Does a car speedometer mbp kw8zojyvhs9(f*/ /i *(dl reasure speed, velocity, or both?

Can an object have a varying speed if its vebv6 fuk 8uoj3yb mm7a7ken6 :6locity is constant? If yes, give exammna 7:76jkeu6ubobyk6v3 fm 8 ples.

When an object moves with consto-g; uwlf il1 8,u /141 boarhxnsha-nant velocity, does its average velocity during any fu1aaobwn l-;rho4s/xni1,uh1g- l 8time interval differ from its instantaneous velocity at any instant?

In drag racing, is it possixpxhixv41ik9kd) 6 wsghm 7f/: 2sv*r ble for the car with the greatest speed crossing the finish line to lose t1v v)xsiis *h6h9wr :dmk27xf4 pkgx/he race? Explain.

If one object has a greater speed than a second object, does the filxpt bwx um:6mr.:r(5rst necessarily have a greaterxupwrtx: 5rmm:.6bl( acceleration? Explain, using examples.

Compare the accelerar.c ptqmn8am c6a6 +3ktion of a motorcycle that accelerates from 80km/h to 90km/h with the accelerati kap nm.+atqr8c366cmon of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocitylw-r)h+2ro) wdy pvjqj3q8 ) o and a southward acceleration? Explain.

Can the velocity of an object be negati9tk jtq s:2zc,5 /h7tvbp2dsrve when its acceleration is positive? What/sj 57z2hsr,vbktp9td:q2 ct about vice versa?

Give an example where both the:zexlmz58.fqi2 ) hqkkdd4z;gx e c1. velocity and acceleration are negative.

Two cars emerge side by side from0 bwq ge8t+zb lkf)9)m a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnet gkwq) 8bb90+lm) zfel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, givl4v3w93pw uc ke an examc3l9pv3 ukw 4wple. If not, explain.

A baseball player hits a foul ball straight up into 0tyn; pi unj;9the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the tu pj;n ;in09ycatcher catches it?

As a freely falling j bled77l7o1bobject speeds up, what is happening to its acceleration due to gravity — does it increase, e lb71jdo7l7b decrease, or stay the same?

How would you estimate the maximum height you could thr/cwg igbo7fc f :e533 u,2ortpow a ball vertically upward? How would you estimate the maximum speed you could givo/3 3 f: ut groi7cwpg25cf,bee it?

You travel from point A to point B in a car movinum 2(oc9+ 2aytfltfu z7-svl1yah1z 2g at a constant speed of Then you travel the same distance fromlt f 1+2(ahvf2szyou1ty2mlu 7z9 ac- 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 string with ten bolts tied 5-5ahb k69qd3jf k1p zvlk+hgto 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 incr flz3gj51av b5kkhh6 kq+-9d pease 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 co hav:0prgf s-f.9xd5instant acceleration: a rock falling from a cliff, an elevator movingra5 pxhs 9v0f.:dg-if 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 original posi1jva+jcr,jc-m;a t/ h tion with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistanc ;ahj t1ja,+c mvcj-/re is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero accel4nt7 j6om2ev. ; fn mt/xqoo0xga,f6weration at the same time? Give examples.6 ov gf;7a2j/.6qx0enontw t of4x,mm

Can an object have zero acceleration and nonzero velocity at the cs kw sx,ro5aps728uda/vcmqs3( d- 8 same time? Give exampl5cdu sxvca/d a(p7 sr8k8sq32 ow-,smes.

Describe in words the motion plotted in Fig. 2–28 in terms of lf fm :gq)umw 2:/pljj-4k a7zv, a, etc. [Hint: First try to duplicate the motion plottedjj:gau4 wzkmmq2)- 7l :l/pf f by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. j1n-:w g+lyrwxe ft498jwjq ) 2–29.

  What must be your car’s average speed in order to travelp z,rbawh a(8)g:zr2,th1buz 235 km in 3.25 h?    km/h

  A bird can fly 25 kmmdpmg 4yi ;0u qu+e8tioxfu06 bk.:dnpa9 ) )k/h How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the 7ncbcso)o y/g21ct0o side for 2.0 s, how far ot1c )/2o sgc07cbyondo you travel during this inattentive period?    m

  Convert 35 mi/h to + fcyf 7nbngmma4b*qp,fzj, ; b.)d 8qkw3 1cs
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frb .( 2x*gh;tavv)4nq x8mztruom $x_1$ = 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 13:d yy hvnx::f n9)gut f(*y0ux0 km. It then begins to rain and you slow to 65 km/h You arrive home atdhun fyx0n: guy(v y):*f9x:fter driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning fl6cq) 0xb xbo,cash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time 06oc) ,xx bqcbat all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete lap 2059yu wt y/h+2i7ghmrkss gqs around a quarter-mile track in a total time of 12.5 kwhmg2qgtri/70y 95 yhs2s+ umin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traine9zyhoy:r w. b5)x7nwk r in a straight line, moving 116 m away in 14.0 s. It zy hwn:.97bor5 y) wkxthen turns abruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel bfu q)2gszub-99l (g ytracks. Each has a speed of 95 km/h with respect to the ground. If they 9sug9bl ) (f2bg-uzqy 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 long will 1fs +4mr(ixb lzji kyc54::x hit take the car to reach the truck?ixsjhkry z(ilb4:5mx + 1f4c :    s

  An airplane travels 3100 km asui(r*1oyd6ds d1.y7de) xw st a speed of 790 km/h , and then encounters a tailwind that boosts its speed to 990 km/6dery uixd(wdos.s*s 1d y71 )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 rou4m k4m*p : w*-gvhuqvwnd-trip in which the oumq-g4pkvw*wum* 4hv :tgoing 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 km/h.    km/h

  A bowling ball traveling with czt8g66 m( odjfp1+qxjnj84fw onstant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler he8oz6q pd 46x+1wfjj gj(nmft8ars 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+5of5 -nu0(ixwknlnd average acceleration -(ifo w05d nnlk5u n+xin $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is hezccrxtq w )fm200 r- .7uz5aluae4n, er acceleration 0 lua4et,c2e r7x)5.zqfcz0nu- arwm
(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 acceleration oxvaiq;e2 t-*tr +a7-g k flmk;l*o(tq f about lqge +(aa;lx t-o*7k rm f-q2vi;kt*t$1.6 m/s^2$ 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 spemo:oo./ g gjk)ed travels 110 m in 5.0 s. If it then brakes and comes : ) o/jg.okogmto 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 at t = 0 ah2ta/nn.bb 7q nd 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 oq /bh.n a2nbt7n a graph.

  A car accelerates from 13 mrjc26r5x4f;wm e yk b-sz:6bs /s to 25 m/s in 6.0 s. What was its acceleration? How far did it tr 6;rws ck64-bjeyz5 smr:2fbxavel 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 was its39axy uxv+ lsdh,b x1b61mck4 acceleration, asxx4y ,c6bdv+3ma1lu x1b9ks hsumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s fwq6fpk5+ dxch (ow hyo(b 5b6/or takeoff. How long a runway is needed if the (constant) acceler6f x ( (/wohpy55dhk+wq co6bbation is $3.0 m/s^2$ ?    m

  A world-class sprinter ns):lh/ d etv*l) 5edqcan burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. Whav 5*:n t)eqd/des hl)lt 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 unifor5w ni5nrfw i2y.a6hq:mly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel in t5n hi2w5a.6nfy :w riqhat time?    m

  In coming to a stop, a car leaves skid mat erkt*pd,o( t.6,jui- e:q cjrks 92 m long on the highway. Assuming a deceler-, deo cq6utkrje,j.:(*pi ttation 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 the car compresu-cmt3;2sjc 8vs)+v3g* jl rcq3 rxo fses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of t3 cfxv*rcc+rug t;2)3q-s 3msjoj vl8he driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed 5w/snqu:*h;qwazfy (of 95 km/h and human reaction time of 1.0 s, foqu/5snawfq :y;w z(*hr an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for thes sf.jc* 37flg stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/sa1 tn7ibr;.aoe2y eg wh(geiz k t/(,) on the highway. The car’s driver looks for an opportunity to paszg e2wa eoi t(1nthyge/.ra7)(k;bi, s, guessing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to completpljw(.w1a*qm3 0.pw f uxpq,qe the 10,000-m run in less than 30.0 min. After exactly 2 qqq,0puj 1.*fpmwxw l a.(p3w7.0 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 an intersection +crb5hc- vdg3just as the traffic light turns yellow. She knows that the yellow light5- b+c3r dhcgv lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum 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 cfc+ uoplg(nsxy3rs p :v1f;*90b r7wkliff. It hits the ground below after 3.25 s. How high is the cl +frp w; *kocn 79by01 vxrfspg:slu3(iff?    m

  If a car rolls gently di) ph9uzt n fjt*70+i($v_0\,=\,0$) 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 l fkt/p8um,r ,(grsv 0)ap5shre,5 wsair 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 ball 3.0 s after throwing it verticar+r5bu0d* tbd q7u;i elly upward. With what speed did he*r5dte;rd0u+qu i b7 b throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and fal8kzv )t7oi ,c;hr7 jbso1 si*wls under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a functisz*kh ,i)7bwij vro781c o st;on 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 di3f0j.mj;t o a height of 125 m above the Earth, a package is dropped from 3imt0 jf.;d oja 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, 3r haky 67at -7)fym1khmg 1coshow that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). Thisy-g r omaaf1h1 ych6 t7k)7m3k was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (aj /ig4r6bbh d+ug,-g9cqsp bq8,jt/r lgebraically) that a ball thrown vertically upwa ghbcs 6uibqt,j8 rj+9-/b d/qgrp 4g,rd 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 wi,icb: 1:jelw vth 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. 2–18z; 4iqwy1e0-zt n+ ubci7lm,x (or number of photoflash+i wb0 y7z ,le4;-x mtcuqzn1ies per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a+ih865ek tfscx rq*9k window 2.2 m tall (Fig. 2–32). From what hei9r6hq8kf x *skc5+ie tght above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the soun9 cjh1ff/b.mqd of it striking the ocean is heard 3.2 s later. If the spc/j f 1bq9h.fmeed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozz6eemp ::09 0*eyr mujjrcb,jhwq6v9ele for a hard stream of water. You point the nozzle vertically upward at :me0 brw9meh6cj:r 9yj0 ,j6p eve*qua 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 verticallm+3d f.hquk.g y upward with a speed of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. .gku fqmh3+.d2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward ,8olqlv 8 rf :dcrh)o+by a window 28 m above the street with a vertical speed of 13 m/s I ho,8 rdclov+8: lfqr)f the 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 velocity of a traify09r(5 cg:5xw pwkng n 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 acceygcp55:rgw9k w0( nxfleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straightt qk3n/ : 7ggpz +gjou+ov6wh5 tunnel as a function of time is plotted in Fig. 2–28. What is its inso q :jg/+nk+6gz5t3uo hwpv7g tantaneous 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 acw98hn :08 pqu3c okptvcelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shift w hcpvon03qtp:88ku9ing 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 imvfk o(-0u qj+5 d,,xnu) pqqof the car in the previous Problem (Fig. 2–35) when kqu)q qn-x m+ jf( ,vp,0idu5oit is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the dist g9d nmmxq4 +cx pr:)o3o-s)nfance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whce nvd.e 28a1eose displacement as a function of time is given by Fig. 2ee2 .v18dcnae–28.

Figure 2–36 is a position versus timeiw xj -dkp5qh+rhh(xk p9.x68 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 negativ+hi xp.kdp8x5x9j h q6k-hw(re 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 m abovepm acu 7p);/rl a firefighter’s safety net. The survivor stlp)acr7/u; m pretches 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 hs. s+.b, fmtkwhat it is on Earth. If ah,s. .b+f smtkn 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 bn*j:jps 79 l ifk;nql3y an over-the-shoulder seat belt has a good ch7s9lijkn3 fp; lq:* njance of surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road belowp+ze f/ s1noi7, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s ,z/pfesi +n7o1 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 colli ;8e5mti1m/ ,.w yvdw,ildnfysions by hauling them up on a crane and dri/wwd1,v5difl8y me n.t ,y;mopping 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 Earthdwplu ,amjht a-n/ ;-u/- og3y travels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acceleration from rest.g1 wwc :n m0d l,l2;ybv6/sstk The front of the train has a sped1mt cs;2,:w/l ngs wbkl 60yved 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 Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m aw0npc n9x5 e;a0l9jw96bek nbbove the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below w9 een;x0knn 0b 9wcj5 p69balthe surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapikj o+s eh l7jx+k-z uci,1w7h:d transit system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculae kx+c w+l1ioj,:7j7-kzhuhs te 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 for fish. S; 9nyxo ttv8fm4w 6x c-7yu1xpuppose 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 wha-9ywyv8tn oxxc1; um 74t 6fpxt 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 which gvkn /bs-sm,. a golfer strikes a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 -b,ms/ vn.kgs 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 constqbig3oo 7atyu5lp82v;hxvt )8bv7 -iant speed of 6.0 m/s Just as an empty box car passes him, the fugito8vaygtb 28qho3t)5v;piix bv 77l- uive 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 second stone q,-nj87c.lu +bkdme6v dnfe 76zqq3k is dropped 1.50 s later. How far apareq-uq6 q.ldv,876nbf ekk z73+ cjmndt 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 course of a5a ;393 tclgr-ho orys time trial lasting ten laps. Ifo sh3r5tra- ogy9cl3; the first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountain pass as he moveszvwu*:58h coo 6d 5fpf at 18 km/h . At the bottom, 4.0 km f*o du 5vz6fpow5hf:c8arther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first child can bounce up g (3-fw/,wrx) ch upt02d )kl0tyvsabone-and-a-half times higthrug,kpl)v(w0x - 2yb s0t wfd3ac)/her than 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 1jq .q.ze sl.x7o:g,oak6k ,wri1pg*n.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 ,.q :pj.o6gsrwe 1lg7kanoqxi *.,kzcar 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 baseqt4 tfupzf4+9 m ab c+:amvwus,+6sg,ball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body tots+pvs+m uf m,uzga,wcqat 94+46:bf the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from jhh94ljt rav2k g )/(erest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fig. 2–42. Each inr)ye,:qkt z 3xtersection has a traffic signal, and the speed limit is 50 km/s . Suppose yo rk3:tqexy,z)u are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder travelinxytb/*emhw *rw7nbor +1 0 fp,g at a constant 120 km/h takes off in hot pursuit. The poliwyhworxb m1+ fn*7 *r0/,b petce officer catches up to the speeder in 750 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 fv zhpxvkb87(.b(y;; g sepg8 arom the roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at the samezpag8sx8p vk hy;(vg( eb;7. b 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. irpe+)pd9 zhh,afib o482r33ni 4ri h The first stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony a4d8 ohinr)hpr ezp9ii3rif 4,3h +2bof 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 freexhrvqjmv p 2s8w8 0+u8-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 airwx 8rp0sv +2 qhvum88j resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt toa m o978piah-) mdfk f;lbn;)g 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, nf-l)d;9 ma8hf7);gbi amo kp how fast 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 avaf*rwamk b5 w zcj2aeh5z6w )y*b;87p5o9 qa speed 1.5 times faster than Joe can. How mankbb wwwj82z ama*y5pa67chqrz5a95 e v) o;f*y times higher will Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the ground belowqop4od(j/i 2*rm dx, k you. You drop a idojx,qk(d/ or4*2 p mball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to 3s2eoobo2m p)b mms ,0ti*h3t find the height 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 thopmmsimo3boe s22 ,*t3) bt 0ime 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 graqd (5mdypn: 8:z5ka-jrm0, htgqv 8 typh for two bicycles, 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 bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which j05qdvt(q-gn:5myymtph k,dr a z8:8bicycle has the higher average velocity?