Does a car speedometer measure speetlbr:l83f*as js vq 46d, velocity, or both?

Can an object have a varyi 6hm;8eksulk7ru vh+2h6vv 9zng speed if its velocity is constant? If yes, give exahul evv;2 vsk h 6z8+6ukhr7m9mples.

When an object moves with constant velocity, does its nixewoips4se v1.4,7gc*s9 o average velocity during any time interval differ from its instantaneous velocity at anw 9,gesne 7ocv 4oi p4*sxi.1sy instant?

In drag racing, is it possible for the car with the greate edv1gd9 pmorgp4iex3 31otkf1.d9cr 04o x,rst speed crossing the finish line to losed rm1vokixegp oo9. d p3r41 c94ge,t3 r10fdx the race? Explain.

If one object has a greater speed than a second object, does the firp/jx p18xj ws.mx1 j k,ted,6ust necessarily have x pxjxpt ,j1k/6m.ds 1e8,juw a greater acceleration? Explain, using examples.

Compare the acceleration of a motorc bxd5juy3b 5*+4mducbb 17t r ek6 hmqrlny(;8ycle that accelerates from 80km/h to 90km/h with n7y5brduj c8;3ed+bbl5r *bxyu6(h t mq41mkthe acceleration of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward accelerapi1 5b;t- j4w ruq0)1xewtsn.q4nxb ttion? Explain.

Can the velocity of an object be negative when its acceleration is positive?/;u;2 zdrf 4 rh 5kzpe9opc3mm What about vice r/2ep9m uzr5cfh3 4m;kdop z;versa?

Give an example where both the velocity and acceleratio0/thlheg k1 25 am6ppbjd*dil q,i:e( n are negative.

Two cars emerge side by sid- -ozie6)jac qe from a tunnel. Car A is traveling with a speed of 60km/h and has an accel )e- qco6jiza-eration 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 ass 6nnujq1(5z8pkw: lj0r vf,e its acceleration decreases? If so, give 05 j:r(q svej,plnkf16 unz8wan example. If not, explain.

A baseball player hits a; c1f c+pb6xjk( lgkm7 foul ball straight up 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 traveling w gl k1f(bcmkx6;7cp+jhen the catcher catches it?

As a freely falling object speeds up, what is happening to its accelerr l1(kn)oe- tzation due to g knrozle- (1)travity — does it increase, decrease, or stay the same?

How would you estimate the m) a fft3lj oeet x7vuz6)),bj-aximum height you could throw a ball vertically upward? How would you estimate the ))e ,j63-f t7tb)ajzfovxlu e maximum speed you could give it?

You travel from point A to point B in a car mo3pzvo ,h 69xk*zbn9ebving at a 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 the entire trip from A3xbep,9 knoz*9hzv b6 to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string withdfpiu w 0*8.kdyg7 *sy ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease ne0g* fsku. ypw87 iddy*ar 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 acce8u-s bq: 2al7ljtyn r*leration: a rock falling from a cliff, an elevator moving from the second floor to the fifth flooy2 ql-*8l7a j: utrbsnr making stops along the way, a dish resting on a table?

An object that is thrown7x8f c;we csv6 vertically upward will return to its original position with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The accelerationw6e7fs ;cxv8 c due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration atb/yeil+7vs 4m the same time? Give examplvi74/yleb sm+es.

Can an object have zero accv:sb2aa +y(hpjkd6yc0a79z,u fymhb9 d8ub6eleration and nonzero velocity at the same time? Givecazhp8a y :f ad9 6svu0 u(yd6m+b9,kby jh72b examples.

Describe in words the motion plotted in Fig. 2–28 in terms of v, p-s:fg0c9urw1 aowj9g; lv+a p xb e64a, etc. [Hint: Firsa wsg9pfp1xb4jg0-6v9e+ ;cuo : wlra t try to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the obje7j/o pec .y+ ,x9 .,uqglkpqar.,ida gct graphed in Fig. 2–29.

  What must be your car’s aver:iuf ,d-lu mx(age speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long doesdeub-cxv b1 4cm;f/ sxu:j0e2 it take to fly 15 km?    h

  If you are driving along a straight road andbp ih jx9p46n+ you look to the side for 2.0 s, how far do y b6pp9+xh jin4ou travel during this inattentive period?    m

  Convert 35 mi/h to - ztjenx q:y*8o11 oou
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frod*nfg; q1e-l fm $x_1$ = 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 steadilhsdr:.i cr1khew (p 1+ 1i3isxy at 95 km/h for 130 km. It then begins to rain and you si ecwip(idk. +:s1 s1r1r3hh xlow 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 lig,5l mkg ypnh 6ibgg429htning flash and the ,lggh956 mbg iyn42kp following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps+g9tb.8 i j4 umv6xheg6p ak-i around a quarter-mile track in a total time of 12.5 minh+6ag.69xg4 umjt8 ibi -kpe v. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer i-sqpixr lm 4plu .,su*s-. wu-n a straight line, moving 116 m away in 14.0 s. It then turns abruptx4,puiw-s.*llpu m-q s -u.rsly 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 s 5+wt- ,iq pofrb*8jsr ;z-zdw)k j*kother on parallel tracks. Each has a speed of 95 km/h with respect to thw f+;j* -*k t-,swo zpdkj)bzrsiq5 8re ground. 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 km/h is 10:s/vink.a1c t / klnfvc5wc*10 m behind a truck traveling How long will it take the cart5f1scvcw/ i v/k *nl.nc:k0 a to reach the truck?    s

  An airplane travels 3100 km at a speed ofv 2 +p/4qsn6yjzpqo-ic9 o 9 hs:jvo1h 790 km/h , and then encounters a tailwind that boosts its spee6vo1p qncvj2oy/ssh: 9z+i- opj9qh4d 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 complete roun1 k*x;.pj jnmxd-trip in which the outgoing 250 km is covered at 95 km/h followed by a kx1pmn*.jj ;x 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins aq , o:umoz,a:i:m6ehhccf1 5ut the end of a bowling lane 16.5 m long. The bowler hears thq,co6i5uc aoh he:1uzm,:f :me sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h e8 +c/13;dl8fxfj yogzzvm9wx1+v ys in 6.2 s. What is its average acce+dsvzfejw 39z;v1+ m xl/y gxyc818 ofleration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is her acceleratbvnew33;z62(jh yt)wv kcw1w ion k(jw;23zv w )h3b6tnc ewvw1y
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile is capable of an acceleratiok30qeogp +jic b:bv/ 7n of about k3 eqp0+bjo:ibg/vc7 $1.6 m/s^2$ 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.:.;d)7i5 cik dzm9b chgv +sxk0 s. If it then brakes and comes to a stop in 4.0 s, what is its a5;cg+d s:dz9 k m.xci kb7vhi)cceleration 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)z 6z 9k+ddh:ow fysi+ftjm1 (zc;5aj moves in a straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Displa:5 zyfj9 jkd)zmh6za1( f+o;sc wdt +iy 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 itrmu 9nbp rq2*4s acceleration? How far did it travel in this time? Assume constant acceleration. m*p q94r2ubrn   $m/s^2$    m

  A car slows down from 23 m/s 4sh31aek f6v eto rest in a distance of 85 m. What was its acceler1ase v6f4k 3heation, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s fork8t2)zwpkrb :cf,wi(6d +8/uy do lyf takeoff. How long a runway is needed ifww,ukoflfdkb /yy:)c i+ zp6t(r 2d88 the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter cawe i+x-o,lrhfgx xb3x)15 w.b n burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average accelera f+5xixbl).bx 3 who,wer -gx1tion 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 mg/c tyrib m-, 4+iurjc8. lhpc+w08tl/s to rest in 6.00 s. How far did it travel+ pl,c8itjr./cc g+h0lm-ibtru 8y4 w in that time?    m

  In coming to a stop, a car leaves skid mark;elcv 72b3hs is 92 m long on the highway. Assuming a desce; 3 2bh7ivlceleration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/hgtuo(+zolnt3:98 cz s 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 of the driver during the collisi on? Express the answer in terms of “g’s,” wh8z(cuson:l t3o tzg9+ ere 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a c,:ah+u9kx-gz*untyh *:g. ,xpt 8 eohj:ujc rar with an initial speed of 95 km/h and human reaction time of 1.0 s, for an acceleratio*gxkyguhua-t t+ :p8rz .ne, x o*h:,9j:jchun
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation f:w :6yhsorae1)w1 v;xkqsmw+ or the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s d //hz-8s2hx cqywal 4vriver looks for an opportunity to pass, guessing that his car can a cylqswhh4/2 8-z axv/ccelerate 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 exa(o p7ey4hr .8o+ xoner ;a*wgactly 27.0 min, te4r*yxa. ; 7owphnr8+oog(e a here are still 1100 m to go. The runner must then accelerate at 0.20 $m/s^2$ for how many seconds in order to achieve the desired time?

A person driving her car at 45 km/h approaches an intersection just as the traff 0aqaz,due3;fcvr81 gic 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,arau z1qc8gv ;df0e3 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 cliffne-; k /ybl3lw. It hits the ground below after 3.25 s. How yl3 -/;klebnwhigh is the cliff?    m

  If a car rolls gently r9h*j 7 2o+dpqzwa-7pgxl/nl ($v_0\,=\,0$) 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 udf. axi8;(bbvp 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 throwing oqe)( /5wegkeit vertically upward. With what speed die5wk/g eo(q )ed he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and fallp4tc0h+ uc*soa(, ol uf cqly:e09zh6 s under the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has faul *s: 9chl oyoqfh0p +0, e(c4uaztc6llen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a speed of 5.20skniv4)bom,rjl h/9.s9 x wwi1:wl5 p 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’9k9il5lb.w vn/xhsr1wp j4 im) w s,o:s initial speed equals the helicopter’s.] t =__ s

For an object falling free 6q -nv1,rrc aana/fh8de)y-l ly from rest, show that the distance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo./a,qa-16fac n- rhvnry8d l)e See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a ball thry rjrq z;8x*7jfec(:o own vertically upwa q*7e( :x;zcyrfj8ojrrd 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 speer*ha4dy h( z4*up5g*/ cyrdwcd of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between nye0a41*3sk q7c 4s 4ag. o(czsv)y* qbxqgooeach photoflash 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 the ts4*4aoa3vn *g xg 1q4o.c( 7qyes0by z)qsko cop.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a wind vmkqx2dl0 9j/ow 2.2 m tall (Fig. 2–32). From what height above t9 2dlj/ mxkv0qhe top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it strikina2qfuv-8bqz 2 ise:t* bpnt*.g the ocean is heard 3.2 s later. If the speed of : -u2b*e 2qt*ntzvpbi 8fqas.sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozz dbe;/g0bvl:b,o -j6mv 0xt agle for a hard stream of water. You point the nozzle vertically upward at a bbojxbvv 6g:mt/- lg,a;0d e0height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown verkn ,bg; )q;amdd ,+mhwtically upward with a speed of 12.0 m/s from the edge of a cliff 70.0,n, b;wmdg+ dh;am qk) 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 tht-/ysgm x6:v s ,xo l31vxiv5le street with a vertical speed of 13 m/s If the ball was thrown from the si6 /:os3,l5 vy- mxg1x vslvtxtreet,
(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 veloci dr ec*,j-bbv6ty of a train as a function of time. (a) At what time was its velocity greatest? (b) During what per*,vb c6-rbj deiods, 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 h6( sxi8z q.iaq1z*d4 sx-kr ostraight tunnel as a function of time is plotted in Fig. 2–28. Wh x4ixqihza861k* .qsdoz (-s rat 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 accelerate approximately o4 -ufoqhc( x7)irk +tas shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve repkqocif- u)7 4 oh+tr(xresent 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 tv utqx q2vr4b3h o6m/mi:0 pe*he previous Problem (Fig. 2–35)eumm64v bqtq2r xv* opi3h:/0 when it 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 th,) r3r/ tlxtj.aajn y7e distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function o 0 r3e0ud.ysexrh.t )pf ti d0se xrerh.0).yp3tume is given by Fig. 2–28.

Figure 2–36 is a position versus time graph for the motion of ,-;vckdnq1e b s 8a:1e7ljgt van 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 object positive or negative? (g) Finally, answer these same three questions for the 1cvaje1 -snvk7; 8d :btg,lqetime interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’s9-id/oy+3gmcsn(n kn7 bu bb1 safety net. The survivor stretchegso mcy 1ki+nnub 379-/b(ndb s 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 gravijzv9eu-,x 6 fn;m97rz e,ed oity on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocij-z9 6u;dir,x ovf9, zme7neety?

  A person who is properlygee/ruo - 16mo)mk pu; constrained by an over-the-shoulder seat belt has a good chance ofo-6 o;mpu/1reu gk)em surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, bu1/aw(ka: rs 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 kno(kbu /1asw:ar wing 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 /5yu:xeqh z1,xld41gep r9 hm tested its cars for front-end collisions by hauling them up on a crane and dropping themx h5 4 ml,q1eezg/x9rp1:udyh 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 travels;fai8bx m:a /h;vvg2 k 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 acceleraym3x7;.5 hu)c tntnh stion from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 mhns7u.5t 3ct n );hxym from where the front of the train started. What will be the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water’s surface inqcy82 f i;n/wdto a deep pool. The person’s downward motion snw8c/f ;i 2qdytops 2.0 m below the surface of the water. Estimate the average deceleration of the person while under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transk7wvv0v b uv9:it system, it is necessary to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train tvkv:buwvv97 0o make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight down when diving focykne,1kozp u0; o;x)-g7yb l r 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 foebu;) y- pkk07nyc 1,;x lozgish 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 strike*v:)pvnc -o e0pwwka )b8t;/ pz1fbals a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing 0a v*/8;ctfp-p :1 ln)b)kwwvezbopa 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 l2n )hpq*hedidc8+q 2 6.0 m/s Just as an empty box car passes him, the fughdqc di h*2)n2e+pl q8itive 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 ikep1;.;tplms)l51 t wsb1yp s0od6r cs dropped 1.50 s later. How far apart are the stones when the second one has reac l)5;1 rltp6 ydkws1p m0pt.bo1es;cshed a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/1c+xnj s6b pr5h over the course of a time trial lasting ten laps. If the 1p6xsn +jc br5first nine laps were done at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour d /h ,0tzlc ax;82f qe9ersfmg*e France crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, h f t z0fr;ee8ml,c9ga2qs *hx/is speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolines. Th2 krg hha;bk4(e first child can bounce up one-and-a-half times higher than the second child. The initial speed up of thea b k;hrhk4(2g 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/hubm 9l((2egh n;wem0u/u70lu xsvfs1 overtakes a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have travehl b0v(su /g1fn 2 m0s 9xue;7ew(ulumled 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 baseball8ix)2 moyn b14 hzt0wj with a speed of 44 m/s In throwing the 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 accelerz1wnb )8j0iyh x mt42oation of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an (q;ul,8lb:nb)wn mr/wul5 pxn x7 yb: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 intersection has a(eh9v h vw(d hyupm7/jm,02da 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 gm da,7hwyh/v p 2(de9vm uh(j0reen. 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 codv+jpvmv71q up d +g13a rv*i.nstant 120 km/h takes off in hot pursuit. The poli+qvd1 vj p3im u1v*agp .7drv+ce officer catches up to the speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from t/ xhtm 9vv4z7g:arqr4he roof of a building; 2.00 s after that, a second stone is thrown straight down with an initial speed of 25.0 m/s and the two stones land at7qtvzgrrxv m94 4/a:h 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 fir72r4 ,l(v;+mm wdwnynqvjo9bst stone is thrown with an initial velocit;+ v n9oydw7m2(lj mwbrqv,n 4y 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 should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it takc9 d+yp2nq5ozo0 g 7/er x:jfge 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 speexg0+ 2ydn/ofr cp9 5jzg:7qo ed 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 (-u +oxme qs3wy; 6bhmsend the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor qh 6mwxe- s;3(y+bumo 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 fsm1: bxdu 5a1times faster than Joe can. How many times higher will Bill’s ball:xus11a fm5 db go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on the grounkcf75 6uf/j pad 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 to you, such that it just comes to rest in your hand. What is the speed with which your friend threw ta5jc 6u7f kp/fhe ball?    m/s

  Two students are asked to find the height g 4,bza1tl q,m*yehr *m6og;k of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. O mg zm; 4 g*h6,e1tarklq*,oybne 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 graph for two bicycles, A and B.ti1(2upnb(x / h9 yfll (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicyc yh19u l(xil/nbft (p2le has the higher average velocity?