Does a car speedometer measure 8ti/9 * bpbiaaspeed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If 4x t ) kbl48 ghjc3kuny2):prqyes, give exampj4 tlp48nkq)r3 )2ykbxcuh : gles.

When an object moves with constant velocts /p)*wau rwrka8a 6ij2m 5.kity, does its average velocity during any time interval differ from ia)/*8i rwk62ujrt5s kwma. p ats instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing 8rwxtoc7:r/r g,e w*zthe finish line to lose the race? Et8/o:w7rr,zw* rxg cexplain.

If one object has a greater speed than a second obb y; 0 kg6em/oe.fwyxs+ hh91aject, does the first necessarily have a greater acceleration? Explain, ;m0g.fke1w /h6y+oy9he s abx using examples.

Compare the acceleration of a motorcycle that acc lhj l 3vurrvl5bz +lt0s);*;celerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest tov+ls h5jr*)buzlr;t l 03c ;vl 10km/h in the same time.

Can an object have a northward velocity and a southward acmjnpk:cdcidgsr :. vb-): 3a*celeration? Explain.

Can the velocity of an object be negative whaq58m-:(vv1mceu7 bw) h lqkgen its acceleration is positive? What aboua:wc8e l-)5 m (q17qvkbvug mht vice versa?

Give an example wherc +6y/tpc7 +i2uba svje both the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel.:x rt:(l-bh)8umyk eu 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 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoningubel- :xrm8yh):u tk(.

Can an object be increasing in speed as its acceleration deca2za/4cshh0+cz k t5treases? If so, give an examahz 5t+c 4 t0hkac2z/sple. If not, explain.

A baseball player hits a foul ball straight up into the air 0814auxiq ;;fse1xdoht54x odye8lr. It leaves the bat with a speed of 120km/h . In the absence of air resistance, xodq4 0 584ehxoei1 ;f ldt1xryu;8as how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, wfbv3noks:0 wbk5 qiw/7u50 vzhat is happening to its acceleration due to gravity — does it increase, decrease, or s/v5 0zo vn5k bs37ufikw 0w:bqtay the same?

How would you estimate the maximum height ykk4tw bp- 1;k2ugz q)kou could throw a ball vertically upward? How would you estimate the maximum speepq-b;)u kkt 42kkwzg1d you could give it?

You travel from point A to point B in a car moving at a con u7)s pdt75;p5giq hdtstant speed of Then you travel the same distance from point B to another point C, moving at a const dtgq;uip) 57pdh5ts7ant 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 vertgbxqra2:2+vux2lle g r i;w -7ical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at 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 t7l:+x2ql -a; u2brxrw vgg i2ehe clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: imv : viqh5tw y-,.ik+a rock falling from a cliff, an elevator moving from the second floor to t - vki:qi h+,.imtwv5yhe fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return toicf7u8.s0x,ebh k emv 5(m 9ax its original position with the same speed as it had in( e0h8 9ix7m.s5bmf vckxae,uitially 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 direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the sa1o dk nfzo 5ivcpp+e(:s6l twzo*29k*me time? Givezkc9*sznt f:(*+pw o6 i1edop lkv 52o examples.

Can an object have zero acceleration and nonzero velocity at the same time? Give/kf5 fggrlmun (iw7czm3s: ( . fk cf(zgn35 mm7lr:wgs .(iu/examples.

Describe in words the motion plotted in Fig. 2–28 in terms of vukd-a+mfnwc c:(n k 9v7 hxu8,, a, etc. [Hint: First try to duplicate the motion plotted c:unu x-dn9wvf+ k,m( k87hacby walking or moving your hand.]

Describe in words the at* 33 hazg xns oz 67.zclmo8/k.(frmmotion of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.25 p,- 6av3k50vx0-izwaw lo eln h?    km/h

  A bird can fly 25 km/h Ho,1jc*qqa2 d6nke1y ku w long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.rf8+kwwx 4 y,dqiev+10 s, how far do you travel during this inatt ewy8vd+q1 wx fi,4kr+entive period?    m

  Convert 35 mi/h to p mk6l- db.u;i
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves flq5uf kc.c3x. rom $x_1$ = 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 fromgtx;)lhp-.l.es3rrsk1 p s /z school steadily at 95 km/h for 130 km. It then begins to rain and you slow to 65 kpstszr..)l1hgl-r p s;ke x3/m/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning fugievp kj- ja)7 gi(e w5pz7+py-vze/7a*l)vlash and the following thup)j--*5y7ipezezgvvk) l7iuv7 jp ega a(+ w /nder 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 rule.    m/s

  A person jogs eight complete laps around )ve7cjm 7ice,06 i izkk*- m*gozpkf8a quarter-mile track in a total time of 12.5i7iko k e, i7p06v8mzz*-cm*jg)c fke 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 -8-3(ai zobvaqkr-s vline, moving 116 m away in 14.0 s. It then tu s-3i za(vovra-8b-kq rns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Eap+ym(z s* *t d)ui0zz.3uaqgpch has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it b 0 isp3(dp *gmz.y)tuauzzq+*e before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck travela 4kju o0pil:-ing How long will it take the car to reach the tru:o-kupali j04ck?    s

  An airplane travels (r,f(1h o d8p sa+tv at51tsyo3100 km at a speed of 790 km/h , and then encounters a tailwind thdtaf15h (ry+8t aots os( v1p,at 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 average velocity of a complete round-trip in ,dxmom a2kq x/ jbr 94peimop9.; -nhhi9/xz:which the outgoing 250 km is x o94 qkipn.x/ra,-x j9mho /pdiz2:bm9em;h covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with*pflrd* ,c 3cs) )0eaq9xld zo constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the9p)c*ld)q o,dz3s 0xfcearl* 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. What is its average acl t em)m7yn5:wm j*-lwce)ln7l -ymwjem w*5:mtleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. Wha4dk/jcmr3 pp xcy*(xrjf93fz6--);d vczt b b t is her acceleration /vckjm-fxx; p4bd6rdrfzj cc-* )(3byzp39t
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a psq9w +(w-yb9cg kmi r5kx z7j/articular automobile is capable of an acceleration of abou5sw9gkx9r+ b/7 w ( ymqkz-ijct $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m i-k c(g rcqh:.f8jzms( n 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its accelerzg(jr:f -kmqhs c.8 c(ation 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 k5x*k6j4elb pgq l a1/ qave)4t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimatee)jpq 45 * le gaxqlkv64a1bk/ (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. What was its acceleration? Hooqb f59ac6xqnbt8 d7z-4*r grw far did it travel in gqctr* 4b5qz 9-abx 6r8of d7nthis time? Assume constant acceleration.    $m/s^2$    m

  A car slows down fro jn5l3jn+no :(d0m mdwm 23 m/s to rest in a distance of 85 m. What was its acceleration, assuwj:n o 0m3dj(dnl+n5m med constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takxi g4.n1egq-xl2ptg*i ke/f 8eoff. How long a runway is needed if the (constant) acceleration is fg4t8.enq i-gxp *x1/l2giek$3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks *0w (im xr:l-yvs+k puk-.md tto essentially top speed (of about 11.5 m/s) in t- k(lm s ur*.p:dxtiw +vkym-0he first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s sqiu- m5 vpm9ejy+( -lto rest in 6.00 s. How far did it travel in thami95q-u m+p-evy(s jlt time?    m

  In coming to a stop, a car leaves skid markscd* 3k*+r nvu140gnhfh6n ps l 92 m long on the highway. Assuming a deceleration o3sv06n k *rnf+1 hc*lg4u hdnpf $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h str.t v 60sznkow-ikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.8 s tw6.n0-ovzk0 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 initmyd2hac+spq+n+o ;u2pi d5x/ ial speed of 95 km/h and hup/p + m+2o5cu a;h2yqnisd+dxman 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 equatiof xgj9.7 8fqnatsb8* kn for the stopping 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:ea6h t wxneks1ny mmi28:thf ,8 ;bi;/s on the highway. The car’s driver looks for an oppwhmsi b12m ;6;xn8 th:yfetneia k8:,ortunity to pass, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to completz3wj;r; cfqw +e the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at 0.20 + 3fwz;wr q;cj$m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 .,vk s+zk;k od0 h1l;0f .rjsny2tp,nroanm*km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the lightk y0rn;2 ajrnpl*ksns+m 1 ;.,okhd .t0ofv,z 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+r-t h3w0m7gt mo9cbn ground below after 3.25 s. How hiwt9mg+n ro b0ht-c37m gh is the cliff?    m

  If a car rolls gentlye0(wijhm /x0k,-rpl / g7zf zr ($v_0\,=\,0$) 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 witk w)p7p4ssrx/p 2/h akh 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 thr7scuxh*;u e+nly3,gdowing it vertically upward. With what ce+; 3udnu hslgx,y7* speed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest aw bl84s6 u ljkus4o84xgcgrr;h* 7*swnd 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 . Ignore air resistc4k lsbx8wws 4ou84jhrsl6g 7* g *u;rance.

A helicopter is ascending vertically with a s 4 ,4efx j0b/l rlzlq:yyz*)pgpeed of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground?zl/g*b, ejypx4)0y r:fzlq 4l [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object fallinusx ;yd.k2)(ov +kyn wg freely from rest, show that the distance traveled during eac)vx;n(d+koyu2 sy .w kh 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 2–21.

If air resistance is neglected, show (alp1i n u25*wsc +0rluhxgebraically) that a ball thrown vertically upward with a spesh 2* +150lncwupx riued $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verticallymz7h7jmh3bk 1jm u wt mn7.8c+w* s oidz*)6zi 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 photoflash l8i )-j,anbzt / (hzguof the apple in Fig. 2–18 (or number of photoflashes per seco(iu8na/ t ,b-j gzlhz)nd). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m talll.reit*;o i:j (Fig. 2–32). From what height eri *o.lji:t ;above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the of5un(,cu g9mycean is heard 3.2 s later. If the speed of sound isg cf nuuy59(m, 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You bpo (dk5bobp(-/(t5he .tqyapoint the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear (qa/o5d-y bbetpp 5b(koth.( 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 12l)b:d)vn0 q ,u8qmuyh.0 m/s from the edge of a cliff 70.0 m hd)0qm:bn)8 yulquvh ,igh (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the stree4qc ;jk4l vcxbgjb/ 1f 6fue::t with a vertical speed of 13 m/s If the ball was thrv:g4q4x;bek1fcl jcfb j6u/:own 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 y+b zv-o*;ixw time. (a) At what time was its velocity greatest? (b) During whv*oxy;i+bz- wat periods, if 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 alonas38ygznbx)o 0*c ,ei g a straight tunnel as a function of time is plotted *bg y0,i)oxz esn 83cain Fig. 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 automobil3ai sqkjz94qh,r c:l0e can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The sha3 rjs:49zh lqqci0,k ort 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 k-*sj:l5f0 pxk:ogu m3be4ji car in the previous Problem (Fig. 2–35)5j:kl4x: pu-eo0i f*ksjg3 bm when it 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/7 sq4r pav*h qs1ewpt8w9 ux* the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functio*,v(yy ad3lt dn of tiv*dayl d3 yt,(me is given by Fig. 2–28.

Figure 2–36 is a position versus time grapknkgwn7g6w5f12 -zl vh for the motion of an object along the x axis. Consider the time interval from A-gk17n5wn 6k 2lgzfvw 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 interval from C to D.

  A person jumps from a fourth-story window 15kpt 9uskdm eh8 zdv4kk :hn-(5yc 9q46.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m bek6ts4 9hq8kke4mz 5(hpku- dnvcy9 :dfore 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 what i/5)ssqzeu +nst is on Earth. If an object is thrown vertically upward on the Moon, how many times higher wilu)ssq +n5 es/zl it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt8 he9.mbf :u zmtgmy* h r*)sryn84mrf**8pgo has a good chance of surviving a car collision if the deceleration epoyf fz t* .*mh8r)uhrymmnb8g:s49r *gm8*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,n4bop fnjw .k9ily s+ .ws41:z 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 trwf4:.o+ sbp1il4 n.snyj9zk wuck 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-en++a kt,m1neect0dqr qawv 3pd5k8:*3cx 6hva d collisions by hauling them up on a crane and dropping them from a certain hk t61qph3xc rmd5a:,qe *c kw na+devt3v80+ aeight.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels aboutt.bbytn6 p3 o7 $10^9\,km$ 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 accelcyuryv 53n1pjp03d* teration from rest. The front of the train has a speed of 25 m/s when it pa 3 53*y1dv0jtupcp rnysses 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 Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface into a(a3+yj t m)mma deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleratimmtj3ma)a(+ yon 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 v43*xzhe87tyu ma ( uwnecessary 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 t8x mu4*w(3 7uyztav hehe 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 down when divccvowy3r 8h8 kvroe1l a9.i87ing 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 mustrhvkcy7o ec8 v o3w88.lia91r 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 strit8u1 akjgl7 8xks8wv:kes a ball is planned so that the ball will stop within some sm8u t1jg v7s 8kaw:8kxlall distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, 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 spe(hh8pvn)k oz ;ed of 6.0 m/s Just as an empty box car passes him, t 8hovpn (;k)hzhe 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 buil s2 jha)o7b6bdding. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a spebj)hsado 6 72bed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course /8 d;tv uz., fz(ucmdb xkjq78of a time trial lastinm z8kj8v fz ;,dxutuc/b(d 7.qg ten laps. If the first nine laps 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 1sg))5,ylz9y0i.g a 6 uxzhnhs8 km/h . At the bottom, 4.0 km farthery9gzu gh)0x. sz,i5) an6sylh, 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. nch* cuo ):itl-wa72oThe first child can bounce up one-and-a-half times higher than the second child. Thc*c 2o:l-tou h7n aiw)e initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/y+sk7( -ms,sp+j6 7mndn 2fb hta tz)xh overtakes a 1.10-km-long train traveling in the +bt+syssp mdtam6z-f7xkjn 72),(n h same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    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 basebxjjl * 5 ajnz: 1s3grfpn921dfall 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 it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motionzs jg xjn n21j5*lfaf:19d3rp.    $m/s^2$

  A rocket rises vertically, from rest, wi:uft*d-gu-)r0p+eh. x li et e6fpir;th 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 has a tra 1(hsa o4fte.186a ;idvqbmcg*kq 1 hzqdc y,-ffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights ,cs1q6e8aqat1c hi; - y*mk od4db 1g.hz vq(fturn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 fzk9die;b 9.f km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maiz;9 fi.d9febk ntaining 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 roy+yx qk52feu2i0dsr/ of of a building; 2.00 s after that, a second stone is thrown straight uxir2+q5 02y /sydk fedown with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stowxo 9/euuagm 1qp*euu ah( u/0a n8t: 7.az.xfne is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of 7u0. eneu:9q*p mxg/u uao(ahwxf /a1u.z ta8a 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 resistance, how ksow adp(q xp: zf(ky3w,5-p)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 wow( p5-:s k3ya,)ozx dfwkpq(puld 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 teebr 7c-psb( 63 1lenbhrough 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 r3esbr7- c6(lb 1ebep nate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a u42t.h 2wqmcfspeed 1.5 times faster than Joe can. How many times higher will Bill’s .4w f2q2utchm ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stan7 dhv 3yi1+ujl-cwwp9 ds on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such 7l ipy1dc3w w-9u+vhjthat 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 buildin15yf;zgl z*42vla-or)oy 9 ugzbd, ckg using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference dov ylry)dg o okz1,g59c ;zlf*bz-a4u2es the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A -sntyx (5f6xd9, ztpxand B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At whtps-,6t9f(nxx5 dx yz ich 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?