Does a car speedometer tax5 x 3y 7qf3mxxq x) 5tig2bd,jw+3wmeasure speed, velocity, or both?

Can an object have a varying speed if its velocity is constant?457w n dotx*xd7y ept4 If yes, give examptd4 x74exdynp*ow 5t7 les.

When an object moves with constant velocity, does its average velocity during c4ftwzo9b00 q any time interval differ from its instantaneous veloco09fw c 04qtbzity at any instant?

In drag racing, is it wb0iir 7djczu762v3z e u5*ysjz :vb:vt8sk - possible for the car with the greatest speed crossing the finish line t:jruv80 * zsbs3:it-wv2 ye 5z77vk6duzcibjo lose the race? Explain.

If one object has a greatep .xwk)k10eqvkph.j l3hds:0 r speed than a second object, does the first necessarily have a grd ke. vjhw q)1lxp0s:p3h0kk.eater acceleration? Explain, using examples.

Compare the acceleration of a motorcycle that accel 3e zk tyl m44srq09lcy+e07blerates from 80km/h to 90km/h with the acceleration of a bicycle that accelerates from rest to 10km/h in the sl90t3r 4cszle0e4+lykq mb7 yame time.

Can an object have a northward velocity and a southward avj hl78psjca-xk,z( .cceleration? Explain.

Can the velocity of an object be negativepal-je 5v5t;p 3bkt*a when its acceleration is positive? What about vice vera;t ep5 *vapbkjlt35-sa?

Give an example where both t,erz0af; yxnp )5hsz9a :2wkvhe velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is / 5ns,trxj5px*6h .(x pbfnoutraveling 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/5p xurf/ ox* bx,h.nj65sptn(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 a5glf+zjn8g5 jcceleration decreases? If so, give an examplej +5l8fgn zgj5. If not, explain.

A baseball player hits a foul ball s31tr8d8r3zsy/k)epfo1j tw dtraight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resistance, how fast will o dk/d f8rj3yt )81wr 1pzte3sthe ball be traveling when the catcher catches it?

As a freely falling object speeds up, what ic9vm c 1rbi(+0 abdwgi) +eg w*hwv4m(s happening to its acceleration due 1wmwi)r9e mb(g+b cwhgc i0 vdav+(4*to gravity — does it increase, decrease, or stay the same?

How would you estimate the maximum height you could throw a ball vegjv/ updiqc3 ( +t-v)grtically upward? How would you est +/vi)q ctdup3g(j-g vimate the maximum speed you could give it?

You travel from point A to point B i qz6modpl4pb0( 7fu8yn a car moving at a constant speed of Then you travel the same distance from point B to another point C, movi b7o zy(8fp4d 0m6uqplng 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-ml:m glcc/ dn5th h8:e5-long vertical string with ten bolts tied to it at equal intervals is dropped from the ceiling of the lecture hall. The string falls on a tin plate, and the class hears the clink of each bolt as it hits the plate. The sounds will not occur at eq :h5/cg8 tlche:ml5n dual 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 wv 2b*1053o.wqnw er vblci5xp7v c2f bn7m5ufrom a cliff, an elevator moving from the second floor to th 72cbu pwcn vwvfv5qbn3o05rblwxm25.* 7 e1ie fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upwar. )y6 x3n9ln+homcigyd 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 altereln3n+o 9mx)gy c6iyh. d, 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 acceleration74itru ;y pjet;1po/ v8 (lusoc8,v es at the same time? Give examples.et8p; coyuvp rt( u1/i, ovj4l;87se s

Can an object have zero acceleration and nonzero velocity at the same te:3srdt/) avrb2d o0r ime? Give examdv)o3bs 0d:r atrr e2/ples.

Describe in words the motion ploawn.kk9ec1 nu b-b9a/ tted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplic1 - ec n.bwk/banku99aate the motion plotted by walking or moving your hand.]

Describe in words the motion of the object grap/rp gdqc+0 .ached in Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km ;r8 t. sno em)3ievk fw0v(em)in 3.25 h?    km/h

  A bird can fly 25 km/h How long does it take tn9xsk6pgp+p;vg /lke1s d6s 8 o fly 15 km?    h

  If you are driving along a straight road and you look to the side,:zx a;tvz3gz for 2.0 s, how far do you travel duringxzg,; t3v:a zz this inattentive period?    m

  Convert 35 mi/h to tb mcxt7wlb 1w od6gt3u +q040
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fro+.2bg/ massl 6gwpz8p ztce17m $x_1$ = 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 kg 5d iukul;)3am/h for 130 km. It then begins to rain and yl5i3udu ) ;gkaou 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 between jg)o)mcp bv,gv,-g ks571oibh uef- * a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentially nb-)g, gp7vkub c ohjm-5e,f s1vo* g)io 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 a total tim kitnf6)w 3a n3;cges7f fac+3e of 12.5 min. Calculate 67k3fsn)a ewc tfa;cgn 33+ if
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from )-a-qeh/+1 v 2 ph(vkt cmupdpits trainer in a straight line, moving 116 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. Calculate tc/ maqp2pu( 1pd-)khv h -ve+
(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 tf hu/zkdxt dt9 29gw,,racks. 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 eachtd9,zf/ u h9,2gtdxk w other? (See Fig. 2–30).    min

  A car traveling 88 km/h is 110 m be9(xj5: jf:jt xoms*:a28 x iyp/k tugo)wuy(uhind a truck traveling How long will it take th/o( 8js:9x x:oj k5wy ut pux*:mfg ti)(2ujyae car to reach the truck?    s

  An airplane travels 3100 km no7ej+mc8c t1 at a speed of 790 km/h , and then encounters a tailwind that boosts its speeoc+8nme 7t1c jd to 990 km/h for the next 2800 km.
What was the total time for the trip?    h
What was the average speed of the plane for this trip? [Hint: Think carefully before using Eq. 2–11d.]    km/h

  Calculate the average speed and average velocity of a complete round-urkito waa:7*d3m(9q trip in which the outgoing 250 km is covered at 95 km/h followowd3trqi:a km (u*7a9ed 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 a6iw / fh octuipq3(8e(t the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2ifc/io8p ( qeuw3h6( t.50 s after the ball is released from his hands. What is the speed of the ball? The speed of sound is 340 m/s.    m/s

  A sports car accelerates p*/6n 9 y/bhb5 sw icfcct3c 7 2feb;ipry))aifrom rest to 95 km/h in 6.2 s. What is its average accelep9 p6c*hfa c/tsyinb;f25 c )c3i b/b)yi7rweration in $m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0 m/s in 1.35 s. What i) .0r xkf4l4spq, cvy;i c:lcvs her acceleration0l4,yqkccrf.iv4cp)v : lx s;
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a p*fx(r r d92dycvsr6y:articular automobile is capable of an acceleration of about *f6c9:xysr(d rr y2vd$1.6 m/s^2$ 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.fi+6q m,//k wjqz4epfw( tfm .0 s. If it then brakes and comes to a stop in 4.0 s, what is its acceleration e/ipq6qm f f4/kwwm(+jt,fz. 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 ftvy/li/bbkjb 2sj m 3lds.d 85j1t)5car, which starts from rest at t = 0 and moves in a straight line, is given as a function of time in the fdb iybl3 5/1 s.8s)jjbfd mlt2tj5v/ kollowing 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 60vui lneip;04s 7 w:d2u(9vv0fw z lks.0 s. What was its acceleration? How far did it travel in this time? Assume constant accelerationwv7f29 vw0 l d0u4lsz su0;ie(:ivpnk.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 m. What wasa-sp51 nuhi e: its acceleration, ah nsa- e:1p5iussumed constant?    $m/s^2$

  A light plane must reach a speed of 33 m/s for takih/;um8 v3n8jhs ga+t eoff. How long a runway is needed if the (constant) ac j ugmh;a8h 3/8i+tsvnceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to ead (1f1cy 0nqyssentially top speed (of about 11.5 m/s) in the first 15.0 m of the race. What is the average acceleration of tfcq1an0(1yy dhis 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 froml2;tqe yr2 gy3bclawj:q 5.i, a speed of 12.0 m/s to rest in 6.00 s. How far did it travely:.ll32w2 gy5eq,c;rabjq i t in that time?    m

  In coming to a stop, a car37f0o;(,p m7gtk3 l cbkd l6rk5ggnl r leaves skid marks 92 m long on the highway. Assuming a deceleratik6573( grg lf0kgblcrm lok, 3nd; tp7on 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 e 8u452v1 d;ftl.wvsmxkevq0s nd of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average accele w4v 18ke ut0xm.l2ssqd;vf5 vration 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 95 km/h oi 9 zou+d0hc*yni. h3and human reaction time o hici.*y90on z +dh3uof 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 sxgd 0.*s/p f rhqs-l8, w):qk.j czkfa 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 one g )zr0)x:f-g 4hhdzy the highway. The car’s driver looks for an opportunity to pass, guessing thdg0r )z-ze 4 fg):hhxyat 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 10,000o h0z7((uvirlh/tiv 46 trpc(-m run in less than 30.0 min. After exactly 27.0 min, there are still4rupr vi7tzvc(/(h(6 i0 tlo h 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 kmmi 3um r 3m5y4,.vdqbi/h approaches an intersection just as the traffic light turns y5r 3mim qi4b3,y.vm udellow. 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. Her car’s maximum deceleration is $-5.8 m/s^2$ , whereas it can accelerate from 45 km/h to 65 km/h in 6.0 s. Ignore the length of her car and her reaction time.

  A stone is dropped from the top of a cliff. It hits the ground below after 34nf qz* k ycd)5nl qc/7yzxv:1.25 s. How high is the cliff? 5qc7nfv 1kxd*4z/y:zc qn yl)   m

  If a car rolls gently1ub*h phe 6,o6i2 (vyeshqrhg vy.(-u ($v_0\,=\,0$) 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 air with a r6: x3 *riwp9w7zxezwg639 rzp 0 o 6x/rdsvnfspeed 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 v)b0v v+ i:*ma. asylilwt zb*2ertically upward. With what speed did he throw it, and wh2v0 *v*:wytls .alz+ maibb)iat height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influen,i*zmugf*c k )ce of gravity. Draw graphs ofuc *,*kmf igz) (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 speed of 5.20 m/s. At a height of ,815;w-itvcj otajz7tha 0 sn125 m above a- n0jijhwt8st 1atv;z ,75cothe 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 =__ s

For an object falling freely 8a:n ihdozp( fmt rea ,vv6/.ll 69n7ofrom rest, show that the distance traveled during each successive second increases in the ratio 8l,vo a . 766fdh9rplnv onmi:az/(et of successive odd integers (1, 3, 5, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a isw-0c+ nl vjcpx; r/)ball thrown vertically upward with a /cs j-0xlnc)w+rvpi ;speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.

  A stone is thrown verticad-:oi4p 7ejcyv m :.jwsw,e5ally upward with a speed of 18.0 m/s
(a) How fast is it moving when it reaches a height of 11.0 m? |v| =    m/s
(b) How long is required to reach this height? t =    s,    s
(c) Why are there two answers to (b)?

  Estimate the time between eak8zxz z+f*-h0vobmm3 ch photoflash of the apple in Fig. 2–18 (or number of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint: Use two apple positions, but not the unclear ones at thezx3mzzv 8h 0m k-b*fo+ top.]
T =    s
   flashes per second

  A falling stone takes 0.28 s to travel past a window 2.2 m te7 )f1rfmxu/vall (Fig. 2–32). From what height above t)m1rxv7f /uef he top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound of it striking thcvndu 386nk8 kq,ss3ye ocean is heard 3.2 s later. If the speed of sound is 340 m/s , how high i 8vq,8 ndn3c kussy3k6s the cliff? H =    m

  Suppose you adjust your garden hose dso(q-1iqhn 7m/p9it)xzj7 m 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 pdm )jtim/i-q97hs7zq x1 on( away from the vertical, you hear the water striking the ground next to you for another 2.0 s. What is the water speed as it leaves the nozzle?    m/s

  A stone is thrown vertically upward with a speed of 12.0 m/s from thd 3-y0 .tpjt of 5zr;m:ufgb9ke edge of a cliff 70.0 m high (Fig. 2–34). zgj f;-ur y 5om: pfbt9kd.0t3
(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 upwzv 1.h * 2m. ahlfhipzl,lu5p:ard by a window 28 m above the street with a vertical speed m*lp .za., h:l1 hizvluhf5 p2of 13 m/s If the ball was thrown from the street,
(a) what was its initial speed,    m/s
(b) what altitude does it reach,    m
(c) when was it thrown,    s
(d) when does it reach the street again?    s

Figure 2–29 shows the velocity of a train as a fu6l(c 6ltg0-p ie*ms0fvrane * nction of time. (a) At what time was its velocity greatest? (b) During what periods, if a*- e*sp6lv f6( tclnri mg0e0any, 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 along6+ el g tqzuy5.ile.v+ a straight tunnel as a function of time is plotted in Fi.ez5q. +v+6eui yl ltgg. 2–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of automobile can accele gqngiqucnb9/9 ;b: w:v;tm c, tn4d0srate approximately as shown in the velocity94svgqqw ung d 0ntnit:c9c b, :;bm/;–time graph 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 acceleration of the car btg5 xy, 1lm,nin the previous Problem (Fig. 2–35) g tn,5l1bx,my when it is in
(a) first,    $m/s^2$
(b) third,    $m/s^2$
(c) fifth gear.    $m/s^2$
(d) What is its average acceleration through the first four gears?    $m/s^2$

  In Fig. 2–29, estimate thea3 en0sx*z n(e distance the object traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the object whose displacement as a function of l m1n h8 ko2b,wf3swmn+fnn 9(time is given by Fig. 2–2wkwo hn +n(8fmln3f sbmn,129 8.

Figure 2–36 is a position versus time graph for the motion of an object ml lty-d *((0z*(7juq tukyfdgq 8jpr:iv16s 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 z yfsdt8llyi *(u:qvg(k7r (-ju6*qdm0jtp1or 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 windowyi d 7ye c(n6zir5sf -9wv5h5vb5u*ka 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m before coming to rest, Fis neyf55r(6 b59kc5-di* zi vy7au vwhg. 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 gravityj dt1w r.;i3 i*bz;)kf ob4ugs on the Moon is about one-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go than it would on Earth, ass 4 g wur jbbkdso;1);*3iitzf.uming the same initial velocity?

  A person who is properly constrained by an over-the-shoulder seat belt has58b.rv6l7/w5 kf yhy zkn nk+ww gj(x1lld2;y a good chance od hl8r l.7+6k zk5 fybywyw;n(g 1wn/vl5kjx2f surviving a car collision if the deceleration does not exceed about 30 “g’s” $(1.0 g\,=\,9.8\,m/s^2)$. Assuming uniform deceleration of this value, calculate the distance over which the front end of the car must be designed to collapse if a crash brings the car to rest from 100 km/h . $\approx$    m(retain one decimal places)

  Agent Bond is standing on a bridge, 12 m asc2p-1jp q.bj;gl wyp2n 8b d,bove 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 pblwcpgdy,n; bs 2.1pq2j 8 -jbe when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufactur+xk:vxv dn xbjp9* u;)er tested its cars for front-end collisions by hauling them up on a crane and dropping them fr+* :xp bv xdvujnx9k);om 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 ab,w6ik sd 6 rbc+7jd.c x-d2zvsout $10^9\,km$ 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. Th8;/w;cxbtuf -do ,occe front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front of the/ofcx ;ocb8 t;u-d cw, 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 su )r-vre*o p9iirface into a deep pool. The person’s downward motion stops 2.0 m below the surface of the water. Estimate the average deceleration of tp)rvi ir*-o9 ehe 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 balance the:5 cnsrt(v hhx:gvfo +z /n05p average speet/5xspnvr +v:g5(: zo hc0 nfhd of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train 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;9ny,vd mej z-own 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 must it spot the pelican tnz9e ; y-,dvmjo escape? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is o uv+c9uf.c.v d2 a)kiplanned 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 a downhill lie. To see why, assume i.d .ofku9)v+cv cau2 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 tg2fbwbpm0 ck 5hgbf, 0 0.t:ju,h9rbcraveling at a constant speed of 6.0 m/s Just as an empty box car0bwbfcm9hfk.,bp 0 25u 0rj:c,gght b 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 -, f2.zb7yohtyof 6 epstone is dropped 1.50 s lb,z epo o76.yfyt2f -hater. How far apart are 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 cotsr: h,enbn n l1/8g8durse of a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . wha, th88n glbnen:sr /d1t average speed must be maintained for the last lap?    km/h

  A bicyclist in the Tour de Fraex9 yzck8z v+*lw7dr/nce crests a mountain pass as he moves at 18 km/h . At thz ze7* kcy8vwd9x/r+le bottom, 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 cmr) b wjck 6,6z*m-glx-mg4bfhild can bounce up one-and-a-half times higher than the smw4x l6mbz ck--jgfm,*b 6 g)recond child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1. k1 t2mbg6jyv3/oyf. b jv;ac(2gd/tg10-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 cajt gmd2b vo/j1y2tc3.yv bgg6/ak(;fr 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 bas.un*h5zkp (whtz2rgk kknxkm w +6- 25eball 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). Estimahk 5kmzww hxrgk.t +k*nz u22np56-(k te the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration 0gy:s53 ,i6tfz icjavof $3.2 m/s^2$ 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 inter57 i5og nu wq)znlbvy8f c,pk(4 ;txonp )pz:9section has a traffic signal, and the speed limit t w;5 p57oqnl9,z4pnop g 8yn)uk()if bzvx:cis 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn 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 sp9yd jmk7 1wx9-xii fzfe ,v*x1(4/s8rinro gfeeder 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 consimio- j8kwx*,fd/9ev r7 g41 fzrxfx9 1y(sintant 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 second stobtw n9.+37qwf5wjrpq ne is thrown straight down with an initial speed of 25.0 m/s and .fnt3+5 rb9qwpw qj w7the 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 at the same time. The firs ( .a*(c)avbs(ebeebxbby 8,8yety n8 t stone is thrown with an initial velocity of 11.0 m/s froa e b8b,e *ynx()bvyb8(aby ts8c(.e em a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thrown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a f82;bp-ml x 0plddc9x nree-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she w0d82bll d xx -np9cp;mill 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 co-ubecc fndqmd5;5 c 1 lpv,:k3nveyor belt to send the burgers through a grilling machine. If the grilling machine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, 5,n3 -cfcb u5dpd1lc;qk:emv what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vert/n hf 9wu.qcfl tc+1s6ically at a speed 1.5 times faster than Joe can. How many times higher will Bill’s ball go th+fwutcn9/1 q6ch.sfl an Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your frieoxc 5ruan0-,gi3c)v bnd 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-v 50 cog, )xicuabr3n speed with which your friend threw the ball?    m/s

  Two students are asked to find the height of a particfcbs 2+,cwy5n ular 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 in5 f2,yb+wcscts fall. One student reports a fall time of 2.0 s, and the other, 2.3 s. How much difference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position d i olj4rjdb-81xvddz1o9 .h-vs. time graph for two bicycles, A and B. (a) Is there any instant at which the two bicycles have the same velocrio-d j 1dd9l djv18o4zb.xh-ity? (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 higher average velocity?