Does a car speedometer measure speed, velocity, or botj xee2 n+)w+v7d9px/oya i; 3nhdasu2h?

Can an object have a varying speed if its velocity is constant? If yesc0yza v 0a;stn: wt19h, give exawz0cy :thnvt ;0aa9s1 mples.

When an object moves with constant velocity, does its average velocity8rc dygg 3d zu4w;k7t9 during any time interval differ from its instantaneous velocity at ang t7ucdkg wdz 9y843r;y instant?

In drag racing, is i tuvw0*zj3* x) mcrlu-j*3zkht possible for the car with the greatest speed crossing the finish line to r xjk)h*-w0jtuzz3u3vlm c** lose the race? Explain.

If one object has a greater speed than a wp45(e 0p t7ccljfs 5asecond object, does the first necessarily have alep( p4a sj0w5c5f7ct greater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accelerates from 80km:/cv+ziji8ekv5e icn (0 z x givih1;2/h to 90km/h with the acceleration of a bicyclingv0 cchvx: /e 1 izei(j+vz8ki;i52 e that accelerates from rest to 10km/h in the same time.

Can an object have a northwe:x)sqg 8jz 7hard velocity and a southward acceleration? Explain.

Can the velocity of a3k1j dlw gnevx)mw) 21n object be negative when its acceleration is positive? What a 32wve)kl1)nw 1mdxjgbout vice versa?

Give an example where both the velocity and acceleration are nx5xbx2(vy;( l8dla qi q; :xbmegative.

Two cars emerge side by side from a tunw97jg6l +hgh qnel. Car A is traveling with a speed of 60km/h ah6+qj g 9hwlg7nd 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 they come out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acob,1fwi6 *-dz1bw dmw celeration decreases? If so, give an example. If not, expld id-w1,1m*zob6f wbw ain.

A baseball player hits a foul ball straight up intzq 6 fqp m+9pqt-w9fz8o the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will 8pfqq+ 99-f6zz qmwptthe ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening to it5b.bco3 d2, zafe1 5-qoqwqi us acceleration due to grac 52awz o bq5 .oqdqfu,3e-b1ivity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw ru4 -/v bz 3dxjfpmcg:hw-/-y a ball vertically upward? How would you espjvg-/:b--yumzhd 3 f c 4wx/rtimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed of Thenozlui2 9 (9;rm1* jj f2pctljn you travel the same distannrf;t jjl j(m9p * c22z1oil9uce 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 demonstration, a 3.0-m-long verticarh/f0r+xs5)vbc s;a kl 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 intervals. Why? Will the time between clinks increase or dxs0ba/f) hrrk 5v+s;cecrease 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 accel*s8 l4xn a;hne 6-qpph;ey wz-eration: a rock falling from a cliff, an elevator moving from the second floor to the fifth floor making s xa8sp wnhqe; n-e-lz4hp*6y ;tops along the way, a dish resting on a table?

An object that is thrown vertically upward will return iz dj66+qv ny,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, a+qjnvy 66 i,zdnd 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 t oo7*)d,gmgo wci4j2u7um no 2ime? Give exam24u)27oiomo, c7gg mwuonj d*ples.

Can an object have zero acceleration and nonzero velocity at t-ur2yqgc u r06he same time? Give ex r rcq-2yg0uu6amples.

Describe in words the motion plottedyq;s dq+7f/rs0fdtb pu34 hr* in Fig. 2–28 in terms of v, a, etc. [Hint: Firstudq7p0;/rqb3ys df +hf4s*t r try to duplicate the motion plotted by walking or moving your hand.]

Describe in words th *w gekdisrdy1(k1j. )e motion of the object graphed in Fig. 2–29.

  What must be your car’s average)k6v.yuw vpim 8.9u 5*sncwft speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km6pvf vwo;syowuh jw(: 46,zs(/h How long does it take to fly 15 km?    h

  If you are driving als)v) hfn(s wcss,3lv (ong a straight road and you look to the side for 2.0 s, how far do you travel during 3vl(n h()svss w),sfc this inattentive period?    m

  Convert 35 mi/h to ib) n0z(mil c8. aqu84zbeeaz4k 3of6
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves f9,ruhou x 37o z/omb-ct izg 4id,v+3a2 ensi*rom $x_1$ = 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/wn8t d rxu/e*l.g5;a,v8gc zzlt*uw9 h for 130 km. It then begins to rain and you slow to 65 km/h You arrive home after w t8c r, 9g*.t vdn8wl/gu azu*x5;zeldriving 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, eve+4(ysv1l r rw 9mk j*fcxb5(xery five seconds between a lightning 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 from this rule.lfrym 9+ksxjx1e54v c(w *b( r    m/s

  A person jogs eight complete laps m 64o*ja x.dzqaround a quarter-mile track in a total time of 12.5 min. Calcuo*.dm6jx 4q azlate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight libl)t*p f kc78dne, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfw 7f)c*ptd8 lbkay 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. :d2*vji+wr3 7qn7g 0 aiuvvkhwm r1e5 Each has a speed of 95 km/h with respect 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). 5wevimkq7njw:7 *2v 0rvru3da i1 +hg    min

  A car traveling 88 km/h is 110 m behind)*jl *+nmmc4 2phfqokbp l b/-z9mak 9 a truck traveling How long will it take the car to reach mf2 +*m-q4a colpnkk 9*l)hb/bz j9mpthe truck?    s

  An airplane travels 3100 km at a speed of 7907sdh5ikr ju d.97* uma km/h , and then encounters a tailwind that boosts its spee5rd uk as9dji7mh*u.7d 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 t xx/kx0;thwlo(y-n9o r x. 6espeed and average velocity of a complete round-trip in which th-xl;k. o6yxe(t0xt 9wrno /xhe outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits thel pd vy8)q0 /+* w0psdiwv(euh5me -ra 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 hidh mda(5ep+vpq-wsry w0ile)u/*8 v0s hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates from riww4w2-l os ;uest to 95 km/h in 6.2 s. What is its average acceleration iw2u w;sl4o iw-n $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1 ro,apm1-x1q k.35 s. What is her acceleration kqrpx 1-1om a,
(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 acceleration u9ysn 4 bixm b3q*m51u d4p(czn z8)6yrbx8isof about ui s84zuxyb1nqn8ibd (6z b) sr*m9xm45 3cpy$1.6 m/s^2$ 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 81bx 5-u.jcydspnt* /v pi s.fxhsi.5m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is itss5ypic b- u /f..xht 8v*n xsj5.pdi1s acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves indyfi 2u 2dl8vg- 9vl.n ggh7:i a straight lini.dgnh u2gv-ylvi lgf82 d:97e, is given as a function of time 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/s in 6.0 s. What was its accyvi xw./3j9:rtu ceiy1+xr7e eleration? How far did it tv+/9cu7wiiexy tyr1 r:e.j 3xravel in this time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. Whajx-4vv 2jtv ( zxtd(+jt was its acceleration, assuvv-4xjd(jx+t (jvzt2med constant?    $m/s^2$

  A light plane must reardlf j *llp2,;ch a speed of 33 m/s for takeoff. How long a runway is needed if thel ;dljf2 r*p,l (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst9coeqfrt3jr3 o ( bofu/5fa 21 out of the blocks to essentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach t(a9tor /jqcf ef b23oor 1f53uhat 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 r3q- mzmg ic2+-dnp i.in 6.00 s. How far did it travel in that time? -i gmi2p.3n q-md+crz    m

  In coming to a stop, a car leaves skid marks 92 m long on the highway. A58ai.eiud dqw it0 +,3u rs7unssuming 37u .0r tsq +i8uu,didi5e nwaa deceleration 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 tree. The front end of the car compren88b/h0n d acxsses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express thenx8h8d c0n ba/ 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 initf4itwzqk9 7 ,jx:mi)v56uan wt cg1 4oial speed of 95 km/h and human reactn76gjt iutkw vm4aq1:95 zw ,cix)of4ion time of 1.0 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 a ca 6d, whqmfjgg0c-c g9xo: 7y4xr 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 25d:nc)mcfnbb x4 d+b9: m/s on the highway. The car’s driver looks for an opportunity to passxc:dm+ :b9db n4fnbc), 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 in less than 30.0 mzfel;zi. hqyscn3 y.z6a k25 ;in. After exactly 27.0 min, there are; elafqzhy5;3yzs.2 .i6znkc 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 aw;ab(. 3dnb drj-k, tfs 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? T f dna.bdtj(kr3w-,;bhe 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 a29tlt.2ztenb , nh. den2u2la cliff. It hits the ground below after 3.25 s. How high is the clifz2n.hte nn, u22atebl tl2d9.f?    m

  If a car rolls gently tdo;ilps1j75 ($v_0\,=\,0$) 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 upzfssssqob-jfro1 1 d2o*vg v- 0d * d1g8q8jh- 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 throki ys4/:+ mb6x u-eqjlwing it vertically upward. With what speed did he throw it, and what heim6sxj-+ :4u ykqe/blight did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. Draw gra f-hq3wzqk4e 6h6.c/t5 7(mlcrx cx(ak ycv)zphs of (a) its speed and (b) the distance it has fallen, as a function of time from t = 0 to t = 5.00 s . Ignorx7my4wcxezq6at kzhc)v 5 (k-c f.lq(r/ h36ce air resistance.

A helicopter is ascending vertically :5w sgmwwk( 1zhb;x:m with 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.] t =w:5 m; gm1wk:xb h(szw__ s

For an object falling freely from rest, shomvvt5 m ,e0c-sw 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 Gali5-emm v,t 0svcleo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) thatq) l0.hry,:wacaz1h(a i:cc k l c75wlwlyv4. a ball thrown verticallcc, 7w.cy4yl.z(1i:hwa) c0rlhw5lkqa a :vly upward 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/sb l2 r;13r vmdqzl.mq)frb )o+
(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 Fi 11f3il2pumcwg. 2–18 (or number of photoflashes per s fuplw1213 cimecond). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at the top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m tall (Fig. 2– 9f,.jswvs o:);sb kyd32). From what height above the top of the window did ;ws:)9yv.kjd sfs b, othe stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking the oceddzhq +.,x c2dk wv:d2an is heard 3.2 s later. If the speed of sound i d22hdkdc xw: vd,.zq+s 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle for a hardmnsw/k5/ 8dh w bo6im4 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 another 2.0 s. What is thewn/dwikbh5s mm 684 o/ 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 y2w g xlu5wb2kp 3:n9dz1zy.yedge of a cliff 70.0 m high (Fig. 2–34). pw5u:zy2b23x kng dw91ly.zy
(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 stre.gco q9a8c41bqvb0xq et with a vertical speed of 13 m/s If the ball was thrown from tb c8q9g0v xo bq1.cq4ahe 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 tittp,wm(r ww 35n d72tbme. (a) At what time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) Durin b75 pt3twr(nw,t2dmw g what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a stra ug-o/+uuw sk40tw sm,ight tunnel as a function of time is plotted in Fig. 2–28. What is its uts -,os0gk/mw u4+ wuinstantaneous 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 as shown in th(hw+ejqk-z y9; dt mc5e velocity–time graph of Fig. 2–35. (The short flat spots in the curve represent shifting of the tzdmh w+;9e( j5q yk-cgears.)
(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 previousj(myr1e,m rexk./p1 -m c2c nt Problem (Fig. 2–35) wemjm,y/r(c t2.1x 1rp em-cknhen 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 traveledw ka:wml 0b *bs x,)a.ij3s3xi during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function f wlx 0n)ah (1u ro+v.+qmkuc:of time is given +q ok1cfum0 a(l)hnw: +rvux.by Fig. 2–28.

Figure 2–36 is a position versus time graph for txxtit7 yn7.4iu d2yxd xf.p46he 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 p7x2uy.fx7.x 6iit tn yd4d4x D to E. (d) Is the object moving in the positive or negative direction? (e) Is the object speeding up or slowing down? (f) Is the acceleration of the object positive or negative? (g) Finally, answer these same three questions for the time interval from C to D.

  A person jumps from a fourth-story window 15.0 m above a firefighter’sb3)ue- 7r ujwm safety net. The survivor stretches the net 1.0 m before coming tower3j- ) uum7b 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 Moon6 4rer u4 ten7eksp 7cc-cq4r; is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will i et4e4;crr 4q-ueck7prc6s n 7t go than it would on Earth, assuming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has a gis9 3z )it5sau6f4e a6id k,zuood chance ofs3uf 56d9t4 a)z u sa,ez6kiii surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on5: tw;h9+x7l sj r2hn pn6ojxmhba/:g a bridge, 12 m above the road below, and his pursuers are getting too close for comfort. He spots a flatbed truck approaching at 25 m/s , which he measures by 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 to65: n9xh72l+rhs; n awg bo/hjx :mjtp make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cars ozb;5(11c3 evv3jb lq-9nl(yww jifco w8w 7bfor front-end collisions by hauling them up on a crane and dropping them (lo b5vj8wyb;z1w wwofq(391-j le 3nciv cb7from 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 trad4 jjel6 3:i/ vckik3deii:: gvels about $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begins unifor,,up)ksvob* j0-q8w d qk4)/u8ao bxf qznw l(m acceleration from rest. The front of the train has a speed of 25 m/s wh/zkvu 0a(sq l q qk,n ,8-jof))8bdwu4*wpo bxen 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 dimtjay 10; u(z 2l4gbqnp wemu26 3wq+uving board 4.0 m above the water’s surface into a deep pool. The person’s downward motion stops 2.0m3uyewa2pw16z4 0uq b jmg q; +n(2ltu 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 necessary to balajt1hy o9)rg3f nce 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 tfyjhg t)or193his problem, calculate the time it takes a train to make a 9.0-km trip in two situations:
(a) the stations at which the trains must stop are 1.8 km apart (a total of 6 stations, including those at ends);    min
(b) the stations are 3.0 km apart (4 stations total). Assume that at each station the train accelerates at a rate of $1.1 m/s^2$ until it reaches 90 km/h then stays at this speed until its brakes are applied for arrival at the next station, at which time it decelerates at $-2.0 m/s^2$ Assume it stops at each intermediate station for 20 s.    min

  Pelicans tuck their wings and free fall straight d ykvgd,hw4.7 down when diving for fish. Suppose a pelican starts its dive from a height of 16.0 m and cannot change its pathwdk7 v h.gd4,y 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 wit-+npzb orr(iaz0+ zq-sf6h3p h 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 qnz-s z-a6hp ob(zf0r+r3+ipan 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 hiq4n nk . ly1.rmhc6 t3zynf zw7(-n1dop on a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, the fugitive starts from re6ln1nynyrdt7w f.h-q zk.icz4 1m(n 3st 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 h8ajjz t kz +ec0.z-rqjp*zl 4:igh building. A second stone is dropped 1.50 s later. How far apart are the stones when the second one has reached a speed of 12.0 m/z-z*8je .0j4l c: azpq+jkr tzs ?    m

  A race car driver must average 200.0 km/h over the course of a time gdw3y78xz vv9hp3 d n.trial lasting ten laps. If the first nine laps were doneh7 g3 3xvwnv9z8y pdd. at 198.0 km/h . what average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Fyw) ik2 +-jlpyrance crests a mountain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What wwj-y+l)ik2yp as 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 bouncek5 sahc2; gz.z up one-and-a-half times higher than the second child. The initial speed up ofh;z 52 gkzcsa. 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 jau9rnj o 82nt 1lig+7ubimn op,z 5-0a 1.10-km-long train traveling in the same direction on a track parallel to the road. If the train’s speed is 75 km/h . how long does it take the car to pass it, and how far will the car have traveled in this time? See Fig. 2–40. What are i nio7g+5-lj9uj zn tma10 b onpr,u28the 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 t8bnfv )ghgs;pk) j/ic*n*n x,hrows a baseball with a speed of 44 m/s In throwing the baseball, the pitcher accelerates the ball through a displacement of about 3.5 m, from behind the body to the point where it is released (Fig. 2–41). Estimate the average acceleration of the ball during nxh* )nvpfb j)n*/sgi8k;g, cthe throwing motion.    $m/s^2$

  A rocket rises vertically, from rs n;w68av duuf;d0 fel37njv0est, 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 Fig. 2–42. Each intersection has a ey- q 0tsj ;x0id6o5fs2o.q mztraffic signal, and the speed limit is 50 km/s . Suppose you are driving from the wesot d5m0.;xsifqs q2eoy-j0 z6t at the speed limit. When you are 10 m from the first intersection, all the lights turn green. The lights are green for 13 s each.
(a) Calculate the time needed to reach the third stoplight. Can you make it through all three lights without stopping?  ----待选择----yesno 
(b) Another car was stopped at the first light when all the lights turned green. It can accelerate at the rate of $2.0 m/s^2$ to the speed limit. Can the second car make it through all three lights without stopping?  ----待选择----yesno 

  A police car at rest, passed by a speeder traveling at a constanrb. 6zjbczp 2lc i;6z /-oz:pnt 120 km/h takes off in - ori;.zzc:b2/p pn6lzzc j6bhot pursuit. The police 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 s after that, a secocu+n at ibjzbb*42,au8/ssp + nd stone is thrown straight down with an initial speed of 25.0 m/s and the twb a4+j 28n *a,bpssi/czb+ utuo 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 verticaly,5 0xznfas 8kly 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 buildin8 fy5kszx0na ,g and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, (tzc 0qp)qd smc g)++cr0fz u9tb,2bqhow long would it take a free-falling parachutist to fall from a plane at 2 ccmbpz(b0t 0cqudq++rsg)f ,q)z t93200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resistance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restaurant uses a conveyor belt to send the burw3uxbv1:qsh;1 z rrd6 gers 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 conv hvq w ub163r:;zdsrx1eyor 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 fasterpf.ae bn tis8rm( ,f3+ than Joe can. How many times higher will Bill’s f arsb+8mp3n.ti,ef (ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend stands onllpat)i2o7y . 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 compi)2tlaol y7. es 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 heivg jmxi9;e; 6 m(2xvkpght of a particular building using a barometer. Instead of using the barometer as an altitude-measuring device, they take it to the roof of the building and drop it off, timing its fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much differenc9ij ;k mxpem;g62 xvv(e does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position vs. timsfsh u4.dw(, 1uac ja.3ej2d qv h97gie 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 eja sh.duwfdq ,4s( v3ca2i9h.gj17 u the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?