Does a car speedometer measu6m.n+rwux 7 rjre speed, velocity, or both?

Can an object have a varying speed if its velocity is cot 0 m9pgtt9v6ynstant? If yes, give examplestgp69v9 0mtyt .

When an object moves with constant velocity, does itvd,/q8aowb -grrx a* 5s average velocity during any time interval differ from its instantaneous va-x, o v/8a5br*rqdgwelocity at any instant?

In drag racing, is it possible for the car with the greatest speedfrjy 3qm663l. bxqsr. crossing the finish line to lose the 3sy mf.3 bjxqql66r.r race? Explain.

If one object has a greater spepy ,ylxf63xxdzyh oq1 h-.+ c8ed than a second object, does the first necessarily halxy6h8 1hcd +xz p ,.xqyo-f3yve a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerate05tf)/ dpwu9 8mlnf bma d)7nws from 80km/h to 90km/h with the acceleration of a bicycle w0bn p )w7fd5mmn8/tf l)ad9uthat accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and.3lp/u:nxd*si z ,rwxo. j0vg a southward acceleration? Explain.

Can the velocity of an object be negative whels0j nbfg 4fk)tlu+80p /xr)ln its acceleration is positive? What about vice versal04x)lpf fn t0uk)/j8g+lrsb?

Give an example where both the velocity and acceleration are ne;zzcg) ;rgio2*+a hp wgative.

Two cars emerge side by side from a tunnel. Car A is traveling with a spb1lyoeg785espf p3 d5y jz1 *jeed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/p7sp 53yoj5dg*1j 1 l eef8ybzh 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 k 3w9rv/qb/coacceleration decreases? If so, give an exa/o 9wkrcvbq3/ mple. If not, explain.

A baseball player hits a foul ball straight up in+k:kk s)30 w,dcysec lto the air. It leaves the bat with a s30 ke,kc sykw+:cdsl) peed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening 7l5j mhn0oo/ f/zs5ovto its acceleration due to gravity — dooo fz5/5hl 0mvo/7sjnes it increase, decrease, or stay the same?

How would you estimate the maximum height y50mymr4 q* ojgem6z3p* vhn ;fou could throw a ball vertically upward? How wouly*nmz 4hmo6 fp;jv 5q03r eg*md you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at ail*e*gw+i g.o+ pt2pu constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for the entirg.+ptuig *lew *i 2op+e trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-;wkzh x*knnh cn4*5+rlong 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 hean45 n+*r *cxknz;whhkrs the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acaue q 917ty cci835/spm3d hzeceleration: a rock falling from a cliff, an elevator movii8auc/1e53hp3y7t 9mzec s dq ng 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 upward will return to its origi*4d, ydk2*p6ros1mjh.slq u inal position with the same speed as it had initially if air resistance is negligible. If air resistance .hqlm, sudj2s pio*64 *k1dyris 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 velocityp-oerk-mum1 xp zv l.kp b0d5i, bh7p9;yw)+ g and nonzero acceleration at the same time? Give er5- xpz),u gpkmk7o;iwp 1.0 ml9by+edbvhp- xamples.

Can an object have zero acceleration and nonzero velocity at fhrapnj vcv0.)p02d iyhn70(q)3 x i dfmuq2-the same time? Give exampl( n2pid7 nqvf0qmxa yd3 0p)vchu2 j)0.h-ifres.

Describe in words the mork ntm -efd6s, -v:+uwtion plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the motion plotted by walkingv6ruw- e+k, t: -sdnmf or moving your hand.]

Describe in words the motion of the object g;khpgfv7-m3g u*1q ji7q/ tnp raphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 k 5,0sy +n3xhaebp pnn)qx:7w o7.swuum in 3.25 h?    km/h

  A bird can fly 25 kmow t2ggt/, mez-gglkv /r/ +*s/h How long does it take to fly 15 km?    h

  If you are driving along a straight road and you lookg(woqmye zp. u2 zp..;*o km2w to the side for 2.0 s, how far do you travel during this inattentuo.zy gpp .*wz;(weqm mo.k22 ive period?    m

  Convert 35 mi/h to 0ylgi171c;1 nx- /fkrftsydf
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from /;aco d jf3 6j.bvj7gr$x_1$ = 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 steadi ;rsq ulutw1n31ywx6 (ly at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours aw(w xrynsu utl 36q;11nd 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 light bqqmbm5chm, qff3*( v8j95l lning flash and the following thunder giv3l9(hcfm l,*fqm5jv5q8b b mqes 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 6it )3s6xeg c0joc1mn laps around a quarter-mile track in a total time of 12.5 min. Calculate 6t cc3i016j oxs)emgn
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in rzn4h6viz88uk,;m y 0t-/jejj. mblg a straight line, moving 116 m away in 14.0 s. It then turns abruptly ai my6g;tmh0z. v/lbue k8 j,nr4 zj8-jnd 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 ot e(+mjfr/ dbq5fp. ft25x4fo- nfdt:n her 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 thd.f(jpf :5fn/m+foe ndf45xb-rtt 2 q ey reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind aai8.bmbmfx5yy7hn .vz/( sp2 truck traveling How long will it take the car to ixm8( /5z p7.ynbs.b2mvaf yh reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/9js a 48nkfzhcw2 ds8(h , and then encounters a tailwind thatw2j(8ks4h98sd naz f c 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 ipmk3dmhv fun-5(x4xi s+0cp ppb8p++n which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 kmnpvhs m05xd ++u xk+pbpf4pim(p 8 3c-/h.    km/h

  A bowling ball traveling with consta cua3xzrw6( -lzg3 kxw7e*zz 2nt speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. -ewzxcz 7zk lg2 *z363axr (wuWhat 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 ave x uta,v 9i/rcg 7qbabx72a9b/rage accelera9,7x9b2ti qva/ c ax7gb/ar ubtion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from res5twqzt d4k*sb,q /z.es ,6slmwk/zz(e3:g tj t to 10.0 m/s in 1.35 s. What is her accelerationwsge/e zq* tzk,5 st:/.zb6mlw 4kzqst(,3jd
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular autoo rfi;p0y crljzv a zk3x:81j-1pe4( lmobile is capable of an acceleration of abou0 f-1xz ;a o1(vzli py3jp crj4r8k:let $1.6 m/s^2$ 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 in 5.0 s. If s x0s b0 p17sav9htb8ai/bg p0it then brakes and comes tos0shas09x 81g / ipt0vbb7pb a a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest fut;za x 5dtf)1) j;wxat t = 0 and moves in a straight line, is given as a functiod))az5;ttwffxu ; 1jx n of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 s,)- okm smvgr-gns- :s. What was its acceleration? How far did it travel in this time? Assume constant accele-msorks)n-m -vg,s :gration.    $m/s^2$    m

  A car slows down from 23 m/s to r r8g/mqsc zc+m) ,di5uest in a distance of 85 m. What was its acceleration,)cmq r/dm5 ,u+8zigcs assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How 49* 9,bgybpz-eq q jlolong a runway is needed if the (constant) acceleration is4g j,* b 9qb-ployeq9z $3.0 m/s^2$ ?    m

  A world-class sprinter can bpd+ b5l:a:v*at/j 9unt9qt byurst out of the blocks to essentially top speed (of avbq9ytbd* at/j5u 9t +al::n pbout 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.,hadt fxcx -n3 h8)a4a0 m/s to rest in 6.00 s. How far did it traven3a,4a hd)axx cft-8hl in that time?    m

  In coming to a stop, a car leaves skid marks 927g jk )o1iefimz4i*;(2b x gib m long on the highway. Assuming a deceleratf ig 2*g)oix4iz1(7ej ibkmb; 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 end of thejx,lzfst c.d. hu) zfth4s d3:fh07 l1 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 t17 zhl,h)fszstl:jh3 .fxd c4d.0t fuerms 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 p(.ysstg m,l ajx72: tspeed of 95 km/h and human reaction time of 1.0 s, for an accelera lx mtp:. jy,(s72asgttion
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stobf3gau g3(m1 /oid4 :m v*ii;inqptj;pping 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 driv f) (fe8c-vi6( yejsegt2ugb3er looks for an opportunity to pass, guessing that his car can accelerate at 1.0 ) -8iefc2g j6f t(3uevby(seg$m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to complete the 10,000-m run in less than 30.0 min. After p0;zzlzmy 3c ,/gt;;5po ihm pexactly 27.0 min, there are still 1100 m to go. The runner must then accelerate at 0.2/ mzm;,;ocli5p;pzz0 3g py th0 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h(zvw- k0 )eqdw n5v1gh 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(v)wqwdgv5 z e hkn01- intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the groundsiw4s/1m,y qn+ki 5vg below after 3.25 s. How high is th,y ki15 nwsiq4v/s+mge cliff?    m

  If a car rolls gentl xzl,xy;1kkx,y ($v_0\,=\,0$) 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 speed of 22 m/su2mj80gywxt ,u ma34q
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches he31jh245j,ygzkhs t 9zi.( ezd4txwa ball 3.0 s after throwing it vertically upward. With what speed did h x(z1z95e3hjy4tzgkj i.hwtd2 s, h4 ee 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. gudmar:ox- 6 +Draw graphs of (a) its speed and (b) tmr g-6doua:x+ he distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 mxshz1gm 40- h ku-0lrq/s. At a height of 125 m above the Earth, a package is ds 0-m hhr1u0xg4q kl-zropped 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:i:6s, n-qskd ,lolg t tb:fy:ry k7.w freely from rest, show that the distance traveled during each successive second increases::.,k-bwyrnkti yl s: tod7,s fl6g:q 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 (algebraically) that a ball thropgx-8,tdrr5tbyd w*v2vv , :own vertically upwab ovtgd8*,5,yx rd rwp vt:v-2rd with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 m eod* a t.2,ftovg.u.n/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–18 (or numbeb*u;icuy7(+* ek iaxhy0x vg:r of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positionsy xbey*x c7a0hiuug*i ;(:v+k, 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 tall (Fig. 2–32). Fz l w3v-y s2qn:(hwe3xrom what height ablw 3wx(vyeq: 2nh-3sz ove the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, an.sormsg 0flu z/;:j j*yr2r:ad the sound of it striking the ocean is heard 3.2 s later. If the speed ofo:j2*;rzyjg a rum0f.l/:ss r sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your gad5ie+gk g( 6xjrden hose nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–3ik(e jx5gg6d+ 3). 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 m/s from the edgehl2:(xl5x3 ep, bofxe of a cl:5,eh3bpo2 flxexl x( iff 70.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upgka 3qjf od1dg(--x6sm8( c syward by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from th 3 -f6d8s(ycdxogmgjas k-q( 1e 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 wh z92fjml67y ogat 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 magnitude of the acceleration greatestojf7m l 26gy9z?

  The position of a rabbit along a straight tunnel as a fulsy b:4otzp;h rt3 1i40ti h0s:0ueji nction of time is plotted in Fig. 2–28.0i z:e hiht0i3;:1 os y4tjb l0sptr4u What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile canox4;qxc 7y;ibv 2ev1lt j4(qy accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots i;t( q1 i74c;4 vjoyve2xylbxqn the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (F61p rhe5z uu:w7 tv4xcig. 2–35) when it is in 4wpuvh ruztx 71 6:ce5
(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 grsm 5l:nch .uy,qo0- 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 functioyx g6ddpgww3lp4 xc u+v08.5i n of timeydcd iw g 4wp.l+0x8g xuvp653 is given by Fig. 2–28.

Figure 2–36 is a positionf-44u* fc303 .sbm oqabjntxe versus time 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 tnso3f-mc4tb40 j*.qu fex3 bahe 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 15.0 m g (7-5pv2rt fgtxs :i;ubqub/above a firefighter’s safety net. The survigi(gru u;svbp-72/bqft tx 5 :vor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what it is on Earbj2e/rr9 x4wnth. If an object is thrown vertically upward on the Morwn9e bx r2/j4on, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by t8w,r5 e+u*mxmq+fmxq w ,z4n an over-the-shoulder seat belt has a good chance of surv+ f, +xme mt4w, q5uqrnmxw8z*iving 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 brids3k(e4.ov cs we;st.rge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a t3..wv se4rs;(k cesoflatbed 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 front-end collisions by haulingj- kn,d82 .q;k epigkj them up on a crane and 2qji p-k8k; .ek nj,dgdropping 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 travels about *fja 02v w9blx$10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration f8y a u6y8.yalxfu ,vm5od05 ntrom rest. The front of the train has a speed of 25 m/s when it passes a railaft5nm .vxuy86d ay lo5y0 u,8way 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 deep po ew6am d)pq6uy5ic:mly 5,ec .+vpqg2ol. The person’s downward motion stops 2.0 m below the surface of the water. Estiu6)w2ygem5vd:l,6qa ep c5y .mq +cpimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it pjb lgj xw97+9 hwi1lw0c,wk8is necessary to balance the average spwcx+wh99j,80j 7wgl ikp 1wlb eed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip 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 diving o- )8os- cnitffor 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 ev8-o ofi) cstn-asive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with whi gp54d9,hb fquch a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill4db fhg qp9u,5, 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 t q -il -(mdbetd6-84wz qp(y*sxg 6uk0o mlmx)raveling at a constant speed of 6.0 m/s bxdk06() 8suemmytw(oq i 6-pxl*q--gzm4 l dJust as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped frf dq942qxq/ pgom the roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second q9qd 2p/ xqg4fone has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a grhj82h7 7qa dtime trial lasting ten laps. If the first dqra 778gjhh2nine 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 cvmy*gtdn28; r6v:udp k1 ee 7frests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in: 7kemvr1n pg y d2e86;dtf*uv $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines)1vtk7rc ) suf. The first child can bounce up one-and-a-half times higher tha)k v7scru)f 1tn the second 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 overtakes a 1.10-km-long trai3h2-b2sa7 hie nultq hk:dsfy9. h,f*n 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 :7 hhh ky,223ihnf-f9d tqus ab.s*leit, 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 m/s In throwing the basefpz /a)n 8 -qfjnlld)(ball, 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 motion.z8nll ad)n /fqj- pf()    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration od5 4ol 6-tfz:7uri 6dppx 0kmof $3.2 m/s^2$ 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 traffc6v x)5iyi.oemb z- o+ic signal, and the speed limit is 50 km/s . Suppose you are driving from the west eb.+ m6cix5oo i-)vyzat the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120 1) 9ur.bbdlaj km/h takes off in hot pursuit. The police officer catches up to the speeder in 759a ldj).b b1ru0 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that, a second stj8w;598:hxfx, p5flf sqxo:mdm 1i wnone is thrown straight down with an :x8jw 5ff1nmo 9;,x idqxp5:lhfwms8initial 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 aj8;nx +k)-g dajwn;yc t the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony 8ykjxn- dg;wj+c;na)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 resistance, how lon5 ea-gbwn1ss p2-rs2lg would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she wia2s l2eps- 5 rgnbsw-1ll pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a grip9+s w8q 2ecwylling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how 289pw+w escq yfast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe g-plsj jup/. puzv/ ),au3o9rcan. How many times highrsp, /j v3o pupgzu/ )l-u9aj.er will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a clieae39wr0zl402 eck :mmgm p 8sff while your friend stands on the ground below you. You drop a ball from rest arle9z 8 gm3040s:kwmc 2eme apnd 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 heigh( as.i+vxp 2qgn 87 ,/uif.rh n4ckpfot of a particular 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. How much difference does the 0.3 s make for the estimates of the p(rn7oi2g4qu h +8v,pi ffkcsn .x/.abuilding’s height?    m

Figure 2–43 shows the position vs. time graph for twod,ueqc68,lx gm m:j)lmkm . s9i(y, pb bicycles, A and B. (a) Is there any instant at which the two bicycles have ylu9,(6m qmcg,l smp d:).k 8ex,bji mthe 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?