Does a car speedometer measure speed, velocityuv ep79v0bhd anw 23*d, or both?

Can an object have a varying speed if its veloc. j54w5 y odby:;iogclity is constant? If yes, give examplel.wc5yi: 4bdj;oy5og s.

When an object moves with coi4 * am,5me)8mg tsnrznstant velocity, does its average velocity during any time interval differ from its instantaneous velocity at any z45m8ng m)* raetms,i instant?

In drag racing, is it possible for the car with the greatnv*e 36r*(3 nmpb bgy rjg,n2gest speed crossing the finish line 2nypjrbg3 3bg**m(n,nrv6g e to lose the race? Explain.

If one object has a greater speed than a second object, does5tgmas* qh p)0 the first necessarily have a grea5pa tgqm)s 0*hter acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelergptdm+( 6;kty ates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from retk mt(6+dyp;g st to 10km/h in the same time.

Can an object have a northward velocity and 9ps61 jomzrodf+ k7 2xa southward acceleration? Explain.

Can the velocity of an object be negative when its 3vj:3b l2cc ;wy+s6c b(pabiyacceleration is positive? What about vice verb; cibylc3wj+:2bv(y3p sa6c sa?

Give an example where both the veltqfz.mswdu m +:2h* 6kocity and acceleration are negative.

Two cars emerge side by side from a te,mp e5w3c4h4s,y k x6 zmh5otunnel. 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 , e pktzc5hxm5o4w hsm,46e3ykm/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 depqtxs,;ue+wh3j.1h ddc,; jm.x+ k e zcreases? If so, give an je +. stcdew dh;+x,13x u, zk.q;mhpjexample. If not, explain.

A baseball player hits a foul ball straight up into the air. It leaves the 6e hst6ln21 (k7azoambat with a speed of 120km/h . In the absence of air resistance, hoh7t s6( 6aa2 l1nkzemow fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is hnz w6 0ydvy.q t* ):(,j2al aupiluvs8appening to its acceleration due to gravity — does it increase, decrease, or sty6 .tulyvn2pzia*(dsjl,u: q a)0v w8 ay the same?

How would you estimate the maximum height you could throw.fxhe n 4ckt:7 a ball vertically upward? How would you estimate the m7xthnefk :c4 .aximum speed you could give it?

You travel from point A to-q. qf,rb+ks s;kgj 6u 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 entire trip from A to C 80km/h ? Explain why or why rk-+ugs6q ; s,bjfk. qnot.

In a lecture demonstration, a 3.0-m-long vertical string with t(-z36vm8vq 1nfjiz bv en bolts tied to it at equal intervals is dropped from the 3-i(f8jqzvv 1 b6znm vceiling 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 rocd h.7 b2bqt o2(pbca/qr/ p2slk falling from a cliff, an elevator movinb7ob/btp2/ 2(2qpd ac.rqsh lg from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its orig ;796zyinquc uinal position with the same speed as it had initially if air resistance is negligible. Ifiy7c;9n z6u qu air resistance is appreciable, will this result 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 velocity and nonzero accelewdlr20w is9e6.er ee5ration at the same time? Give examples.eli r.5e69wwr esd0e2

Can an object have zero acceleration and nonzero velocity at the ( ( 9lpm7(vcm obvxi,tsame time? Give 9((ovbm7 l ixc(vtpm,examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hini/ 4ya()la ihnt: First try to duplicate the motion plotted)ha i /(n4lyia by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. 2–29.65ofmnu/3)iv jj0bp y

  What must be your car’s average speed in order to travel 235 km in 3wsi +.jzpm72d.25 h?    km/h

  A bird can fly 25 km/h How long does it takeu8 0/ji;* v tgy9nq2gxj hg/jv (lm;ct to fly 15 km?    h

  If you are driving along3jq+e3 b6 uk fijm9zdb k/z3p3 a straight road and you look to the side for 2.0 s, how far 363j +p3kf ei/qk 3bzbzmudj9do you travel during this inattentive period?    m

  Convert 35 mi/h to pckz1 jlw:-k*
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from rg41r(oiv zd m.ad+)n,. ey*rkun ;ol$x_1$ = 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 steaowwc nbm. bp2q06g-6ndily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h Yo-opqg nmb w 6nc620.bwu 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-thum6 y ff/fv t+/xoxt.oa(n-dr n9b, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, vtfxxot / . /n+yn(a drf69o-festimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a : sy *c l-8fy22an .hdc(sqbhdquarter-mile track in a total time of 12.5 mins q2.bydasndy(h h2l* c:8cf- . Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its tra(hmk,qg+o8 n1o6n kgyiner in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculay nqo6k mk 1g8g(no+,hte
(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 p9)kh/ keyi;-q6 zt; qwq;h4kj g uca4yarallel tracks. Each has a speed of 95 km/h with respect to the ground. If they ar; 4yg;hiky 49c;keqkh qwu) -at6qj /ze 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 k3v4 dlh9x;vgtma y;: How long will it take the car to reach thea mg khdyt :34vlxv9;; truck?    s

  An airplane travels 3100 km at a speed of 790 km/hz+ahb /8y)ebu db8* uc , and then encounters a tailwind thateuh8dbab/c* 8 y+b) uz 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 and a3h *dw hg,)yhrverage 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 break, and the return 250 km is covhh3rh,y) d*wgered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at the end of a bomy7vhexse46ujb )9 1o9bw; miwling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s. e 69sex hj4v1m 9w)mb7biu;oy    m/s

  A sports car accelerat-r0mudbd 7x5ces from rest to 95 km/h in 6.2 s. What is its average acceleration dmcd 7- rux0b5in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. cjidnx40g qs,: y3ne2 kcy6q;What is her acceleration 0k :n4 3ji e2cgq xscn,6ydqy;
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobiled77.y og n,mnq is capable of an acceleration of abouty.7g nd7oqn,m $1.6 m/s^2$ 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 brak83kaxg3sh+iq es and comes to a stop in 4.0 sgi +q8xks3h3 a, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 c.g*u7qp-m )b7)zpl wi idg.hand moves in a straight line, is given7 .pq-7gcp) wh i* uz.d)bmgli 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 Table and on a graph.

  A car accelerates from 13exsu e2 a7j :(gbnlmg+g6 x)x+ m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assux:+xggxbu) le n me6sgj+a7(2me 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 hr04ww 6 b8q6vxa6rsa2su h y1acceleration, assumed con6axwysqrv68a1rh bhws6 02u4stant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway is4 doh/-c umo6yq7 ygi9 yg,ih3 needed if the (constant) accel 6goodch4uy/gyyh,7mq 3i9i-eration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of 3 s.s hip66d(rdpmv;9+fx p h 6myzs;ho0;uvjthe blocks to essentially top speed (of about 11.5 m/s) in the first 16mdhphix 96r3mp(zh pfj6 sv du;+ 0s.y;s;o v5.0 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 insi,iu gb4 whh,xd42hw.ox v/ ) 6.00 s. How far did it travel ini)/uwg42hbd .i hxo,,4vwsx h that time?    m

  In coming to a stop, a car leaves skid marks 99fiuf0 p8v m:j2 m long on the highway. Assuming a deceljf8v 0fp :mu9ieration 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 -bhy:m.w iok6hsilxr3q/c- : the car compresses and the driver comes to rest after traveling 0.80 m. What was the average accelerxrw -i i 3qmblosy6c/:k-:hh. ation 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 fory7e xu9cyl mt47z(pf0b844yvj: e nil a car with an initial speed of 95 km/h and humantcv8ex4bniz:7f0 l94ymy4u( p7ej yl reaction time 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 xq esuxm-5)dak nl p/ue+ev/-x b+;;athe 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 highway. The car’s dre/lr m.5fv nr:rld/r7 iver looks for an opportunity to pass, guessing tha/mdrfn.llr75rv e r:/ t 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 2l(jsw1 tj ei n.bs jwtas+7zw)u:2jnx/ vr6, the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acceleas).76t+ xjv iujs, lj1tn rn2b:/ww j wse2z(rate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 3,728yrs 4tmm mv*a9wu myxiukm/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turnrwix *u3m 8ym94sautm, y2 m7ving 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 wp3k (5 n tidrwmq fr.9a gj7ul:/o2i(a cliff. It hits the ground below after 3.25 s. How high is the r t/ina5i(7fou(dm rp 3w.jglq wk 2:9cliff?    m

  If a car rolls gently (pk*nmiod6 0h: eme4/b k,k2uyc7+ cdu$v_0\,=\,0$) 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 u8etent9 ) (jlsx8.rax 3pcdsrc6 1v,cp 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 after throwing it vertically upward. With u ui5ril8v7j ;what 8 ur ul;ii7jv5speed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Dh 3ezm8xzf4l)ai )ks5o1r / umraw 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 resistancoeh)mi zl1u84 rf )s5az3mkx /e.

A helicopter is ascending vertically with a speed of 5.20 my0rwr15 yhug2/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it t52ruw1yr g0 hyake 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 that the nlbd4 2rdu9o6k a9c)vdistance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown bl69d9c2 bokv4 )raundy Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (/y uz9s+hr r8*)6schwc z8oed t.zwc(algebraically) that a ball thrown vertically upward with a scw( 9 r/+ rzz)e88tu.chc whozy6d*sspeed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speedaiq3yemqh;9 d+xl *-b-oyyl7 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 (or nuln cuto9tc *50mber of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not then05cl9tt* cuo 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 g.kg0 5r (ys+ft:gtv r(Fig. 2–32). From what height above the top of the window did the stone fall?gg :0.vs gr(tyr5+tkf    m

  A rock is dropped from a sea cliff, and the ssgm4 * o9rw s9-1piibround of it striking the ocean is heard 3.2 s later. If the speed rii rg4*pw1 9sbsom -9of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard s./4c yo;q x;6aypywultream 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 is the water speed as it leaves the napy/cyy u4x qo;w; 6l.ozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 n rp7/tle7w3sqn g12f m/s from the edge of a cliff 70.0 m 3e7sf1 rqgnp/lw2t 7nhigh (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 win8 bd66 aweie3uu2 3jcadow 28 m above the street with a vertical speed of 3dau8ecej6w32ib a u6 13 m/s If the 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 vfi2i */w01v2z*7djo4ajqbl(i xnoy zelocity of a train as a function of time. (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 coiol 2i/f1a2nyi *qzj074o*w bvz (x djnstant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel ,4v aupo2 wgxx o7y32aas a function of time is plotted in Fig. 2–28. What is its instanx o4x3v2upg 2awy,7oataneous 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 i 55ms+x dorbh(n the velocity–time ghb md(+s5oxr5 raph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car iz 3 hlx03vq-n. h.lvs/.fkyijn the previous Problem (Fig. 2–35) w3 ihh0.f/q3 nvls..jv-kyzl xhen 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 tra9v* uhkcpv .8ye ,9ffry+p g;nveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displac6bn hl-y w9 ,yb87mbwxtyqu*7ement as a function of time iw8b x9 nl,yyb6mtuq7bh wy-7*s given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motionh l:j,3 9oq6ij -sdiiy of an object along the x axis. Consider the time interval from A to B. (a)i, d l9y6j3hosq-j ii: 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 four4 .fzpi0q6n.ipp*, l ku egyo7th-story window 15.0 m above a firefighter’s safety net. The survivor si*q6kg. e7 yfn.4pop,u p i0lztretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to grav)xq0 afa,:tzh +nn3l/ qhs5 pxity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many tf+ha)q phnsn5:xl0 3zq /,axtimes higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat beu +jan4t (z3a5)h jgn+zvoqh7lt has a good chance of surviving a car collision if the decelerag )h+( zntj4+znaj5o7vh qua3 tion 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 the road below, and hiih4g 5o)m()v:i v/skmz ad00 v7nhr ;u 8gfjips pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of ijup0k:vm0z)v mh5(rdso/; a hivigf8) 74ng 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 cgr1sc/q b(xe.zm; ug ,s;bga7 ars for front-end collisions by hauling them up on a crane and droppiu b1emq.,/ zxgg a7gs r;bs;(cng 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 travels aboutx )0 aiomcr-*s+, wsgl $10^9\,km$ 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 aauy6ws)5 s ;p - nb69ofrmdh po-:p/c*wmio4gcceleration from rest. The front of the train has a speed of 25 m):wg4osuwm5 omi6p9r; p y- dbc/sfn*p6a- ho /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 diving boardhe lj*l6dns 47)d cc ,fis8pz;(p, krc 4.0 m 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 whj)p84 z *csd(nc dpisfll7; hrc,6k,eile 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 thevqcw2bvr; af v pwlj*tqf vetp6/*4g; 6/,s5 x average speed of a train against the distance between stops. The more stops there are, the slower the traigs 6qpva/wwjpt*f;rxq 2fvv ;/lt v*b,e645c n’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 wingso95,dp be s+scdb3aq4 6yun+ g and free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, atsasu4cp5+y q no9e3d, b+6dgb 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 golfev6baw- *rwk 3/f+eudx r strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) iuw/f+w6* ba-3rkde xvs 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 t;0 9qp7 h5pjbw )ndkw9i id4wwraveling at a constant speed of 6.0 m/s Just as an ;njkwp0 wiw d495pbd w79q)hiempty 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 high building. A second stone vap+6u k)d7cq is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of 1c6)7vk p+ duqa2.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trial lastio+ r1s8qvfai,jfxj) i1p5za * ng ten laps. If the first nine laps were done at 198.01 +1 a*jzi jr a,ix5sqf8fv)op km/h . what 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 8* w5uy3hq)-y voegq p18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleo8qh 5*)uw3ypvgq-ye ration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bouncen3lq++8albm;w nim+ d up one-and-a+3mdw8q;+n ibl alnm +-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 a 1.10-km-long train 0i52(s1miyvpb9wisuu 8m e,c 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 take the car to pass it, and how far will the car have traveled in th82i9i( ,5 i smu0yu1vepsbm wcis 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 a3(f hjel;ymow j;t6; v baseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it ; ;yljvme;o3(w hjf6t is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rie49 b2xw;;-b lqcu cp sv7u+mest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersectioxo.m0gr0i u6 dv+vqz8n has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When youi6 +r.o dmx v0zqgv80u 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 constad b0zdlfb-/kxfg85: e28z n zcnt 120 km/h takes off in hot pursuit. The police officer catches up to the speed8zf/c 8z20n-d: zk dbglefx5b er in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second-u/ mt6 uu li)r,hjkk7 stone is thrown straight down with an initial speed of 25.0 m/s and the two sthrlu-,umtj7 ) i 6/kukones 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 p8q7y 7kd 5dbsat the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-fl s7pyk 8bdq5d7oor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air r g:thofhw6t)k 0wsz)4mg of: due)fz)g j :;f8esistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would ))w8)tg )fftmj gh4g zw::hf0;:6 ozuo dkes fher 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 beled+mzih:bvrk 60 u 8wdl ,b,m2t to send 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 travel? If the burgers are spaced 15 cm apdib zh08+,k2b:e6lumv rw ,dmart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.54kfjhd6)zs9n r 7ca t9sb* ly5 times faster than Joe can. How many times higher will Bill’s b6sz*crd l 4s abj5f)9k 79hytnall go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground beloma vqq6/tu:4xw you. You drop a bqqm vxt6 4:au/all from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a pargsy2:+ zzlf7pticular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, tiys gzpf+:2zl 7ming 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. fe +1dnu 9r:7 yfw)*y pzqwn 5au83bsw(a) Is there any instant at which the two bicycles have the same velocity? (b) Which5d8wf +7*fn9u)3py wu:nyqe s1w abr z bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?