Does a car speedometer measure s5gsdqlt+ait: 8 ygt) b t80+pdpeed, velocity, or both?

Can an object have a varying speed if its velocity is coph 6.o*ll+iof z).zpgnstant? If yes, give exampll zpl.z*g+oho. p)6 fies.

When an object moves with constant velocity, does its average velocity duri3db2oeqm 3;bttz;:b n ng any time int t3qto;n;:mb bz2bd 3eerval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with t6 d zqophj:+4osk(4d8 osf(lj,s g pk2he greatest speed crossing the finish lzkg of d(pkjs648o( 2 +h ,os:j4dlspqine to lose the race? Explain.

If one object has a gregw 1tm5ptjt4 5ater speed than a second object, does the first necessarily have a greater acceleration? Explain, using examplep5j t wttg4m51s.

Compare the accelerahlrj3*ah c*1ction of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerat j r*3h*c1clahes from rest to 10km/h in the same time.

Can an object have a northward velocity and a sout(u2an*3 stl 8t:3:ge ac gzwuvhward acceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? bo+0 lqwfd p db-a*0g/, ho+gzWhat about vic/opdqfobga, +g+0hz wlb -*0d e versa?

Give an example where both /y * nvglaw0v3the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a speed of 6jhg hgw.f.0z .0km/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/z.whf.0 jgh. gmin . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases?6 4nbt1xu e)xa lawqqzt 5+ d3y:.ek:f If so, give an zwf aq:+d )ekbtn4e5l:.ux3at6 y1x q example. If not, explain.

A baseball player hits a foul ball straight up into they +:a dn db23t8nncl wm-4s/jo uta(3l air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling wh audt8d3(4 wj +bll/ot3 nacmnn2y-s:en the catcher catches it?

As a freely falling object 12g,eojn o efegco9* n5xu 2.espeeds up, what is happening to its acceleration due to gravity — does it increase, decr2fge5jng, .xe o ene91 uc*2ooease, or stay the same?

How would you estimate the maximum height you could throw a ball verticall( 4odr,bkg7 xjy upward? How would you estimate the maximumdbr ko ,(j74gx speed you could give it?

You travel from point A to point B in a car moving at w mnpk;)) tko by+7ggoaz3 *p3d.fu96sf+mq ia constant speed of Then you travel the same distance from point B to another point C, moving at a constant speed of 90km/h . Is your average speed for t96+p i m*. 3+o;kb)3s)upqtz ffyg d okng7wmahe entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long ver p6dj5 yj6p+nl4t5fgntical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string fal dtlp6p5jf6nyj45ng+ ls 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 of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at constant acceleration: a rock falling frot12v i8w iwsszs0 7n:/qrjbg2m a cliff, an elevator moving from the second floor to the fifth floor making stops along the way, a dish res87q nj:2s/s02zsgt ivwr1 biwting on a table?

An object that is thrown vertically upwae /s -w-so9./qbmo veurd will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, wilw./ mes q-- obs9euo/vl this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at mb+ii qdk8 j(-the same time? Give exampjbi kdqi(8m-+ les.

Can an object have zero acceleration and nonzero velochmaz(+(zl r8 dity at the same time? Give ex8(zlaz rhd(+mamples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, ,)92jh imwyvp0pg ureiwa,e*qj t* 4)etc. [Hint: First try to duplicate the ,iejwh*p e, w)2tvq0jga)pm9 yiu4r*motion plotted by walking or moving your hand.]

Describe in words the mbks*nps+f *q0 otion of the object graphed in Fig. 2–29.

  What must be your car’s avbko2g 36p q47glf+uoe ;joo:serage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How longu4 xadb n*3k a(ke( o4dsw)cky83d gul0r3 a.z does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side fobo3zclvo1 0 n4r 2.0 s, how far do you travel d oolz 0nc341vburing this inattentive period?    m

  Convert 35 mi/h to (uww6 a3c*u9i )dxqel8in8og 8t/cldc+c( us
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball movesa) 9ytr0 mnbfb7k8td4o( lp8 c 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. It t ) uvm1yyo;uc: /g(yfkhen begins to rain and you slow to 65 km/h You arrive home after driving 3 hours and 20 yo 1 k(c)yfu:u;y/vmgminutes.
(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 flas6f2:e(z b 0gitrhcad6h and the following thunder gives the distance to the flash in miles. Assum at6dgzh:b 02i re(f6cing 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 quarter-mile track in a total time2i7uk hsmnq -+ 7sdiw, of 12.5 min. Calc- sw+u i7m,ihn kqsd72ulate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its traine: en3j0/ync cbh zmydf* mj/yuh/1f 00r in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops half y/00mc3y /h/d*mnjecz10 fyh bjnfu:way back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a specmx. ba1h )3z+ .nskdwed of 95 km/h with respect to the ground. If they are initially 8.5 km apart,. n)mz1wbcsh.x+ka3d how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m mn,.avvti0 3o a;zhlo);x-hobehind a truck traveling How long will it take the h m; v3;-x,0az lo voio.)hntacar to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounterd 2;mts(f) efogosc, 9s a tailwind that boosts its speed to 990 km/h for the next 28fef )2dcss go 9tmo,;(00 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 6/hntd sbfa9+b8j3 inex v*xwpt0;8)ymc:xa average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hot+byh x)38 xia 8n*d0p:9ba fsn;tve jcmwx/6 ur lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constfg2c4 gmm7+ kfant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound+mcg4mfk 7fg 2 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 u49pd dydyl) )s. What is its average accelery )4lpdd)yud9 ation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m+j6j(ub v*w ( q8hagkr/s in 1.35 s. What is her acceleration b*j +a uwk6vg((j8qr h
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular autom0 lxevi/daqwf*7 )*ymobile is capable of an acceleration of aboul* ma*vx/)fdqwe0 i7yt $1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s9 d7 ahxooroa5 ugb(if0( b2z1oa0rf 1. If it then brakes and comes to a stop in 4.0 s, what0(01ahrgo 5a127of r oo ubabz(f9 idx 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, wh7diof3n 5e9 z;r00cvx khrpb3ich starts from rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its accelerapre39on;37f0v h0xbirz c5k d tion as a function of time. Display each in a Table and on a graph.

  A car accelerates from xo( (q* *aeasviof.k)13 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceleratiokao* v x((e i)aso*q.fn.    $m/s^2$    m

  A car slows down from 23 m/s to rest in ai1 f67kf)6sk3cjzisb distance of 85 m. What was its acceleration, assumed constant?i 6f)ssc jz6bfi37k k1    $m/s^2$

  A light plane must reach a speed of 33 m/s for take0qnk-iz kmbz j;i(0 5noff. How long a runway is needed if the (conm0(;kz 5kb-z0 jqinni stant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks9xm twhnfp//5 to essentially top speed (of about 11.5 m/s) i5mp/ htxf9 n/wn the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to i/:yr0 tv f3gu:8lms m b0p5durest in 6.00 s. How far did it tds5lm y0 gt:u/3 fpirv 0mb:8uravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. *1v x-vrxzmt,;.ac a eAssuming a decelera;,ctvv.r- x 1ama*xeztion 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. Tje0 3u nacz5:cey 7s7+msdk:mhe front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,”c 7am k eu7:ss5cnemy+3 :0jdz 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 ini39,me, nlfxd gtial speed of 95 km/h and human reaction time odx,e9, 3n fgmlf 1.0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance p/i j: rtifpoo (acp*), 9wt6udq1:mxof 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 dkyg8d9x txeo*m+8a1 gils.; going 25 m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can acce k;e +xo9 tddgy *is.m1l8g8axlerate 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 in less than 30.0 min. After ex5pgze; b6u t*tactly 27.0 min, there are still 1100 m ut t;*6z gp5beto 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 ju5ryz (b/o6h0diy bd)j st as the traffic light turns yellow. She r yyz o0hi/j()bbdd65 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? 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 clif6 mcyj0 hn6x8rj1y0pr f. It hits the ground below after 3.25 s. Ho1xjny6 h0my0 c rjr68pw high is the cliff?    m

  If a car rolls gently (j0- :mq z2e:svub+ca t$v_0\,=\,0$) 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 .cc8kwg wr1x3ir/)a5qsr x: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 vertically upward. Witm.lw..(uba*rx o kwqnw,qcc; 2v 1 mh,h what speed did he throw it, and what height did ma; ,uw..ovm,ww l12b q nq(.*cc khxrit reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity.h21n+t(f qxx/k-i1 : k gtarcy Draw graphs of-t121+xk(:qgrt kfin ah/c yx (a) its speed 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 spem/6 o8/ 9r)2 4u,pwu ckv;njrz rflktced of 5.20 m/s. At a height of 125 m above the Earth, a package is dropped from a window. c 8wu rzvk,r9cu/l;nto/f62 )4rj m pkHow much time does it take for the package to reach the ground? [Hint: The package’s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the g(i5y0j edp0ddl*0u ndistance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. Seed u j0ipey 5(nd*lg00d Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thrown + yzb+,a , :rcjfiinl7gm4ej :verticallg,jeil+:+ma znyc:brfi j74,y upward 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 m8mzsb y/):2w)un pay n/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photo;e6 xlmzirn9s :-u/cjo /5 gwaflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at thelaego:mu-x ;srnwjz/c/ 5i69 top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to trave yu u.oswsvp)y4m 5;m7l past a window 2.2 m tall (Fig. 2–32). From what height above the top of the window did the sto)umsov54y 7wuymp.; sne fall?    m

  A rock is dropped from a sea)b5cx3 ycq(vh.oh,5c -2z c mtkftz ,w cliff, and the sound of it striking the ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the zzbx(-c)2whmq t5, 5vtch,c .3yo fckcliff? H =    m

  Suppose you adjust your garden hose nopyz; 3 iwcn1xmy(1u0j zzle 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 water striky uwc;nm31i1x j0pzy( ing 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 bb9 9r695+zj/tlebo,ixhj oc with a speed of 12.0 m/s from the edge of a cliff 70.0 m high5o+9b9 rc 9jb6x,h b ot/elzij (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a verticvzx1 .u*djwj6 n oh7hyq3.l. cal speed of 13 m/s If the bal 1l z. wxhq.uj 7yno*hdj3c6.vl 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 velocir4h pts 7idz)t /;u0/tz4rvkm ty of a train as a function of time. (a) At what time was its velocity greatest? (b) kt/ztu0r)tivd7 /zs4hmp4;r During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel aa 9o2cpzf6x d)s a function of time is plotted in Fig. 2zp) 9dfox a26c–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelbjer6in04ger v+p n 1 0+)8aksjor)hterate approximately as shown in the velocity–timr0gj)es8j 60r pbo +a vk)ni+1nt4 rhee graph 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 ph stgxbin qh*4 , 6 33aulnqpqp5f-.o2revious Problem (Fig. 2–35) when it is in b3 -2hxfq*hq 4s 5 pigtnla,uq o6.np3
(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 distanck2u6 3ki hu g ka(4oqx65nwd6 whz4f6xe the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacementcky/, yjxrlk3 q560t6va prl0o3 i6et as a function of time is given by Fig.realty06j c03 ko/ ivtp 6l,k5q6 ryx3 2–28.

Figure 2–36 is a pos0 m;r8ukersp96a prnwl5*4 v eition versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of 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 objectw5 pp06 slar84e;u9kmvrr en* positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefi*b* l; a+ z;6zcd24ac+ztmroog ucu 2vghter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fig. 2–;+udcc*b 2*26;+u looazzrtm g4a vzc37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what it is on Ear;-2 i.3leo,wnrf o smmth. If an object is thrown verticallyri m,-l2wns 3o;ofm.e 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,hz(7:j wpqrz7s c ,mhu:k2xn by an over-the-shoulder seat belt has a good chance of surviving s:h7ukzhr2( xmwpzq n:,,jc 7a 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 brip0 2g*ectoj/zdge, 12 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 meae2 g/j0tco* zpsures 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-end6yi) 4 fvuh:9qwi3g p2nndk/z collisions by hauling them up on a crane and dropping them from a certain he9izv qu)n6hw2pgn d3:4i fyk/ight.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels about 2gil3 jgj5-o*uor )sh$10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train be5j ck0xea)00k 7jxbym +7nt mhgins uniform acceleration from rest. The front of the train has a speed of 25 m/s kmcexn+ 07t)5 07khyxjm a0bjwhen 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 aborb vi4r9td 7x.wrgg03hwq9 c 0lex/0 vve 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 averac0/94 rd 9rwxqhet ivbx70lrg0gv3w .ge deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid tran )kkqrc2g/ 1/ dhguhp,sit system, it is necessary to balance the average speed of a train aga2uk/kgr, hh/)p c1dq ginst the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight dor exnq;tl8,0j8 daubp 4mx 29vg mo)2lwn when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once comxav28mlxu)tg d0ejq8mobr4 9,;nl2 pmitted. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes 3d)qn lm, j*hc0 ar o-p2hbet6a ball is planned so that the ball will stop within some small distance of the *p jn)qtr ,-hhc3l2mb a0 oed6cup, 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 speed of 6/v* mc6dvge;ki)y a)i.0 m/s Just as an empty box car passes him, evc/)6kid ;g )mv iay*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 bumn6-bgd1 qs1chh(pjj5z6 a7*-t vjw lilding. A second stone is dropped 1.50 s later. How far apart are the stones whe 6aq75 hjwglc- j11dzhsbv(6n-t pj *mn 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+eenke )c d,bnv((g,4co(9p.j dwkrw a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . wjw, ()do9 k.ee, c p rve(kcnnwdb+4(ghat average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Frahs qrlr(7oa n u5:4x,bnce crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (insn :a(o uh,l4bqr 75xr $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. T4w 8tq4.zgq gfhe first child can bounce up one-and-a-half times higher than the second child. The initial speed up of8 .zqgwqg44tf the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-lonmaw f)a tr .br0:oue79r 9zdk1g 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 thibrz0wf9e7r:r9k mo1) ta.d aus 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 ad pk:7s5fia -8s5y9c zuvca5 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 the ball dvd :zca7 s5i5u98cp5fsy- kaauring the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accele4l,7or8) v alwu,, l7rfzjzncration 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 hpcwlv3o9 )p-nas a traffic signal, 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 intersection, all the lights turn) co3 9nvp-wpl 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, passe m/heiq88 :l ghsv8,nrd by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, mqvhrs, : l/mh8ngie8 8aintaining 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 bcyqln,8yv 8 8xmtxm ( /9yv+qxuilding; 2.00 s after that, a second stone is /q8x8cx(nym9vv +y,yx mt8ql thrown straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is thrown rd n zgdwnjg(ok*/*-(with an initial velocity of 11.0 m/s f *d* wg n-o(/jgzkdnr(rom 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,l+0h4it3isyta;x( e. lt duh; pkx7k8 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?dlhkx3utyt h0+ie;i .;xps 8tk4l 7a( (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a grgq*1z;ce ygn( illing machine. Ife;gqgzc(y n*1 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 burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than J24 rd*p0q0g gtnkn yj+,;;6h(ai,lkgnt nvyj oe can. How many times higher willv gtkr,d2(0,0n*tpnj;gyh+4j;iygan lnk q 6 Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands ohfsd.ri/ hf:codb+15 8hv a4 rn the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up tov1ho ib/hc:df ra d s85rf.4+h 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 height of a particular building using 6xg22eckz qb4a barometer. Instead of using the barometer as an altitude-measuring dez4 cg xkeb622qvice, 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 gr widtv :: fh gje/myr,j3f:39yaph 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 instantane y:/vmf9 hyj,::jde3f3ti r wgous velocity? (e) Which bicycle has the higher average velocity?