time, if any, is the velocity zero? t =    s
(d) Does the object move in one direction or in both directions during the time shown?

  A certain type of automobile can accelerate approximately as d47 1,w d4ezph abx7adshown in the velocity–time gra 4b e17d7da a4phdxz,wph 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 acceleratio*on e u,15qj3 lr a/ z/mja-qukv1mz-vn of the car in the previous Problem (Fig. 2–35) whenmr jaqzej1o/v3-u*k -/l,5uz q1 an mv 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 objeru+bt2r5 *awr/d)bj q ct traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for th5obi wokfg2br*032x*. ljstqt1k2lc e object whose displacement as a function of time is given by 202lwj cok 5biblk*g2 x.tos1t*rfq 3Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object/h uj g8rm3jl7h9m xx; along the x axis. Consih j7x; ugj/h3m r89lxmder 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 pr skn.cdyc /x4 va1iup, n*xd,(9e0nm above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2xkd xi n.e1rd(9v0p *uc/ nan,s ypc,4–37.
(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 xcs ocp a0z(:*4 .(wzwotrc a+Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Mw. os r*xoaac c:z4z(cp+t(0w oon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained/ b n)s(ai. 0swnajuj7 by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration dn ia70(nbs ju.s/a)j woes 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 the road below, and his gh xzdmwp+pj57d996 vpursuers are getting too close for comfort. He spots a flatbed 9mj96pgph7xdz +w5dvtruck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collisions by hauling ,e ..jzo;oz-hx vp 6lvf/ik2* ve1ecdthem.*jod.k1i;fz vvzvpeex, c 2 /6loe-h up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth trav yw/gd 0f*w3 l)whlz-bels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from -m/n*c76uear b( mwfc rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is stanf ac m 7e*rnuwmb6c-/(ding 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 diving board 4.0 m.fu v+ih2v: o ,r1m1cywaz6y q 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 whiif2r 1w,+vy1 v :cmz6aquo hy.le 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 7 -gv.zt/ga8me 2kszywh1g -mcl1ysd n;uo2 ;the average speed of a train against thzu.v t g1me--;8wm1kcsga;yo/l7g h dz 2ny2se distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving for fish. 7rwebpb *1 swp-)vo )h4zy*b bSuppose a pelican starts its dive from a height of 16.0 m and cannot change it)p*bz4sbobe7 - 1)b* ry vhwwps 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:5vhf gcfa*g: a golfer 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, inff:*c5av h:g g case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freighbocak7exez:j hiwr0 u-n1 kp kj7e. 8-:hgx9 ,t train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive startsc- ua:h :ex x18er7b,. p k-whz7ko0jginj9ke 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 high buildi45o kjbtja (vse( *lue:w t2)1kj 9n/fj7iiuqng. A second stone is dropped 1.50 i etv:5wu*f9jo2ni / e(t lqk)jj7kj1ua( 4bs s later. How far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 j 7rh* e63(x:sahaafq 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 main*qhsaj6 7fha3e rx( a:tained for the last lap?    km/h

  A bicyclist in the Tour de Frzfmt9 jzh b*j)z-8prrm q 8s+:ance crests a mountain 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 acceleration m98:j+ -z)fztbmqz*p s r rjh8(in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. wjtf 6 4uajdk4 (rhn7(The first child can bounce up one-and-a-half times higher than thfhtua6kjwnd rj4 ( (74e 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-lo b 3ktxtg*ha.k/q,cldh526 d2+nsfhgng train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it.2dxnfq h2/b ga shtd*5t63ghlkk+, c 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 wittp 1g7xtk 9d)dd2-x45hnsvgbejd)g6 g4mb 7oh a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behide4b)ghsb -opm6 tv dj dtn1x7) 2xd49g5g7gknd the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with a2(. 9w9oxt:kj1umra.xcbl rf n 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 a traffi;x0gxuqwv.z 7p,6 exxc signal, and the speed limit is 50 km/s ,; xw67 p0q.gxeuxxz v. Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 km/hf 2n-ar oqsdmz1hc2:2mfz0 1g takes off in hot pursuit. The police officer catcd os1-2r21a q:h f fg0zz2mnmches 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 roo qsj 82t5sc-zwf of a building; 2.00 s after that, a second stone is thrown straight down with an initial s8 2ss5-jwct zqpeed 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 akz/+hljd8symel 7*n 8o.35b tv y0o wot the 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 after 4.5 s. With what initial vel 0odw8+jte yko/3zly lnbhm5os7.v 8* ocity 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 tac6avi(. )3uzfj 1 i;geql/lhqke 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 pelaqe q lv )1g6.fiu3z(/;jich rhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to 1mq+y;qjch6 ap 8 l.ypsgg;dk*5caw5send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt trh6s clq a1 ;cqp+m5p5 wadj;gk.gyy*8avel? 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 tha(jy/j m.5.j zbvbeqj2s.6ynjc il+n-n Joe can. How many times higher will Bill’s balsjz+cjbv/2j5 jq6. e by(n li-n.mj. yl go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground b),l 8ve akww.jelow 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. Wwk.a ej8 ,lwv)hat is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular b907txl6p h9hun ccg5v*)clxnuilding 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 much difference dopgc 96* h7c5xhu0xnlvn )ctl9 es the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the posi uie,2z;1 xoxvcge8i+tion vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highes,g2z1u;oicxi 8e vxe+ t instantaneous velocity? (e) Which bicycle has the higher average velocity?