Does a car speedometer me;f85ibu sop 1rasure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant? If yescn44m)3) 1ji) u h0pqqrktyh b, give examp k)cq3jqn0)4ympirt4u) hb1 hles.

When an object moves with constant velocity, does itse7 x-3cd xp b5aalhxm8k 2b:s- average velocity during any time intervalcbbp2lse7-maah 8:5x-d3kxx differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the l9d,x0.jv;xdkkq tqg(c r e e)ua(38jcar with the greatest speed crossing the finish line to lose the race? Explain.( 9qdvt(38x;. k)jedux , rcge lka0jq

If one object has a greater speed than a second object, doe o .8z)ae+:ykyp ti:ygs the first necessarily have a gz)a :i+ty:kpgy .y 8eoreater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle thatu2 y8v2 7zougt accelerates from 80km/h to 90km/h with the acceleratitu 22g7vzu8oy on of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northwansh,e/sd( 7yx qq4dla; 2ft2 gvrwb79rd velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? Wh3s(jl 5lenn0 skyte,0p+ uq-dat 5k-+l 0jlnn0,uetp3d(eyssq about vice versa?

Give an example where both the velocity and acceleraa(y d9cxv)e-vg /er6ation are negative.

Two cars emerge side by side from a tunnel. Car A is traveli9yw6 k wta ug+lo(xi43ng 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 ilgw akt(xoy9463u w+the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleratiocnp (whx6v1vphz. zzrmdt* 6b.m8si+:b3 / yon decreases? If so, give an example. If nibh: zrns+ 681pz*/yhcd6vtzwxv.. 3omp m( bot, explain.

A baseball player hits a foul ball straight up into the air. It lea/9h3 c+cte-*r ul5lv s 0swpgfl2sj,wves the bat with a speed clshs l/vc -u39wsjp +lrfg52 t0,w*e 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 objtefvl1x3w z4v.u/l tr.5xji7ect speeds up, what is happening to its acceleration due to gravity — does it increase5tflxv/.7jwv4 rlxzi .1tu e3, decrease, or stay the same?

How would you estimate the maximum height you could throw d- r blvj3z*6ao8qua6j-x v 7b i;h3bya ball vertically upward? How would you estimate the maximum speed you could give 6zl6bb;yq*ohvb avr -jd37 i 3auxj8-it?

You travel from point A to point B in a car moving at a constant speed of Thenidb:t.5x od*eh+ vhv1 you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your d .i5o+v 1xtbde*vh :haverage speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, mq 3-m()zs sv3qi0wbv a 3.0-m-long 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 hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Wb m3i- qq)v(mszw30vs hy? 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 constanvjkd)6;2d gqb 5 -)p /7(u z dhkbed9pb;rorjqt acceleration: a rock falling from a cliff, an elevator moving from thjrdzk rbh; 7-d)p jv/p9q( bdu56gkbo2 ;q)de e second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown verticgxt:cxih oy9my (a psmd5*7 ;3mc:,w yally 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? [(;3t xdi9 5chyw:yaog:*pcmxmy 7ms,Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at :mjnsjvw(py 9,:0.rl *3ueuqyj od ; dthe same time? Give examples wojdv 9p dn,eljmq0(*:;:r3yy.j u su.

Can an object have zero acceleration an9jz9ul3 )3zpgq fp 6 eq/+kveauz8p5ed nonzero velocity at the same time? Give exau p)vazeg9pqej 83kz6q9/+ef5p luz 3mples.

Describe in words the motion plotted in Fig. 2–28 in terms of )1pqx 4f7* sjl .vo,(ldiraia v, a, etc. [Hint: First tryx4 afdvoli(7p.s )rajl1 i,*q to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the obje b-w+6 qwj uvgeog:4z9ct graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235+/ m90es*m me 2s zf 2b8ue/yw aexqi4qz;n7nq km in 3.25 h?    km/h

  A bird can fly 25 km/h Howrm9+6e.27 hnsby80lxr gso l i long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to taq :qqyor4c)s:k g*5 hyv .:yzhe side for 2.0 s, how far do you travel duringo4)ya q:qksq: y.z:h g*5 crvy this inattentive period?    m

  Convert 35 mi/h to *or;l 0 f jscm7yf /cp**9fksu
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves mxp6.in8 gu;n from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

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

  You are driving home from school steadily at 95 km/h for 130 km. Iz0eqwg9r/lk .u0+ayoe czo ,:t then begins to rain and you slow to 65 km/h You arrive home after driving 3wz0/ :g 9qcku,.er0 yzl+ oaoe 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 fl5b8noq) tplh i2v k2z8ash and the following thunder gives the distance to the flas8l5nv iq pt)z 8b2h2koh in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a ym;ej ;8)ff vwquarter-mile track in a total time of w8em;)vfy;jf 12.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 116 m awaye ,tmq3- ,utjovf 04 ym09ahxn in 14.0 s. It then turns abruptly and0ou,fn 9 -vm,ttqyxh 4j3 me0a 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 tcgdsbc499 6*zyxb;zother 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 loyz *gd 9ctz c;69xb4bsng 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 travel 2w,cx -2k xk;vvknl,q7(a1ua dveux8ing How long will it take the car tovdc7w,( uxkaq2 ;,l8un xv1kxv-k2ea reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounters a taiu(mwy(zf:om.y6 3acz ;zz6 ls lwind that f:z .zmy w zluoy3s(6za;c(m6boosts 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 g bl+ (k+ uj04rhs*,qyaqjd* ra complete round-trip in which the outgoing 250 km i*h0j(b+*y4qd l jrkgrau s+ q,s 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 co i3jrvq 2: msa5q4ez6gnstant 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 release6iv2q:mr ag45zs qj e3d 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 aveytspm:g,+ln j, vf80 (sev8jmrage accelerat+fgyl0, j8 je tsm(vn smpv8,:ion in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest ts)lh)6yjny/- ft-rlvf e7p 7oo 10.0 m/s in 1.35 s. What is her acceleration l nsfh)-ojlyf 7/pr6 v)7 t-ye
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobileg sfhc9i w9o4+ is capable of an acceleration of aboutsocf 9g4w9h +i $1.6 m/s^2$ 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 q+67uigj(e-m3 vu0r hl u0fmvm in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleration r0hqu3mmuev( g07if6+ uv- ljin $m/s^2$ ? 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 car3.*8glix .tqnut*ws vsmbd*(, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table..b.gn*q iw xlst(u m*3* tvds8 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 47 rz;9fry kyhzr3uj 2m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume c4r u;f9j 3hk2yzryr7zonstant acceleration.    $m/s^2$    m

  A car slows down from 23 op wo7q, 5k zus1wc6sn-b0 n wc1/0bvom/s to rest in a distance of 85 m. What was its acceleration, assumed constan-ozkscwo/p u0nnw6c150vq71 bs,wo bt?    $m/s^2$

  A light plane must reach a speed of 33 m/s x6nq:4sy zk)v for takeoff. How long a runway is needed if the (constant64:zqvy nkxs) ) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentiallypyc 0vf3 h:e 1n-7nmuqnbv+c 2 top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this spucf7e:nvbynvmh0c- p2 q +n13rinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest 6n6v a p.1zn2 ne:pz olvm/nr4in 6.00 s. How far did it travel in that tin:/1zz6n eal4 pp6n .v2vornmme?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assu79c-+oos7uupj u e2dcming a deceleracoe-jo2uu7 +sc pd 79ution 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 compresses ank rl-6q q8pc+/d shd0qd the driver comes to rest after traveling 0.80 m. What was the average acceleration of the drldcpq dks80 qrh+/q-6 iver 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 init,a 63oj7quokyial speed of 95 km/h and human reaction time of 1.0 s, for an acceleration3y uo6oaq,jk7
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of a cammzsqbr8/ + .ar 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. Thv. dpkn 41yi*w+ y/lsye car’s driver looks for an opportunity to pass, guessing that hipslnyv14i .+*dk yy w/s 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 complete the 10,000-m run in4gy6kxm5 0 drx less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then accelerated g5kx 46xrym0 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 approachespn ciko7-:1g9 r 0ldc pl4w+zy 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 (7cz1 : p yp9g4kdrlln ocw-+0iFig. 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 cliff. It hits jiu1mmd on86oary9y9iz k.4:the ground below after 3.25 s. How high is the clifm.8yj 9nrozm 9doiiya:16 u4 kf?    m

  If a car rolls gently (u. bu1tdgh8*oh4-1 z mh2i ysg$v_0\,=\,0$) 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 speed8-huld2 tihv3 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 throwq3grazc 2rg n5)*zy* fing it vertically upward. With what speed did he throw it, and what heigc 5y*qan*zrr 2gz3f)ght did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influ ejo(syrp l/ u b;hz/1.axp yh7z50k(uence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = ((jklpy;yrup z.1ohu xb0zae 75// hs 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20 m/se*h)h cu)ff(* hkv1ogmqoc00. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the groe1c h0qvkm*)(f0h*o )ho c ufgund? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the da)b b*46z ::i3ciun ims-bzfaistance traveled during each successive second increases in the r6m)-a:bi4bz 3 *ias cfz iun:batio 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 (6lhl d6w3 0,rjo6owjx;jxpk. algebraically) that a ball thrown vertically upwarphr.xl6ojw;l0x3 wo jj6 dk,6d 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/s 2 dpr* xirjgu0.hw00i f1qmd;
(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 photo rmm-)c5sm zdwdh1 6mqf7a95cflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Us fdd 5rhc)z6-1mms5ma cq9w7me 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.sjv ,b2maz h1nnpm/c3;ix z :. 2–32). From what height above the topz :/s cmhzj2 minpx1,a;bvn .3 of the window did the stone fall?    m

  A rock is dropped from a sea clif pdw7/vbt7 ,mi9e ep:gf, and the sound of it striking the ocean is heard 3.2b iet79 p ,vw:7de/mgp s later. If the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust yors.0bb5oqi. f ur garden 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. 2–33). When you quickly move the nozzle away from the vertical, you hear the wars.5iofbq 0b .ter 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 thlphx0 wir7n 1*e edge of a cliff 70.0 m high (Fig.*n i1 h0lx7wpr 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by ad 5+1hmcleb6df j/g(e window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from td (f+ 5hmc6geedb/ jl1he 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 tr*qq3xpz90mvfu :4tjpa) w6yg ain as a function of time. (a) At what time was its velocity greatest? (b) During what periods, if anm*3 0p6 vf)jwpa:xq ygzu4q9ty, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straighzfm 81itcs3v7t tunnel as a function of time is plotted in Fig. 2–28. What iz7fs3tvc8 i 1ms 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 aic-j xiz2a:h5wo5n3 u ccelerate approximately as shown in the velocity–time graph-3:aiiu2 ozxc55nhw j of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleration of the car in the previous Problem (Fig. 2u9jm2 ad97n aj–35) when it is2djn u7ma99ja in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled dur3f6 gy69ifr 0vhjf fpz /b .pe9rlzx)7ing
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph c1 a f1:(+n ims/zjkwrfor the object whose displacement as a function of time is given by Fig. 2–2wnikrc (1az+ f 1m/js:8.

Figure 2–36 is a position ver053ksv88o zzasr( wkpsus 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 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 acc8sav 8zk3kp (r5osw0zeleration 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 ab-/u*4)kfrzev o 57vjsd*qa9x4 qtwitno0 y.c ove a firefighter’s safety net. The survivor stretches the net 19uvi 0 ej**tyqa7z-so nd54/o qxt.ckvrw)f4 .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 onhp1 xu d9m kpk0-n8k-t the Moon is about one-sixth what it is on Earth. If adx -phptk1-n098 kkumn object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-th/ b+e ob+-mglrv5 (ixhe-shoulder seat belt has a good chance of surviving a car collisim+hxgb5ev (b-lo / +rion 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, 7v /gj d e-e+)tx-xpny12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the trx/+j-xt)y7g p-evndeuck 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 c7 * k)-vdyqb s7qeh;foars for front-end collisions by hauling them up on a cr;efq-7q 7 )b*kydos hvane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth8-0 sw/vutxhe 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 l,johqmehl-d+x)i c ry4s;;9uniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is stancl e ,q4oimrh;d+y-lx s jh)9;ding 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 dtl 7jcn 3;x0zlxwl:c7m-:5 b;l bexfdeep pool. The person’s downward motion stops 2.0 m below the surface of the water. bzxdn l:5 :0c-lw73tmlbelx ; fcj;7xEstimate 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 tran-s s5+pn.jqi qsit 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.s n-qsji+5qp. 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 whenfyl4-x//r.oil2p x wz diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the suixfo.-/zpl/ l4ywrx2 rface of the water.    m

  In putting, the force with which a golfer strikes a ball is plx qt y(nv7k-ujm6,+o 6e 8f0gys-f jzkanned so that the ball will stop within some small distance of the cup, say, 1.fx(k6z-yef-7s,nugm8 t 6+qyjkov0 j0 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 c:g;fohyr*1q,(o wtu aonstant speed of 6.0 m/s Just;rg*otyq(h o1,uaw:f 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 from the roof of a high building. A secon z(9wmi)zfcw06kw q-od stone is dropped 1.50 s later. How far apart are the stones when the second one (mq-o kz9zic 0f6www) has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/hfvik1o+ 3gc+ 85 v0onegrjue, over the course of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintain5n+v1g8 c,i+e kjref ovog03ued for the last lap?    km/h

  A bicyclist in the Tour de France c( sp41r6pwuuubqah w1y 42 xr+rests a mountain pass as he moves at 18 km/h . At the bor bs1q+ay4px4rh6uu 1puw 2(wttom, 4.0 km farther, 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 tramel *so x/zne 4gn6o 6-f*ogk-gpolines. The first child can bounce up one-and-a-half times higher thg-*leeo4n-snkg o 6* x6/fzo gan 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 overtak )7a6lxz eo.ypgg/(jl es a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–4 ejl.)(7zogla6yxp /g0. 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 4w f))cco cz4z/4 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from )f /c4woccz)z behind the body to 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, fromx3pn5+s cy+ axz6:9ya8f wgnr rest, 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. 2–4dahd.;t jnc5)mi 75n j/dapy12. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you ar/5n ydpjd; c)htinj5da 7.m1a e 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 travem+ctm5qnt qp tw2n1am635 - lpling at a constant 120 km/h takes off in hot pursuit. The police office+q -t 5pc3lmtntqm5nw 2 a16pmr 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 from the roof of a p/ es0k5gi1 -h u;hs le+prm/abuilding; 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 same ti m5rgu -h+//p;se p0i1 shaelkme.
(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 f/k )v.b5; :aceen hav-k 0vpbeirst stone is thrown with an initial velocity of/c kn-v0ke5epah.)a: e bvb ;v 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-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 resistandm yivw7r*17j ce, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resista7jw 1v 7yidm*rnce will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a con0e ,s(f/-l pxco 5pcw-lnk,jbveyor 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, hb (lkp w - 0,5,csnje-pfc/loxow 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 v kd4 43yzfx:ttxh4 s8pertically at a speed 1.5 times faster than Joe can. How many times higher will Btp4fs48 :x thx3yz4 kdill’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 below you yki2u moin673 gd*e 6nsh5f-b. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to3dn27 i-io*mgheuf56bskny6 rest in your hand. What is the speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particulare/my niao)931 ehg/dw 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 thei / aymg/h9 e)3enodw1 building’s height?    m

Figure 2–43 shows the position 3jigg( bhg+gh yj* d87vs. time graph 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 hg+(idygjjggh *73b 8acceleration? (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?