Does a car speedometer measure speed, velocity, or bothol q.utse0f-/bv upm q0yl*+on1k9: 7lir 1ue?

Can an object have a varying speed if its velocity is constant? If y c5eezdi5d 13fes, give examp icd3ef1e5z d5les.

When an object moves with constant velocity, does i6ln;-mcp2 )/ a6a/a vxgaemlqts average velocity during any time interval differ from v l;ge/aa)p2xl -/cmn6m a6aqits instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speedkliblr7g hp-9.er:c qfv 7ke/tsn1 9: crossing the finish qsp -c7vktnk. e :9g9le7f1/lhi :rrbline to lose the race? Explain.

If one object has a greater speed than a second object, yuqhuo l*04o 44 q;nqpdoes the first necessarily have a greater acceleration? Explain, using exanh 4pq;yq 4l*0uoo4qumples.

Compare the acceleration of a;qzuux05b 8hd motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle thau0 ;xuqhd 5b8zt accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleratiocv qz6za/o ;h712 i7ctnts7 djf7/smy n? Explain.

Can the velocity of an object be negative when its acceleration is positilo.uyv:xn - spx cd-)1m- l-fave? What about vice versamy--vcsl)nuod 1-- lx:.fx pa?

Give an example where both the velocity an7,6 p:fteg vb4k;z0yh /rhhgjd acceleration are negative.

Two cars emerge side by side fromvy3mejvfxw; ,i-c47l a 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 acceleration of 6-j emxfi;c4 vwl y73v,0km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If sops c0pdu cfc9 rst46+), give an exampl0)ppcc9s 4u+r 6ft dsce. If not, explain.

A baseball player hits a foul balls+a:2d7asfj.8 *zg2qhxz 3kcbif(m l straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catche 2f(g jl*s sb8c+z i2 h3amadx.zqf7k:s it?

As a freely falling object speeds up, e)gmq-tk;wf *what is happening to its acceleration due to gravity — *k;gmq-tefw )does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically x)j z3/mod6yt e- :hoeupward? How would you estimate the maximum speed you could gz6mhd exo:-t/3)j oye ive it?

You travel from point A to point B in a car moving at a c3/ l/bdddr0fap 4e/m6wsvi 0constant speed of Then you travel the same distance rm4w06sld ef3dbd/v0c p /a/ifrom point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with w 4:crhutktry /t3b )4ten 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 b3 brykurtt4 wht4 )/c:olt 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 falling froz:(*phy0syk wst1pg( q xbz 63m a cliff, an elevator moving from the second floor to the fifth p hzwytq 1(bx *kyssg0(6p:3zfloor making stops along the way, a dish resting on a table?

An object that is thj j.onp:t5:sn rown vertically upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? o::snp .jn 5jt[Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity i w /wpbfvz+7:lln,m) and nonzero acceleration at the same time? Give exampwwp7f/l+z lb),n v m:iles.

Can an object have zero acceleration and nonzero velocity at the sa( ;ncg-f lrs ft28mrjxno/ af*5e 5(nume time? Give ( mn582ff;n (tuxc fl -j*as eogn/5rrexamples.

Describe in words the motion plotted in Fig. 2–28 in terc(so 4mkvr+t 9ms of v, a, etc. [Hint: First try to duplicate the motion plkm 4r(9+otcs votted by walking or moving your hand.]

Describe in words the motion of the object grap0v -dxv.2acq1 mlzd+ bgt1* qahed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 h? r sq+ wwsq-y yj+*o8ly1z/fd:   km/h

  A bird can fly 25 km/l82en av-zz+hhm:v w 7h How long does it take to fly 15 km?    h

  If you are driving along a stra/r e nr, b;gq*0ldly1night road and you look to the side for 2.0 s, how far do you travel during th elyr, lngb;r0*d/1nq is inattentive period?    m

  Convert 35 mi/h to v4 rz8x/xtmrar gde6o-qt ;wm(c u8 :7
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball movesjp1y f5ky q :vw +ep*odd);ol(fd+f7 a 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 steoqe )7b9vdbtf- 8rd.i3 qd1 zk/i*yz madily at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrie di/ b8zobm)d9dvr1*qq-y7iktz.3f ve 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 g*e)s5e.sjey nk*lu .e6qi *c seconds between a lightning flash and the following thunder gives tl *u s.eg)e e6yn5*skej.i*cqhe 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 rule.    m/s

  A person jogs eight complete laps a7qco wnur;.e5v5 lh /ground a quarter-mile track in a total time of 12.5 min. Calculate gl5n.5; 7/uohwc evrq
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straightdhupwm(bm3m ,q n23 (7htv*bj line, moving 116 m away in 14.0 s. It then turns abruptly and gallops h pb u w23nm3td, h*7mvmbhj((qalfway 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. Each has a speed::tpy2ge9c4hu.y( dra xg-c s of 95 km/h with respect to the ground. If they are initially 8.5cgcx:yg.9 (4-atydr:esup 2h 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 behs/vw45o0rd1ftaju 4i4 jagn5 ind a truck traveling How long will it take the car to reach th4f4u5 01/ arsoa ji4vtdg5 wnje truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , a jzmj*o pc-d)*nd then encounters a tailwind that boosts its speed to pcod-j)z j**m990 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 r61tq ykcjc6tvcw+ ey*ap(t.(ound-trip in which the outgoing 250 km is covered at 95(j +qyc6ack tp*1ttycw6e (v. 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 end of a bowliy g 8o5q1wg5*x5a6ixthyq2au2edds .ng lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is releasy q.xa25t 5d 62egouix a1q*ydgswh85ed from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelermdkaw5a1 4j( kppdwq;;e v/.phg) u2 xates from rest to 95 km/h in 6.2 s. What is its average acceleraed k;m12xg;u) wh pw/avq.k45pajp( dtion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her ac3bqtmkd1 u m 0au9 j76zxj1hr)celeration173maju 1bdtq zkh 6)r0xum 9j
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capablwc73hvwr w,s9 e of an acceleration of about 7 9,h3wwwvscr $1.6 m/s^2$ 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 constanoibc7 4t)( pkdc 1tjp:t speed travels 110 m in 5.0 s. If it then brakes and comes to a sto4p)i 71(k btccjopd:t p in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = .vl/(u hf.si99x3pt*,i 5fx kamzh lvz7i7lj0 and moves in a straight line, is given as a function of time in the following Table. Estimaxx izpt. a m*i7v l9hzj9kihf5f s/v.73llu(,te (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. /-x clikzebr nhz9dm )ko.kbeb05),; What was its acceleration? How far did it travel in this time? A/br) ecn ; x9)5b-ik,l. kmboezh0z dkssume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest incyg1ya*+zz j 4 yb:aj u*,hx7xu 2nq2a a distance of 85 m. What was its acceleratiuy7cb4*zna yz: qaj * 2u,1+xag2hxjy on, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s foi9 ay4f k0)l, t:z-fnjgb i6jtr takeoff. How long a runway is needed if the (constant) accel0 -tlbf,ikzj4 9yifj6)gn :ateration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to es3 1g8o 2g zi)nlqkxxc,sentially 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 it take her likgo,nq1x82x z 3c)gto reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed ;d-ydf2v;1i+ mxajbl of 12.0 m/s to rest in 6.00 s. How far did vdxjd ;-i; yf +a1lb2mit travel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the fzw+mlm +xkf6 r(54twhighway. Assuming a deceleration of m(z+ mt + 6x5wwrflf4k$7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. fl eo-d9:vkl3y0 og3s The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during o-0 3 fg:le93vyskoldthe 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 km/j5wt6 (xfej )ky.a9imf1+xn n 8fjx:mh and human reacttfx1:+(nwjax k)9 x6 i fmyjef jn8.m5ion 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 uuzl)zss(5- yof a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s driveo;,ao-56o joleu i a2fr looks for an opportunity to pass, guessing th2aoe lioao5of6;-uj ,at 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 30.0 minax*06bw w a.vbumf8y1 . After exactly 27.0 min, there 6m8.v w*y 1aawxufbb0 are still 1100 m to 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 45 km54 itqt * 0q2sfirky+9gk4ce z/h approaches an intersection just as the traffic light turns yellow. She knows that the 5 9fce riy2gk4zq *04t ktqs+iyellow 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 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 the wr k24*a 4(jfjkk izp*ah8 b;wground below after 3.25 s. How high is the clif* 28 j*kr i;z4kphwja( 4awbkff?    m

  If a car rolls gently7iphz+d -6dsk ($v_0\,=\,0$) 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 mfqja +1x/gd1n; or1 ointo 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 tb; 3o9e/c gfmw hvsobqr66 2cem.65hdhrowing it vertically upward. With what speed did he throw it, and what height did it rd ;er63oq chmbsv.e 26w56fgch/ m9obeach?    m/s (Round to the nearest integer)    m

An object starts from rea8 ufnai l7(e3c5i a4glonz)+st and falls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignorzgi n3 7laoula8i54ac+nfe( )e air resistance.

A helicopter is ascending verticallnzra*knvmck0 *18npi er +u pa0tk:0/y 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 packartpk0v r0uap nanzck+/:*m 81ne0 *ikge to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling free9fef dq7,7 hecx/gmj iln/.5oly from rest, show that the distance traveled during each successive second increases in the ratio of successive odq,c .em5ij9 fx7 7eh/flnd/god integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algey3up7i *rpt3h r:;iblbraically) that a ball thrown vertically upward with a spe3rr*i p3bpyh liu7;: ted $v_0$ 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 dql9nllx /2ar rh4/9f of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of thejhzj5ds6 tkq pk 18n:) 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,tsj8k:)1p 56qnhjdzk but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past *sndekg1ee kk1,9) jz a window 2.2 m tall (Fig. 2–32). From what height above the *) kje9eznk1ge,1skd top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and tt9)ihjy(xf v,c9w-n-j a mfv :he sound of it striking the ocean is heard 3.2 s later. If the speed of (ahfm:c,fny)9-9- xt jwvvijsound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzla0v 6bv1 g+ycye for a hard stream of water. You point the+cva0b1 vg y6y nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a spes*b t4)7x i48q myxvzo:o 19onqic p,ced of 12.0 m/s from the edge of a clifxm pn 8:oyix9t cqcqio*b v144)sz,7of 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 abor(8 fx0nzw ic,ve the street with a vertical speed of 13 m/s If t8 n(xrfw c0i,zhe 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. (h3q/eet zao4 fwv17 8aa) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitudta7qaho/v e4zefw1 83e of the acceleration greatest?

  The position of a rabbit along a straight tunnel as 5yj)w ( j4qvz/6emshsa function of time is plotted in Fig. 2–28. What is its instantaneoq )j6y e45/shzsmjwv(us 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 approyw;y1: poil9cximately as shown in the velocity–time graph oylp yc:;owi19f 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 in the previo8 xhv5bz+nd*c,. x y7;xulctous Problem (Fig. 2–35) when ib8x ,z;o+u7*d vhxc. tlcynx5t 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 ohfnja xgri hve94 0,+.ee0) qwz.*ahb2a.ijk bject traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose disnhdsrnzskn u0 7- )7-oplacement as a function of time is given by Fr ku7-h)07n onzn s-dsig. 2–28.

Figure 2–36 is a position versus time graph for the motizm2 h-mebh *y3on 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 obj2hhz *-my3me bect moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a pi11bjefha q9tjibl.i0a*l k-u+ q;5firefighter’s safety net. The survivor stretches the nel -q+5it;* ul9 0pb.ijjaekb11qi haft 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 gravity on the Moon is a.3. .puva /pq u)kzws4po.p aubout one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it woukuua4) pppzq/. .pv.a ws.3ould on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoubz5y-i x:i)eq709nkxrjj c9 dlder seat belt has a good chance of surviving a car collision if the deceleration does not exceed -:57qnbjzyjci99 x edkrx0)iabout 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 brid39f9n r f9(y cv:ju anw9sis5rge, 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 how many poles away the truck should be when he jumps down from the bridge onto the truck to make his gwf nsi99( n9j urcfv39yrs:5a etaway. How many poles is it?    poles

  Suppose a car manufacture;hfajtk* nt1e8bw* u9sp/ . prr tested its cars for front-end collisions by hauling them up on a crane aeh ;k9n1.b* turp/pt* jf8ws and 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 kc1:i6,b kbp4( cyxxstravels 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. The front of 6ygg(+7u :xorj 8lprxhn+qr9 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 starten7++r896xgyh jp l:ogux( qrr d. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board:dr0+ g ,tz cnp)7ehvx 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the wa), vdpcrx7 h0te:ng+zter. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid 7a)4k6i(sdr erkpd,)k nqk m2 transit system, it is necessary to balance the average 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 im6 4 )2(pknd ),sqdi7 kkekarrn 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 stra3:z+ura:(cf c t a)jbzight 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 c+:t b3)a rz:u(azjcfmust it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force c8p zxss237fnwith 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 fc7 s8z 2snxp3missed. 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 freight train traveling at a constant speed 029 yekfuo 0urof 6.0 m/s Just ao0ry euf20ku9s an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from t4bkmq+ li20rs55knkg he roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones w4qrkk0bl+m5k 5 2n isghen the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over pe nq i3hcbghyg7x0- z(l;;qt. /q;lq the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what avqpe70hghi; ( ty;zb q;.xq q-l/3lgncerage 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 18 m rvdx.k )8hw3gm7:xaatt 56ykm/h . At the bogtmha7m3 kd8a) 5x.vt:w6 r yxttom, 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 ((awi.i hrk/ttwo trampolines. The first child can bounce up one-and-a-half times higher than the second child. The initial speek(a.tw(r h/iid 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 overrqh9(lw 9;on ( b, y5gxlh,erd/r:utrtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 79o/5 ,rrxr :b(gt; l9quw,l(nry hde h5 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a ba ywj;hwl;i*z1049ufi ghkwhns;l- q (seball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the w-g(fh*l 0y wnh;kzhjqil u4;; s9iw1ball 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-v. kc7 qv30j -peyh(5,bwtmf -yrffb, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each intersection *0 r4)fcsqa2s i(ghtmq-x t;bhas a traffic signal, and 04f(mbqcstq2its; - a x*gr)hthe 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 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 consta1dor,o.h)vzs 6tk*bml vk p/( nt 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintainidtk bmrov6 *.k zv /,ho(lps1)ng a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second c0bu5o6 lu y6estone is thrown straight down with an initial speed of 25.0 m/s and the two stones5ube o660luy c land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is thrownyq+,rz(lp6mh 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,q l+ py6z(hmr. 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 v, jsmu/ /b kn/wk4 n);deuox/lcf+a5 it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her riv/wxba /o5 elcm/u)nf s4udkn+k; /,jpcord? 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 uay/u;ubcg .6(g-ce dwses a conveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If th6ed/ gu -acw (.gyubc;e 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 b1 0b9g yutb,tvertically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go tby019,tu b gtbhan Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the g j3nhi,4 :f8 k+tjapdxround 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 your hand. What is the speed with whit: j f,japhn dkx8+34ich your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building using a bait8bpst: kg7 /d fi(*nrometer. 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 0.3 s make (s tk/ipd:f g*t78 binfor the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles;(+2sfreaz q jcaa6(y , 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(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Whicaa2cqrj(s+; y(a z ef6h bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?