Does a car speedometer measure speexr-jli+cx 2/ kd, velocity, or both?

Can an object have a varying speed if its velocity ipmo0qy sa:9 8v.mp;os.3 j f6ut pauvpj4:bq3 s constant? If yes, give examplespj sa.8p6 f.pa 3y pq su:9m;3otq0v4:uvom jb.

When an object moves with constant velocity, does its ave(pleh nkal8,6 rage velocity during any ti(eh6knpl ,l a8me interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with thei5b.wot)i f0f .ag3fu25 pvgd greatest speed crossing the finish line to )fiaf 3w.d0tp5big25ufo vg.lose the race? Explain.

If one object has a greater ww3rcv dynb*. dp4ii4hhk*4 -speed than a second object, does the first necessarily have a greater acceleratipi.nd ykbw4*vc4h wdh-4* 3r ion? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 84ibf f2 m8ql4ep:qf ;q0km/h to 90km/h with the acceleration of a bicycle that bp4:qfif qq;4 82feml accelerates from rest to 10km/h in the same time.

Can an object have a nca,g2y8oo -oar1 j88f:fgpu ;kdaok9orthward velocity and a southward acceleration? Explain.

Can the velocity of an object be ne/3tn ucofg 6f4-p+pyf r9he.b gative when its acceleration is positive? What pgbf f3r u/o-+6chpfen 94yt.about vice versa?

Give an example where both the velocity and ) bdeyl6 2wnb;acceleration are negative.

Two cars emerge side by side from a tunnel. Caz.emi 9 avxvvx1 19oo)0xx e3fr A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the oth911 e.ex3vz axvoi vxf xmo9)0er as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases?xmgb+ zl 7lw,l3ver:3kxg: ( p If so, give an wvxgb ,7+mlle3rlz( 3:k :gxpexample. If not, explain.

A baseball player hits a foul ball straiw1q4 ud:a7 e*2hocuxm+mib 5z5b)sdl ght 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 catchasu41ub *l2moe+zhwdi7 qb5 cd :) mx5er catches it?

As a freely falling object speeds up, what is happeninl/q-zz. q rwcn;23ty * u(fwweg to its acceleration due to gravity — does it increaswwz-r qcf lu2y/.eq; t(z*n3we, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vcmg-gc cz 1s38d2.ahvzg((hcz 6r/ io ertically upward? How would you estimate the maximum speedvd-6czos (h3r8gagc( zih 1gmzc./c 2 you could give it?

You travel from point A to point B in a car moving em7(:y tjm) ll/uvk4jat a constant speed of Then you travt v(mu74/)jl l:k mejyel 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 not.

In a lecture demonstration, w)jazd -l2pjts* +c7v a 3.0-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 clicj vldj tz+-a w2*ps7)nk of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock fallis.z xi8hybers (gf f 0w:y;d(3ng from a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting wszr (8g0(x.dhybff3 ise;:yon a table?

An object that is thrown vertically upward will return to itsq+2 domm2+ jbn original position with the same speed as it had initially if air resistance is negligible. If q n2do+bj 2m+mair 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 z je.m *ovxm6)cero velocity and nonzero acceleration at the same time? Give 6emmj*xv)c.o examples.

Can an object have zero acceleration and nonzero velocit0-) 8rqrpvx6 al* ;ixmfxvxd00vrho 1y at the same time? Givev* la- ix)0 moqrx0p;0d rvhfr1x xv68 examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, etc. [Hintbz o6)eiaubsld*3a: g w1:t6 g: First try to duplicate the motion plotte6)iueb:a lb3wg a:o6 g z*t1dsd by walking or moving your hand.]

Describe in words the motion of t fqqtd0:8+ cjuoio ,x-u30wv bhe object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 h? fs*qy6om t(2yc:r2v e    km/h

  A bird can fly 25 km/h How long does it take tonf.*ns4lt a8c fly 15 km?    h

  If you are driving along a straight road a qg.)vu v-yv1snd you look to the side for 2.0 s, how far do you travel dur)vgy uv 1-qv.sing this inattentive period?    m

  Convert 35 mi/h to f7 dd.kfe vfa-6j,u r/nglc43
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fo*b)ztqq *8bx*b -c1-8tvhqy e2 mtndrom $x_1$ = 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 beg 1wg,2up7r un9ypra.s. s6mwnins to rain ar ,7pups.gw6m 9y2s.nr1w n uand you slow to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning flash aj;3 l8rld-mgand the following thunder gives the distance to the flash in miles. Assuming rg-38m;lal djthat 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 r1/a mzj)e vwj)0*sf paround a quarter-mile track in a total time of v/z0 j)p1)mwajse rf *12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away fd ql (r3knql0 ym:cyso1m,0j30tw5gin 14.0 s. It then turns abruptly and gallops halfway back inofjwq0 c ,r:gl3myt3q0kd1 m5(sn ly 0 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 othr(fc16 z; 0 ybayl;llt y7st2ets.-fjer on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be tf7s tsf .l;yzrlecat;01yj62y b(-l before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travee; z)dmvwk3 h,ling How long will it take the car to reach the truck? 3hm;ze )wvd, k   s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a taic u+xto qgy89/u wgb09lwind that boosts itsx0tw 9qyu9cbug8/ g+ o speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-trip ikn;,y/ pl66tn- xpus6iriq.z8 pe y1pn which the outgoing 250 km is covered at np; x.ztyq 1pi/ep6si ,yrklu6 8-p6 n95 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 speedxgbs1c./ di2)+vsafl)n e; k w hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his 2 wif)svgsb l;1.kn /a ex)+cdhands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its4 zu7lf3mowzaq zou6cj/v(41 average accele u 446mozo 3zz/lcvu17a (qwfjration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0a k +a.b)z)mkr9zxs q) m/s in 1.35 s. What is her acceleration rxmas z9+a)) kzbqk ).
(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 zlq ao2q,dx0 wd20xl/leration of abouodxqz0wa/l 022lqxd,t $1.6 m/s^2$ 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 7k9c* xaik(a4mn+x hhit then brakes and comes to a stop in 4.0 s, what is its accekh 9xxcn ia(4 km+7a*hleration 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, wof9 ugn 31euukw7+e/shich starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b)ogsfe 9ek/3unu u1+7w its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates fromt8ov.i1 dhnor4 k3+5 q1ku-smw y;tu ye,xf*j 13 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travesf3y,18odtt4yq1 ; *x uvhmj- ikon.+w5e rkul in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distan z(unfz2(q+3yfag: lqce of 85 m. What was its acceleration, assumed c +:3azqfguf l(qyn2z (onstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runw k6w -aefzv7/g-q9l -tf yvf)gay is needed if the (constant) accelerafvw-gk/-ez7t aqgv9 f - 6yl)ftion is $3.0 m/s^2$ ?    m

  A world-class sprinter cmc:* mim8c3jx 3w1nbqr c 6k2ban burst out of the blocks to essentially top speed (of about 11.53 x1n:rwci bmmb j68kq3c2cm * m/s) in the first 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 n v/)oaz s0v/ qu1*ttt12.0 m/s to rest in 6.00 s. How far did it travelo) /tnv ta/s*q1t0z vu in that time?    m

  In coming to a stop, a cj 8mc h(rj4uz ;1i2raq7uywf f*q61c qar leaves skid marks 92 m long on the highway. Assuming a deceler f 4r1c a6qr 1*mh (qqwuyujf8z2ijc7;ation 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 c 9a5okqmao w-iin70 xr/zs9 03a: vyfof the car compresses and the driver comes to rest after traveling 0.80 m. What was the aver ya0ocm i k q0i9 a5/-vsw37z:onr9axfage acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed rh4c4l ;)hvc8cgxn l:of 95 km/h and human reaction time of 1.0 c 8)hxcl4g4hnr;c :vl 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 stoppinc1lz*fpyn2 :r g 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,oj i.onekk,7sg; hz - on the highway. The car’s driver looks for an opportunity to pass, guessing that hsi-eokno 7 h,z;j,k.gis 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-mb r ln6x2)z).,lg1f l9odadh.zt)q io run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must ttrqb )z9 ..olx2a zll6gddi o))1f h,nhen accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her cars+fn;vcv n8wl 7i, lrm rma+1*l*. tyv 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 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 intersectiola;w ltrv cfn,+*i*mm78 ly+ rvsvn1.n before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground belo: vblqaw-4(x hs erf*19ql;new after 3.25 s. How high is thee fvl9ehx-q1b4 (r :lqw;a*ns cliff?    m

  If a car rolls gently y + yaflnwon(e:32k l.*6ap ss($v_0\,=\,0$) 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 intolc u -.vg92mqz:tdyxt,n4cg * 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 wha ptnb8uyj-9+i2g+fnwgyo:g b1 q.ue) -* oqeot speed did he throw it, and n 9p q+b+y1o-g)2i tee jno:qgy*ub- wu.g8ofwhat height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw grapbzsm1b0f5i3gqj,qj .hs 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 resistancq jqmbj,g5i1zf. 30sb e.

A helicopter is ascendyb qlk 8u,8ed8ing vertically with a speed 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 tyd 8 8q,8elkbuhe ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that thi v)bk + xi10gbj+e;xee distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Fixb 1g+j b+)eiiv0xe;kgs. 2–18 and 2–21.

If air resistance is neglected, show :xxu.7oe5v r e(algebraically) that a ball thrown vertically upwoerxv: 75exu. ard with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward wit3lsdz tyv)u6y e7o2vw89rmq- h a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflaq5o7uvrq s-bf )kz0 9ksh 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 the top.] )u5k70q-fo9vszrbq k
T =    s
   flashes per second

  A falling stone takes 0.y rp;q8lpk4d7 28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the stone fal dq;4pl7r py8kl?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oce(*:l by+vjrssvp *l 4jan is heard 3.2 s later. If the speed of sound is 340 m/s , how h bj4s ps v+(*:*yvlljrigh is the cliff? H =    m

  Suppose you adjust your garden hose nozzle fowq(8j6,wt4q*.k q n.jht eumfr a hard stream of water. You point the nozzle vertically upward at a heigtj8w u.ntj q.4m,( ek6*qwhfqht of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 mk3-,;mkuzp,t uaxdqqcc87o - /s from the edge of a cliff 70.0 m highd,muk8q 3ck7qc atp -- ,oxuz; (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 pa.5jdjv-+fq m8ksooe / ss upward by a window 28 m above the street with a verticald /jo.8v kqos5e-+mf j speed of 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 velocity of a train as a f-f :sg4y3orry unction 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 constan34yfsy rog-:rt? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit aloyvr a qod5+m+/5 -ocf dha.ok4dg,cm:ng a straight tunnel as a function of time is plotted in Fig. 2–28. What is its instantaneous velocity ok5 cya d -m: d,+mgqroch+d5ov4/.fa
(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 automobilec/,o(tz; uudmpy5u h5 can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting oyuo,5 ;5mu ( /zuhcptdf 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 wxi 4c+3p)och go96dcacceleration of the car in the previous Problem (Fig. 2–35) when it is in oc3c x +ocdhp4wig )96
(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, estimatewg g gehmi2kwnd+,mw8.ved*+n j (iwtaq)- 9- the distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph fo9- vy c9,jwt-khv;hv :p m(neqr the object whose displacement as a function of time iemn(9;-:jpvqwhtkv,h9vy c - s given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of an object aloc cfy7p+1vjro,d qp ),ng 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 negative? (g) Finally, answer these , 1 pjr+d)cocf,p y7vqsame three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m abov hcpux/47c +zye a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. + cxychzp7u/4 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on thksz 1svgg u/1yj u./4 wsiyl(;e Moon is about one-sixth what it is on Earth. If an object is thrown verticalgs1/w1 s4 v/zyuisl; k ju(.gyly 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 constrained by an over-the-is g wzyk,pei +u8.3h0shoulder seat belt has a good chance of surviving a car collisio + w hg3iypsz.0,k8eiun 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 bxdjx :q0kd9.6y0jjte sl8 zm 2ridge, 12 m above the 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 9q s :dzxd 6j tj.l0j8emkyx02how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collihq; oslf1 ,3 v;yyoinz2 y3,emsions by hauling them up on a crane a1nql h 33yvys; z;,fm 2ieooy,nd 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 travelsq7n0e-c-q 9 gzdublqwjtuf*g- fv 34: 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 ueb ;gt5bzbw d 9kq qcf,*6*n3fniform acceleration from rest. 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 bdb q9c eb5;*t 6g3fnk,q*f wzwill be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving byn5h7(yt0uap t) ph ey;h2ah(oard 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface oey5 t pp y)n2(0ahhh7t;ayu(hf 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 trmn6 zl dwg3w8,ansit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there arem83g6,wdn wzl, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fbqjsp-o ey86 r(tt +,ball 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 what minimum height must it spot the pelican to escape?sye,(ot8 p+-rtjb 6bq Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so than+p2zfgn6g z.mi . 8wlu6/g jut 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, /u68mu zgg +wpgfl.jnz2n.i 6putting 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 constant speed of pe1p39kj2 nbv6.0 m/s Just as an empty bpev2b nkj9p3 1ox 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 st4b- ( *;nb p;6plzwicqi:kfuqone is dropped 1.50 s later. How far apart ar*lcni 64i;b p wuf;bpzqq( :-ke the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200o6tjf0+l9 faq)7g hp 64a0qteeno1c i.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/hl664tqfc1 aeg e90q0fj opo)7tniah + . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as h t w /v 59-ky*z2+d.ait9vlv5aa3xqkgjqy jz:e moves at 18 km/h . At the -k g 9tw.kqxi/a:9az y d5*j+l32qvzv ajvt5ybottom, 4.0 km farther, his speed 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 trampolines. The first child can bounce upf+vz8.h qy:.bqof w2k one-and-a-half times higher than8byq. zvhf +k.q:o2fw 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 traveling insj9x . la6l)o-h.dmgt 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 this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t-o jm6.9.slaht)l xdg =    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 pe,umc3wzd5b,z 4*pra,3n s b a speed of 44 m/s In throwing the baseball, the pitcher,pdep nrz4,m 3abw35*,u cbsz accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerationk17 j.s1rsmu v 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. Eac 4osqvr;+x tcu-fv/qn; wz35lh intersection has a traffic signal, and the speed limit is 50 km/s . Supposn5 uvrz+cq /34sq o;v;xfl-wte you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a ckwd sb -ddr)7d5h4u3: 8njkl sonstant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m,j:d-d nd sh)rd3k5 7skb 8u4lw 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 seconc3wt/n53xq4rw x+t ybd stone b+wxcrt / xyq 34t5n3wis thrown straight down with an 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 same time.ahytah m/el6sq*d/3 l ;-ss;x The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a buildinhas6xy//dh-s*qt; 3em sal; lg 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 resistance, how long would it take a fre39,s; sjeq hp v+5lkl ouy,f2me-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speoh3+sl 5mkuje,p ,q2; l9f ysved to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send tho0*whjw erzo cwhz 3g7m /52-ue burgers through a grilling machine. o wj/uhgw w3ze7mh2*o5r -0zc 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 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 time.qrjdkphy32b6 )kdc( 73yc zzs faster than Joe can. How many times hbkypqdz c3hdy(3r .jk7 )2 6czigher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on theo jhci on-+3p0 ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in y0+phni -ooj 3cour 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 buildingl uere 4;p/2 tut+nuy4 using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How mun ;e etyl 2utr44puu+/ch 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. iq1zbh1:si( j . ibe3y(a) Is there any instant at which the twoiszq1:hjbe31 by( i. i bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?