Does a car speedometer measure speed, velocity, okto4j+a5b l* nr both?

Can an object have a varying speed if its velocidg0xz djs s)m)io( ;5gty is constant? If yes, give examplessj );5 odggi d(mxzs0).

When an object moves with constant 52jy 14bphin evelocity, does its average velocity during any time interval differ from its instantaneous vehi jn1b24e5y plocity at any instant?

In drag racing, is it pos9)- ctgz0r.hr0bhd :jv9g pe0u a)qxgsible for the car with the greatest speed crossing the finish line to lose the race? h09d: jhx)rc.p00 gzt gr)eqv9ga-b uExplain.

If one object has a greater speed than a second object, does th.y( ysv8,f ,hw fdb7cvpv m/.xe first necessarilvx.bc .,wdh (m/7yfs,y 8vp vfy have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerla+sg 2z(.qnq) c;8edcn m .c4bmyo7cates from 80km/h to 90km/h with thbc +2g(lc)n4;n.zocm qa . dm yceq87se acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a aofrd9v6 8la6a0d(nv northward velocity and a southward acceleration? Explain.

Can the velocity of an object be negative when i zi/o8h lrfxb f3l9a77ts acceleration is positive? Wha7h /8i3aolff rb79lxzt about vice versa?

Give an example where both the velocity and acceleration asuwh 8ac-tjv2v, cm88re negative.

Two cars emerge side by side from a tunnel. Car A is traveling win kyw z09x/l+x+evb o9th a speed of 60km/h and h0/ x9 b+n9 ezkylxwvo+as 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 tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If sy v4sgg,3 5dl)nrrh r+o, give an example. If5y+rgr s,3l vnh4d)r g not, explain.

A baseball player hits a foul ball straight t;amw3s +ka smt7n)-hup into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will the ball be m m;s)atw+7 3tknhsa- traveling when the catcher catches it?

As a freely falling object speeds up, what is happek0d)w q( 3yxsef9rvowl0z-+xning to its acceleration due to gravqxov )+yk0lef-w(z30 d 9xrwsity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically upw ep5 ,h5adb 7jeco+ 6yz9*miwbard? How would w ebj *mi5bop6+7ec dy,5zh9ayou estimate the maximum speed you could give it?

You travel from point A to poi gwr3 uoer6sg()0 pms1nt B in a car moving at a constant speed of Then you travel the same distance from point B 1 g3rsm6w)0eorpsu( gto 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 to rd(sb(t 2wzi/fykk p;41gu4k1nllu, 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 tkzd11ul4,w4;gy lsun(/pik ( tfb2r kime 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 ji3 rnzfx4 9-fis not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making sto39 ixjnf r-z4fps along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its oe wyooz zs2elsl67-y:0r2:9e muadb 5riginal position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is al6eyssdu-:m o9 r2e 07 ay lob5w2elz:zways in a direction opposite to the motion.]

Can an object have zero velocity and non3g +ndsa+a)ir zero acceleration at the same time? Give exam3i g)d+a rasn+ples.

Can an object have zero acceleration and nonzero veloc-jq erocbv/t)tp ,*ha;gg7t 5ity at the same time? Give examples.5gv jpg7beqc-tr to ;t,*/h)a

Describe in words the motion plotted in Fig. 2–28 in terms of v, a, zh, yz+ds r/4qetc. [Hint: First try to duplicate the motion plot/ zqdh+y4zrs,ted by walking or moving your hand.]

Describe in words the motion of the objh1t6 uf 0qlf*cect graphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3.v2eb*qn(6k e m25 h?    km/h

  A bird can fly 25 km/h How long doe +xsjki ,f.n8w qkcp2 x6tgvna,e241dyv( q4vs it take to fly 15 km?    h

  If you are driving along a uz3oaad6)fq8 straight road and you look to the side for 2.0 s, how far do you travel during this inafa8 3)6a zqduottentive period?    m

  Convert 35 mi/h to q+p 63d xs6pfom;/z ey
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromqi)dj nr9ed )5-u(h0 fi3-.abx trymc $x_1$ = 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 then begit;td tscb w t5(ys34l9v0kqg:ns to ratt 53t9s:gv(y q0dl; cbs 4wktin and you slow to 65 km/h You arrive home after 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 fus *hfx)tp65r2bu tq (lash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light * rh fqp6)5(u2bsut xtarrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight cfu5;xizjz+ wb xns 9sg7io-06omplete laps around a quarter-mile track in a total time of 12.5 min. Cal0nuwbixx6 +soz fj5i- 9;gs 7zculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, m-jnr+a ,ku6 thoving 116 m away in 14.0 n+a6- kjtru, hs. It then 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 paralle;q0qye- y m(sr7d8 htsl tracks. Each has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apart, how long will it be before they reach each other? (See-hsrq(;yq y ms d7e08t Fig. 2–30).    min

  A car traveling 88 km/h is 110 m behind a trucdxth,ch.fn*vo .yr ,-o 4c8 vbk traveling How long will it take the.c ,hy bh*fvn8dvo-ro.4 ct, x car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encountersa1i y7fto5 ry, a tailwind tf,15 a y7yirothat boosts its speed to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity dj q+ aw.-jtgfp/2g9uof a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h2ufj/-d qgpjwt. a+9g.    km/h

  A bowling ball traveling withj1l7 bpdhb ow)+o:cj; constant 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 bh;pbl :o jow+ j1c)d7released 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 avee ui1 j:d2 nse(x*ybhh4dc +o0rage acceleration in04*cdoi+ey2( 1 eh u:hdxsbjn $m/s^2$ ?    $m/s^2$

  A sprinter acceleratn2) x8wamsr oik .x.pmzq6(i3.mmi ;ues from rest to 10.0 m/s in 1.35 s. What is her acceleration s6na.iriik)u(mxm; .w8xm q 23op z .m
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular a1zf1wv ,r)emy/zgn p-, cgxr/utomobile is capable of an acceleration of aboutn/x,r)zwyf,vrgm g 11-ez/ cp $1.6 m/s^2$ 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 constantu+kk-0 v:/m. kpqwjr:sev0ym5 t *a ks speed travels 110 m in 5.0 s. If it then brakes and tuqym v 0evjw*as +kkp:5 k-0s.rkm/:comes to 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 stauqi0ov x edbe 3.3k8.wrts from rest at t = 0 and moves in a straight line, is given as a function of time in the following 3xbqev 083oikdw ..e uTable. 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 1 *pt)(sy ;il-,qb5v rnh7ixrt3 m/s to 25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time?v*- ,7rqirn;s (tiyp t)5hxbl Assume constant acceleration.    $m/s^2$    m

  A car slows down from ra zn, hofij1x .x+- 1jmq- e6ov,0spf23 m/s to rest in a distance of 85 m. What was its acceleration, assumed constantaxr-p ,6x1q o+0zf js ,e1vijhmn. of-?    $m/s^2$

  A light plane must rirkvbg/sku4 tu31y1ocmhe 8( l /de2 ;each a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) accele(o;evh1ec4bgku 3d2ik/18 u ly/srm tration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top speed 1-c*jf-xzsq g (of about 11.5 m/s) in the first 15.0 m of the race. s1-jg * cxqf-zWhat 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 rest in 6.00 s. H 2w,wxoks jd;8ra3do,p:9bki jxh b1)ow far did it travel in that 3 ;b,,)xpokorij dwhdbk 1sa98j2:xw time?    m

  In coming to a stop, a car leaves skid marks 93j u q.7 1nxk10sbqyba2 m long on the highway. Assuming a31.kqbb u0j sqayn x71 deceleration 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 comqjkj-8ky8 ak8 presses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the co y -8qakjjk8k8llisi 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 of 95 km/h ani wgvj 3:n1c6dd human reactiv1:3cwgjni d6 on time of 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 distanc.pzra453a6 zl, sr.pay8gttbe 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 bd 5e4gm2 ;9/rpi(s6m u8gsx )jyjptuaw6h6d m/s on the highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate atjwe6p5aps/h2gr uj96t 6dbx8su idy;m)m 4(g 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, ,4.vcz8ywf2 diwvkr9000-m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then acd4i.vw 2rw,fz89k cy vcelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her carmsm;qd*pkt5 rj4.ci)3 t a c7q at 45 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the inter;k) 4mt 5tdaqrj73p.cs*qic msection (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 from5dfety2.e 8jo the top of a cliff. It hits the ground below after 3.25 s. How f d.ey2e5to j8high is the cliff?    m

  If a car rolls gently :uaf;r9xrrj4t1wz) k0 y s8fo) z;hdk ($v_0\,=\,0$) 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 nea;y5g0 :cpk0bwjm,ixdrly straight up into the air with a speed of 22 m/s
(a) How high does it go?    m
(b) How long is it in the air?    s

  A ballplayer catches a ball 3.0 s after thn, e,y xdjn;hb68qa4trowing it vertically upward. With what speed did he throw it, and what height did it reacxya8hdq46 bjt,ne,n ; h?    m/s (Round to the nearest integer)    m

An object starts from rest and fall-t bjr8z/5ejts under the influence of gravity. Draw graphs of (a) its speed/ brj-te85tj z 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 ve rqj/f sf:t0 tq1kak:3o)-y jkrtically with a speed of 5.20 m/s. 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 ground? [Hint: The package’)f-t1o:y:kat fq0 kj rkqj3s/s initial speed equals the helicopter’s.] t =__ s

For an object falling freely from rest, show that the distance traveled durinh e9jq.j 0h.6uomhl*t.k ;muyg each successive second increases in the ratio of s9o.mj* 6heu y.kqh0;mulh j .tuccessive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, showq 6 fk/d;xli.(th .gyo (algebraically) that a ball thrown vertically upward; l /gfxqo.(idk.t6yh 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 +f8f: 0phvje: ee8u tbwith 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 bet-jf 9w4nxut,i +mvw v6ween each photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is aboutv 4i6tvun,mf +9w wx-j 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 window 2.2 m tall (Fig. 2j :begmb;nh 7f1bx6) ,v vd1uf–32). From what height above the tojfdn,;v6fheg x1: 7b b)vum b1p of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is hed:v ) fmrksa(j;w:- zeard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff?:mskef dvrw ;-z j):(a H =    m

  Suppose you adjust your garden hose nozzlx9zn e6uw:qy)xj:* iy nlb4*ve 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 qx6yx9 nl :*iuw4b :venzy *j)the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from the e.jzg-of+2+khz/ad x( iq)fd 5t znt4y dge of a cliff 7jx hz5z4t( +z+naki) dg- y/.qt2ff od0.0 m high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a vertisk)p-(adod9igf g-.c cai.sfgod (da9- cgp)k-l speed of 13 m/s If 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 traing0-s7t52x5o onsdz hp 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 perio5psdz o25t0-gs 7ohnxds, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a )c/n eqv34e/wrh tg4a straight tunnel as a function of time is plotted in Fig. 2–28. What is its4t/4 qa3h/cnr eev )gw instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate appromt2ojg1ym5*i +7 ajuwximately as shown in the velocity–time graph+t*gi5uaw2 7m1jyjo m 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 acc x (lln gldo,qs4p-dtl3-d4; meleration of the car in the previous Problem (Fig. 2–35) when it is i-s md4g, ;lo dq-d tl4(l3npxln
(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 traveled46p :3ewv 8cozc*ugc e: x4kyc during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacementuw6d qk 2h(tl. +jzngd14tw9g as a function of time is given by Fig. 2–28. (d6nwd gtlw.+2k ugh1jq9t4z

Figure 2–36 is a position versus time graph for the motiongy ct,olh5 dp:) mxt)- 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 slowid-go5:y,mh c)tx)p t lng 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-rctbb8 u o6c7d o1vw.yrb i1xx- 0*n)sstory window 15.0 m above a firefighter’s safety net. The survibib8r*t b7vx.oc)1dsc-o1 uwx 60 yrnvor stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth wh8+ki qm- 8x)dclwq 2f ;ie(chtat it is on Earth. If an object is throw(2dlci+i e8 )-hxc8ktmqqf; wn 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 dx.:+j k9l pafan over-the-shoulder seat belt has a good chance of surviving a car+. fxpd:l j9ka 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 standinv . :j)p6s :e+vfleu(eg akn:jg on a bridge, 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 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 eun( :kalgvjf:e).s6jpev+ : getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars for front-end collih ro kr6(oov/ lh*9:tbsions by hauling them up on a crane and dropping them from a certr*6h9 vl h kto:br(/ooain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth tra-fe2 o.v46xu lol 6gefvels 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 8( jkiy73ionruniform acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What wi kio8ny3(j ri7ll 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 qmx*; c8uvmmo:h)waj;-d /wo4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the person wwoc/u: ;dqvm;a ohjmx-m*)w8 hile under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessary to balanc -lu4ir x)5vdsd)zm b5iw)u;r e 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, calculate the time it takes a train to make a ;vsl )) 5)i-i4zmxuur5dwdr b9.0-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 wingjb(9ec)ecj4 x s/vhh+s and free fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its sc(e c+hb/j4e)vj 9xh 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 surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planned so that tak vu7 m2ur v3z6xz6l7r1smyq:v6ao6a8 5jnd he ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is mmz v6duoarmlu5vv s8a 6 637kz :qy271xn6ja rore 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 conytql2mc8 f3z: j:ts f8stant speed of 6.0 m/s Justjmc8 s:t 3 t2ffyqz8:l 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 second stone is dropped j5k *.pnvj z;kmeha3x.d9k -h1.50 s later. How far apart are the stones when the seh9.v.dne kp 5xj; -k3mzkh*ajcond one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 ku9qhqcxqxq(90(dpx 0b.1x hsz6y ,yzads6 (ym/h over the course of a time trial lasting ten laps. If the first nine laps were dy ,q x1s06 p9xzzyy(q. 9bq (h6xuxdqas(0hc done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Frd9dmrid vj; ,7:hs45e 4 cnew3znl3xzance crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his ,9;icze7jx d:s44h dw n3 e5dn lr3zmvspeed 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 trampolg-5re2mzzg o-.h 4vm xines. The first child can bounce up one-and-a-half times 2 zv-mm heg-xz 5gro.4higher 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 travel t o(j260qqnloing 95 km/h overtakes a 1.10-km-long train traveling in the same direct2t0jq6(n qolo ion 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. 2–40. 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 sp :pghym;0v xj6tk t4/need of 44 m/s In throwing the baseball, the pitcher accelerates the ball thrxj ; t6/k 0vp4tg:hnmyough a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, fe0pht11o4/a xxjjz a8 rom 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. 2–42. Each intersectio lo75)ngfvt 5xn has a traffic signal, and the speed limit i5vonfl5g7t ) xs 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 green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constant 120c a9*nz vyj16t km/h takes off in hot pursuit. The police officer catches*cv6 1a9 ytnzj 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 building; 2.00 s after8k1cq qan*4w v(+ vztz that, a second stone is thrown straight down with an initial speed of 2caq4z (+v v1qkw*8t nz5.0 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 upbruprdry. -b+3ei* *f at the same time. The first stone is thrown with an initial velocity of 11.0 m/s from a 12th 3f.-prr*dier *+buy b-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it16a8wxrk(5u1w nsjo t 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 resistance will restrict her speed to perhaps 155t(asx w16 u8wkojnr 10 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burgers through a grillisln,ow- -e;7 qlzby3b82 wbreng machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in ;b-n-yb37w2,oes lwqzb8el r burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times faster than Joe canrr 1(d/w7gs, iw xyk2g. How many tr7/1 kyg(gwdw xr s2i,imes 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 grou)s mp7gpt.o kdiy rq890up7n0nd below you. You drop a ball from res.)7mg 0ppi o dk80u9qr 7sptnyt 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 find the height of a particular building +tv6 0g(st-5dee6zed mvgpl 6using 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 d 06edt(v egpmez+6dtlvg 5s6-oes the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the posit1q,ad5:lh t nzfi3kn qs*lcy n2n 6,-wion vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity1*nalnk3 yqn5c, n sl6wd,zt 2ih- q:f? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?