Does a car speedometer me1m h56t;jm2c)h35os ljl tlwfasure speed, velocity, or both?

Can an object have a varying si0omh+: .a tqdpeed if its velocity is constant? If yes, give examples.m h+at.0q o:di

When an object moves with constant/x, *rg(0b7lmm8wpj;oktb 5 p4jeqkh velocity, does its average velocity during any time interval differhbwm4/(txq8eo;j bp rml70,k g 5kpj* from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speea6j7 m9f k)jdmd crossing the finish line to lose the race? Em67ad mkj 9jf)xplain.

If one object has a greatep rb;z4bn5s 8qr speed than a second object, does the first necessarily have a greater acceleration? Explain, using example5z ; 4nsbb8rpqs.

Compare the acceleration o1. jtprev;z)om;:u jqf a motorcycle that accelerates from 80km/h to 90km/h with the accele ;ove.)tjjqm1zu :r p;ration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity fx)x 7xr8u/su and a southward acceleration? Explain.

Can the velocity of an object be negative xcpqs6b lwdi5/7fy7*c r6s8lg7, sal when its acceleration is positive? What about*x/cb ssp7yaws 7g r68dll6il5 7f,q c vice versa?

Give an example where bo35;ogr 5b5w k o)n 8wb suv5kofgq4f+vth the velocity and acceleration are negative.

Two cars emerge side by side from ( mkb95we*wq za tunnel. 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 km/h and has an accelerati5kbe ( wqmzw9*on 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 accelera+1ipx 5u8d6dps7zx zrepw k.*tion decreases? If so, give an example. Izerip wdp.6u7xsdk1+*z px85f not, explain.

A baseball player hittzk:w9-cm2mse b0b8kx q81uzks4 p4 t s a foul ball straight up into the air. It leaves the bat with a speed of 120km/h . Inx:sqt k98sb-kmzb1 u4 wk c mzp2e04t8 the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speedsgz)qpmvyn,;k 22hl*c kfo9siu r( 8y( up, what is happening to its acceleration due to yo(phy ;,n(zv28ukikg 2 qm*9)clsfr gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball v fdm8-:nj/d ylertically upward? How would you estimate the maximum speed you could gi/jl- md8fyd: nve it?

You travel from point A to point B in a car moving at a8gt g0q6z6zjw3 sfu*h 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 80km603zswt z6gqgjh*u 8f /h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts vwiplg a1(d l9d)0*,x t j4xzwtied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, 9 )(x *l4d 1daj tpxww0vg,ilzand 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 acceh0 1vt 4 fqkf0s (y ,6rpk,mygkpc,+mnleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor ma 410,mkr,t(npf hy m, 6pgsc+y0kqk fvking stops along the way, a dish resting on a table?

An object that is thrown vertically upward + 1bnldlaiy p6-9 zlk3)z0soo will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this+l0 6 b) kzda9ilnzo13yp -osl 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 acce 7k7mw,d /j ivol60glileration at the same time? Give 0i7,oiw /lj7kmgl6dv examples.

Can an object have zero acceleray hgb j,v(./*7bjwciyu v js;ks2op83tion and nonzero velocity at the same time? Give examplvg*ow7vbpj s 2(,hyi ./y8bs; cjj3uk es.

Describe in words the motion plotted in Fig. )cbj(pu**s+fnqccp7 zfpkmmn8 )zq u y .b46-2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plof puc*k cp yq)8zqn) mfcz-.su+( 4p7bbn6m*jtted by walking or moving your hand.]

Describe in words the.ob2r3rdgstadj 77a , motion of the object graphed in Fig. 2–29.

  What must be your car’su)s3tcyf (ne jl55w0e average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly00al vk0kp2yyi d7g 2,,fmopu 15 km?    h

  If you are driving along a straight road and you look to the side for 2.76d v 9d0mc4e 7rkesco)stz*wetp+ 9q0 s, how far +r 9 w*ssc ve0t4)cz o 9em7dpkq6d7etdo you travel during this inattentive period?    m

  Convert 35 mi/h to j nvb.. q ard 0 xg01r3y9*lbcody0pi0
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves z3w bc1d)u4 yspvo;zm/ 2hd)sfrom $x_1$ = 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 q)j)6aav8mf f6 dlu71slq xz 7km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minufs6a7 z1 qjfu))lx6qd8l7 vmates.
(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 lt8x(ztjn-/s nightning 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, estimate the speed of sound in m/s from this rul /z(ntt8sjn-x e.    m/s

  A person jogs eight complete laps around a quarter-mile track cq,fcjy +)+exz c ,4awin a total time of 12.5 min. Calcul,czq4cx w e+a f)j+,ycate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a y-wequt7am q: 9,nukm;s5 oc/straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in yqusm9 7oatn:c ,5e;kqu/w- m4.8 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. Each h1dildnlsrzs cu 1: zm.,cl *9*as a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will lz.d,l911sr u:d nc*is mlz*cit be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How longmb;sd 8-mu yg- will it take the car to reach the truck?m8ysm-g bud; -    s

  An airplane travels 3100 km at a speed of 790 km/h 27gqmd.o /t9hr 2j jsm, and then encounters a tailwin .rmmoj2qth 7 d/gjs92d that 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 aver8b 5r tvv*k8kkage velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/rkv8v58k *b kth 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 spe p,rq4d 0brc;v))xosied 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 hands. What is the speed of the ball? The speed of sound is 340 qx)d,i4 s;rporb)cv0 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 q) hwekw5:(udzmko:3z( qc*.yqbok9s. What is its average accele*:q.( w k)q3k mobedc :5yqzu(z9okwhration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acrw g hh*82d:mlcelerationgrwmld*h2 8 h:
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile nyy/ + xzl53onl jny-/is capable of an acceleration of abou jl-nzyox/+3yyn5 l n/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 sp(*p9g:y 4c7fo oluqroeed travels 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, wh4q (:rofg7yp olco9u*at 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 wsg8akv3(e3d ky:x6:ag 3:bsm5ruu i and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a gra: aduse8u :kv 36xggyim(:k sa5 rbw33ph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. Wha5gxlns: 0 p)lwm)rat: t was its acceleration? How far did it travel in this time? Assume constant acceleratiotg 0r s: )la)n5xpml:wn.    $m/s^2$    m

  A car slows down from 23 m/s to resm( g+s-ufq ib :fa( i;fxrn;o+t in a distance of 85 m. What was its acceleration, a;x+(r; fub(fi na q-im+fg so:ssumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How long a runway x/9j 5l +ehrjsqajo 2 ;o,pvt:ktu;/wis needed if the (constant) w;j,o ukoj2q;+are/hjtp5/vts :x l 9acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentiag)tohql4l y42 lly top speed (of about 11.5 m/s) in 24gq)y4t lholthe 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 uniformlygoh: b sa08kuogeo/ hv6.:3 rs from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that t eh gb:vg:kr 0 ahu.oo3s8s6/oime?    m

  In coming to a stop, a car leaves skid marks 92 mjf8nx2d d::h i:1bt7 .htbb ip long on the highway. Assuming a decelerati:idt 2dxbhbh8t 71b j:fp.i n:on 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. Theqa.gcl tqon2 ouomn0 k-rq6 );;mcf0) front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was )f- 0a. m2o0oq;nq6lqun cm;c tgo k)rthe average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 95 k4c2m*pie jo(y6 (e tg scy3lt5m/h and *e 4 32i sjl((ectyc yp56omgthuman 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 the stopping distance of(71rfg l abp ;q/aj:bi,txv1 jc3n(ff 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 hig,f me .foju+zl*dd6s( h ek::lqs1w(z hway. The car’s driver looks for an opportunity to pass, guessing that his car o,q fl+s *zmz(k1.(hejwl6fused::d 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 compvuz( nxf4 )ofbn5,a /slete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to )oub5 z( nfnavf/xs 4,go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 4wqo0dt j 0p-*zt/2ycl 5 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,/tdzw pl20y*oc -qjt0 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 fromvib:q+ k7wvu)v2(sps the top of a cliff. It hits the ground below after 3.25 s)ki b(sv7vvs p:wu+q2. How high is the cliff?    m

  If a car rolls gentlcd +hf6,a,oeqah -(qty ($v_0\,=\,0$) 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 straigzz xx92asn(q4 ht 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 throwi l3aqo0cp ld10/zz+ctng it vertically upward. With what speed did hc+01cdp30zqlo/l z tae 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. Draw grm;d)xu /orzm 0i4r6d kaphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.mkurdo i)4/x6mz0 d; r00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m0 dobd9u(udu+2vuc p6 sl,*ax/s. At a height of 125 m above the Earth, a package is drop* ud,oluddup vb0s( ua 2+x96cped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from resfxc4 hqyl ogl/5m3zc i+(+6z kt, show that the 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 Figs. 2–18 and 2 m6xg+/lkhzflqz(5+ o4c3i cy –21.

If air resistance is neglected, show (algebraical4qigc6+aufl2jw +e(ely) that a ball thrown vertically upwarc g+u2fae6elj 4q(+w id 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 with a speed of 18.0 m hv93bzft z74e/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 number r(g9 t3bpac, lof photoflashes per second). Assume the apple is about 10 cm in datc b9,r( pl3giameter. [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 w6y yfu2:p2 dwl- f p)wapg1zn:indow 2.2 m tall (Fig. 2–32). From what height above the top of the)a2:wp wfzf1yguln-p p2: 6 yd window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is hepm:hnf.p( (ufnt 8qw5ard 3.2 s later. If the speed of sound is 340 m/s , how high is tq5n fwnm(f (:8phu.p the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water.ys(+alf9h, 3z2q9 mysuw6tsl You point the nozzle vertically upward at a height of 1.5lsawsf9+l 2y(qyhst3u ,6m9z 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 verti,iwfi 93 n(nymcally upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34),yn nm39f (iwi.
(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 upu j9glva. in52ward by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the s av5u29njgil. treet,
(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,ldi de0v (pg-unction of time. (a) At what time was its velocity greatest? (b) During what periods, if, 0e l(pddigv- any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel x 8o6-yt8 rdiuas a function of time is plotted in Fi8o8dy-i ur x6tg. 2–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as s.lxre .;rmg8n hown in the velocity–time graph of Fig .xgn.r;8mre l. 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 in the previous Problem (Fig. *8g zi c/8ycn-duwa d.2–35) when it /8w*a d8 gnccdzu-i.yis 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 objec3 y( sqm4t7lfrt traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objecslubj x q3vl9t,b8j* 7t whose displacement as a function of time is given by Fig. 8x9lvbtjbu ,*q37j sl2–28.

Figure 2–36 is a position versus time graph for the motion of an object apz 7k.osrv,owp ;./:jub g3gnlong 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 same three questions for the time intervalbsr.p / ,; j. zg3upn7owvgo:k from C to D.

  A person jumps from a fourth-sto*mt5mgedcpfe n 187 i/ry window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m beforen1cmgdm58 f*t7i /pee 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 gravity on the Moon is about one. jcfoa3m/h: z-sixth what it is on Earth. If an obj hfj3:cam.zo /ect is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat6v0 md84trzml belt has a good chance of surviving a car collision if the decele8dt 4mvr6 0zlmration 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 his pursue1cfw/dv qy .lqd/ /)bcrs 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 it/v) fcy qbw c.ddlq1//?    poles

  Suppose a car manufacturer tested its cars for front-end colliipbfl h+3 *n8xsions by hauling them up on a crane nxli fph3*8+ band dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth trav-to3 c(ori.cnr;,1tnt bpn-l els about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from oro,tfcy.ft- n( qld 88g m7mj*iy9) vrest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Figft. m) j78g *,v(-flmiqoy8 9r dtcyon. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a do w0bp urvp83 z9m8pn,eep pool. The person’s downward motion stops 2.0 m below the sp 98puzv,bm pnw0r83ourface 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 necey ve 1:6(tg d()nhwmgxssary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s avwx61g)ym :( hn eg(dtverage speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight dowm i l31j6wamc5n when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannc1awj6 ml3im 5ot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so that t lu.rtqqt8y+ain 7:qy wo)/ p(he ball will stop within some small distance of the cup, tqiq(). q8o lu 7ytw pry:+an/say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates 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 freigh+i8 ,wc8ap wxj4lyf82 muy vt:t train traveling at a constant speed of 6.0 m/s Just as an empty box car p2 luwipxvym8 yaj +8:fc84t ,wasses 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 va /jm+)so m,v1 kbv0hbuilding. A second stone is dropped 1.50 s later. How far apart are thesamj0+vv vb )1kmo,/h stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a time trjnp * 3;wttauc/f)n 5kial lasting ten laps. If the first nine laps ;/t tkw*pannjuf 35c)were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moves at km 8e2z z rl4shb)fxg* 9-nf:t18 km/h . At the bottom, 4.0 km fartf9g xzmebzsn* 4rk- l:ft8h2)her, 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 up on 9stap,i j68d dph/ou)e-and-a-half times higher than the second child. The initial speed up of the secondt8)9spdj/ ha6u o, pid 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.dt+h vbtwbq- y-)9hokju s87 -long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What ad)o-wjkh b 7qsy-v+8b.hu9ttre 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 wq2q75vzo3 s rbaseball 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 iv qz3ow 5r27qst 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 acceleratio 8o+ilkuo((kin 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 intersk2k( b2rcx*ho7b oty4 ection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speedc4 b2o*rt7kky2b xho( 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 q3puf2 90 u wrqhk82+9jx v7xh6nhcgatraveling at a constant 120 km/h takes off in hot pursuit. The police officer catches9n vx qg6j k3c08r +9hapxqf2uh7u hw2 up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the rofi;rcrh:leh4ia pn*v62 6s: oof of a building; 2.00 s after that, a second stone is thrown straight down with an initial s4si:hfcr2l envp6 ior:;h* a6peed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stonewu77zin(qko if*rj.4 is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity soi(4kzui qj*7f 7 .rwnhould 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 free-fall22on ;1(bz4w b:o vxjl5hlvtiing parachutis4 x:otll2; bin (jzv v5owb1h2t to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a gri ax9zj-z ;z*8gn;pslkui23ii lling 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 apart, what is the rate of burger ;ixip9ki;-na3 zzj 8usg 2zl*production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertua; ,7m(ieoeq4 hkm 5xically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go than Ja o54e( umi;e7 ,hxkmqoe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ;3wup cn czwi4 cy/8qdr)4 8wsground below you. You drop a ball from rest and see that it takes 1.2 s for ri4n3w8ww)pudcsz8cy ;/ 4cqthe 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 part -z.1fbwo1 t5o 8mcudbicular 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, timing its fall. One student reports a falcfz1.8bu t-o1 5b omdwl 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 posalw j( x8-9m- 1ba,op3vf 7jetyecyi 2ition 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 accele9jvx7(imlypw e,tc -fo a8- jab3ye12ration? (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?