Does a car speedometer measure speli80 avxrpk+- ed, velocity, or both?

Can an object have a varying speed if its velocity is constantyf- ;( wp.agq )i(l1ps 3gubcharn7 w/? If yes, give exag) (w ;3sir7f(bwn uph1clq.- pyga a/mples.

When an object movesihyq q*ie0zq3 * j *6u,twx9pq with constant velocity, does its average velocity during any timeq*qy t,e3puz6iq* w90*hxjqi interval differ from its instantaneous velocity at any instant?

In drag racing, is it possible for the car with the greate )z wstj:.:hbpst speed crossing the .:bw:zstpj h) finish line to lose the race? Explain.

If one object has a greater speed than a second object, tqwe8s+) o4z.ukkz +adoes the first necessarily have a greater acceleration? Explain, using example)szwa.k 4+zkoqtu+8es.

Compare the acceleratioj (8(wkvlx +zkn of a motorcycle that accelerates from 80km/h to 90km/h with the acceleration of a bicyclev kk((xw8 j+zl that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southwarc;e1uz :h09 .mexonnht q.ph9d acceleration? Explain.

Can the velocity of an object be negative when its acceleration i2ehtc+ozyh4c.-p 9e cs positive? What about vice vcpech+. o24ceyzt-9h ersa?

Give an example where both thwamhqw 494( ;ocay d 4 fdr*;)xh3cluye velocity and acceleration are negative.

Two cars emerge side by side from a tunn54d* jck8nkhjm6 u1v xel. 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 the other as they co4kvmh*1kuj8n x5d6 cj me out of the tunnel? Explain your reasoning.

Can an object be increasing in speed as its acceleration decreases? If so, give qzmrn*0 wx-+ ,rh qt:q(+nuyg an exampmnyw r-rt z(u: * +0,n+hqqxqgle. If not, explain.

A baseball player hits a foul ball t8y0l;81;yzgovb+ ah nsxj*z straight up into the air. It leaves the bat with a speed of 120km/h . In the absence of air resista l0xogvsa +j tybh;z18; z*ny8nce, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speedumr)bvvg 7d x/ju-*4us up, what is happening to its acceleration due to gravity — does it increase, decrv x7u *v-j)mgrb/ du4uease, or stay the same?

How would you estimate the maximum height you could throw a ball vertically -si9hs* f;pyij5dr6y;o7v9x ,a j :ih lgs9ysupward? How wsso7ypis j,i* 5fyr;yh -9hg9:d6l ;9vxasijould you estimate the maximum speed you could give it?

You travel from point A to point B in a car moving at a constant speed o+pm.1zi p:lhdouezu9u7vm(zry* w3 *f Then you travel the same distance from pouzhlz1* uupmyd9r:vwpz. oi3m(7 *+eint 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-oyx9 /z26adsmn8l 9vh long vertical string with ten bolts tied to it at equal2x/8y9hvdml9s6azo n 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 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 constan guwrr-7 ,so2r v9:tqct acceleration: a rock falling from a cliff, an eles grt2rvu:,c- q9 orw7vator moving from the second floor to the fifth floor making stops along the way, a dish resting on a table?

An object that is thrown vertically upward will return to its original positio,jcjlh+r )o/an with the same speed as it had initially if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direcc), ohj+r/jla tion opposite to the motion.]

Can an object have zero velocity and nonzero accelerationl*wy01k ks- ek at the same time? Givew0k y*s1k- ekl examples.

Can an object have zero accehtl9w0 4q.bz /i lsi0uleration and nonzero velocity at the same time? Give 0z /qhb4 is.w90tlu ilexamples.

Describe in words the motion 8)-ded,vp d9ek r tf4knep 7u3plotted in Fig. 2–28 in terms of v, a, etc. [Hint: First try to duplica)dr3 t8u -7pv9f k4e,dndpekete the motion plotted by walking or moving your hand.]

Describe in words the motion of the object graphed in Fig. yfm*(q v,tu 5,ku4rcexzgh/:2–29.

  What must be your car’s ave;zx n;j8x2pbf b3ehpi 5 ./ssnrage speed in order to travel 235 km in 3.25 h?    km/h

  A bird can fly 25 km/h d9nwm6 hh/vim2yadl:j9.9mt How long does it take to fly 15 km?    h

  If you are driving along a straight road and you look to the side for 2.0 yg1 h1egj;*lss, how far do you travel duri1s* h1gy ge;ljng this inattentive period?    m

  Convert 35 mi/h to i.mj,jnak 03 x9 2o 0cdb.tj6+xyccmy
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball moves fromzaq9 v))zauio 1kc 848s) wdxg $x_1$ = 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 steadie 3l- nfdl ,imdk:b-7oly at 95 km/h for 130 km. It then begins to rain and you slow to 65 km/h You arrive n-bf 3l,dk i:md7loe- home after driving 3 hours and 20 minutes.
(a) How far is your hometown from school?    km
(b) What was your average speed?    km/h

  According to a rule-of-thumb, every five seconds between a lightning-nkczl* 8 had7tmtf .v7q07 pg flash and the following thunder gives the distance to the flash in miles.nf.hv-k78q7 a *7pl cmt0dz gt Assuming that the flash of light arrives in essentially no time at all, estimate the speed of sound in m/s from this rule.    m/s

  A person jogs eight complete laps around a quarter-mile track in a total tiym (isv+tmk , d,:6wjktr;;fime of 12.5 min;jv +fy:s;m wrtkikd(m6,,it. Calculate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, moving 11,4f m*0rws9bpd lmkk9 6 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.8 s. pkb9m 9k 4sfwl*m,0d rCalculate
(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 cacfnzgl42 xz1*; 6jztracks. 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)6;ajzczzln cg*f4x2 1.    min

  A car traveling 88 km/h is 110 m behind a truck trave*qku nnj-z0ywm ++.eyling How long will it take the car to rk *+qwm0 nny-eyz+j u.each the truck?    s

  An airplane travels 3100 km at a speed of wj/u09e8jqu *d 4tr l /xgv5 h8t(so5uyguoz 6790 km/h , and then encounters a tailwind that boosts its o6j/e d85vw*u/go0tx(s y 9 4rg uzh5qulu8jtspeed 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-trj .t:okfogle9:zf :6zip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, an l.::g:f oztoejfzk96d the return 250 km is covered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hits the pins at tudqz5o,x*g1darf ::zj d jg (nzo)b /)he 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 ball? The )gog/ q *:b juf5)z ,(zrxdda1dn:ojzspeed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. Whayap,mfg,da +6t is its average acceleration in + a6y,g,pd amf$m/s^2$ ?    $m/s^2$

  A sprinter accelerates from rest to 10.0xc4k+m*9 qn yw m/s in 1.35 s. What is her acceleration*wcq+k9xm 4ny
(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 acc ;0x vvt*.xtsceleration of abouts*.xvt0t;cx v $1.6 m/s^2$ 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 1 ) n1spi6tci/ xx5m4e.gc7spq10 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s, what is its aci nt)xm76ci54ep. gc/1qsp sxceleration 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,bl t* /hmgz5oeuo*a/6bl1 l1 iv( wtn moves in a straight line, is given as a function of time in the following o*/ 5wb1uti61balzn*he(/, vt l omlg 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 ityg o)5i8o 6 :olvwwpq8jd o20hs acceleration? How far did it travel in 2:dloovq8ohyp j)58ow wg60ithis time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 m/s to rest in a distance of 85 mlhd k7nllfc g..v+u.-. What was its acceleration, assumed const fklcg.ld n+lu-v.. h7ant?    $m/s^2$

  A light plane must reach a speed of 3c9l z8net0.si ;h,ji)le vo ,r3 m/s for takeoff. How long a runway is needed if the (constant) accele0sjrv.9eoeinl 8;,)t,lhi cz ration is $3.0 m/s^2$ ?    m

  A world-class sprinter tx6aabu 4e xj,d6x (l*can burst out of the blocks to essentially top speed (of about 11.5 m/s) in the first 1laa6b4xteu6x(,j * dx 5.0 m of the race. What is the average acceleration of this sprinter, and how long does it take her to reach that speed? $\approx$ =    $m/s^2$ (retain two decimal places)    s

  A car slows down uniformly from a speed of 125u.zg 4dl7l0dxr dq o2.0 m/s to rest in 6.00 s. How far did it travel in that time5ogrdz xl0d7u.ql4 d2?    m

  In coming to a stop, a car leaves skid markscv:2k fcs/sbxul70 r6 92 m long on the highway. Assuming a decellvr 0sub2k: x6c7c sf/eration of $7.00 m/s^2$ estimate the speed of the car just before braking.    m/s

  A car traveling 85 km/h st8+u 4rnbih0rprikes a tree. The front end of the car compresses and the driver comes tuipnh84 0r+rb o rest after traveling 0.80 m. What was the average acceleration of the driver during the collisi on? Express the answer in terms of “g’s,” where 1.00 g = 9.8 $m/s^2$ . =    $m/s^2$ (retain two decimal places )    g’s

  Determine the stopping distances for a car d)uj;m+1 qu vx61ztdmwith an initial speed of 95 km/h and human reaction time of 1.0 s, for an ad +zm;jut6v d1umq )1xcceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equationxj55m pw)wyi bs+8t k6xrux6. for the stopping distance of a car is $d_S\,=\,v_0t_R\,-\,{v_0}^2/(2a)$ , where $ v_0$ is the initial speed of the car, $ t_R $ is the driver’s reaction time, and a is the constant acceleration (and is negative).

A car is behind a truck going 25 m/s on the highway. The car’s drd7 apty69ek etg(uj6 .iver looks for an opportunity to pass, guessing that hi69ut.egt(76pjdky e as 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 64:e6 -:3 plnacqf n q3zxvlbsnkff2630.0 min. After exactly 27.0 min, there are sti63lcl:q3na 4vk n26 qbnf-6fpx f :eszll 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 aptwxe -w:91la e1h dz pf/c4ig)proaches an intersection just as the traffic light turns yellow. She knows that the yellow light lasts only 2.0 s before turning red, and she is 28 m away from the near side of the intersection (Fig. 2–31). Should she try to stop, or should she speed up to cross the intersection before the light turns red? The intersez4hpxet/li-ce9 wgad: )1fw1ction 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 3qqxf eizz)t2 e3ad9; :.25 s. How high is theixzd9zt f3:e)aqq ;2e cliff?    m

  If a car rolls gentlh+da3df1qp 46tj ,vtj y ($v_0\,=\,0$) 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 mgd10qyx q84yd )y/ jainto 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 throwing it vertically upward. With whatsf umtj 8z9nl.)3/u lp speed did he throw it, and what height did itl8ujlu )pz3/ 9.tsnfm reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls under the influence of gravity. xl2iwf)u(8 hjDraw graphs of (a) its speed and (b) the distance it has fallen 8(l ixhuj2)fw, 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 pz+zfx9uku ,3 a height of 125 m above the Earth, a zkf u x,zu93+ppackage 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 from rest, show that the dislcol * arfu2-2tance traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5, e*u2lc2ol-a rftc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebraically) that a bapf3m8w-z -hry ll thrown vertically upw-mh38rzfy - pward 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 vertical/6ap 7qtqltg2 ly 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 each photoflash of the apple in Fig. 2–18 (or numbeytv,n8n5 1q(bp e7zzsr of photoflashes per second). Assume the apple is about 10 cm in diameter. [Hint,nyz spbq5(78 n 1evtz: 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 aei mu,gl ng894 window 2.2 m tall (Fig. 2–32). From what height above the megui ,98n4lg top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sound oxo 2 5czkgg xk,xq05;of it striking the ocean is heard 3.2 s later. If the sxgcog,zk 52x50ok x q;peed of sound is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust y(jpyybrcu6 pp)a8l 1 ;our 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 the verticalal)8 1 p( p;yrup6jcby, 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 speedx*dd *6uz,jhs5h- fw t of 12.0 m/s from the edge of a cliff 70.0 ms* 5 zfu wh6tdh,j*x-d high (Fig. 2–34).
(a) How much later does it reach the bottom of the cliff? t =    s
(b) What is its speed just before hitting?    m/s
(c) What total distance did it travel?    m

  A baseball is seen to pass upward by a window 28 m above the streed vha4 s1f9gi:8e2sq yt with a vertical speed of 13 m/s Iffs8ea2i1vg h4: qs9dy 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 function of time. (a) At what,x ap:fac p8,djmy2au2no :3y time was its velocity greatest? (b) During what periods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the am2on3xpf8y:dpc j, uy a,:2aacceleration greatest?

  The position of a rabbit along a straight tunnel as a function of time if,2nxmk+ja g0s plotte+n g,mj02 kfaxd in Fig. 2–28. What is its instantaneous velocity
(a) at t = 10.0 s    m/
(b) at t = 30.0 s What is its average velocity    m/s
(c) between t = 0 and t = 5.0 s    m/s
(d) between t = 25.0 s and t = 30.0 s    m/s
(e) between t = 40.0 s and t = 50.0 s ?    m/s

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

  A certain type of autom2nsptobx2 xzn j 476y9obile can accelerate approximately as shown in the velocity–time graph of Fig. 2–35. (The shosbj74x2z 9tnxyp o6n2rt 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 in the previoui6b qf27 oczmp(kh(.,qg)k z ps Problem (Fig. 2–35) when it is in)mq .7k z,pqhkc2 pb(ogi6(fz
(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 obcl ;5a- 4yev miq+vcs+ject traveled during
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph gw)3n cfu28fh3apwt/ for the object whose displacement as a function of time is given by Fiffhc38p w2wugt na )/3g. 2–28.

Figure 2–36 is a position versus time graph389fom-*v tdx9 thrr q for the motion of an object along the x axis. Consider the time interval from A to B. (a) Is the obje99tr -3hrtf mxd* ov8qct 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 from C to D.

  A person jumps from a fourth-story wil 5)b afw1pw-indow 15.0 m above a firefighter’s safety net. The survivor stretches the net 1.0 m beww f-lb)a5pi1fore 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 ton13 thajo+i6o gravity on the Moon is about one-sixth what it is on Earth. If an object is throw j too+n6ia13hn vertically upward on the Moon, how many times higher will it go than it would on Earth, assuming the same initial velocity?

  A person who is properly+ 9kmok9 7o8glw rz/uv constrained by an over-the-shoulder seat belt has a good chance of surviving a car collision if the deceleration does not l7k+r zvok/g 8 99mouwexceed 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 bridg +o/n+xa(7ib 81,e rgs sk bvww1zegd4e, 12 m above the road below, and his pursuers are getting too close for comfo87x1esg boigsn(/bwdk a wr1++e4,zvrt. He spots a flatbed truck approaching at 25 m/s , which he measures by knowing that the telephone poles the truck is passing are 25 m apart in this country. The bed of the truck is 1.5 m above the road, and Bond quickly calculates how many poles away the truck should be when he jumps down from the bridge onto the truck to make his getaway. How many poles is it?    poles

  Suppose a car manufacturer tested its cae37dq mqk6mq4 rs for front-end collisions by hauling them up on a crane and dropping them from am dk me47q6qq3 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 travel;am1gk -3 ymig9d-5yc )kqceks 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 unifort xw0 *tt.86nqi:ivnzm acceleration from rest. The front of the train has a speed of 25 m/s when it passes a railway worker who is standing 180 m from where the front o*xnvn 6:08 q iwtztt.if 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 1jh3+ c)y lvcrboard 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 average deceleration of the person whilehrcl )jy+v1c3 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 ave *o0 mh4mqmbem/b(p5 drage speed of a train agq mh05 bbm4dp/e( m*moainst 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 down when diving for 1*7o b*o fior *; pxllc0 we38ilm)srofish. 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 to escape? Assu3; p1m io 7cwsoxelib r*0 f*l8rl*oo)me the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikesme5.ae(jlqcjyv6q+ 2 a ball is planned so that the ball will stop within some small distance of the cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particularj( .jae6q v e+qy52mcl green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on a freight train traveling n:6 :tr)qbxr9ri8ogk at a constant speed of 6.0 m/s Just as an empty box car passes him, theok ):rtgirbq6: r89x n 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 1wjg p.qv j/j8building. A second stone is dropped 1.50 s later. How far apart /.vwj81pqg jj 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 course of a time triargq4-unek;6avw 3 6 col lasting ten lv66go q- wunk e34;acraps. 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 crests a mountain pass as he moves at 1jmrd4z ;qb/s rxn;lm k a6,w;wm (;qd.8 km/h . At the bottom, 4.0 km farther,x d/rqm;k; wrnzm4dl,ma( q6;;.w jbs 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 tj l2s-h2k810taa an ra.)nfuwrampolines. The first child can bounce up one-and-a-half times higher than thw18sn2a k2a.f0hl)tr ajnua -e second child. The initial speed up of the second child is $5.0 m/s $.
(a) Find the maximum height the second child reaches. $\approx$    m(retain one decimal places)
(b) What is the initial speed of the first child? $\approx$    m/s(retain one decimal places)
(c) How long was the first child in the air?    s

  An automobile traveling 95 km/h overtakes a 1.10, hj(/z q0;wmo o -/bpd4fxdco-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.x ojwh(omoz/qdf/bd 4cp ,-0; 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 o3q)es0a q*11 5mjnn4sr,yox -wx awc44 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. 2–1xa,)ec 10m5* q3osonwqn r y4 -xasjw41). Estimate the average acceleration of the ball during the throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with -:u hfy0u;wfqjce p9 2an 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. 1 ;e1isxc aiai-2 1tvqEach intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are d-e1xa ta1vqii ;2c1s iriving 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 speeder traveling at a constant 120 km/h3 pmf;b3q89ri 7zdl4wx df)um takes off in hot pursuit. The police officer catches up to the speeder in 750 m, maintaining a constant mf 7l; m3)u3zwb8q4f dxid9rp 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, 54;v1brcn,*9dthxisvbme c)0mi*qf .qupz 7a second stone is thrown straight down with an initial speed of 25.0 m/s 9c 5vi)ux b.;,qi 701df*c mbpv*4s qnrhetzmand 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 at the same time. The fi+ sbtxr5u wgi16cxugl6v:6w /rst stone is thrown with an initial velocity of 11.0 m/s from a 12th-floor balcony of a building and hits the ground after 4.5 s. With what initial velocity should the second stone be thr5/16xt+6 ggu6 :bscuiwxvl rwown from a $4^{th}$-floor balcony so that it hits the ground at the same time as the first stone? Make simple assumptions, like equal-height floors.    m/s

  If there were no air resistance, how long would it take a free-falling parq2,pk d dal:z9achutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? What would her speed be at 350 m? (In reality, the air resis9 dla, q:pk2zdtance will restrict her speed to perhaps 150 km/h .)
   s
   km/h

  A fast-food restauran,k 5muf(p5-y wgydp g,t uses a conveyor 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 ud(mwk5 f,pp- 5yg gy,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 ealr-.jg9 xg7 xnf1 0lvertically at a speed 1.5 times faster than Joe can. How many times higher nl.rfx-9x0g1g aej7lwill Bill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your friend soqes378i bx 0ztands 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 7obsz q38iex 0the speed with which your friend threw the ball?    m/s

  Two students are asked to finda-kp6mmv 3gsgs598 ej the height 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 j3gms6ke - 9 m8svpa5gdifference does the 0.3 s make for the estimates of the building’s height?    m

Figure 2–43 shows the position/ia2b5hyp )( gsnn3my9;el.jsf zm 7c 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 9bfh2nicejmnp.ly a/s;s my 5z)7g3(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?