Does a car speedometer measf/cgtux vii .x4)it3qwc* , ,lpwei50ure speed, velocity, or both?

Can an object have a varyingo5 mw f+l(j0qf speed if its velocity is constant? If yes, give examples.m0+ wlq fof5(j

When an object moves with constant velocit brxx xo2u(zn+9 t,l;ly, does its average velocity during any time interval differ from its instantaneous velocity at any r 9zb(nu+lxl2;o,xxtinstant?

In drag racing, is it possible for the car with the greatest speed crossi3s 0j-;x2 (fikfziya mng the finish line to lose j; xmys-akf3f(0zii2 the race? Explain.

If one object has a greater speed than a second object, xrlm7f9pyv 21(p6 gqrt, id3ddoes the first necessarily have alq 1f9rpx(ympi,6 d73t 2drgv greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates frokeyttbr,0i pe /,q*8w m 80km/h to 90km/h with the accelerationk,btw,0pt8erq/ y*ei of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward ve uj -:)pwoy))qm -bfavlocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration isv ,sx5au :),v u/st 9kri8suzg positive? What about viceu tku 8ssz/vi95gvr),suax ,: versa?

Give an example where both the velocity and accelerati3+x+krzq j*i d8k *nbjfa,.-gt w/q/lr xy: hxon are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a pvw8o9t(4 bxm/cokt- speed of 60km/h and has an acceleration of 40km/h/min .84tb m co-9/txwovp(k 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 speed as its acceleration decreases? If so, givenwjtu 5rnp ( j8cauhk:x7-n(; an example. If not,rjhj57(a:n x-k;twn(cuu8 pn explain.

A baseball player hits a foul ball straight up into the air. It leavesei*k 2xrtslx;h*(*k8n0r jgq 8/z wos(fnhg- the bat with a speed of 120km/h . In the a zq ;gte hi *os/f-nr(kw x*shjr80x(k*l82ng bsence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling objy+us vfl4;9n9 uq;uysect speeds up, what is happening to its acceleration due to gravity — doesy4l;qs +s9;u f9uvnuy it increase, decrease, or stay the same?

How would you estimate the maximu i6g:h 4,s 3qhhollbf5m height you could throw a ball vertically upward? How would you estimate the maxoh ils,h h3gfq65 b:l4imum speed you could give it?

You travel from point A to point B ing7 : v8r6q ,bhuhnq3gt a car moving at a constant speed of Then you :n vrhhqq7,bgugt 3 86travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical st8p 7 9xo)xm2fle ,rwehring 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 increehxf) 2po 8rxl7w,me9 ase 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 isfz m ju7as86tsm 4u*0g not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making stops afzss6j m*t8 4g0umu7 along the way, a dish resting on a table?

An object that is thrown vertically upwardf.,i//bqb-a f6iu7eh /bh ypk cx)we2 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 al/. 2,ku bi6 y)f-bxf /wcep h7ei/qbahtered, 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 veloci8m yt 1w bxlzu5 kcl/5dvir.3(ty and nonzero acceleration at the same time? Give examz3 l rk (xw58 dm.u/ytl5cvib1ples.

Can an object have zero acceleration and nonzero velocity at thz dg1(g63f eiha 8g)msm3*ppge same time? Give exampless3mpi8mdhf 6e z1)(3gg *gpa g.

Describe in words thew-d+ 3:+3x jpmed /qgrg:rblg motion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving your hand.]lj weg/mg+q: :drbgx rd-+p33

Describe in words the motion(mj; tmht g.k:n:l/rz of the object graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.2f 6-q,5ktvb- fraw9wf 5 h?    km/h

  A bird can fly 25 km/h How long does it take to fly qe, bo9an2n zr717vdx15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 c-,w:.xradvrvr/ qb vwhgyl1,+ c1-ls, how far do you travel during this ir:yg1wacx ,-l + r.dwhv b-vclv1rq/,nattentive period?    m

  Convert 35 mi/h to f:nl w(3ab5b b.s3d*wpjj qn irja :+*
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fkndn 7z1arv r:i5rraie+6 9-zrom $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 km/h for 130 km. I nk .a5h5x/skft then begins to rain and you sloan5s fk5/hkx.w to 65 km/h You arrive home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-taxwbib(ed(j4 o(y7 r8humb, every five seconds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arriio7(by d4rex(j (w8abves in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complui0bj bmn-b.-w3qm jc1w r8b:ete laps around a quarter-mile track in a total time of 12.5 min. Ca-cirq .:u 8b -1bm30mjwwbj nblculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m away in5/5(6e g khaf; mylp.)d+ 4k. wg6usssf nigme 14.0 s. It then turns abruptly and galsu i+mf5gp54 en dkwsfsa/6glgm ).yk .he ;(6lops 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. Each has a speed omjt7 3,ytu ocoac/2p k9ma+4tf 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it bjamtc/4oy+ ktt aco 7mu, 92p3e before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behc t5a0ysa vw: 3yjk):yind a truck traveling How long will it take the car to y c:0jay) 3ykavs :wt5reach the truck?    s

  An airplane travels 3100 km at a speed of 790vz) gf/pq*y a7 km/h , and then encounters a tailwind t*z 7pgqvf) ay/hat 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 j 4bkv,td.*;vs;3vo ha4urdq in which the outgoing 250 km is covered at 95 km/v;3qu.br dt,;4dka svv jho4*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 etr .zf )v*z65hsk-k6 dxjka, the pins at the end of a bowling lane 16zv) skkf z-6 j*t .h5xaed,r6k.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its average *mo g y3xbzk;.acceleration ingxmzko*; y3b. $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest tqkjs3wxem-f d;8 :ajx;r;o 5go 10.0 m/s in 1.35 s. What is her accelerationxg-jo5w ;f ;daesxr;qm8 k:3j
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleratio:awne5(sng m tl 0-rf,n of aboutsnlfa(:0r5 - en wtg,m $1.6 m/s^2$ 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+diuyq esjo7j( x *64tn 5.0 s. If it then brakes and comes to a stop in 4.0 s, whtdq4sie6y7o+xj *u(jat 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, whic/ar(ies p2m; d)vo;11ytxd a oh starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Ta/)d yi(a2r1 tae;ov;mxpo1sd ble and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s. What wsgaabu 5:z09* mqxx6fas its acceleration? How far did ifxmb*5xq s 96zg0au :at travel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What wa(c 8:z4psclby cx7qaf 3q+l0-ojj7h ts its acceleratio4q(hjp0qy8c+-oxlt:lf7 c 7cz b3asj n, assumed constant?    $m/s^2$

  A light plane must reach afubl2c;be72auvb(*c s+ ro5 enux) 2rze;qc7 speed of 33 m/s for takeoff. How long a runway is needed if the (constant) accelerationc uz (;2rnv+2)aq2* bub 5er7ocb ;x7esefulc is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blockb,v/tu9h j1*zzflpf -s to essentially 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 lu9flt1bpv f /z*,zhj-ong does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniforml/5me9 z 9ba gpgtutg1-y from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in that time? p/1t-e g9bmt g9augz5   m

  In coming to a stop, a car leaves s74de o, lnka1ipkv 2l;*iut8lkid marks 92 m long on the highway. Assuming a deceleratid7p84o*nlk2 t ,i1k;luv ale ion of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree. The front ee k/*ljaci .l8nd of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” wi. je/l kl*8cahere 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 s ki lizav;b0,+e+,rglpeed of 95 km/h and human reaction time of 1.0 s, for an acceleraib ;ikz,,l0r+eg+ a lvtion
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a car i n;h rj0ko *vrpp 1h9537igfdss $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , 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 trur8cw skxjy9. 3t)+r9yaw zm9i ck going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can ac8tkayr.my) z3iwxrwj999s+ccelerate 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, 9lnfu9 dg+c rg:gl7b:b; fnd2000-m run in less than 30.0 min. After exactly 27.9rbdl+d7l n:u 9nb;c2:gfg gf0 min, there 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 approaches anz9g edh6p.g, w5jw5 e icf-y,f 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 sf5dwjye6,9hz igwc 5ep-fg.,he 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. Ipaz)1 k)9e z-mt 6nrpst hits the ground below after 3.25 s. How high is the)apns-9k6tze)p1 mz r cliff?    m

  If a car rolls gentlyy. (1axee( yra ($v_0\,=\,0$) 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 with a speegav ( .h4kw4oz(lhwh7:mtvc 9d 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 throwingubw+k6qvif3c z*r w. 4 it vertically upward. With what speed did her46iw wbfq* u3+ .zcvk throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gpqpv o 5mtt((kc3-l8 oraphs of (a) its speed and (b) the distance it has fallen, as a function of time from t3v 5kq(tm 8p(ol p-oct = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/s. At h hq1(4a(xdu; .iwwtbs, z v1wa height of 125 m abov4swz( b( hh; ,dtw1wxa1u qi.ve the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distandjb 6p.0zj(lnce traveled during each successive sebz.(ndlj0pj 6cond 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 neglrcphnbs m7/ww5c.phx7 x(2d2 ected, show (algebraically) that a ball thrown vertically upward with a sh.dc(rmx pc2w7h2w5 /nsbp x 7peed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 m/i8 r8mmh2ae.yh54kow 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 en x+o 9(ec2v b;gr4, bxuecfl9ach photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two ap+9;ce vu ,lo9r4bcxfeb (xng2ple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to,bts n;+fslrc ssa+*: travel past a window 2.2 m tall (Fig. 2–32). From what height above the top of the wilss; stn+r c:bsf,+ a*ndow did the stone fall?    m

  A rock is dropped from a sea ij,p*y n*w7eu ; e)jelcliff, and the sound of it striking the ocean is heard 3.2 s later.l;ee *wy )7i u,ep*jjn If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of wagbz99k ys5+f /rwk 6heter. You point 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 verticyr6 99bkk/+s5 zh gewfal, 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 m/s from the edge ofg.6c jxabuz4tr e+r89 a cliff 70.0 m high (Fig8gtu46bz j+ racr.9 ex. 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 upwpzmq g,k p+ +8kn+alb(k.ac2xard by a window 28 m above the street with a vertical speed of 13 m/s If the ball was throw cbkx++mlgp,a2.nk (a zq pk+8n 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. (a) At )lt6 y)mdv,xb2pl4 ve what time was its velocity greatest? (b) Durin4x) v,lpmv2by e)lt d6g what 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 along a straight tunnel as a functiocuq.mdc w/x8k4unqptq 5+: ,n heyh/4 n of time is plotted in Fig. 2–28. What is it nq e.hnc58/wp:,udq 4m/k uqctyh4 +xs instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approximately as sho/ivwg sv8/ae .2)greh 7t(n ymwn in the velocity–time graph of Fig. 2–35. (The short flat spots7yi2n).w (tvhemge v srg /a/8 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 v g/x+1pez3c 0y7hdei car in the previous Problem (Fig. 2–35) when it is in/10 vpyx e +ceidhzg37
(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 **kawm*)l xuwf4qy k3object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for i2avpj/iw uyn) .q7 (rthe object whose displacement as a function of time is given by Fig. 2–28. w jaipuq72 v (i.rny)/

Figure 2–36 is a position versus time gr 5k9(n:tw17km*xthbqe6t spkaph 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 wm* 19x:n phtek6kkb(s tt57qobject 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 firefighter’s samx)m 2*0gq y :/umboed0b4valfety net. The survivor stretches the netbl/qd)b*o m2v0gyx:m0a4u em 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 fb0nbw 9nywz70z6y9iacp;*qw x e0hr av198 fon the Moon is about one-sixth what it is on Earth. I;a 1yw7ypf00c*bx99af9zzw rbnq w hevi86n0f 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 over-the-shoulder seat bxs khk5o,v3q 7elt has a good chance of surviving a car collision if the decelera x7v,oqs 5k3hktion 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 bnzbelu w*c4 fqkt3f5y -t-5i ( a(dg4tridge, 12 m above the road below, and his pursuers are gettin(t 4wfb45 d-ik*qf3u ytzn(gtl e-c5ag too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for u88o8x-zfty g bd+2abfront-end collisions by hauling th byx+ao 2buzt8d-8fg8em up on a crane 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 trazbizlgm/ -u (+csy kah,m1 ;sz7bfw..vels 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 begia sm+4j8ukpdkoz2a x:ffu7h5sz c8r6 q+w* z1 ns uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig6f82s u + ms1*qak a z748xhowkrj:5cudz+fzp. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s susnz11d;/ihsj rface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceler s;j hnsd1/1ization of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid tr; k7kvl1 f8,xdhbja/oansit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, t,k;8do/7blv ka x 1jhfhe 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 strsnu,7 5sq1vytraq 2g 7aight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the wat7nvstra,g 5yqqu27s1 er.    m

  In putting, the force with which a golfeju84v. ):n8oii8o qtpnt5 t sxr 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 missed. Accomplishing this from ani vos:j45 o.qnxntpi8t 8)ut8 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 7bc,k6(isjo j;vt+t qin traveling at a constant speed of 6.0 m/s Just as an empty box car pasi tk6 bjj ,vc7os(tq+;ses him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A s q+*vuu1c5 6heven z53qye0f gecond stone is dropped 1.50 s later. Ho efu651n 0 v+5qhe c3veygz*quw far apart are the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the xgo*8 27vu vpsxazk hff(/19a 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 fx2 ohvx9 sf7 8apzu1k (f/*gavor the last lap?    km/h

  A bicyclist in the Tour s-:m .qg2 dvyd jucym.ro6a(.de France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, hisjyacs v 6(urmd.mdogy.q2- :. 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 tw qhlg(m: mo 33u36gfbyo trampolines. The first child can bounce up one-and-a-half times higher than the secon 3 qm3gmh:og6(flu3yb d child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h ovt ( i87 xbroc*1 judw;mu*h;kveop.0v a b;sh)ertakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–4mhrvvis ;70c u *oh.p*da;towk(8x1eu j;b)b0. 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 oo3zq y /a fy:r1+w9baaf 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 oayra1+3/fbz9 wq a:ythe 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 accelee:6/inku.1na)fz v rpration 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 inten1o+t1 p/kc7+g uf;jpav:uprrsection has a traffic signal, an;+pc1jag+p7rvk n : 1f upu/tod 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 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 l sz0t,j e(u om(9cwt.a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acce,mtj.t9eou w0z (l(scleration.
(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 sea x:bh9dnwq5+*v1cr-qb w5 xu)ir- pfcond stone is thrown straight down with an initial speed of 25.0 m/s andq*pnad x-+ whuxc5r5 qfiw -b1)9:rvb 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 stone is thrown 3(s *e;l4o j)mwwqy :mtycy5 xwith an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a ly 5tyscy3eq(4o)*j w mm:;wx$4^{th}$-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 resistanc8c4io3d0 g8w)zr bpqle, 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 resistance b4p0cigzqw88od l)3 r will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through :vy4sq7 at:7p coxqq+ 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 rate of yq7t4qsoq::7px ac+ v burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at5- c5z873aj-ecitinj13eis lsrn( j q a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go thaje 5rts -1 ia-e8z7jjin i33nc5qc (sln Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of; agmgkqd 5*phds3p vq31ge. 2 a cliff while your friend stands 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 yo1v3.hsq35kpg2*me g add; g qpu, 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 particulakgd fvs0-13a2 hq6es wr building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. whs0a f3e6sqvg dk21- How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. tim h+y2p/b nue1wuumimf7m xq .i;vma62gx9 2 6re graph for two bicycles, A and B. (a) Is there any instant at which the two bip6ua; mgmur/2 q+wb v9xi iuymn6xfm 721e. 2hcycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?