Does a car speedometer m usr7h(x iqk io8ms,(7easure speed, velocity, or both?

Can an object have a varying spc,1ev 3n.tg24 :t hwywi ff+lmeed if its velocity is constant? If yes, give exampleehmtl:.,3 +2v1fif t gn 4cwwys.

When an object moves with t78q06yc )nokcf7ce)v2vzfhconstant velocity, does its average velocity during any time interval differ from its instantaneous veloccf)826tkz0 cvh co7)nq7vy e fity at any instant?

In drag racing, is it ;6oe8tboi3j k possible for the car with the greatest speed crossing the fie3oo i j8ktb;6nish line to lose the race? Explain.

If one object has a greater speed than a second object, does the first necessa3)cs)mtx ) z8e0 ff+mk3jc*wddm x3gj rily have a g)3x jsmgxd0f)mf cw e )3t+km*zc8 d3jreater acceleration? Explain, using examples.

Compare the accelerati) cfexfg;z1 y.on of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration zf xc fe.1)gy;of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward acceleration? Ex-nmj 1o -diavt 3j g,dq,9+nvrplain.

Can the velocity of an object beu j9+tfh8gg p*l-s,ij;o 1j/kppem e9 negative when its acceleration is positive? Wha1+- hpp8 upstgmofl9kj, ei /9 ;jeg*jt about vice versa?

Give an example where both the velocity and acceleration are negati l,wjbcqc.1t4vd0 n q4ve.

Two cars emerge side bm+hck;p7x +mu1z ,tr :ao i jkxc34p4ly side from a tunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 41k4czhlo 4,xpu i7 a +pr:ktm+m;cj 3x0 km/h and has an acceleration of 60km/h/min . Which car is passing the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, giv8ff 8*lxa ,bcpe an example. If not, explafx,8* b8l pafcin.

A baseball player hits a foul ball straight up into3-(u9fbb mws r ,j7v1;dkodqjpttn0; +c, shq the air. It leaves the bat with a speed of 120km/h . In the absence of air resistancjrhc ,n -(9;1qdb3ttpk sdb jq; 0+ovus, w7fme, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is hap9iue6 a3+f)(wpn odqnpening to its acceleration due to gravity — does itpe+9 n36du woaq()nf i increase, decrease, or stay the same?

How would you estimate the maximum height you could throw u +);n35kebl)xwsrv)bwd paev3 o +(da ball vertically upward? How would you estimate the maximum speed yv3ak3rv)b;) +ew db nsod)(ul5 x+ pweou could give it?

You travel from point A to point B in a car moving at a clese0ucy, g0 dk5n:,gjhc 8r -onstant speed of Then you travel the same distance from point B to another point C, moving hc :l,n0gy- rejud0k 5c8sge, at a constant speed of 90km/h . Is your average speed for the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical string w- e1n*qkfr4iew yt dj 0yx): vf1a1q.gith 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 ofqg*e)ayvyqnfkxf -1:it j10 r14e. wd each bolt as it hits the plate. The sounds will not occur at equal time intervals. Why? Will the time between clinks increase or decrease near the end of the fall? How could the bolts be tied so that the clinks occur at equal intervals?

Which one of these motions i 2hdunhv)81so 9gf5 gss not at constant acceleration: a rock falling from a cliff, an elevator moving from the second floor to the s)g 8snhdv 5fg9h2ou1fifth floor making stops along the way, a dish resting on a table?

An object that is thre uqhvd4v0sl73a0y z2own 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 acceleration due to air resistance is alwaysu2y 0v0zh 3s7qve4ld a in a direction opposite to the motion.]

Can an object have zero velocity afasy*: c /ri:ond nonzero acceleration at the same time? Give eyifc/:a* rso:xamples.

Can an object have zero acceleration and non8 lpw) zcu+) wf9*tv+xzt qayh-b3jv7zero velocity at the same time? Give examplej c +lw)qpt8 z*7zw-f 3+vaxh9ytvu)bs.

Describe in words the motion plotted in Fig. 2–28 in tgo+ l+- 9gtk6js-5gvv3vzi xx qx+;qoerms of v, a, etc. [Hint: First try to duplicate the mik ot-xv+-9zqg qlgx3+ jvx;+o vgs56otion plotted by walking or moving your hand.]

Describe in words the motionz lyv,r-7;8ox cbzvk4 of the object graphed in Fig. 2–29.

  What must be your carekg2;ru86wlv we 1+ ax’s average speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km zulhxadb.;8 r.5in u2?    h

  If you are driving alon tlwtl +n/6(m*s met2lg a straight road and you look to the side for 2.0 s, how far wmt+temst 26 *(n ll/ldo you travel during this inattentive period?    m

  Convert 35 mi/h to v,.7isq gy)ge
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves frds4: 30pvkgf 2m2mvgjpy t21 com $x_1$ = 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 thew x4 w p9yrixw1+,(ktmn begins to rain and you slow tox,twx1+w ypwirm( 9k4 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 lightx 2;h dji2adr5ning flash and the 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 farxd 2 j5d;ih2rom this rule.    m/s

  A person jogs eight complete h.jnf bxl)ka+d8z+ wee.t 45ta 3fus:laps around a quarter-mile track in a total time of 12shau: 43et.awf. 8xbfndj)tzl 5e+k+.5 min. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a strairyez5)8gs;cqvq wfzl/6c *gc4 *k mw0 ght line, moving 116 m away in 14.0 s. It then turns abruptly and gallopsf* ce;r4w5v*6mws/qqky zgl08c)gzc halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tra7 v9t sfr2+unp1uj dj1cks. Each has a speed of 95 km/h with respect to the fd1 sjnr2+tj7uuv 91 pground. 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 a truck traveling How long wp r-k r8pw: g2i r,c(aca(*djaill it tak2r-idj* (rcrc , (8kwpaap:ag e the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 f9b8i7yp:om0sdb*vn km/h , and then encounters a tailwind that boosts its speed to 9y 0pbvnm7:*bo sfi 98d90 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 completki2kn8heh wai3/i* ma5zb1m3g3hv d5 e round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the retur1hd8i3 m5/ez3km2i akgvwiba5h3h * nn 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits tu:irfj1 p/j,fqdk,atr j 5j/0s8m+a g he pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. p sj0r8ajqj i ug+1k,:f/5 rfmtajd,/What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car acceleratesc2ihd 0yc4 f1mm/h1rvhzl)g9 from rest to 95 km/h in 6.2 s. What is its average acceleration in c904i/dz )1y hc 1mmvlhgf2rh $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 il*2y g yu6:1l(g ddsem/s in 1.35 s. What is her acceleration 6gsdyg *i(y:u21lled
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular a03w+(jitr0:u sxe dar l+o;cs utomobile is capable of an acceleration of about it0rclued 3or:+as j+ sw;x0 ($1.6 m/s^2$ At this rate, how long does it take to accelerate from 80 km/h to 110 km/h ? $\approx$    s (Round to the nearest integer)

  A sports car moving at constant speed travels 110 m in 5.0 s. If/ux/k+him 73aqi0scvo 9s l.g it then brakes and/7 m0/h+c3v9 sgaqkl.usxioi comes to a stop in 4.0 s, what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = rmdz6 ca6z: m n5i:d9*gzpi9b0 and 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 fu in9rabpi9 d:6cdzgmzz:*5 m6nction of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to it+d: :bbyy+16w 5vb2 nx qexb25 m/s in 6.0 s. What was its acceleration? How far did it travel in this time? Assume constant acceleration +b65debxv1xn2:qy bw:t+iyb.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 mjv ekk0/eig6r08 l :jc. What was its acceleratvc60jje 8 lkeikr:/g 0ion, assumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takeoff. How lon 4+akqypi1 ,yng a runway is needed if the (consy i 1,y+p4nkqatant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially pjbogp65-i)ivu ; u c:top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleratjbi5 ;pvucg6u-)p:oi ion of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 12.0 m/s to rest in 6.00jb*fm( q +n7 mduce-z; s. How far dimne fz(bq;u-*7m+dc j d it travel in that time?    m

  In coming to a stop, a car leaves skid marzx wla0z5g:jc-b2 n3fnabhs+1 -/ b laks 92 m long on the highway. Assuming a decezwna/:cz 1 n -2g0x3b- jalsbf5bah l+leration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a treegr :n*t.bz(a2nrmlt8vi /p f)9 y7myw . The front end of the car compresses and the driver cv/lnarmmtg t z.np(*fwirb89 :7y2y ) omes 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,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car with an initial speed of 9hy; /zem77/ 1bqhhf gh5 km/h and human reaction time of 1.hgz;7b hemh 7f/yhq1/0 s, for an acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distance of(,rfkylaq(z5 swi6/zk4 g p 8p 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 dri xkgxmrxc.i1z /u// nlu-f6d2ver looks for an opportunity to pass, guexzi1f 6mkrn-/d lu2/guc x/.x ssing 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 complete the 10,000-m run in les /lnfvok (aegr (6v,r)s than 30.0 min. After exactly 27.0 min, there argf,o l6)(rvr n/eak v(e 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 approachee:f*c u qqddqr 1048*ewgoh-t s an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide tq8qh 4*o0u d:gw rf1e*-dcqe. 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 tj wj3 yt cmk h79hs;e.7x;5hxfop of a cliff. It hits the ground below after 3.25 s. How high is the clm h 77;j;sxhtcyfj39kwe h.x5iff?    m

  If a car rolls gently u2i 6d j1g5k+ wfn6k bh8ft7sn($v_0\,=\,0$) 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 thejv/ba6uluwa9 7bco. n2*2uir 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 it verticallyc8+ *ys7w k.nfp;gjea v1gqd; upward. With what speed did hsqnwjk.v p e cd;g7fy1+8g;*ae throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the infa/aefpfk: +g 0hu,5aeex;b 1sluence of gravity. Draw graphs of eh/xf f;k5us+p0gaeb a: ,a1e(a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignore air resistance.

A helicopter is ascending vertically with a j ,yl(ugb : 9yuih0i2aspeed 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’(iu lug 9iy,:jah02bys.] t =__ s

For an object falling freely ks 4gt.)s2y0x,y 2uph rpjp.y 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. See Figs. 2–18 and 2–212)4yxy pp2jtkr u .0.gp s,hys.

If air resistance is neglected, sm. 6ruvuh 3tw)zna-- jhow (algebraically) that a ball thrown vertically upward wit3 nj6utz-ra ).-umvhw h 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 *0*p fitg6es)dl 2vs d(4sjw rm/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between each photoflash of the apple in Fig. 2–;yo4hh v2 0dwe18 (or number of photoflashes per second). Assumwdvo e h0y24h;e 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 4xbr(- dru6u db4/cqs 0.28 s to travel past a window 2.2 m tall (Fig. 2–32). From what height above the top uub(dr6/4q sd 4x-rb cof the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the ocean is hh+) -w qfsuk8ieard 3.2 s later. If the speed of sound is 340 m/s , hh-kwiu 8 f+sq)ow high is the cliff? H =    m

  Suppose you adjust your garden ho06:osy bbs( aicq-/j zse nozzle for a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water striking the ground next to you for anotherq(-s/o6 sb0 zcaby :ij 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a 8vfp c y1hu1a7speed of 12.0 m/s from the edge of a cliff 70.0 m higup v7c8 h1yf1ah (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the street with a vcvxome*s/k.y x n2 h3,ertical speed of 13 m/s If the ball was thrown from the st,2vnkh em/*xo.cys3xreet,
(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 functio9gol3t jgk/ pic0nj 5*n of time. (a) At what time was its velocity greatest? (b) During what periods, if any, was the/j 3gc09i*5 ltpngkjo 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 stx/f/ci3 vv yw ;ocg8:graight tunnel as a function of time is plotted in Fig. 2–28 c/;w3 ovgvfc /i8x:yg. 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 appr7 95xfz(xenfv5.xk23dp qc kz k.eoo/oximately as shown in the velocity–time graph of Fig. 2–35. (The short flat spots in the curve represen.(odeke/259.ckq5fk3x zo xxnp v 7zft 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 previous P.w07 hpkpd 0ezrtp ak ki09x02roblem (Fig. 2–35) p0i kx0kwt e7dp0. 9kp har20zwhen 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 xwm0s vy9g2d( m-8 0ohwrgx4ddistance 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 functi): dmq2id2 hhcon of time is given by 2m q2dhdihc):Fig. 2–28.

Figure 2–36 is a position veu /72t9g wo/g;xafo9r+c g ohmrsus time graph for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive o2h9um/+aro;o 7wtgc f9/go x gr 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 fourthd:/ x)ckfxzu 9-story window 15.0 m above a firefighter’s safety net. The survivor f dcxk :xz)9u/stretches the net 1.0 m before coming to rest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about one-sixth what it - (n v 1*1x8wk/enelzb:vxk ldis on Earth. If an zw1ne :/ x (8vek*n1lk-db vxlobject is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained byqp1e soa gkj/( g.8a.9lual s4 an over-the-shoulder seat belt has a good chance of s/pe9u.4 kag q8(j.alos alg1s urviving 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,/4x 1wsdng ts+ 12 m above the road below, and his pursuers are getting too +sw1 ngd4 txs/close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tg41osv(by8d7 hf h xy+ested its cars for front-end collisions by hauling them up on shvofg+( by 71y4 d8xha crane and dropping 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 travels alyjz9tljc+h1 g 2 8nluo,m8u1bout $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins unifaj65s cofxk 6.86xj(a. ahai oorm acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m f6 .a6.8j5ax6ko facshojxia (rom 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 into a deep p .ges49f xkberiq c2,bza .x 9tqkm;9-ool. The person’s downward abcm exkb9e.2x9 q kzi-qgr4s.; 9t,fmotion stops 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 transit system, it is necxan5x sj z4w- z u)j.oo,q(y;fessary 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( o foxnz,);w yz xs-4j.uqja5 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 when diving for fish. Supp;9mdc/ qw u x8:d2 ftlfl(iz,dose 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 minimum height must it spot the pelid :ld q fmtwiuzdl;x 28f9,(/ccan to escape? Assume the fish is at the surface of the water.    m

  In putting, the force ws 9pxk5ozd 2*l-1fd ztb- eed6ith which a golfer strikes 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. 2–39) is more difficult than from lx zeftbd-k1-6p5zds *2d9oe 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 jv53lzo* u *nuat a constant speed of 6.0 m/s Just as an emo*zj*nu v3l 5upty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone is droppd,z:zew t 6g .7bl6hhied 1.50 s later. How far apart are the stones whe6ti.l w dhz,hg7b:ze 6n 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 c-ika x0w)jci,x 5i6y pourse of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . 5ixwya)60c, j xiki-pwhat average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de France crests a mounta mw*hq b. gov g(hg/+:,byakm 9+dlm;jin pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleratiolwybgk+b( gq* ./gjhvmmh m+d:,9 a;on (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampolmh4jss.- k,zt ines. The first child can bounce up one-and-a-half times higher than the second child. The initial speed up of the second chil zh.-k4tms ,sjd 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-lon51pukti hi5 4qg train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are 4iphuqit 5k 51the 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 vjmywbh 3;u xe57kc (r2wn7+v In throwing the baseball, the pitcher accelerates the ball throu+ uxy3e7n;kvhmbcw5 v j2( r7wgh 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 accelerath-m-;mrhhj dr 8 nyd2)ion 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 zug:/txm se),has a traffic signal, and the speed limit is 50 km/s . Suppose you are drivings xmu,:z/e)gt 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:eke2crw /sl4g.xmb )- z )sdh, passed by a speeder traveling at a constant 120 km/h takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant acce.)c k2mrb-)d/ h gl:xsez wse4leration.
(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 gl:pro 6jvyi 6w68 g(3 str1f5rypqn: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 at the same time.ypqg3g 66v:5n8lsir1ptf o( 6wy rrj :
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone iybq--hre l:q 7s thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the gr- q7e -qhrb:lyound 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 take a free-falling parac1nx5mzxwx,s + hutist to fall from a plane at 3200 m to an a ,wn1zsm+xx5 xltitude 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 burgbzf 3zo/ckv+4ers 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 belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger3 /vzz+4f bcko production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 y.xli:+ ywi;9b v3rut,z281giswpf vtimes faster than Joe can. How many times higher will Biiwy ws l 9,t;1xivfupv+3r8.2 zy:bi gll’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands on 18n .jn e6l4 lpyzbas*udee, 7the ground below you. Y*e6.e 48e1y7n lnbs , juzapldou 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 the ball?    m/s

  Two students are asked to find the height of a particular building u.p.k:b :qky -qomog.u sing a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One .gqqoyu.- bo ::pkmk .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 dziz fvx5z9.( and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has t9z(fi.d z5zv xhe larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?