Does a car speedometer +f 8* 5wh:zs5* tp w+ temxigb(x0hxnvna8 o(vmeasure speed, velocity, or both?

Can an object have a v ys ,da0/p/dquho6,eearying speed if its velocity is constant? If yes, give exa0e,6q /duehapds o /,ymples.

When an object moves with constant velocity, cwn, bp;64 gzcdoes its average velocity during any time interval differ from its instantaneous velocity at any insta46czc ;n,pbgw nt?

In drag racing, is it possible for the car with the gregj k+h(vft*4n atest speed crossing the finish lk hnf*g t(j4v+ine to lose the race? Explain.

If one object has a greater speed than a second object, does xj. fe./saatjwpdrr+ (5 j:6tthe first necessarilyfp.:r( +s. 6 twjjaja 5txred/ have a greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycl*ootxkd9d8l n3jr3l1t0f8 pa e that accelerates from 80km/h to 90km/h with the acceleration of a bif9aojprdt0l*xn k t o183l8 3dcycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward a0l0,c fda(jm xm4xsf*cceleration? Explain.

Can the velocity of an object be negative when its acceleration is positive? mqk(d fq:9l55u8 jxydWhat about vice dq5:xy8 9fmjqdl( u5kversa?

Give an example where both the velocity and acceleration are neocq5y+z6sqhfjn ; e;d imd*)0gative.

Two cars emerge side by side from a tunp;- awo x.*,phyoqm t5nel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h aa-h, p*mx ;.oq 5wotpynd 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 s*:a mitj ,2injjs7*dl /lmr0 wo, give an example. If njiwj 0 nalr*smi, */j2td ml:7ot, explain.

A baseball player hits a foul ball straight up intdd6ma: 6xhdw31pf x 4xo the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast wild 63hxwpdm1afdxx:46 l the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to its accelp okm7 r5yctb+m 16hh / nsbc,pf+w(n0eration due to gravity — does it increase, decre y1cks+h6(w m no+5tfh07, rcn/pbpbmase, or stay the same?

How would you estimate the maximum height you co mijzmjalp . *v40rh*.uld throw a ball vertically upward? How would you estimat*0lm.ph j4* i m.vrzaje the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of Thenwq+8 qo4knrxttxrt8h 5p+a36 you travel the same distance from point B to another point C, moving at a constant twk rq+txop axn8 43h68rt q5+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 ti joi h+s8lx-af;4yip 8ed to it at equal intervals is dropped from the ceiling of the lecture hall. The string ia xfyj8;l8+o-s4i hpfalls 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 motiqt( z /3(lsbc;apd oj1ons is not at constant acceleration: a rock falling from a cliff, an elevator msqlcd ( /z;p3(1tj oaboving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to isinttxyvt76+h *rj4)d p; y:lts original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, 4tl nty6phdrx: )+7st;ji*yvwill 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 velock/7 dynw- *ziw9gq5o:t8 jsddity and nonzero acceleration at the same time? Give i79kdt/8*wwqgos: yd5 zjnd-examples.

Can an object have zero acceleratosrg 1h ac-s4.ion and nonzero velocity at the same time? Give exam.s4 coas-g 1rhples.

Describe in words the motion bod71x wh4h*5lz8 pebplotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplicate the moth8z 1 x4*od5bephlw 7bion plotted by walking or moving your hand.]

Describe in words the motion of the object gr;fcrs)-r* 2: rjj yxhd(c: ozwaphed in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km i;o -tg8 3bzy eglvl6b0n 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 kmofbh o.lr45t4nqco ;) ?    h

  If you are driving along a straight road and you look to the sih : oyrdl k2id*(:3fsade for 2.0 s, how far do you travel during this inattentive period?2a*yslkd(f: r3h o:di    m

  Convert 35 mi/h to jat jinx5f vvle66-7 5
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frov1 d ylyrdf l5,vx6434v6wab gm $x_1$ = 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 t 2rv0amzn6 ;*+iud tr(og+ j1zh8kat95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrizt 8r+ozah(0+dgm2;urt 6kai *vn1 tjve 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 lightnzfkoj)bw a4yt h8-65ning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essent8w64bk)h yf5atzo nj- ially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps arjg.;s a;pf,o7 v5 lyeround a quarter-mile track in a total time of 12.5 a;f ,sl;j yp 7.ve5gromin. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer inofj9v92e 0,hx 6 rsbpz a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 pj 2 ozfrxv6h9sb,0 9es. 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 parall/y(guaqfd*d m-; lb o-dfa( d7el tracks. Each has a speed of 95 km/h with respect to the ground. g f/oa7(dd- d* -qmfb(lay;ud If they are initially 8.5 km apart, how long will it be before they reach each other? (See Fig. 2–30).    min

  A car traveling 88 km9 :v(f7adlo27 riavan/h is 110 m behind a truck traveling How long will it take the car to reach the truck? fal a2v(79nvado i 7:r   s

  An airplane travels 3100 km at a speed of 790 km/h , and then encountery8opc,m u)*cku;d dn;s a tailwind , y8;dcmnuk)p*u od;cthat 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 of a 1(juo oow7y b.p05:l jwxz,mvcomplete 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 o ,z wl7o. o0j xw(mjp:ub51vykm/h.    km/h

  A bowling ball traveling with u: (u eaoxfpw8m1up/ngzj4 7z,ld i19 constant speed hits the pins at the end of a bowling lane 1xwgo8upndu 9l/f(:p11iaje 7z zm4u ,6.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/0e2p0g tzept7h3e: ehb z 2v91 2hrfbch in 6.2 s. What is its average acceleration in:e9g tvc30e h bh1p2z etrf2zhp7 0be2 $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceler4:t); p5 sj0du liquvoation dj opl;:)40 u iqvs5ut
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a2jqk-bmzd f -,o 8mif, particular automobile is capable of an acceleration of aboutm-q dib-8f2,zkfjo, m $1.6 m/s^2$ 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 trave decpqoip p/rj5rdexm m2)6;6p9.s s 6ls 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what p6 ip pd;)sqje/2mdr emr66ocp sx59.is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves in a st (l e90sx 1d24nwpsegloy .be;raight line, is given as a function of time in the followig0pxs( dny4e. wb el9;1ls 2oeng Table. 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 m/s to 25 m/s in 6.0 s. What was its accelerat h7 (s:5n:vlkdlu lax(ion? How far did it travel in this time? Assumellklv(hd: au5(7x: s n constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What was its acceleqsnl6z5 ek 3d;,t6y knration, assumed constant? ynn6 s3eqltk,d 5;6zk   $m/s^2$

  A light plane must re1k3a8fm 5plgq ach a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) acceleration l1qk m83fgp5a is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially to tphapr 6ck7*gi0l2+ dp speed (of about 11.5 m/s) in 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*c 7iplk6at0p g +2dhr 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. How far k,; fmlt2fo/n did it trf; ,m2 l/tfoknavel in that time?    m

  In coming to a stop, a car leaves skid marks 92 8v:y -lqrlny4f g,2u qm long on the highway. Assuming a deceleraty ,-lvqfynq g:8u 4rl2ion of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km4rtvt 6c1bj c*s 4xn(y k6yz8i)b0niy/h strikes a tree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration n) rc(*y1nyyjvts6i044c t 6bbki8x z of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a carp:wmvg3f(j s kx(q *0r with an initial speed of 95 km/h and human reaction time of 1.f 0(r 3 g:(s*qxjvmwkp0 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 distancengzsaox80yb9a-5 e 1u of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on td3kv,kmuld(- fg )0 zahe highway. The car’s driver looks for an opportunity to pass, guessing that his car can accelerate at 1.0,f(gu m0k ddl- kv3z)a $m/s^2$ 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- 31i hbv+i:pclwa29lb* gdq9wj(2rmp m run in less than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner must then :blcb*2m +1w(lraq pih 2g3 9iv 9pjwdaccelerate 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 just as thj ,paqmns 58cv(oex2pnw+:l6 e traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before tmejwc:6s8a,p+ pl2 ov5nq xn(he 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 the grounb tm .now:(*,d hy/urwd below after 3.25 s. How dny: .owwrb(htm,* /uhigh is the cliff?    m

  If a car rolls gently ( l:swc s,ri wf,8mbyzbu1g vj 3,)v0fv*4l7si$v_0\,=\,0$) 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 speedt 61(zu legxn*t5nt.*h;rwe8 j o8 fc6 c.gpid 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 aftf8 :ujcfgl0ytp3d) 1jer throwing it vertically upward. With what speed did he throw it, and what height did it reachjgc1u f)8 ydtlf0j:p3?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the in pa g+ cf+no4uco tl):gfv2hj :z1:.z5e(nqk efluence 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 = 5.00 s . Ignore air resista1czggh 4:pcu .f v5fk ) :za+e oo(t+nlj:2neqnce.

A helicopter is ascending vertically with a speed of 5.2: q2jskncyfnbwb k)z59 / 2bg;0 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How msjb22yc:)fgk;/b knb n 5wq9zuch 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 lboedtk0245c v7+;ga6lkghm rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers dgv a0e+mlg6k 2okc;t hbl754(1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, sho(i5 g67kte, ynjg zg*ow (algebraically) that a ball thrown vertically upward with azi7 gn5y*je,6tg(og k 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/shr 4t7e23mjr,og ; bda
(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 photofaa8a ogvk2kr d s43+/olash of the apple in Fig. 2–18 (or number of photoflashes per second). Assu/v 4da3kk+ oaor8s2 game the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to t. z47wpko1-n7uccz o aravel past a window 2.2 m tall (Fig. 2–32). From what height above the top w p.k ou-c7czz7 14oanof the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of i5 z+t qtzbl+6tt striking the ocean is heard 3.2 s later. If the b z+5zt l+qt6tspeed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hard l9(yb+s9 3z tqky xig- ps5w. ykofrup0/-wc)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 striking the ( rp- + py5u9-/wxtwosq . bf03ycygkkis9zl)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/si1 zm 2;9 eigxip afyfwz03;/z from the edge of a cliff 70.0 m high91iiia pz/f3zmw;gyx0f2e ;z (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 abovuv*c4*afep;m 7 a.bple the street with a vertical speed of 13 m/s If the bam*.7cpv;a bu 4lpae*fll 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 train as a function of time. (a) At w-fy,vcdd/+ rwnsx d6 a g+19gwhat time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the accelg +6vad1r,9y-+g dxdwcs wnf /eration greatest?

  The position of a rabbit along a straight tunnel as a functiob8e/u x d71 kcum)ev/kn of time is plotted in Fig. 2–28. What is its instanud/kkmv 7xeb e/c)u 81taneous 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 q)jsg -b 5rsq vt 1(-ojc4wjv7approximately as shown in the velocity–time graph - qq4vr5gjj to(7csbw v)s 1j-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 prevk ; i-k.zien(vious Problem (Fig. 2–35) when i. z-v;k iink(et is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate the distance the object traveled during6-q h;zc i;dee*-f b7 r(/wg pxj( tjc4hkpcv/
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a functionc+s vyktzp s4d8k44buy l 5j/e/6mzn0 of time is given by Fig. 2–5 c+t6sz jypbz4 v48ysmn4uk/e0 l k/d28.

Figure 2–36 is a position versus tif6l:n-,l z axwme graph for the motion of an object along the x axis. Consider the ti: n-6zlfa wlx,me interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefigkve fu53w1u hrd jd(jv96qoxpz1+.4dhter’s safety ne+.jh13ew 6d1zxojfdqvud5 94pkvur( t. The survivor 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 gri; (e nlflk6ldb0b q*-avity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward q-l lbkif(lben;d*6 0 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 constr(*x 2.q whl8x swmxee89x t**kdaf2moained by an over-the-shoulder seat belt has a good chance of surviving a 8.f kqa9txd xsme *8ww ho(x*22exl *mcar collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m above the road below, and h4 c3ion1jcl- lcn/pd hpqh/-2is pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by known- hcco2p dq/h/ n1 ci4-3pljling 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 its6)a nmv3brhwfu +, v)k cars for front-end collisions by hauling them up on a crane and dvnk)a,b 3) w+ ur6vfhmropping 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 Earth us,. g. dgadm1.:id fhtravels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins uniform acce(jtn4ljt go* ,leration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the train started. What will be to4tj j*tng,(l he speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving boamka4n2l k*(, +xgbdtq:mk mt(rd 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of the personq (m bx mtt*(gklk:,knda2+m 4 while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is nec28pwzk:nb e5ndtis-6essary to balance the average speed of a train against the distans p6 bw5 idzk:nen8-2tce 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 down 5y pfzzp,h, v.qpui78/jz qa*when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what min7iqqfj,/ .z8ua*z zy,pv h5ppimum 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 i 9d1/j :,(fxltllv tzos planned so that the ball will stop within some sm lv,/1l x9to d(zjftl:all distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freighd.85nnxg(a p9d vgw a6t train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitivn anwgv5d.d8(pg ax9 6e 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 secov y4 eher;oi(sjl8w3t/mu0 0znd stone is dropped 1.50 s later. How far apart are thj eysv8hr t0zwl3 e;4ou/(0ime stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the course of a.2oj4deu; zv 9ksjb0u time trial lasting ten laps. If the first nine laps were done at 198.0 km/hv;jdjk. e0zs4o bu92u . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mountanszpbj)t 9+e2:bc7 -x5fa ; /a5 lze, fkngbnmin pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is s2)f z;5 5+f ba,jpagme:9nxk7cb tne-zlnb/75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. The first chil3p;wjzzc *;vdz qtw: q3 oke* 7fbh7b5d can bounce up one-and-a-half times higher than the second child.3z*q;zwfv 7dt;eq bk5pc 73h w*ojz:b The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling i2w iua24 3-svk gshmta,7mwb /n the same direction on a track parallel to the road. If the traigu,w7- /t3mvi 4k sam bwa22shn’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 speed of 44 m/s In throwingn(qc n /u,gaeddonqm 9s/n752 the baseball, the pitcher acceleratqd nqn7/sc9 dn(u, m2o5gae/n es 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 during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an accele3hz 6*cxftd7zuw(e( eration 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 z+e8n7xvfok,) dczm 0. vgpsngjo,29 in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . S7ponj,go .8 e s9cgvvx ,+zm0k)fz2d nuppose 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 sz 8;mobs)vv; zpeeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 b;)zv8v;s ozm 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 tajc 5 cblq+.52mu* ku;43bd nyzzzx*lhe roof of a building; 2.00 s after that, a second stone is thrown straight down2 .k cu+zac3bqlm5xb5*n4 z ;*judlyz 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 firsy .dmp b+j 6+a/im*hzxt stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity /dz*i. p+xj 6h+am bymshould 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 res7djg i:m8t -zxn7 u2 wjdhp.;wistance, how long would it take a free-falling parachutist to fall frot :dwp2nx;jw- .dijzug 877h mm 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 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the bur 9rv9 +lmuj.jogers through a grilling machine. If the grillilru9.jv+ 9j omng 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 Joe can. f8j+ug 1d 6qdyaj;e,m l .bqh0How many times higher will Bill’s ball go1yq+ , bd.g hmlq;8d0jfe a6uj than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands qdk b70 26ku4x8nvyrm on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend thennv b6mk qkd 784uyrx20 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 tof(u s 8wbht-)r find the height of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and 8 u(hf -bswtr)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 position7.7v cgct9o4wgow z*w vs. 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 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)zwvt.wgc7o*wo9g4c 7 Which bicycle has the higher average velocity?