Does a car speedometer measure speed, velocity, or bo*/e ge)le,z jxth?

Can an object have a varying speed if lw2ki 0 /(ttykt7) vvpits velocity is constant? If yes, give examples(ttlvk0 kvpy2 it7w/) .

When an object moves with constant velocity, does its average velocity during +eu(wxmw )j4 j 4t+wufany time interval differ from its instw twfuj +ju4xme(4)w+antaneous velocity at any instant?

In drag racing, is it(;bw7 d y9emw-xabs8 ui8 8lpy possible for the car with the greatest speed crossing the finish line to lose tydp8 9lbx mu8(bwsy-7a;we8i he race? Explain.

If one object has a greater :d k0c;3sg:,pftcw vt speed than a second object, does the first necessarily have a greater ac:0w;sp:, tg3kcfvd c tceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates fz m, y6m-u2 t,7jcnikvz 05jqsrom 80km/h to 90km/h with the acceleration of a bicycle that accelerates fro,z56j km0mvz ijyc 7nt-qs,2 um rest to 10km/h in the same time.

Can an object have a northward velocity and a a cjv-4swuw- f (+tivg jx3.;xsouthward acceleration? Explain.

Can the velocity of an object be negative wr:geogl sw-pi0g9- ef+-gt l ;hen its acceleration is positive? What -ol9:g w lg+0gg-spife; e-rt about vice versa?

Give an example where both the velocity and acceleration are negatmf1de/deuytx+. x:t 8t-yb : yive.

Two cars emerge side by side from a tunnel. Car Anc6** 4)7 saoclzo ewi is traveling with a speed of 60km/h and has an acceleration of 40km/honc 4c wea6z*i )*sol7/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as itsb cze.1b. lod89f hqy; acceleration decreases? If so, give an examp81z;dc. lby9o.fbehq le. If not, explain.

A baseball player hits a foul ball straight up into the air;6*-ml 9lpbdtmj+ir w,t1 f wv. It leaves the bat with a speed of 120km/h . In the absence of a*wj 1wt6;tvl-bi +mp d rlf,9mir resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to3y8 uh ea)rrzc,lxo)5 its acceleration due to gravity — 5xh) crz)r8uea3l,oy does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throzrmbhffg qn ) 1g)8v 34:7hwc/2txi sgw a ball vertically upward? How would you estimate the maximum speed47c:/rg3i8zv 2hmw fgqgxbt)) nf 1hs you could give it?

You travel from point A to point B in a car moving at a constant speed of T- nw6 rioc,gvs*)ur i0hen you travel the same distance from point B to another point C, *6socwv,)nr- ui r0igmoving at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string with ten bolts1 gt v3km whss0 -+nfm+n6p(6n(errh o 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 orm+ne+topn1 (0 h36hkfvsrsn 6mw( -gf the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions 8+*i v.in/7rh fekqyhis not at constant acceleration: a rock falling from ae7 .h +r/q*ykfnh 8vii cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticau9 w)flfr.3 kjyk3j4blly upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to airj3) f9yrku4 fk j.l3wb resistance is always in a direction opposite to the motion.]

Can an object have zero velocit mx;f 76oueqp9y and nonzero acceleration at the same time? Give examplesfe pqo9; 6xum7.

Can an object have zero accelerat4m y+qy okh zfc+zh/n4*mo )r4ion and nonzero velocity at the same time? Give e+ n4yq4m*r fzhhco)/m+y4 zk oxamples.

Describe in words the motion plotted in Fig. 2–28 in termsxca epe agq7p9dz528:3ubk v6 of v, a, etc. [Hint: First try to dupp63bup7:xe2a 8ecqaz5 gkd 9vlicate the motion plotted by walking or moving your hand.]

Describe in words the moth)nt/e7v6zfeg7+u m w ion of the object graphed in Fig. 2–29.

  What must be your car’s average speed in owt)t 5c )2.zsr9 yajylrder to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 3 :elg.fbx, r 5*wy,)g 3wleqey3hapl15 km?    h

  If you are driving alongyxy-gh0hk d1n :w: -ea a straight road and you look to the side for 2.0 s, how far do you travel during this inattentive perio: y -ahxnygke:-w 0hd1d?    m

  Convert 35 mi/h to 5l8n2omiker 1b ;m(n+)b0a aiitk5b1f,ug ol
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves from g; 5msahwxh vro .3q78$x_1$ = 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 mmk yk wf ejdl(7:79l8km. It then begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 minutymmk :8k7(wedjf 9l7l es.
(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 sel 9n920/ihmu tzribx2 conds between a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrrixz29 tn/0l9um 2hi bives 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 a quarter-mile track in a totm ytt*(jgm)t7j5 96ebi xk ,7i2vg3fx /ugaekal time of 12.5 i2x79vtfy kbg5m (/t*gj3 iu76)a t,jxekegmmin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m awq0xiky6 ( 8+r rjy*mabay in 14.0 s. It then turns abruptly and gallopsy6 xr0ymbqi8r*(ka +j 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 approtixis9 dr3w .t1s 8o6yach each other on parallel tracks. Each has a speed of 95 km/h with respect to the ground. If thsxwtd9 iyio.3r1 6t8 sey are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a truck traveling How pxq) a*i46wsx8 i:c6jfm lw,v9vk.b ilong will it take the car to reacp :l8ki6 si9xf* 6mw jq.a4,xv c)wvibh the truck?    s

  An airplane travels 31 yz , )yge4f 1e:uf2hdtujtk).00 km at a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/h foe,u4 k1tz jt gh)2)e:y .ffdyur 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 veih*; wu4 ly)yy y;j t*ra,pl5ylocity of a complete round-trip in which the outgoing 250 km is covered at 95 *atjwp) y54ilyuy;y y,hr;l *km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant spe c qu,4ms0qt8zed 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 relea u,0zscqm t8q4sed from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates fro1dfrrszx f 3cc40jlfj r l 8*.s1kq--br,uet5m rest to 95 km/h in 6.2 s. What is its average accelerls4 , u1k5lx3fjfs. dretj1rfr0-cb r-8zcq * ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates frmk;2/hbd/ ;c jradc: rom rest to 10.0 m/s in 1.35 s. What is her acceleration /jar;rmkc h d;2d/c:b
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable kz v wor,(u(y8of an acceleration of aboutzyr kvo ,8u((w $1.6 m/s^2$ 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 travel2qkhhgb /gann+ m2ds:7s58i a s 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its a2 nb m8h+5a2 sggihnk:d7qas/ cceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t fe+t bmg,jnd wh27qb1b1k8 ts)b( y;d= 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 Table and o (sd1t b2jd,8nmhwk7f q)+;y t1egbbbn a graph.

  A car accelerates from 13 m/s to 25 m/s in 6.0 sf g3,87m/msne6 b88q*)v1 nf h d ysfdhvcyz/v. What was its acceleration? How far did it trav vmbf*3fq/sm 8 dy8e8 chyv f1n)/6,nshgz7dv el in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distanp+j ql+ em86 wu av.u0z6krk3oce of 85 m. What was its acceleration, kluv3+ozp0 rqk.+6 wju 8mea6assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How l.czcldv y35spv 77wt- ong a runway is needed if the (constant) acceszc t .7v vw-p7ycld35leration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top snzh1dpv:+ czn( s+y )qpeed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average accel+)1(sc+qzph nz:dy n veration 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 w+ )pv1(nq gyxm/s to rest in 6.00 s. How far did it travel in that timey(p gqv1) nw+x?    m

  In coming to a stop, a car leaves skqd d x45/ dgh*6nbx)ptid marks 92 m long on the highway. Assuming a dec 5)x6nb*gq/d4 xpd tdheleration 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 thjtm4hwsp/ 6 p1e 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,” 1mhw4pj 6/ sptwhere 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 9vcbvawh+g74e)yb 8s,5 km/h and human reaction time of 1.0 s, for an vw4c8y,hs7ge+avb )b acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping d)hpr; ,zcq /e +iuko5sistance 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 driver look1w9 f wrv0*gcfs for an opportunity to pass, guessing that his car can accelerate at 1.0 *cffwv w0g1 r9$m/s^2$ 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.a +0hyrnwd; atp8hgq6 glk:5.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner0p8h5t hang.rd 6g; qy lk:w+a 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 an intersec oj zue:+tt)jyj 9.,mition just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red?uz,o:9yi. jjjt)+tme 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 grmp*2r4w kus ,nrqk*jon(sd 6)ound below after 3.25 s. How h2nr(ns,dj4u )pqswm *ork6k*igh is the cliff?    m

  If a car rolls gently ,q* gy63slx4 bpzh d6g($v_0\,=\,0$) 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 yk5udfl r,lbued4 sw4.yv qfn5f+92 ,air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a baubm xoj;lrmrl7x44 k) i8d o,/ll 3.0 s after throwing it vertically upward. With what speed did herjl 7x4 )/ibul4 ,;omr mko8xd throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest ani2/hn mhprq6( u3fq0ld falls under the influence of gravity. Draw graphs of (a) its h62mfq0n( l ru 3qi/phspeed and (b) the 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 m/s. At a height 19 p*rq2r b;:0xij;hthpi;0imsrn m x 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? [Hint: The package’s initial speed equals the helic;;thrqx i :p;0 ri2j 1 xrshn9mi0b*pmopter’s.] t =__ s

For an object falling freely from rest, shvdlm0 :)m6wfqw1s o* xrq.pl 52/ lcamow that the distance traveled during each successive second increases in the ratio of successive odd v*fd2sx6/pl:cwmw l0 a rqo.5)q1lmmintegers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance isn7 pp/c8mn jm(yei*z33 ocru( neglected, show (algebraically) that a ball thrown vertically up (8n*7/3cipurzpcj onyem 3(mward 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 verticj1lf4q89u qe bally 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 of the apple in Fig. 26 pi 7(zrw b.sykf6ni-–18 (or number of photoflashes per second). Assume the apple is about 10 cm i 6k6f(r -y 7swn.zipbin 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 tall (Fig. 2–mv 9t4xqfu,g 032). From what height abovmguxvf q,90t4 e the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it stz.s v(qi6o hwhh0wu1 )riking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the clifuh hwh)0i( oq1z6ws.vf? H =    m

  Suppose you adjust your garden hose nozzle for a hard stream o+oam+x*sa ro4tu f 7/mf water. You point the nozzlm/a7+ *ar4t oum+x osfe vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the edg-q4dgkm9+rn r6vso g 4e of a cliff 70.0 m high (Fig. 2–34)9v 4qg4gd+o s 6-kmnrr.
(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 m2n- r9ypd/vuby a window 28 m above the street with a vertical speed of 13 m/s If th2dm/nyr -p9vu e ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the venox5po2zbv6. d p+ *ujtbya)t gz,(; slocity of a train as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitd t6 bn;)jbx5.p+stovz*g pyaoz(u 2,ude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time is plok 2zxdk8()plh tted in Fig. 2–28. What is2 )xldz(hk k8p its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate approxi-tn i rmequ2j3:s -dt;o fft*:bj8j/a mately as shown in the velocity–time graph of Fig. 2–35. (The short flat spot8j fi :mjne qs3jt*ta-2/-rtb:duof; s in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car inxi2e(rhhe j lf(62y 2e the previous Problem (Fig. 2–35) when it is in l 2e2jf re(xheh62iy(
(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 object travebwu7mjvl/t6 um/.+ u09q wiez led during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacemltq soi mdz q0)s3,q69ent as a function of time i,slmqs6 9iz)3oqd 0tq s given by Fig. 2–28.

Figure 2–36 is a position versus time grae 6fott10 7 itm;ag u35dy/ bddn49izuph for the motion of an object along the x axis. C69d o /15m eztnfuia utbd304g;i7tydonsider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (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 55d0qhuhl1rpr.;i*yh2n7:u ri f brhm above a firefighter’s safety net. The f7y:unr h. d* q1h5ilrhhu 5r;0r 2bpisurvivor 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 abok w6 :x*vawz3 u 7tesxp78css9ut one-sixth what it is on Earth. If an object is thrown vertically upward on t wxca67upxve7 st*k938wzss :he 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 belt has a 0mws,l:xhqak7 -h ,j.7* mbr8 ibxmig good chance of surviving a car coli .,x:k70imxw8,-rajlqbb hmm 7 *h sglision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road 3 zbw,i 3.jbzcpz(bdc; *6srrbelow, 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 r(rj .*;iz3 bdzwc sb63bpc, zthe 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 f -4q,nd f4eg.mzz;a uyor front-end collisions by hauling them up on a crane and dropping them from a certain height.gf,z. mzqu4 ; e-ydna4
(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 trav(w s((hcrqoc5 + v:wnvels 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 beghv ) p0-x+xe c7m6- o5cf3vjlxc,xl zzins 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 sph3x lexcfp5mjc lx-6z+v 07oc-x)vz,eed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a divinpaj4(d d:y82cw 2giq ag board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the perso:i 84d jp2aa2y (wqdcgn while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapidsnj9)./g+dm;dfnb hniy* l8d transit system, it is necessary to balance the average speednd m y*d/id+jgnlhs8f9 .)n;b 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 antc1ng/lme d/m )z.6eg ,mvkx)d free fall straight 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 dv l1mgm/e)e)z./ x6 ,n mktcgminimum height must 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 strikes a ball is planned so thatzv y (qpo s(gh0s;1w:d the ball will stop y;0pd(ws1 (zqgsvh o: 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 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 x*ya,q j dg2w8 8ows v2im05vgspeed of 6.0 m/s Just as an empty box car passes him, the fugitive starts*s2 jwy 588iq2vgd o0a,gxvmw 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 fblm2-t x9 /jxfrom the roof of a high building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed ofxm/ -x2 ftjb9l 12.0 m/s ?    m

  A race car driver must av6j6fdtue07ut o:v0qterage 200.0 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 0o ft6qt6uuvd7ejt0 : 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 movm 7* 0gy0lqxugna.)py es at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h g nlg) y07yxm.a0u qp*. What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child cx.tr lbpo)* i s6hx5c2an bounce up one-and-a-half times higher than the second child. The initial speed up of the seconx ph sbitrox2 )c.l*65d 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 train travelingkkvou b: 45e)ddfd3v2 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 tb3d2)vvk k5eud:o4f dhe 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 af(xb9eiq 7z+ a baseball 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 tfea9+i7b q( xzhe ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accelerationc9ozl(th)lz7 -ehu3k i)( n ow 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 traffic ya-x5uf/ /kb)yr*r8nk4h y bh d+zpk5w:n 0n bsignal, 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 /nfhp)yxnkbu0+ 5y ka-k :nd/yhbrw5 zr * 84bintersection, 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 akqi12wkwffu z0m 188.up -v vit a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaini1puq v u 88kfvmi1zw0w2i f.k-ng a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a p :jl6+j;8kpcoape,4x qm; ljbuilding; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stone j;4jl+pq: ;p kxoe8lpc6m,aj s 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 stoqg-h ez9 d0n9 jeu*id6ne is thrown with an initial velocity of 11.0 dhne6ju*i99 -deqg z0 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 $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-fallnchh bl4h4w.m1cy+7day h9 .ting parachutist to fall from a plane at 3200 m to an altitude o b944cm7.dchy lw aynhh1h +.tf 350 m, where she will 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 c o0mhbny-r)xsa/b4 /pby:jb 9onveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in buro: 9bb) ybyms b4/jr0h-/pnxagers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe can.e83gbvn ogmx.b2 l,7nwzm8 :f How many times higher will Bill’s ball go than Jogb vb82 :g.fn3wz onem8ml,7xe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff whil;qs65p8pmebyx7/)hkq :xrf e e 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 b;fpe 5 hmqrx7:xps 6/8ybkqe)elow. 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 height3f 1 /1xn)sl r1pffqsd of a particular building using a barometer. Instead of using 1sffd1 xsn/pq) 3 1lrfthe 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 building’s height?    m

Figure 2–43 shows the position vs. time graph for two bicycleamwh/jhq,nwz5- k 6. z(1 5wj;fupyccs, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicz j.zkycpwaq, /jwc h u1;hmnw5f( 56-ycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?