Does a car speedometer measurey aeg7gz1z */ec-zdojj*n 93q speed, velocity, or both?

Can an object have a varying speed if its velocity is;0bb.7lykzg1rrmo pokk r:3 ; constant? If yes, give examp;1om .p 3kklbrkzb 7gry;:o0rles.

When an object moves with constant velocity, does its average velocitfj3 q ,m/4szkhy during any time interval differ from its instm,zqfkjs4/h3 antaneous velocity at any instant?

In drag racing, is it possible for the car with the: x8ep 0v:w ,uygtm2dah42g j1pa+xrz greatest speed crossing the finish line to los +hx2 g8waj:g1rvedxm2u , 4tpp0za y:e the race? Explain.

If one object has a greater speed than a second object, does the fir5sslr ;:dt u*kst necessarily have a greater acceleration?*u ;ks tlrds:5 Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h to 90kmc+ b+ up++9vzpz2yk.4mo hn ly/h with the acceleration of a bi4ouzybh+n.29ml +z +p+pvc kycycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a south 3q b 5c(d h/(elvm7b;euf.kwlward acceleration? Explain.

Can the velocity of an object be negative3p xo* 4qr-caw1um2n20szqua when its acceleration is positive? What about vice vmnu42*-w 0qco 1ra zua p3x2sqersa?

Give an example where both the velocity and acceleratiof,lb5mqtk1k c ).o u,:p ecd4hkt6be0n are negative.

Two cars emerge side by side from a tunnel. Car A is )7q:t5hw9rr s(m *v omg9yp dy10ydhitraveling with a speed of 60k dsp:m7yry15 w9g0rt( vq 9d )yhimo*hm/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speedgmnu a 0mczc(r98iu+ :lbt ;luhn26(v as its acceleration decreases? If so, give an example. If not, e( nmltuc;:2 6r +b8 cnmhlu( ugvia9z0xplain.

A baseball player hits a foul ball straight up into the air. It leaves tx4ib/:g(;mp2yh nn jphe bat with a speed of 120km/h . In the absence of air resistanhb ;n4 j xpg(2:n/pimyce, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happeni5my 1ovfrhjmk zcnw:pfmj3s f7-5us +/ d/: k0ng to its acceleration due to gravity — does it increase, decrease, or stay the san-75o+vfhm0u:ffsk /jc mm: 3 rp wjkd 5yzs1/me?

How would you estimate the maximum height you could throw a ball tas+is ahxkx8p w4az2g)(g 4 6vertically upward? How would you estimate the maximum speed y+s8z ixw(k4 a6 pshga gx42t)aou could give it?

You travel from point A to point B in a car moving at a cons7:j4gr)jr swztant 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 jz )w: 7sgrj4rfrom A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.llb+ -fxj1**kzi/ sxu0-m-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each uz *kjx*x+b /lfil- 1sbolt 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 q5g 2w,zlvarir bpv/8ivfk3 e3e )v*5 rock falling from a cliff, an elev pq*/evrv agbvkw338l5iz5v)e, r2ifator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically :wt4vb5wmdl+:r vn-d 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? [Hint: The acceleration due to air resistance is always in a dirlwdd:4m r:5n+b-v vwtection opposite to the motion.]

Can an object have z mzm(uos1 wtc*( 7l(dl.lpg)f ero velocity and nonzero acceleration at the same time? Give examples.1)ulpzfg c*ts(o( (dm 7 wl.ml

Can an object have zero acc6qn o5;cpo )yfeleration and nonzero velocity at the same time? Give examp5) n;qo fcyp6oles.

Describe in words the motion plotted in Fhq6n b;mpax(l)lz yb(vf+e 2 .ig. 2–28 in terms of v, a, etc. [Hint: First try to dufeny( .(lqx2ap 6h; vlbm+b)z plicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object grapj-*q u,sor 1 +pv9fts;d cva+yhed in Fig. 2–29.

  What must be your car’s average speed in order to travel 23(:jd + 8p; 1*agzkl;3fyeml tclgi)ki5 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 :p, 0d: ospuvjkm?    h

  If you are driving along a straight r v-prjcyfv0, e+f 2zyfpb. 6n -,mtb3road and you look to the side for 2.0 s, how far do you travbyff-fy3,-0 ntp + z2rv,r bpem.jcv6el during this inattentive period?    m

  Convert 35 mi/h to ib e1a0st(;kyel js6.
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves.ge1wxo6f9 z f from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily 4 (69lb lapcf4yeyyc5) qvf/ mat 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arriv y)/y5c q4v ae(blc694fpmfyle 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 fiv/ w3 x:b;jdv)akkx6khe seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at al 3xd kk/avwbh;kj x:)6l, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track ixn cv2wb4e)6 on a total time of n)x4v6bce2w o12.5 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: w,obp 3jnud8ch,xo/ 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.,d hu,co8bpnx ow: 3j/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 approw-o 1x0 g;f+ 8z(1gzfb: iwijp rmma9xach each other 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 before they reach eachfiiwg x(zjr 91b081g:x-fz + mw;mapo other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How loj15qz fr 9)*ug/etq/nz7tm rss1*m zing will it take g eq5sz1*/zr1tjq tinu7/m f9*z )rsm the car to reach the truck?    s

  An airplane travels 3100 kmx5-zcfj, yd6y at a speed of 790 km/h , and then encounters a tailwind that boosts i5j-dx c,f6 zyyts 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 complety;p8ua nnz 3k,e round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km i 8an ,kpz;yn3us covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the/f2u nligi6 ,q48hs/l cpji d3 pins at the end of a bowling lane 16.5 m long. The bowler hears the sou8g4,li lunhq jp fs//c 6id23ind of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. Whatbh0p4hsayse y zf i /1rrd0:7( is its average acceleratisha: 4sy0r0p eirdf /7h (1ybzon in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest tqs+h cxd4ojw2/cu(q8 o 10.0 m/s in 1.35 s. What is her acceleration + c w2xoc4qqu/hj 8sd(
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a par)cck6p2t:yzf 8:yq -9cv tx7uwb o.giticular automobile is capable of an acceleration of aboutwckq: yvz)8-7bt 6c:9.g u xcof2pt yi $1.6 m/s^2$ 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 u tmdx1ui,mub9( 9s9i m in 5.0 s. If it then brakes and comes to a stop inbu m9(idtxu,im1us9 9 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 =)q n kr ,7udq1dwtu2k. 0 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 astwudnqr)k12u q .,7k d 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. What was its accrc 4k7uh0qtw 2)jk 9wseleration? How far did it travel in this time? Assuj0sht7k)kww 924qr c ume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rd(fwg gt.kg-*est in a distance of 85 m. What was its acceleration, assumed constantd fg w.g(gt-k*?    $m/s^2$

  A light plane must reach a spd yj)f6m//n 5r la+/1qmr5h .mzok cldeed of 33 m/s for takeoff. How long a runway is needed if hmrr f+a)n dl 6qjm/ly5cok.md/z/5 1the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top spejjk/;ius 9 f8e hl5sd qf70+feed (of about 11.5 m/s) in the first 15.0 m of the race. What d9qfjfikls;/u+7 0e jhs58efis 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 speezhuvh eor78yg;w3ip0 s w+6(dd of 12.0 m/s to rest in 6.00 s. How far did it trave( 3hhdy+wre zwsvo;u70 igp8 6l in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highwacz s0kbu4vfl5rye21 b7u i4 v7y. Assuming a deceleration o4ifuzbk4 c0 2b7l1r5vv sye u7f $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front end o*fw5+-zki7 qgxr u3qff the car compresses and the driver comes to rest after tf-+k*u735q zgf wxiqrraveling 0.80 m. What was the 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 ofh nlv uf6 zqpj4 2ds*5 05x6m.vmwr(og 95 km/h and human reaction time of 1. 0nrvwxmd6ohu6 p5l f5g4 q2sm*zvj(. 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 stoppixae+8(ok1 tfk;spt 9qng distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s dfvn x4w0dv16 5vw zgrxj7op (.river looks for an opportunity to pass, guessing that his caroj f0vg6v1x(w5 dvnrzw7.xp 4 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 4e5 poay 67ykhthan 30.0 min. After exactly 27.0 min, there7y6 ap oey4hk5 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 km/h apprreb yfe,1uw) 6w 4aqc3n0,llcoaches 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 intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum decel 3f q 0ea6ly4ncrewc, 1wl)ub,eration 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 clif1u jk(kgn mhc i6is2/)f. It hits the ground below after 3.25 s. cg1k/ u(6j2mk i)in hsHow high is the cliff?    m

  If a car rolls gently ( 7m,+lvq0lfzxw /+ yx zex.y.l$v_0\,=\,0$) 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 into the air wu-)6at m7c(nsor-vz m ith 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. Wit0il u :bc0 :lb8,g;vmnut +ijch what speed did he throw it, alv+cc0ubbjuln:8i,0m it; g :nd what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravityg0hi bvzol6n/f bu)6 :. 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 . Ignore air ri6zluovgb60hb ) n:f /esistance.

A helicopter is ascending vertically with a speed o5w) w5ut8lnni f 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 reach8w)w5nnu5 itl the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled 8a:tbu e idf:cuu/p/) during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). Thisp8cd)t ubau :/ue f:/i was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is nl2r.w ugt) 9d4+ vlornv+v3uyeglected, show (algebraically) that a ball thrown vertically upward wiy 3t. ln2gwl9 ru)od u+v4vv+rth a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verticww+ (m h)4ychql(7zpnally upward with 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 photfe8 zq*3z gpoli.9rx u0so3q8oflash of the apple in Fig. 2–18 (or number of photoflashes per3. 98po g* zqz o0fe8i3ruxqsl second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to tray.u1oy n6v tr y3:s3oivel past a window 2.2 m tall (Fig. 2–32). From what height r s6 y: 3yon1ytv.3ouiabove the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and th:+it:,dkqx .7d olph he sound of it striking the ocean is heard 3.2 s later. If thtk:7.hdh,xdoiqp l: +e speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hoseww6r2zt)l d; l nozzle for a hard stream of water. You point the nozzle vertdtrwl)l2;w 6zically 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 speed of 12.0( xsvujl.y/s:qq-un)*2nstoej q8 4yfx3c0 t m/s from the edge of a cliff 70.0 m high (Fig. u0e4yt-t ./sus2osnj qlqn y vc*3qf)x:8x( j2–34).
(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 wit vwkq gr-hyj/:7f+/hndow 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the streefy t/+wg:- hjhv7 qr/kt,
(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. 9k5n ;h f;yzzk(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 constant? (d) When was the magn5yf kzz;9;khnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a s7 qkk7upy;p;function of time is plotted in Fig. 2–28. What ikk7 psq7pu;; ys 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 accelerat;rb(ojh 2.hm :)utnezcd cv xf+hi200e approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shiftij nz)ohh2riv(utdxc; 00+. :cb he fm2ng 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 previox4 )cdvohj x5*us Problem (Fig. 2–35) when jx*d ocx5)hv4it 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 9au3sjnk9y4z7jh2vpud tf ;8vw-k: z the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t grav gwtf:k.iof jw7s+5+ph for the object whose displacement as a function of time is given byvg +. wot5wf7fj:+ski Fig. 2–28.

Figure 2–36 is a position versus fr;-xn5*+oc,ia tyhatime graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (ga* tco-f,ri+n y;ax5h) 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 b;a16en6b)vq ) iu*pot(co zk)m: bwx a firefighter’s safety net. The survivor stretches the net 1.0 m be*x q( c;bub)1n tiwza ob6v po)e6m:k)fore 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-sixth whate6djpkl* + 8:jhhxz,b it is on Earbkhzj *ljd,px:8eh6 +th. If an object 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 ov 1rhb2: 6:hwzjnh; i0/c n2yyx/zky joer-the-shoulder seat belt has a gooj:2z 1hh/yn :wory/ibhcj26 ;ky xz0nd chance of surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m abh(jo/27 uwalnz/:(b p 5aefpmove 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, ana/b:2/pa((n7 e pmujwhf zlo 5d Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end dc5, dtii8;phcollisions by hauling them up on a crane and dropping them f ip d,c8tdih5;rom 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 travel mfwq2c/t(x m5s 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 accele16exai+/q -iab5fsm mration 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 will be the speed of the last car a+i61am sm x- e5bfa/qis it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving boy f,5)6.asoxgpx0bjr iq 8zy1ard 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 ,a xbo)igyx6z 1jq5s.f0p r8ythe person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessardg/oqn +(nn )cy to balance the average speed of a train against the dista)ngn+o d (/cqnnce 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 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 straighx m fh-d9 yz2rak1m.8st down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change it.mrm -y9 axsdfk2h8 1zs 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 wit -dbqerf6a +g3h 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 b dgrqe-+6fa 3or 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 freight tra dc9+lsm+wgn*x0cg zew8 .j,gin traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts f * 9g,wj8 g+ewm zc.n+lx0dgscrom 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 roof5 )e*lgieo, yg/ p1lzo of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has r1lez*)5 og yiolge/p, eached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the3htb3;plg c5 j course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained for th;chlj 3p5t b3ge last lap?    km/h

  A bicyclist in the Tol-sna*n:ghknlyof r4 c 7 :*9dur de France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 knr*la9g4*h:-flyn k:s7 odcnm 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 boun+-d6 y(xlro6 (7ih zh xn+mz:k5cg hksce up one-and-a-half times higher than the second child. The initial speed up of the second m(d7r6 l +ziohgkc6+s-(n5: hyxzk hxchild 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 tr(uz 99m555bcemztbf 5 nl5q nxaveling in the same direction on a track parallel to the road. If the train’s speed izmm xq9unc5e b55 5tznfl b9(5s 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 =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 zdcw8 h8ztj h1;gfwlr 2 632ns) cjw*hm/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body wj;1sc 8 z wl 3)znh8tgh6dh2wrfj2*c 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 acce4oezctr9m)ec9v ls,*o h8q 7 dleration 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 intehk 1(ef.5y4;ix j vcwfrsection has a traffic signal, and the speed limit is 50 km/s5y jexi(4ff1h ;.kw cv . 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 t/naull/6rvibi ( + ntm y;2(om-vqe7kraveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constan/6uk(/ v(lqro-mv;na 2nim 7ib+tyelt 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 ron,xdwfc6b,f5az. : hmof of a building; 2.00 s after that, a second stone is thw:zh6 ,.b, nfmacxfd5rown 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 vertical m-x (.l oavjxv8t:1mbly up at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from( j l8bv-xm.v: a1xtmo a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air reywrlvt4p (v-9 4 tu-josistance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistanc oyw-l-t4v9(ujr4p tve will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burge73nqm(3*sb0tsh1z,w nypmw s wpqhr1p;+: nb rs through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the ranwybnbw1zm phwn+p1rpq s: 0q73 *st ,smh 3(;te of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times yvi2 a(r(skupi;* i a0a56vg xfaster than Joe can. How many times hig *0ys kipx(ra26 av( 5;vauiigher 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 the gr)iyoo q;cir- :hmp1t:jn k08zound below you. You -q z m1:hp: 0ro);tkjoi ic8nydrop 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 which your friend threw the ball?    m/s

  Two students are asked to find the height of a particular 5cfuy.1t l2o nbuilding using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of thcu.2tf ny1o l5e 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 for the estimates of the building’s height?    m

Figure 2–43 shows the positio)9zs2gjxd w wgkqf26q in c69/i15 zbsn vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles hd2s gi/jc9f6 zkiws)9qqwgn 1 b 265xzave 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?