Does a car speedometer measure speed, velocityx7sy,x6 1sreo , or both?

Can an object have a varying speed if its velocity is constant? I c( 5 -2 :kcdcd(qqe8nqeb*cqmf yes, give exa c mc 8dc:qebk2n*dq-qec5q((mples.

When an object moves with constant velocity, does its average ve,(amo7gv jzjx)xf8 5 flocity during any time interval differ from its instantaneouf7z, jx)ax( fo v8mjg5s velocity at any instant?

In drag racing, is it possible for th(9k9j q xl65vk5zikd7 +.gcr mo sz5wze car with the greatest speed crossing the finish lix+wc(59vgkqom z5 . d96lkj rzk57s zine to lose the race? Explain.

If one object has a greater speed than a secon j+bg4w+iy4ds5 6 bzixxc3s, jd object, does the first necessarily have a greater acceleration? Explain, using ,5dbgsj cb3 jyis+6x+izw 4x4examples.

Compare the acceleration of a motorcycle that ac7yma/c0v nm6xo m-h5kya +l* fcelerates from 80km/h to 90km/h wi+ fn7yy/mak*v05oxmhm6 l-c ath the 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 accelh// hjl nz+ 8;,jcfqpteration? Explain.

Can the velocity of an object be negative when its acceleration is positive.je ;r7h),07iej4uo pmbta rn ? What about e ur7ajohipnt),;jrm7e 4. 0b vice versa?

Give an example where both the velocity and acceleration are ri)*18qpqofaeg u 27vnegative.

Two cars emerge side by side from a tunnel. Car A is ya-l + 10 sz/h7mifipltraveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing the other as t/l i- fz7ps+1miya h0lhey come out of the tunnel? Explain your reasoning.

Can an object be increasiy-hz3zh)- xf nng in speed as its acceleration decreases? If so, give an example. If not, ezxnyz3 -hhf )-xplain.

A baseball player hits a foul ball straight up into thc 4uxmjjj5x yo+g7:5(g1uoq q e air. It leaves the bat with a speed q qy75mxj1j ugcg5(x o+:jou4of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is ha3/) h(sl+w6 qwqms ,hoyb ,30f namieappening to its acceleration due to gravity — does it increase, decrease, or h0+3 e(f,shq6,/ wy ob lmniqw)a3amsstay the same?

How would you estimate the maximum height you could throw a ball -:lp)i;ghx g/2h/owa 0tl0zvp* t flevertically upward? How would you estima-ze w*tl/v0 xopg); i/tpgfl:2 ah0lhte the maximum speed you could give it?

You travel from point A to og3,yh 6rycqpt3 wyj8o4**yipoint B in a car moving at a constant speed of Then you tra6yi oj* hyg4y8w3 t*co yrqp,3vel 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 A to C 80km/h ? Explain why or why not.

In a lecture demonstrati;ap3qqh/x;a l2o4y)(.6dpsri+dp:z yv hj zd on, a 3.0-m-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at equal time intervh .zplh;p/d;zsa 2)3droaix qj46:yd+py qv(als. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions is not at c(siwt; uvq0xh43ms8(vm zob*onstant acceleration: a rock falling from a cliff, an elevatozm(vosv(t03q x* hmbs ;u4 iw8r moving 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 its original pos )vrie rz) ),kqg-v ,l(rk/p-mev:lcfition 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 ,:vrkc ,)qerlfzlkvp/vr) (-ei- m )gdue to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and non 4vqd4t7w:g nhzero acceleration at the same time? Give exavn:4d7h qwgt4mples.

Can an object have zero acceleration and nonif 9tc*3mfe(zpes t 9p8pom *f vjj(.+zero velocity at the same time? Give e*pfzm +fv*pjt f83o(i te9ecm(. p sj9xamples.

Describe in words the motion plohz z4v1)+qv:q/los5yjbz, ry tted in Fig. 2–28 in terms of v, a, etc. [Hint: First b ):5+hzq lz/sy4 ,oqyrv1zvjtry to duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of thex3ju/-;upr i t object graphed in Fig. 2–29.

  What must be your car’s average speed in order to74tbw rv-f4k x5 9zndr travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h +9vwgnsqt*h c/mg 7l/cd4 p k-How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the svz7,t q*;t 40z:x3yenb 6iu h6h rsqfxide for 2.0 s, how far do you travel dur nuz0e f*3 tz :h66tih4xys7, bqxvrq;ing this inattentive period?    m

  Convert 35 mi/h to d5 rgk152eqgb
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro4 vige: cmon.0m $x_1$ = 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 be-/am;h0 b ,ei djlud:agins to rain :hj iau; aeb-m0d/,dland 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 be +rxrjjm4:k k/tween a lightning flash and the following thunder gi:jkm+r k xrj4/ves 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 around a quarter-m( 0bpy7fvejq4tf b(w6ile track in a total time of 12.5 min. Cae7wp0fbtq v(y6(4 fjblculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainu0 h6a po;sra-er in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculauspr- ha60 o;ate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. Each has a speed s gs6+ hkfku-(of 95 km/h with respeg6huk fk(-+s sct to the 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 110 m behind 9wg;hj x6oo3; nnr)4ntm :rwsa truck traveling How long will it take the)jsmnxg3 wno;r9t ;n6 r:w 4ho car to reach the truck?    s

  An airplane travels 3100 (g1r 8w 4dbkxslh z;;8c pge/qkm at a speed of 790 km/h , and then encounters a tailw wch;/lrdgq g;pb 8xk1(8 sze4ind that 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 complete roundam*sojtv; 5f :tb3bm: -trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break,v3b:tomb*s ;f mj :5at and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveliz)-u:9i+2pa ypqiifj ng with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hpi:2u ) aipzj qfy+9-iitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. Wha ln1p,b.ev3,8amdlq vt is its average accell8la1 m 3, .venpvb,qderation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What is heei+hqab l;73 sr acceleration eqbs; i7lh+3 a
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular automobile i bn/.bvb80ou hs capable of an acceleration of aboutnbvu 8/.ho0bb $1.6 m/s^2$ 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 sjp-/xp4 :;0 u+ pojifkwfj8 icpeed travels 110 m in 5.0 s. If it then brakes and comep:poiu4cfjp-j0x j+ k/f8;i ws 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 starts from8 ybp ,o*7y(czdyqe,8gp l hl* rest at t = 0 and moves in a straight line, is given as a function of time in the following Table. Estimate (a)yph ,* 8 8lzyo(ecb qgy*p,7dl 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 accelerati8nxnsw)w md13 on? How far did it travel in this time? Ass)sw8xdw3 nn 1mume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 9axd* mwbsie6a2,+p lkgru 6g-o*1lb85 m. What was its acceleration, assumed c*ga9k re*+dglb- b2lpos 6w ,6iua1 mxonstant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff; +y1z r r+i*ot7fuimc6ld5pyxa-;a f. How long a runway is neei*a6dpx y a7+1;c5t u; -lzmfy +firroded if the (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst oucu)/jptqr88h/ t pq2a t of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0t88r/cq/ p uat2h)pqj m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/b) r ieqqy*fo+5:s3zys to rest in 6.00 s. How far did it rb iq+s3zeq)* y5y:oftravel in that time?    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. Assuming)fb+t ly3/ jgk a deceleratiblt +)gykfj/3 on of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikesnbz0qc;5lds : qpg(7s 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 ongsq(;:07sc qp 5 zbdnl? 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 caf pd,x(hkc 2wkouo,eb;/ ee72r with an initial speed of 95 km/h and human reaction time of 1.0 s, for an acceleration ;2ck/okfobe h xd(,,7ee2 wpu
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for q4wsmidn q. 8pygahon:/a mq:* n1l/2,j zgo)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 highw 19i 7mnm xk;*.0mrktlrd0 ltyay. The car’s driver looks for an opportunity to pass, gueslm krlnrxi k;*7mm tt.1 9dy00sing that his car can accelerate at 1.0 $m/s^2$ He gauges that he has to cover the 20-m length of the truck, plus 10 m clear room at the rear of the truck and 10 m more at the front of it. In the oncoming lane, he sees a car approaching, probably also traveling at 25 m/s He estimates that the car is about 400 m away. Should he attempt the pass? Give details.

A runner hopes to compl ,hju*wy +6gllete the 10,000-m run in less than 30.0 min. After exactly 27.0 min, there ayl w6ljhu+ ,*gre 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 tr.9uuz:c) iuli0f,wek 9ub:eb affic 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, o:)iuf0uzl b,:ee9.iu cku9wbr should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below after 3.25qzr 6h+v 9rbs9 s. How high is the clibh+99rs6qz v rff?    m

  If a car rolls gently xrui2:cycikl w.u/8 n 6hml -l1;are7($v_0\,=\,0$) 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 straight1egj+r q) jedprz i62.6ayv+c 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 tv t7bemq *o90qhrowing it vertically upward. With what spe*e9 0mtb7 vqqoed did he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls uybevp ln1tq nmh;bl h4; kq4z8o 1:;d;z-rxs 2nder the influence of gravity. Draw graphs of (a) its speed and (b) the distance it has fallen, as a function o1hbl:pzqs4d-nyrl1xqo h;vbk m;nt;2;4 ze8 f time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically g,t br-ozp t*61:vbk fwith 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’s initial speed equals the helicopter’s*: 1zbpfrg6vtbot - k,.] t =__ s

For an object falling+kfubf; 5;p j. vti(xx freely 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. S5v(fubi;k+.x pft;x j ee Figs. 2–18 and 2–21.

If air resistance is neglected, .iw6+5 dw3/ysmc c(tqtcx v:(s agzl;lq 6if3show (algebraically) that a ball thrown vertically upward witf ii53(cd/: 6 lg+vz6swl q ;w. ytc(t3samqcxh a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown vertically upward with a speed of 18.0 (h gwlj84p ei1m/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 eacoe fja gjtoag9nbd+/113 kd,5 h photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: 5 jtg1 +oja,go9efn/ bkdda13 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. o cb/v5s+s-yg2–32). From what heb5+cssv- /go yight above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking thp7yg g8hg ovtn*) 4k1ak8x9krd.o +vze ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high is the cliff? 4x n9 gvpg)78v8tdhkyag *z 1k.ookr+H =    m

  Suppose you adjust your garden hose nozzle for a hard stream of water. You pf .*nw1yjlw fu)y1r a1oint the nozzle vertically upward at a height of 1.5 m above the gnwfy.)1* 1u ywf1 aljrround (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 vertically upward with a speed of 12.0 m/s from the edgeodnyry;s. z5,,er mf ( of a cliff 7r r f(5ns,o;emy,y.z d0.0 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 byfvtb3,gz h7 0 n,eez4i a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from 4bzhz 370fe,give tn,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 x 8(h)o 0gl4rf xosky3as a function of time. (a) At what tim4xs(yo0 xhlgkf3)o r8e 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 acceleration greatest?

  The position of a rabbit along a straight tunnel -z tft m91h)+mlahczpx 2rb.:2q9hrias a function of time is plotted zp.ch2q r:h9r ha9) fz+ ti1 blxtm-2min Fig. 2–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accelerate a 8 rs.xzpkg*jfpl9 k(zw;m,u(pproximately as shown in the velocity–time graph of 9z w.,;z gluskk* mj(xp f(8prFig. 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 cpoeil 76 a-o*vkdw3u3pvfe +he mnsj9/ +ru(0ar in the previous Problem (Fig. 2–35) 3( u3/e* - pdoe9v6p0sfnvjeo w m+ui+h7rlakwhen 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 the distance the object traveled durv2y/lar;lq5tm ,u px:a0fw l uz5 q,:aing
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function z7nth0 dtu,m,of time is given by Fmtu h07 d,z,ntig. 2–28.

Figure 2–36 is a position (18cia rc,bg6 bg ,uz:l.vhph versus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? .g cg8(i vbbal:uh p ,c61zrh,(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-s rvj.o-2h0fmp tory window 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m beforjv. f-0mp2rho e 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 what it is ob)*oy. 2 harwen Earth. If an object is thrown vertically upwar 2w *.oe)hbrayd 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 cbmln7v i. wiek558d.d7 ozil7onstrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if theebv lokd.d7 7.nwi5m7l z i5i8 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 ro1yb chi,htks *vumw4fw:cp-hvd.opn 7v /010ad 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 qm h h70 cw*u :vivbpdp1 0ck1t.o4/ywf ,-hsvnuickly 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 t:mofeaq c k81yhp:6v9s+ 4iax ested its cars for front-end collisions by hauling them up on a crane and dropping them from a certain height 8moiksxe+9 vyc: h:qp61a4fa.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels about.kais6 f/yi*dp2w5p s $10^9\,km$ 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 acceleration q21xaye204hf:w1 d(f0tnmjmf t d1 s ffrom rest. The front of the train has a speed of0(hns4fm 2fe m 21 :tw1ytdqd0f jx1af 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 the speed of the last car as it passes the worker? (See Fig. 2–38.)    m/s

  A person jumps off a diving+kxd*t m2o2(t ir*++emv)f lw foi2jc board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surfaw ti id)x*fmtov( * crjlm2+o2+f+ e2kce 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 transit system, it is necessa3:ryxcxjvb. ee4 l;j4 ry 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 timx yv.4:; jlr3e xecbj4e 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 h 8unep3e:cje rnwl2* 4x(j4 qfall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot chq*: 3w 8n r(n l2hp4e4jejexcuange its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height must it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strik68ui ejei yl m59umf-;es 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 this from an uphill lie (that is, putting downhill, see Fig. -e9m;ml8eu yif5 u6i j2–39) 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 tr +i(;)m kalmciain traveling at a constant speed of 6.0 m/s Just as an empty box car +ii)m(a kcl;mpasses 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 2-e1yuqbrsh:aj a16j8+q dbz1.50 s later. How far apart are the stones when the second one has reacj 6b8bqe2a1h1uj: -+yrdqs az hed a speed of 12.0 m/s ?    m

  A race car driver must,tx+g4nvl/ wc.,spy g/ vplz6 average 200.0 km/h over the course of a time trial lastingsp ,+lpyw 46cnlxgv/tgv/., z ten laps. If the first 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 de France crescbh 0kb ,s32imts a mountain pass as he moves at 18 km/h . At the bottom2 3b,i0mbhsck, 4.0 km farther, his speed is 75 km/h . What was his average acceleration (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two ta e.zu3nc8t7:dfhuf3 rampolines. The first child can bounce up one-and-a-half times higher than the seco8zt uf73he:fnd c3ua.nd child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10-km-long train traveling in fkv,krk5tn;ag l5ft2u u74f 2the 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 fat27 k;k5fg4uu5rfknft2,l av r 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 speexnyf;u -zww*w s*p k5,d 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 (Figwpw;z5xyskfnu,**- w . 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with al0/e: 5asi f xx -vzhswhut6,5n 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 , yw*iv8 /ahszshown in Fig. 2–42. Each intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit vh8,/yzia*ws. 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 co tp: a(zjr2xeeac 5z41a8n,hxnstant 120 km/h takes off in hot pursuit. The pol, 2(rz5xezx8 pajae4ht: 1nacice 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 the roof of a building; 2.00 s3(nk)er9 bp vdiu* j y8nze3)z:c(ar8u4rl a w after that, a second stone is throwne n (n9b8 4rdyuirw*)re(j)3pzzlvk3a :8 uca straight down with an initial speed of 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown v5 re-mkzbc(j5ertically up at the same time. The first 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 should the second stone be t(cjmk55b r z-ehrown 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 resistu:b7 e0d+or)hp s5y roance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (Ishrp+e):5r0b7 oodyun 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 .9uo2yiwab5s0 x l. pbsend the burgers through a grilling machine. If the grilling machine is 1.1 byb s.2lw0oua.9x 5ip 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 vertica8m h8sfn,1rgf lly at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball goh8g,1ffsr8 mn than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands o*:k s3jr h+gbbn the ground below you. You drop a ball from rebr+3j*kghs:b st 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 hei f-p+i7e :flbn; +hajo+c+akfght of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof+ffpeok +ja++ h lcn;7 ia:-fb of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. time g75-v xwb7bnd40rhu ,qfla g; praph 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? (q7fbb ;lrgna d-x04wh v5,up7c) 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?