Does a car speedometer measure speed, velocity, or both ypl2.6ib(ffzhf,rf a1k2 hjp w*p+s:?

Can an object have a varying speed if its velocity is constant?j(y; hg+py-jkjz2 *d3d zj eh+ If yes, give exampgj hy e-d zdjj(32+ khp+j;*yzles.

When an object moves with constant velocity, does its average velocity during n5z(6lwv9x)u x xie*nany time interval differ from its instantaneous venl 6uwvxe9)5xz(in *xlocity at any instant?

In drag racing, is it possible for the car with the greatest speed cross lpqcyy:f (p;0ing the finish line to lose yplqcfp( :0y;the race? Explain.

If one object has a greater speed than a second object, d/ x1rgls2eq-g oes the first necessarily have a 1rgge/-2s xlqgreater acceleration? Explain, using examples.

Compare the acceleration o4c f+n0 xsqj6af a motorcycle that accelerates from 80km/h to 90km/h with the acceleration jx+4f sqc6 an0of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Explaq:1cupt,w zr 51ww0,qa vvbn)in.

Can the velocity of an object be negative when its acceleration is positive? Wha) y0r tcscvt5:0cyt) rs:5t cvt about vice versa?

Give an example where both the velo ) oi hhnz1. h8r(6ej/bdo5ovlcity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling wi rnhysg7; k4-mth 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 acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explh 7-n4sgkr;ym ain your reasoning.

Can an object be increasing in speed as its acceleration decreaus(hhu i1f1gicu- v )1ko6:tcses? If so, give an example. If not, explai -u6 :s)1cuhighi1tufkv ( co1n.

A baseball player hits/gax xwm74c n9 a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher cag97mncwa4/ x xtches it?

As a freely falling obje0z28sjgosvo l d7 3lc4ct speeds up, what is happening to its acceleration due to gravity — does it increase, decl3jcl0z sgos 8dv24o7rease, or stay the same?

How would you estimate the maximum height you coul*yc e3 x9*pqodd throw a ball vertically upward? How would you estimate 3d*pcx*y9qe othe maximum speed you could give it?

You travel from point A to point B in a car moving rkn6heuww g 7cx-0y3 9-s:6/phozewjw )(he kat a constant speed of Then you travel the same di:owj/wheek9nx6k h h)u- -p zswg6(7w3yec 0rstance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical4hv4 2/r chcdry hf3t ymi0ez*yw.ti1i785 fo 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 between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occzy2vhc4* 8ed1 /3iwh7mhoifr t y0. t5 rify4cur at equal intervals?

Which one of these motions is not at constant 32 tb11qm3pxai 0aczwacceleration: 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 on a1 3 3qa1xtw0zbp c2ima table?

An object that is thrown wv;n 7yktp;d 8vertically 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: The acceleration due to airw;d n8p;yv7t k resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time:-(1n loyc djrh +ekm;? Give roh+:y-1em ;(cdlj knexamples.

Can an object have zero acceleration and nonzero velocity at the same tim9:e-jd-z 8qsnojgg * v/tuyu 6e? Give examples-gtu*s: -o/nz8eu6vyqjj d g 9.

Describe in words the mdk8h72 zerw5*uh 5e+c ru ptr8j1r 4axotion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to dupkjhr 7r4 r2t8 ruce51+zu x*h8we5adplicate the motion plotted by walking or moving your hand.]

Describe in words the motion gg p n/1/zn5h (4o z;o7(l/bwq wlkcfnof the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25yv; 0wz-z * b iuun,-3vv*qvdo h?    km/h

  A bird can fly 25 km/h How long does it take to fly 14do o4z 0i*fz is9:iy xo*tq;v5 km?    h

  If you are driving along a straight r-q-u let e)rp9k)u2 wuoad and you look to the side for 2.0 s, how far do you travel during this inattenti2u)le 9-uu rt eqkw)p-ve period?    m

  Convert 35 mi/h to lp,dfotn5uld bp 2 h clf/y6s.*/7y/nyaf68g
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from/o sbf-h:+p 1yx8yfi m $x_1$ = 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 schooeuh8at /,fj,rokp2u.1ie kzd7 4a05cd:wdot l steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 h, 05aafwk,:do/e z2i4otejtu1r.pd dk78c u hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash aj4: d xqvz*+qrfg g27kgj.hu0nd the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, es7j q2ujf+*hk.0q4 xvdg:ggrz timate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a to 4cnrju njuyup 4hx71*o,1s 7ytal time of 12.5 min. Cuj4 su 4n1,1 njcy7xo phyr*7ualculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight liner bubd 2y)q9h/um luek*w0f9. , moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway 9 ) 0.md/bueyb2ul9krqfhwu* 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 othe7l;sn9h f9az. 0 aglsar on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If th 9sa.fzl s7;l ag0ahn9ey 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 traveling Hok,ob qkeo2:;i5z jls7 w long will it take the car tols;e2 7bj,kiq:zo 5ok reach the truck?    s

  An airplane travels 3100 km at a speed of -myly 0:l)rbr 790 km/h , and then encounters a tailwind that0r:)yym-lb lr boosts 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 anga v/ c(0t6(k zpr)am s.bvin*d average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch )b/*g(k.mctza 6p(v0i a srvn 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 thr tlw*h:q9 b h93rw7f: -eyemke 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 reler- 79w*rl9kfhe:h3b yq w:te mased from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates f,m1 ,hr0w6ln pjduuho0m y12 from rest to 95 km/h in 6.2 s. What is its average acceleratio0m1 omlu , 0n2 ury1dwj,fphh6n in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates fromlnb .kr//( pxn rest to 10.0 m/s in 1.35 s. What is her accelerationk/pl/r b x(.nn
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a par338h(3msd5fgft qp2v hkx v1jticular automobile is capable of an acceleration of about xgj3vfth8dp( s3 2mf5v q hk13$1.6 m/s^2$ 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 brakes /0kd7s okkrs61i qh.zand comes to a stop in 4.0 s, what is it/kq kzhs6 7 o0ki.1rdss acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from r1( voln7y oyi( bi5:txest 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. Dioiib ly5( vy:7t n(o1xsplay each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What pzinad+8k ;7i g zwmkv:tl:+9was its acceleration? How far did it travel in t tzi: apgndvw iz k78l+km9;:+his time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a l7,hmugczur 6v8qj6 20nor.x az ck8:distance of 85 m. What was its acceleration, assumedzv 68 mc0xuhg ocu,j:6 .nrk78r 2aqlz constant?    $m/s^2$

  A light plane must reace,ji( yr n(xdm.9 ukf6h a speed of 33 m/s for takeoff. How long a runway is needed if thu ((9me dynj.r,ik6xfe (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of v+sk1 iftn-u/v v 4+omr9uw5be96sorthe blocks to essentially top speed (of about 11.5 m/s) in the firsrfruo b 45vve+ws-k9uvs nm/9+t16 oit 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00 s. How far t1 r:oke9zf /jj8(ug zdid it travel i8e(1g:oj/rk fzt9jz u n that time?    m

  In coming to a stop, a car leaves skid marks 92 m lon5y/q(uo6di1 :waw3 )hp dxrc4y(lwwm g on the highway. Assuming a decelerac ohw:ru(4ay5wiw/ yw6p3)dx mlq1 d(tion 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 gnz2 c ,n ::bx)e0k;qsru 0lhqcompresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi rg n,lzqh be0s0 u:2c:;qnk)x on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initialrf;u9i:h,vf 5 f.i:+xb q 4jup.tffcs speed of 95 km/h and human reaction time of 1.0u. ;f.b4fcj + t: fi5,sx9vi:fhfprqu 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 c(r)ir,0ogc) ,5kqh p*np o-rl-pk m qstopping 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 trkdt mu ,7m:n/kuck going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can acdutmk:m/n7 k, celerate 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 th3oka2bx*ow9u an 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must tho ou*2kb awx93en 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 intersection(:n:s.jygjx e 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 jg:x :.snye(j 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 z5n 03k/nhvdi. It hits the ground below after 3.25 s. How hig nnhkd3 /v0iz5h is the cliff?    m

  If a car rolls gentl 003( dzpclvvgy ($v_0\,=\,0$) 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/s c4-+/6ccd+bxaf wafu0 j l adclfep;hx( *1)q
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s po3 ) efpmfg/tyh1kw89ruy 2 +after throwing it vertically upward. With what speed did he throw it, and what heighthp+g91 3 8)w/etfk2r moupyf y did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of ru2ju i+)6 k4gjqulhs4()mehgravity. Draw graphs of (a) its speed and (b) the distance it has fal(4e)4lur2g)6ju +u hihkj qsmlen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. Atjp mp(jhhiv *;9 71ysx a height of 125 m above the Earth, a package is dropped from a window. How much time does m (sphi1hj*pj9v7 ;xyit take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show thl1ka(g +q+hd nw*t q8bat the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galile+tq8 k1gnw* abq hld+(o. See Figs. 2–18 and 2–21.

If air resistance is negle : q/umyb 9gwrkp62w,gcted, show (algebraically) that a ball thrown vertically upward with ar/y9q :6kgb2gw mwu,p speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed ofda0tmd;w i*85vd nftn uo).3h44da 12d jqsfk 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-(3gk.jop/ bd0mqvo e each photoflash of the apple in Fig. 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 ones at thekv0 eo.m (b/p jd3-qog top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tfg7e/xm3ry;q y7:kz kall (Fig. 2–32). From wkx7ek:7ryy3m qf;/ z ghat height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean iqdaiz7 8 )fc2g6 ud72l;bd-q-besqxgs heard 3.2 s later. If the speed of sound is 340 m/s , how high; uqg) c-islg2b dqbe7d 782d-qf6zax is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard streamm-wk f0,/ ( lals;jfwy of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What ilmla,w - jsy0(/wfkf;s the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s unv 0h8s/xf) oyqi5 elh9 *9 vl*bo(tqfrom the edge of a cliff 70.0 m hi89 *xhooq uvy/9q0fbel)s ln t* vi5h(gh (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 upweb 1*:3+ix 0j*m xeu.sdroo5jf ptq o2ard by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown exous1tobx d+pirj5qom2 3*ef0.:*j 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 timen q5sn(5ap 1tp. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of then5tpna( 5ps1 q acceleration greatest?

  The position of a rabbit along a straight6;7j 2uzi fkwr tunnel as a function of time is plotted in Fig. 2–28. What is iu7z;r k2 f6wjits 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 approximately as shown in thef vcg9tr /t-j:-lc c vui:ep4hzz 0.-s velocity–time graph of Fig. 2–35. (The short flat spots in the -9evp4- zvgtuz0 ci:rt/ lh:s -cf.jccurve 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 accelei-2zo / 1.jqo7j; hg8hed5xt flqm-txration of the car in the previous Problem (Fig. 2–35) when 82hl7hq.z-m; 5xtj1djxt -ie /ooq gf it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled d:.k:39fjkgd) ,8je umyopn wzuring
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph fo:1xkw)t hp4 6l1 tg9qtb1sav ir the object whose displacement as a function of time is gis4b1ht)1aqtpk w :69i xvg lt1ven by Fig. 2–28.

Figure 2–36 is a position versus time graph for3 qb 78azm8 5h z0;xxxuc7sjqn the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or nc8s h 7u8j7x3q0 m5;zzab xxqnegative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-v9. +ywqyqf h- )vmjn*4ipd7bstory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m befon7y 9f-vq 4h+mi q*vyjb.wd p)re 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 tp n37vx,e ilq,o gravity on the Moon is about one-sixth what it is on Earth. If an object is th3 e,l7qi,xnpv rown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly ,k1/m) i,qs,qprub-gr ra+x3k h7khlconstrained by an over-the-shoulder seat belt has a good chance ofm,-lsk/3 rqr,kkxgbh)i1+a , q7 uhrp surviving a car collision 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 ;3;qhnqdde)zn- we y)m above the road below, and his pursuers are getting too close for comfort. He spots a wezq)dnh3n) ; e-;y qdflatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many 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 c:cmqa kqn, r3ic8ro42ars for front-end collisions by hauling them up on a crane ann qim 4k,2: ocr83acrqd 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 trav0ys.c3 p refm3ikr-n.els 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 read2ex,g zpsxdl+5, 1jiy9eo-y ):g b vst. 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 worke)gx ,zdvle xyap2+1jig ,5 beyd-o:s9r? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a deep1rmv/ dn+lr6n pool. The perso n+nvd/m1rlr 6n’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 system, it is necessary to balanc/ 3q ujt0sar1 9s7fd 8k-fvospe the average spe0q3tpfso7a-jfrs /8sdv91 k ued 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 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 w7ohokq ;x 6pi+ings and free fall straight down when diving for fish. Suppose ok 6hx7 oq;i+pa 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 surface of the water.    m

  In putting, the forcv zt.0ue pea2f)-.w4n 0t hjene with which 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, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates co.w uv0z en2atj 0.h)4tef-epn nstantly 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 n *myd;9l rzu)freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passezyd)9 um*nlr;s 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 qr*1o4m3+ l c0tni j 7folraf0a high building. A second stone is dropped 1.50 s later. How far apart are theqlf omc jrr4ai70o+3ftl0n*1 stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must averam hmsb )mc8oo/3y 6jy5ni u 2s sdcue27cbm+/+ge 200.0 km/h over the course of a time trial lasting ten laps. If the first nine 5cc emhu)oy7ss 2 y 2 co+6js+/ u3im8mbbd/nmlaps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crestsn l37mdlqz.+a5 cxf-l a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his spzax 5ll7m qf.ndcl+3-eed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampz jac mu7l7twtyed7 )u .cl4+.olines. The first child can bounce up one-and-a-half times hde)uyltu tw.z a.j clcm+7747igher 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.-owr.l.+ox0;4u wcatw 9b5 kscb-s cq10-km-long train traveling in the same direction on a track parallel to the road. If the tra 49w.o; qa kwuwc tbsx5cblo.+-0-src in’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 throwing the y;s,:(r onnsp baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point wsno,(:s n; ryphere 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 an accelerrwy,7r *phe*by7l k5zation 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 interjf +//*whd : ;5qiy mrmxqhzb1section has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving fwxjyr/zih /dfmh* m+q:;bq 5 1rom 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 traveli)khanq/n1uo8uu e84;4y ughr ng at a constant 120 km/h takes off in hot pursuit. The police officer catch hu onku81u;48aqg nu )/re4yhes 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 frvl,9*z hu:6d c hof4kp+ g1oof a building; 2.00 s after that, a second stone is thrown straight down with an initi+,chvdoo l z4u r1k*9fphf:g6al 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. The first stone is thrown f zy4agrod .+onhx+ 5qypc 0q,w; 2t3ewith 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 velocity should the second stone be thrown fro d.n;o5 qczw,3 pe2arq 0xy h4o+fty+gm 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 resistai. p0 aei.yq kwjwxwz 61f.8h,nce, how long would it take a free-falling parachutist to fall from a plane at 3200 m to a1yk,.qp 8jzwawiw0.6eh fx .in 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 belt to send the burgers through m;a nz;8g 3rh0s bl,hma grilling machine. If the grilling machine is 1.1 m long and the burghs h;;8lznam gb03,mrers 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 timapri gm; +fyh71 9oy.ses faster than Joe can. How many times high+yi1y.7 9har p;sm gfoer will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your frien * 967zdb yv*:jwbeg3lj6k znud stands on the ground below you. You drop a ball 3vuj bl n*jwzy:ez7k g 6*6bd9from 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 your friend threw the ball?    m/s

  Two students are asked to find the height of a particular 0yk u2zxi5c2jbuilding using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof o02 ic5zy uj2kxf 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 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. (7wr 2oel4fyf .odb *l s*z.sl/a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration?ss7/r*.lleb2lo 4*yw.f o dzf (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?