Does a car speedometer measure speed, velocigb4 7c6(jkgzs xylwh7 9:t4ykty, or both?

Can an object have a varying speed if its veloci h-ippo+,5iuz 23h: k)xgvdgmty is constant? If yes, give exampleuh2d hik+5 ,ig) :gzppvomx3-s.

When an object moves with constant velocity, f/lq)11 n (qge)vbtm(nqetr7 does its average velocity during any time interval n(/ q1e1e(g )m t)qlnvbrqt7fdiffer from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speecvqtq:1u sc7(t 91wqcd crossing the finish line to lose the race19 qqu tqsvcc1 w:(t7c? Explain.

If one object has a greater speed than a second object, does t8 wn8;8qj; shry5:t8bkdhs oh he first necessarily have a greater acceleratj; rw888ohbn h58dqsy: ;hkstion? Explain, using examples.

Compare the acceleration of a motorcycle thato73v7t7ybv s f kbu(r1 accelerates from 80km/h to 90km/h with the acceleration of a bicycle that ac1y3 b 77stuv(vkofb7rcelerates from rest to 10km/h in the same time.

Can an object have a northward velocxoy qt +kas+,(z2j:utity and a southward acceleration? Explain.

Can the velocity of an objq n qym/tu*5 og.6zoy;ect be negative when its acceleration is positive? What about vice ve6qqm*ty g/o5;zuo ny. rsa?

Give an example where both the velocity and acceleration are negath,h) bvhff;+tk7g7 sa*z+ bcoive.

Two cars emerge side by side from a tunnel. Car A is trave00.jlumyib/gg+rmx+ jj88bl5w gjm 3 ling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reaji+m50x jl+ /lub0jm r3gbmj gw.g88ysoning.

Can an object be increasing in speed as its acceleration dcq+:q.mbp3gf9 v )zzot k o2g)ecreases? If so, give an example. If zpfcot2)g zk 9b3:g v+m) q.qonot, explain.

A baseball player hits a foul ball straight up into the air. It leaves the ba /5c; j3hak1/reyxuvvt with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when thecu hx aye; j/15vr/v3k catcher catches it?

As a freely falling object speeds uh+dv-;d 0oen qp, what is happening to its acceleration due to gravity — does it increase, decrease, or stay the sa -do vndhq0+e;me?

How would you estimate the maximum height you could throw a ball vertically ukl3b p2 w(t9.ibkya)epward? How would you estimate the maximum spei) lwe29b k.ytb(3kpaed you could give it?

You travel from point A to point B in a car moving at a -z1+fo u6u;0xrn6+q ofiirbkwri7 e5constant 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 w f+iurk qz-6oe7n6ibif;wru05 1x+o rhy not.

In a lecture demonstration, a 3.0ut-d0 4e2 lcnus9zzv 8-m-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at eqv uzze20n9d4u8- ts lcual 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 a+xdfbkx- l;k2c*( (vg;s skurt constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops along tb*(r;kl 2;u df+v-cs ( ksxgxkhe way, a dish resting on a table?

An object that is thrown vertically upward will return to its original r :ki+u(o f,ejposition 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 ac(j,rufeio+k :celeration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same time4 dt p+dmlnbg7 jhn6-4? Give exampln-ltb g4+p7d m6jnhd4es.

Can an object have zero acceve zc 7*1js7 dtz+fpt9leration and nonzero velocity at the same time? Give exe779ctd1 f jtzp+s *vzamples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint:oid2: x .zjzye3w cg(tr28 qm4 First try to duplicate the motion plotted by wal.t 4xwj2r3gi y28qzdc:zo e( mking or moving your hand.]

Describe in words the motion of the object graphed is(bi(*tg4hv q se(t(d n Fig. 2–29.

  What must be your car’s average speed in order to fx o yb)+94zcttravel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to ** 9e sq5nu5kh ixy.m)8dx/(xfk gvzz fly 15 km?    h

  If you are driving along a straight road and you look to the sid,tomeos my- (s(2hz b1e for 2.0 s, how far doezm m(hs1oos-2t b(,y you travel during this inattentive period?    m

  Convert 35 mi/h to aa*3/gs a evj8w+ *cjb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball movesd *)q jnrr*zsf7i9uo1 from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km. It then begimzp h7*i/r k9r+s j,mcns to rain and you slow to 65 km/h You arrive home after driving 7mm/sz+c rjk,h9ri * p3 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-th.5f+w8t+l, tqnz inzvmj 7p n*adz5/xumb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miv5p m tl .+zia*/5td+f78jnxn,z qznwles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a q+a jf:b 4lv2scuarter-mile track in a total time of 12.5 min. Calcus4 :bvlf2jca +late
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away in 1 :y7dyx3nlt lej,f-mq9(q-gg4.0 s. It then turns abruptly lyq,j lyn 7d9gqtf m3:--(egx and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. iliczjv j (htlr -u7k40ia8:5Each has a speed of 95 km/h with respect to the ground. If they are initialji807u vl( 4jhlic5k zatr-: ily 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 tru ycmwtrvcx )rrd ;+my*nweb;0e3, 1:e ck traveling How long will it take the car to rebm v cde* rex:+1y,r; cr3;e)0myntwwach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then enc tc6o( 6oahhe0ounters a tailwind that boosts its speed to 990 km/h for the next 2800 km. e660h o ato(ch
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 completeql9dvbm1tu .g:u m /9q round-trip in which the outgoing 250 km is covere lg9 91ud.:tmbq v/muqd 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 endday uie+v00n( of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s(nv +ea0dyu 0i.    m/s

  A sports car accelerates from rest to 95 km/h in 6p./wvl+csfy* pc, -iw.2 s. What is its average accelerat*y -wi l/,p.pfcsvwc +ion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1. ct-4 n4c-fcjz4tla(m.bvet:35 s. What is her acceleration a-m4.4 ncvtb4f(lec z cttj-:
(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 acce -pjyir:a30u68gk - *zpoof mwleration of abou0*- go6 o-kpymr8i fz:a 3pwujt $1.6 m/s^2$ 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 - dlr*(mjl42 br1 pvayit then brakes and comes to a stop in 4.0 s, what is its acceleratp2d *1 b(rma-yvll 4rjion 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 and moves in atz jehd6ob-g5nw,ecb 5ep5k :c7 l:e/ 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.:h dc/ pe,5zc b:b-etjeg5k7e 5own6l Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s *nl:*. :biyce)ap cx pxn2q,a in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceler:ix.ebc a),y pancn2l*px*q :ation.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of :hmn zleeb yw*) *thul9:9n4t85 m. What was its acceleration, assume ezhtlw:b9hu)*9 nt4 : nlem*yd constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s fork1sz02 xtah7ros; yl. takeoff. How long a runway is needed if. ot12r lza7h0xskys; the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks t;txp8 ) 16l qimtk8rp -k o,d)e7*jsqjqwls4w o essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does itqet*7mtwlqs , p;xp i 88j4ojlrs1q)k kd6)-w 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/sc53; mljq eus 18jy +0*rxitd eh;0jvnbdf38o to rest in 6.00 s. How far didij on d jeul3cr *; bq+0dtyx3jmv88; 1h50sfe it travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the 6hqs 9w9x+mga3.jt vp highway. Assuming a dec j6+ .vsqah 9pxwmt9g3eleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 k;4( ihy+h nfqxm/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of +nqx4;i(yhf h 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 stoppie e*vo 1wejt/7ng distances for a car with an initial speed of 95 km/h and human reaction /1eo *t ejev7wtime 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 the stopping distance of a car is:jemz+ t2/ 3u3w/0dop;tn flle3 / vjt+cz sjg $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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 hignbdrz: u;zx.rac-r r wy)9,t 7hway. The car’s driver looks for an opportunity to pass, guednb rr.;t)uy zc:7rrz,w-x a 9ssing 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 30.0y7uzp5 /oe bmbfxe ;9) min. After exactly 27.0 min, there are still 1100 m to go. The runner m7m5 b ;xo)b/zeypfe9uust then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her ca3w5 77fa+6uvdug2l pgjjfaf 9r at 45 km/h approaches an intersection 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 gf9va5fulfd 7 +23a7p jwg6ujm away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits - levye qxfyj/8kc1 y+ xbss1.4,(tdkthe ground below after 3.25 s. How high is t1yqv8y(t-xfd ,k s1k +lee/s4xy .cjb he cliff?    m

  If a car rolls gently (xb8,zbau aha*ev3k8 8ui ;b 4i$v_0\,=\,0$) 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 straigh a(-3t4tuwq2kdfz cvybgn ):-t up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after throwing it vertic6fw( (qzdu n1pally upward. With what speed did he throw it, and w d f16p(quzn(what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravlr fkvl2o-0np2 df.ct7,h nq: ity. Draw graphsrnol, kf2q p2f td7lc.:0-nvh 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 resistance.

A helicopter is ascending vertically with a 7c 2txyff wng9t*v vo-m m6c40speed of 5.20 m/s. At a 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 6m*cv0f yxnmc2-vtg ot94wf7the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, sh61.7r9ewbk vbch )1oo p)ctkx ow that the distance traveled during each successive second increases in the ra.)w9 tcco)p7bkvrkx1b he1 o6tio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, shyr ,rf 6 mklh38u(fd1g00ichub+ae v :ow (algebraically) that a ball thrown vertically upward with a rf8dr0+v13,u0(h fu :b eal yhgkic6mspeed $v_0$ 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 omz 5y4se+ -xfof 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 Figqs bjai l 0sd5nh5bax-3wwti(/ v(r4;. 2–18 (or number of phota q/(dtv5w(0ih5b i als ;-jr43bwnx soflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m a zv 6 ,icyoqxp;76c9n( erja1c 5slh:tall (Fig. 2–32). From what height above the ;c:(an o7ycxps qa,r6zvj6le5 i9hc 1 top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the soundqs.,e f 5t8b3p.esdlk of it striking the ocean is he sf.3 t.le 5dskebq,p8ard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose xz/q/lpy r62q b,2yxp nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear th x y,z2q// yqlpr26bxpe water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s nd gjf(jyfrj:i 69g9+ from the edge of a cf jd9+yg (ijjg:f69n rliff 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the stre6+*m xmob rafozbd7 c,wj 3,jmtg(e-ci9 r.*ket with a vertical speed of 13 m/s If tkbw67g,-(tc.fam,mi9 j dr bo*xze r+cj3* mohe 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 velocity of a train as a function of time. (a) At whatvz av 2fr: ):lwdi2ufk*jq1 d4 time was its velocity greatest? (b) During what periods, if any, wasjl*:z 2fwu2:d va)rfkdqv i41 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 tun0h*eulofh;8n nel as a function of time is plotted in Fig. 2–28. What is its iel0n8 fhouh *;nstantaneous 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 yxj -iwt80n.rn the velocity–tt 8n.w jir0-xyime graph 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 sm6fy*ko)w7 u .dsm8 hin the previous Problem (Fig. 2–35) when ifd m7yo8suk.*sh)6w mt 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 objecf4.f,e e0wlj2w2lwoq lc0b,a t traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t g+*5qxpvcs9va qp1 lm9-t h+mlraph for the object whose displacement as a function of time is given by Fig. 291vpq 95pvc amxs+ -l*lm+t hq–28.

Figure 2–36 is a position versus time graph for the mot2:mwk 5bhm a .+)8hgf5pfd zbpion 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 objeg5:hw p8+kz5b.b)fm apd mfh2ct 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 win6,nh/fnxah)m2pj dw+-6; hbkp ri +lidow 15.0 m above a firefighter’s safety net. The survivor stretches the nf dh+i6 ilpmnkja2+b-h/h)x , 6 ;pwrnet 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 8pjzqcgb -eg t z-/k83gravity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on thgje -bgc/z3-k 8 pq8zte Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a l +*jnoubiw- 6good chance of s +-bl6uojw*i nurviving 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 m above trn3n5gzv(+uneqv( ) nhe road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is 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 vv 3(eznrn ng +(uq5n)it?    poles

  Suppose a car manufact)qq vhrnuy4zxv (uojgm (to4);a p-n+zy/;;i urer tested its cars for front-end collisions by hauling them up on a crane and dropping themo ;r;)xm;younn hz q+4q- ()z/gi v at(jpuvy4 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 l.tay 4o/i0ke.wr2 cn 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 rest. Thug0x4vk.zbo s xz,) 6je front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from whereb) xzu4o0 .,vzksxjg6 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 divinb2udj w (vjd8 y 3afwl*wbby(lj,121tg board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m bel,3b*w1 8 1bwvd(jb2 2jldutw yjlay(fow 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 balance the averagea:as*h.e iku8 speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip inheak.8 iua*:s 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 jp ik6 .evvm)*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, at whatmji v).6 *evpk minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force witc 1y59b yf.xaszz4v8)g xvvn5 h 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, p1xv y5fzz vn98xa5gsv.yc )4butting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling at a co w3pmo.v78 j 5)fcvoe8 dbpe 4rcjio3g2y7) etnstant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from rest and accep2 p5d joje ybi 73v))o84.cr tm3 f8co7vweeglerates 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 pdlcc bz3b ;csx3st);8*pl8a high building. A second stone is dropped 1.50 s later. How far apart are the stones whexp*;za)8 83 tdpls3lc;sb ccbn the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must avexq ttdy7nx, 2gdoxy:3t) v 8l5.7ym tzrage 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be dtygy xxqd7yv tl38z:,o7t 2 . 5xtmn)maintained for the last lap?    km/h

  A bicyclist in the Tour de France cn88c1 m d3zrf8 e jf*(e(d,a rskagaue4oc q*0rests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 kr*( mq8je f8e8sc,oda(z kr a4ge uf10n*c 3adm/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bou88gfq ;r zt/t qj.8cbjm)3swid8:ei mnce up one-and-a- bs88 djr t:q. tj/gm8q;i8mfiz3ce w)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 traq p3b(1i6 vasqveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long ab (3sq pqi16vdoes 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 throwi omo w/hx/3j)zv2ah. sng the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the p h oj/zsahw x/v23)om.oint 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, wrhrue/y 5sl+;ith 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 Figomjo*hje gk :s -8v;/zkdzg58. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the li*g8 -soghzjdkkom vz5 j;: e8/ghts 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/h take 0bwq7-eg 6csm26fs1 o7 r +p g;o*kxgvp9uufrs off in hot pursuit. The police officer catches up to the speeder in 75oq1*g6 vg-cr; 7sgxrow72meup+sk b09uf 6p f 0 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 frdvcojww *a (r t,38;srom the roof of a building; 2.00 s after that, a second stone is thrown straight down with woscj 8 ra3vt;dw, (*ran initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the saqhwn: 7b t(6ulraq2. bme 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 whatuqq.b (lr6b:n7wh ta2 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;pt *02 6vy 5vde jfjtssn08zh resistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, whjv* yptd6j 8 s25;v0sn0th zfeere 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 -ku 4er/-xil s 6p4jjx.i zeovor8/q(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 bxox48j. o/4 v6 kee /qirrs(l-p -izjuelt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times x n .zm xlt) 4it+z ,2(yuxw8caerz3-xfaster than Joe can. How many times higher will Bill’s betnxr . ,3mz+)xy-lw 2ac(8ux xit4zzall go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the grohw -g 7zsr;:1g7 wosqzund below you. You drop a ball from rest and see that it takhs1zrs:o wg-gz; qw77es 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 building using a (7 p, gykmtnj3barometer. 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 does the 07,p( kn mtyj3g.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the po,egmqe *kr8we-k-ox/o*kj +i j)-r ghsition 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(* *k-m kig xe)e-jqr j8h,wk+o rego-/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?