Does a car speedometer measure speed, velocity, or b*s pr)(qz.4e:jn irkz oth?

Can an object have a varying speed if its velocity id vv*ch5js z14s constant? If yes, give examples.1v*z sdj4ch v5

When an object moves with constant velocity, does its average vex, 4;ypajw t6alocity during any time interval differ from its inst,a p xjy;aw46tantaneous velocity at any instant?

In drag racing, is it possible for the car with the greatest speed crossing t8 hsovaut*qua.bf8wki a()5 ,he f.vh i ) *kwaqub8 ousta,a(f58inish line to lose the race? Explain.

If one object has a go 1-5rza(mbiv.eu1 mvreater speed than a second object, does the first necessarily have a greater accelevaz 5 .rm( v1ei1-bumoration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km/h : yz-p;l cohpkmq1 he4m y*0bes.vv-0to 90km/h with the acceleration of a bicycle that accel:m-c*v.zv h0pqp ;4k1y- hsoeym e0blerates from rest to 10km/h in the same time.

Can an object have a no+k/r1g:cjgdecldj7b ha 2mkj 70f:- trthward velocity and a southward acceleration? Explain.

Can the velocity of an object .x.jb .sugoet4y)j9l be negative when its acceleration is positive? What about vice versa?u .ejgbjx.o.lt 4s)y9

Give an example where both the veloc/yq ufz.7e982um n v9typc7dopw ;(zcity and acceleration are negative.

Two cars emerge side by side from a ter 9b-y* h;grd*zx.fiunnel. Car A is traveling with a speed of 60km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 km/h and has an acceleration of 60km/h/min . Which car is passing *-x fbr9geiryh d.*z ;the other as they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its accelew3ir58g hh5swration decreases? If so, give an examw5sgrw83 i hh5ple. If not, explain.

A baseball player hits a foul ball straight up into the air. It leb6y cv5lk xx5gc8 9;v(pt ihrvep-9 0caves the bat with a speed of 120km/h . In the absence of air resistance, how fc crp55 90itvvyk8- l (xvb;ep6g9hcxast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, wh,. 8hatxjkaui76iw; (+2b vt qhz9wtc at is happening to its acceleration due to gravity — does it increase, decrease, or sta 2t(qtiz9a76h8,buc+i. kxjawwv; t hy the same?

How would you estimate tj - y 0k5dn2o-e. ugr3l+peaf*il1pnq he maximum height you could throw a ball vertically upward? How would you estimate the maximum speed you could give itdj30q y -ko-f rnnie1u.l +a5lpp2 e*g?

You travel from point A to point B in a car moving at a constant speed of 3pt f 9(.xzuxfq0bfz( 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 for9tb f( .xfq(pzux30fz the entire trip from A to C 80km/h ? Explain why or why not.

In a lecture demonstration, a 3.0-m-long vertical strj k3fh9qn8 wsrs 3x-p,ing with ten bolts tied to it at equal intervals is dropped from the ceiling of the fnxh,p39- r8wk js q3slecture 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 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 constant acceleration: a rock falling fro yt,:syk- h77jow rfyb)s 22okm a cliff, an elevator moving from the second floor to the fifth floor m7s-oy2thk),wf j7 by:ry2k osaking stops along the way, a dish resting on a table?

An object that is throwog1 kn8 w)qxa* lg(b70g*7i+b spwpnv n vertically upward will return to its original position with the same swab)(*vwg8 n oi7 pqnk 7gsb0gxpl1*+peed 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 always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero acceleration at the same tij4amfw4w a2m6u13ug wze5 zv 7to3el; me? Give4w3gafz; at4zve w lmue3u1o6 w5jm27 examples.

Can an object have zero acceleration and nonzero velocity at the same time? 2gw 7/7f0mvmv(sjyzy Give exampjmywv s/77f2ymv0g z (les.

Describe in words the motion plotted in Fig. 2–28 in terw::5evh yssc9-p aky 5ms of v, a, etc. [Hint: First try to55 e-vawyh:9 cs:ys kp duplicate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object 7okriom:,n1j 4v9tk8p 0 wspbgraphed in Fig. 2–29.

  What must be your car’s average speed in order to tra r2p.*k4k prbnvel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take to flyxbz+7 l1i 7:nug ,::c6+qqnyicawukwtuoc (5 15 km?    h

  If you are driving along a straight roady; en :yi;py3wi gqz* .mtn+.w.w fvh9 and you look to the side for 2.0 s, how far d9+ wm.qwhyvyig i*nn.z:e fp.3ty;w; o you travel during this inattentive period?    m

  Convert 35 mi/h to 7/f7 p0s-pi m 3brg rjjb1ch3n
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves nac;zw*+ emr5gx5;ql( zi+tgfrom $x_1$ = 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 begins mh6r-1nrwb) nto rain and yow)mb -rh6rn 1nu 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 betwm71fr5b8t5fzb, k m bleen a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrfkb5t58 7,b1mmz br flives 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-mile track in aluyoa95t+/h; d rnnz 6 total time of 12.5 min. C6l oa+d/rnyz5t ;hn9ualculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its train:9boop a 0cbe ejk-a(4er in a straight line, moving 116 m away in 14.0 s. It then turns abjcoa0:eb- be49a pk(oruptly and gallops halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each other on parallel tracks. E8cf6ffb+ vm 0l3: svnvach has a speed of 95 km/h with respect to the ground. If they are initially 8.5 km apar:v6bm3 vff8 vl0fns+c t, 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 trpvdg vjdcmy(yyj x i:f1i2:s0f0, 55xaveling How long will it take i1dfm ji :xcj5yy0:vdx5f0 p2yg(sv, the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then encounmsjb7ef0rssp7 .6t 7dters a tailwind that boosts its speed to 990 km/h for thedj7pbm76rs.st7es f0 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 wi( il1 i sudnu;,nt:/and average velocity of a complete round-trip in which the outgoing 250 km is covered s:;/u(wluni tind, 1i at 95 km/h followed by a 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 a-r+( l.0-pe9p umnrcqqzi u+kt 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. What is the speed of the r e0l.n+ q cm(-przu-k+pu 9iqball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 kmy,splbgk) lx zv(q0 00/h in 6.2 s. What is its average accelerk,0( gvp zxb)y00 lqslation in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. W8 k1,bu ysxk:*d tgce2hat is her acceleration ck:uytsek,bd*g2x 81
(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 accelerat+7kjnc-e x6gmm,rx- mion of abou 6xc+m,erj7 mg-kn-mxt $1.6 m/s^2$ 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 iuewyncw bfxoiz6 e:80s09q 3.n 5.0 s. If it then brakes and comesyx.ceqeu9:0w 3 zbn0w 6f si8o 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, whixrz gy bj+4(q(qp j9g9ch starts from rest at t = 0 and moves in a straight line, is given as a function of zxggqbj9r(( yj9 +4pqtime in the following Table. Estimate (a) its velocity and (b) its acceleration as a function of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/l b./7k( 8b(c+ ltvrom -fpan/zqiy3gs in 6.0 s. What was its acceleration? How far did it travel in this time? Assuopk c+n(mli./vbay tz/7r q38flb(g - me constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest ipqwe g.;xa;fusr5od/ s.g4 (hn a distance of 85 m. What was its acceleration, assumed;.fu;wqs dp(4 s xrgo/.hg5ea constant?    $m/s^2$

  A light plane must reach a speed ofzz o*e ciq:,*a 33 m/s for takeoff. How long a runway is needed if the (conste:,*z* azqi ocant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the bloch+n(r nwfl q ;c-i1j:hks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and hc(i1-+;wjq nf :hhnrlow long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down unifo;la30 vgpir. grmly from a speed of 12.0 m/s to rest in 6.00 s. How far did it travel0. agr vip3;gl in that time?    m

  In coming to a stop, a car leaves ski nr8h4kf ehunr tbe+oq*)q; 7g n/26btd marks 92 m long on the highway. Assuming a deceleration ofb e/6okut8t rqb g)7qh; f+n*n4h 2ern $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h strikes a tree.l,. ,m/jwrpbrnbcc gu3 5(dy ; 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 collb 5w, bycgl;ucmp/r (rdj3n, .isi 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 distu 9wa2t t)c*rgances for a car with an initial speed of 95 km/h and human reaction time of 1.0 s, for an acceler t)r *tgwu9ac2ation
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equation for the stopping distan ;/6l)vc ftluyce 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 highwa qptp7 gsb- 4vn 35x3r/g7zyzhy. The car’s driver looks for an opportunity t5xbtgyqn7-vrgzzh3s 3 / p74po pass, guessing 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 in8wjkfg) ;8;m.dwdyu f9g1e-wyn)k a b less than 30.0 min. After exactly 27.0 min, there are stw ud )kagky8yef-;db1g;n )mjf 9.w8 will 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 z84( kxj2-mti;o u*oar2b lxcintersection 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 (2xxaoj (2m u-lb r* z4t8okci;Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersection is 15 m wide. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground bel6j1lcvtl hh eh/zs1e 58uzvk:al;z87 ow after 3.25 s. How high is the cj6/18 uh8 vvlzhc 7es:lek ;zta51lh zliff?    m

  If a car rolls gentl *yni gdwq2.b v0e,6sby ($v_0\,=\,0$) off a vertical cliff, how long does it take it to reach 85 km/h ?    s

  Estimate
(a) how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high), $\approx$ =    s (retain one decimal places)
(b) his velocity just before “landing”?    m/s

  A baseball is hit nearly straight up into the airn4y0,;l zl hai 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 a(/jmh-o o a8-cal:ds+ il dz,ball 3.0 s after throwing it vertically upward. With what speed did he throw it, and what height did,aj hdlc-dma: +osi l8/oaz- ( it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls underm1e;wh() z tdzb;4qez the influence of gravity. Draw graphs of (a) its speed and w(;ztezmzh;b1 qd)e4(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 speed of 5.20 m/s. At a height of 12szxuuvl:7 n.efx+ *h 65 m above the Earth, a package is d.x *z6vn:u+ e 7xsfuhlropped 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.] t =__ s

For an object falling freely fromg*2ssp33w 3 molts- zdyy .t1f rest, show that the distance traveled during each successive second increases in the ratio of successyp3s3 2yg1dtfzsmlwt so.*- 3ive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is negm:d24*w02y: t:aofbz nezmd9m o7hhblected, show (algebraically) that a ball thrown vertically 4:hz* :zhfom :0en o2m9ymt7wb 2d dbaupward 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 speed of 18.0 m/sy) yy1 i01biykoc5lt j5y o)v4
(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 a.,qtpa o;g- yc )7gswhpple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple qh )tw7ag.pg c yo;,-spositions, 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 o63vmlq9av . x(Fig. 2–32). From what height above the top of the window d3 ol9va.6xqvmid the stone fall?    m

  A rock is dropped from a sea cliff, and theao+.7zsk s.w m sound of it striking the ocean is heard 3.2 s later. If k7w osm+..asz the speed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust yourb9xi2;jas1ao ; d7 wse garden hose 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 2ds aibe9wja;osx71 ;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 spee;cv 5bpeogqj (yx9/xu ;n -5ced of 12.0 m/s from the edge of a cliff 70.0 m high (Fig. 2–34oc-x;n vg c(yqxe ue5/9jbp;5).
(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 d f22y;pm6.m3todjnt upward by a window 28 m above the street with a vertical speed of 13 m/s If the ball was thrown from the; nt2md o2.tjpdfm63y street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a function of time. (a-e.h88ryjjfh ) At what time was its velocity greatest? jy he.frh88-j(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 straigh-cos/ j c*kys8t tunnel as a function of time is plotted in Fig. 2–28. What is ity8*/c okj s-css 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 :9 g/jre. ts6nzb. tchta) btn)7-xcnas shown in the velocity–time )ntb6xbn ctj.a h: t es.)t9- n/zcgr7graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the gears.)
(a) Estimate the average acceleration of the car in second gear and in fourth gear. The average acceleration in $2^{nd}$ gear is given by    $m/s^2$ The average acceleration in $4^{th}$ gear is given by    $m/s^2$
(b) Estimate how far the car traveled while in fourth gear.    m

  Estimate the average acceleratexjh7sue2 8 6iion of the car in the previous Problem (Fig. 2–35) wx68 siu 7hjee2hen 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 :yps1z,qm hig ;j(ektra a m:q/ ddb7):k z,y0traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the 3 (d7cm0-yig,atvwc2;dvq ef object whose displacement as a function of tic3myqd w( -fci,2g;dt07a vev me is given by Fig. 2–28.

Figure 2–36 is a positis/m9,djdun5s p5rg )2sw)-s+am nkk jza+y x9on 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? (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 frdnkdmn )x,a) s+u- 9jgmr2 59ks5+zja/sw spyom C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’ -c6h2 u w6p otuft6i;:mfj*sss safety net. The suru-fhpco tju6fs:s ;2*i6wt6 m vivor 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 +nx83pdd yjao vrmigt6r+ 0.1acy79swhat it is on Earth. If an object is thrown vertically upward on the Moon, how many c0yd o+a6+y1.9 r3mtnj 7dvr8gspaix times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-siw7g* u28b 1vm tlcg(dhoulder seat belt has a good chance of surviving a car collision if the deceleration does not excc*(m2wgvlg8 u7dt1bi eed 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 l/-r mkhpe180r sise h80(tjq above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles h1 8 0(t/8epr-elmskh iqsj0raway the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its( 8fpk)9igpkc.i0o gf cars for front-end collisions by hauling them up on a crane and dropping them from a certain 8(k) iof9.cgkp i fg0pheight.
(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 abou(6y:pcivc: wqt $10^9\,km$ 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 from rest. The front of the tr 6v5w4n6 fkmxvuwec6+;wzv 3kxz 4nc3ain has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front o3nv46vz +6f6wxcvw5e n k ; wxk4uczm3f 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 b 9 jzz3bif, 0u9vsd2fkoard 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the ave 9 s9zb0ifku,2f3v djzrage 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 is2y7- xuv n s7llm8nz8xzct.(r 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 timnmxs2r 7y -z(8c7n.lv8x uzl te 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 fre16v2m 1ag( ;i cspcwbhe fall straight down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its path once committed. If it takes a fish 0.20 s to perform evasive action, at what minimum height mus c;vcb61i mwapg(12s ht it spot the pelican to escape? Assume the fish is at the surface of the water.    m

  In putting, the force witha*l.u gyy h(mvb+x z)bej,s,d7 )8 fgx which a golfer strikes a ball is planned so that the ball will stop within somlsam(vg,ybge*,d+ . bj xh xz8 y)uf7)e 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 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/ibt1erhd i9,m3 zsa87a a) tr train traveling at a constant speed of 6.0 m/ss8 aib7ta91 z mrt ardi,h)3e/ Just as an empty box car passes him, the fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped f;94 0w a7h0m 6) cpslpymlwjeb f7x7ebrom the roof of a high building. A second stone is dropped 1.50 s later. How far apart are 0w74)ph ewsmlp mba709fcx7;6bljye the stones when the second one has reached a speed of 12.0 m/s ?    m

  A race car driver must average 200.0 km/h over the cot n.t0xgf*5s ourse of a time trial lasting 0sg5n. t* txoften 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 crests0ityz0zs av00 a mountain pass as he moves at 18 km/h . At the bottom,st00 aivz 0z0y 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 trampolines. The first child can bounce up kn87) gjf2pec:; me+xi3v )fk.srf uxone-and-a-half times higher than the second child. The initial speed up of the second chin)7 xv2x)3+ i ;fsrjk:pgck.f8eefu mld 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 tshrdld ob6g- +*1gw(rffi +:lkh3 qa,raveling in the same direction on a track ph g1* rd6 ,sa+q gf +rkd3wloihb(-f:larallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are the results if the car and train are traveling in opposite directions? t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places) t =    min The distance the car travels during this time is $\approx$    km(retain one decimal places)

  A baseball pitcher throws a baseball with a speed of 44 m/s In throwing the o--1 n+x (zyq,gw7*hfc fvj eibaseball, the pitcher accelerates the ball g 7enxfj iz-,v( y*owcq1+fh-through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from b(jg-7s7:yzhklhq :j yil8, h rest, with an acceleration of $3.2 m/s^2$ until it runs out of fuel at an altitude of 1200 m. After this point, its acceleration is that of gravity, downward.
(a) What is the velocity of the rocket when it runs out of fuel? $\approx$ =    m/s(Round to the nearest integer)
(b) How long does it take to reach this point? $\approx$ =    s(Round to the nearest integer)
(c) What maximum altitude does the rocket reach?    m
(d) How much time (total) does it take to reach maximum altitude? $\approx$ =    s(Round to the nearest integer)
(e) With what velocity does the rocket strike the Earth?    m/s
(f) How long (total) is it in the air?    s

  Consider the street pattern shown in Fix*y40+4mg of*od2x vh zgb y2zg. 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. When you are 10 m from the first intersection, all the lights tuox4gy h*gz 0yv+fz24b 2* xodmrn 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 qd+3p8moq-x qxb 5v2 da constant 120 km/h takes off in hot pursuit. The police officer catches up to tpvq8 q5dqm 2xb-3+o dxhe speeder in 750 m, maintaining a constant acceleration.
(a) Qualitatively plot the position vs. time graph for both cars from the police car’s start to the catch-up point. Calculate
(b) how long it took the police officer to overtake the speeder, $\approx$ =    s(Round to the nearest integer)
(c) the required police car acceleration, $\approx$ =    $m/s^2$(Round to the nearest integer)
(d) the speed of the police car at the overtaking point. $\approx$ =    m/s(Round to the nearest integer)

  A stone is dropped from the roof of a building; 2.00 s after that,boa*(l+i.w-* r+ l v ter+xylq a second stone is thrown straigqlr+ lexywivr*+ola(. -b+t* ht 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 vertically up auj; mm,y5hwh5 t 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 whauwyj5m hh;m, 5t 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-s4e)pp2 .vm:amghpla ; 8oj6 vfalling 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 35e8p 6.pgmhvp vm42oa)js; l: a0 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 burgers thmm6(nngwb80clvdp 09rough a grilling machine. If the grilling machine is 1.1 m lond(9l n0wp60vncm8m b gg and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times fj+x)h kf ll4n *qef0f-aster than Joe can. How many times higher will Bill’s bl*hkfxef4 -f)0lnqj+ all go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff whmqd-ylw ( y8p.,pgi4dile your friend stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend 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 why- g84pm pw.iq d,yd(lich your friend threw the ball?    m/s

  Two students are asked to find the height of a particular building using 1ln 1,6ogz lhgenv6(px/qh s4 a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference doepq1g,/hev6snxzl6 o lhn4g (1s the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the.t r53*uvbbe l ns/sog/amf(- position vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the hig n(a tms /fg/rl.su*-5be3vb oher average velocity?