Does a car speedometer measure speed, velocity, o5xb2ye+.hbvbjw ,0kk mljt x 1y6wl;3r both?

Can an object have a var:dvcdih5q 7s;w:dx5 cying speed if its velocity is constant? If yes, give exampcdq: 5vw; i5d 7hdsxc:les.

When an object moves with constant velocity, does its average velocity during pu8 kr9owr y,23s0iaeany time interval differ f8p93iwrs0ky 2ora,ue rom its instantaneous velocity at any instant?

In drag racing, is it possible for the car wit 0lxycl6te hf tbt1f+h4(-: n:fjx t1rh the greatest speed crossing the finisf0+:t 1bltx t-1x6nhy ef(h4tcjrfl: h line to lose the race? Explain.

If one object has a greater s85yrqn7 d;arw peed than a second object, does the first necessarily have a greater acceleration? Explain, ua q7;y8dr5rn wsing examples.

Compare the acceleration o:/qv yqe3u)6 dshl9dj gp s3m7f a motorcycle that accelerates from 80km/h to 90km/h with the acceleration3gyeu 6q:9 /pvsj dsq h3l7m)d of a bicycle that accelerates from rest to 10km/h in the same time.

Can an object have a northward velocity and a southward 0 5h kqri3,*yqv n*vfeacceleration? Explain.

Can the velocity of ann;9h 6ozg uof0 object be negative when its acceleration is positive? What gu ; hf069zonoabout vice versa?

Give an example where bd ; soeu xg-s;,3t (5jww(pucjoth the velocity and acceleration are negative.

Two cars emerge side by side from a tunnel. Car A is traveling with a speed of 64m ng) /)3rx,yev qkep0km/h and has an acceleration of 40km/h/min . Car B has a speed of 40 kmx/v epy3 rm4)) e,kgqn/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 qy/1*rp vu4yv)3ca fwhbc: 8sin speed as its acceleration decreases? If so, give an e)r*pc aqvbyc uw :vf/138s4hyxample. If not, explain.

A baseball player hits a foul t:, eb7kq a2ncball straight up into the air. It leaves the bat with aebk7n,c:aq t2 speed of 120km/h . In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?

As a freely falling object speeds up, what is happening c 3g-sci7rj;yto its acceleration due to gravity — does it increase, decrease, or stay tcy7;rsj3g c- ihe same?

How would you estimate the mag- 6 )msi8lm fp4qv3agximum height you could throw a ball vertically upward? How would you estimg 8mafl6v3m-g4is q) pate the maximum speed you could give it?

You travel from point A to point B in axvf9ja3(e)m a car moving at a constant speed of Then you travel the same distance from point B to anothervmfx(9a )3aje 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 vertical string with ten bol1 -3cc 1k3xz zt-ho93ba bagudts tied to it at equal intervals is dropped from the ceiling of the lecture halh3zbcx3z- ag31cab9uk d -o1t l. 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 constanoq8mt .3*o;e.wgfv b :nm,s ugt acceleration: a rock falling from a cliff, an elevator moving from the second floor to the fifth :om q uo;tfm., 3gbwnveg8. s*floor making stops along the way, a dish resting on a table?

An object that is thrown/x+ (iebeme ei(sjx5 + vertically upward will return to its original position with the same speed as it had initially(es exe ib5/x+e+m(ji if air resistance is negligible. If air resistance is appreciable, will this result be altered, and if so, how? [Hint: The acceleration due to air resistance is always in a direction opposite to the motion.]

Can an object have zero velocity and nonzero accelerat 2 amtd:luzr4q)i (. 2h/h*rax)kh rus5zo;l wion at the same time? Give ex )qxza2.uzt ;) r(5wdum*/kir2llah rh h4:osamples.

Can an object have zero acceleration and n0ldrqfwjn7 9 k+ 8ir9ponzero velocity at the same time? Give examplej7frwni09rld k8q p+9s.

Describe in words the motion plotted in Fig. 2–28 in terj9 4/ior4hpfmd 1lva7 ms of v, a, etc. [Hint: First try to duplicate the motion plotted by walking or moving your han a49fijdv/ o7l4rp1hmd.]

Describe in words the motion of the object graphed in bjva 5orgvt b490)f cdg i(c/-Fig. 2–29.

  What must be your car’s average speed in order to travel 235 km in 3w *t*4 )ciof5tule;md.25 h?    km/h

  A bird can fly 25 km/h How long does it take to fly 15 km?)k(6dtzwio / i    h

  If you are driving along a straight road and yjc)m n9bb 65tfou look to the side for 2.0 s, how far do you travel during this inattentive peribb5cn t m96f)jod?    m

  Convert 35 mi/h to 6c9 d98 ibgsgc
(a) km/h,    km/h
(b) m/s ,    m/s
(c) ft/s.    ft/s

  A rolling ball movese2 8svg(dfwj k11-u2,xy8riejnv 3 eg -th:km from $x_1$ = 3.4 cm to $x_2$ = -4.2 cm during the time from $t_1$ = 3.0 s to $t_2$ = 6.1 s What is its average velocity?    cm/s

  A particle at $t_1$ = -2.0 s is at $x_1$ = 3.4 cm and at $t_2$ = -4.5 s is at $x_2$ = 8.5 cm What is its average velocity? Can you calculate its average speed from these data?    cm/s

  You are driving home from school steadily at 95 km/h for 130 km.(. yfh4us hxf-4dpyg,3p eq3v It then begins to rain and you slow to 65 km/h You arrive home after driving 3 yshp43xu34fp( vf- dh eyq,.ghours 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 be ac ; rh187f,oq0ypfdwtween a lightning flash and the following thunder gives the distance to the flash in miles. Assuming that the flash of light arrives in essentiopf1qwdra87 0hfy ; c,ally 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 quarznkbq o5 d/c3 2lb95onter-mile track in a total time of 12.5 min. Calc z9 /q55dbn2n3lo ocbkulate
(a) the average speed    m/s
(b) the average velocity, in    m/s

  A horse canters away from its trainer in a straight line, my tkr1n,d)b -uil,)+ jlbv+n4le nii,oving 116 m away in 14.0 s. It then turns abruptly and gallops biy)ut +4,ii n,d1bkr+, levjl lnn)- halfway back in 4.8 s. Calculate
(a) its average speed    m/s
(b) its average velocity for the entire trip, using “away from the trainer” as the positive direction.    m/s

  Two locomotives approach each othveyr 5i5 (mbx4er on parallel tracks. 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 iev4bm(yx r55each other? (See Fig. 2–30).    min

  A car traveling 88 km/s0 d ttqb8c; qw 9r:,s40ysrbsb6y hw4h is 110 m behind a truck traveling How long will it takes y; rq,06 bshcbwrt089 4syq:b4 wdts the car to reach the truck?    s

  An airplane travels 3100 km at a speed of 790 km/h , and then e0v b6lvk,rc vo9f z6/qncounters a tailwind that boosts its speed to 990 vc/0qlfvob ,z69v6k rkm/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 aveg 64otx v)4htj:+5dttujq 1qurage velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h followed by a 1.0-hour lunch break, and the return 250 km is cg 6u) xjo4tvdtht:5 quqt14+jovered at 55 km/h.    km/h

  A bowling ball traveling with constant speed hiof2 gz ;w/h56hlninidmu.d qdw5(a, 6 ts the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.50 s after the ball is released from his hands. What is the speed of the ball? Thzwhwdgh. l6/mu6 i niqan( 5 2fd,;5ode speed of sound is 340 m/s.    m/s

  A sports car accelerates from rest to 95 km/h in 6.2 s. What is its averagea b cm (grlq5y.4 1l8uq- .k;k1vpfw+y+dbzqq accelerat 4lq-y.cqarq w1yl p v(+mk8kdb;qbz.gf5u+ 1ion in $m/s^2$ ?    $m/s^2$

  A sprinter acceleratei g 9 c/7oqvalqa:(;nqs from rest to 10.0 m/s in 1.35 s. What is her acceleration gq ;(/qov7qc ali a:9n
(a) in $m/s^2$ ,    $m/s^2$
(b) in $km/h^2$ ?    $km/h^2$

  At highway speeds, a particular*m5a9,h zt7 wyhxb,dp automobile is capable of an acceleration of aboua zmh7p*y9 h,x,dt5b wt $1.6 m/s^2$ 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 travelw4:1pvsa iix .ac8h9ys 110 m in 5.0 s. If it then brakes and comes to a stop in 4.0 s,x s9 a.waypic: iv814h what is its acceleration in $m/s^2$ ? Express the answer in terms of “g’s,” where 1.00 g = 9.80 $m/s^2$ .    $m/s^2$    g's

The position of a racing car, which starts from rest at t = 0 and moves in 1/7y4zee3rdrwr bt +ch1 d* xo7x1 4u sybh8hwa straight line, is given as a function of time in the following Table. Estimate (a) its velocity and (b) its acceleration as a functioneh /1d4x+317bs4 h7eh bwdrywu8 xot y1zr *cr of time. Display each in a Table and on a graph.

  A car accelerates from 13 m/s to 25 m/ss1s)szv f(5 km)zbi6l in 6.0 s. What was its acceleration? How far did it travel in th5)1bs z k)v 6s(imzsflis time? Assume constant acceleration.    $m/s^2$    m

  A car slows down from 23 mhgu*ni5n0dv q6)h*gr fx:de ;/s to rest in a distance of 85 m. What was its acceleration, assumed const*nd6g rdeh uih;0*:nq xv5g f)ant?    $m/s^2$

  A light plane must reach a speed ofjapha5f 1z.9 f 33 m/s for takeoff. How long a runway is needed if the h5apj.z1fa f9 (constant) acceleration is $3.0 m/s^2$ ?    m

  A world-class sprinter can burst out of the blocks to essentially top (aqz tt;s o,sppm +-:espeed (of about 11.5 m/s) in the fir:ptos -t smp,aq +e;z(st 15.0 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 12.0 m/s to rest in 6.00d t8g j0hao7gpyb3-v) 0y3lgf s. How far did it travel in that gba830 3gt7phog0 l yj)-ydfvtime?    m

  In coming to a stop, a car (vtrl 8zf3c -o hxgtt9q)ni;2leaves skid marks 92 m long on the highway. Assuming a deceleration vx zn ft-9r lg3)qhi2c8(t;ot 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 s vv1qjs/ o;yux6/+xstree. The front end of the car compresses and the driver comes to rest after traveling 0.80 m. What was the average acceleration of tu x s/ys v1;6+soqxjv/he 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 anm*6a2svn 8 onsd human reaction time of 1.0 s, for a* no8ss6n m2avn acceleration
(a) a = -4.0 $m/s^2$ ;    m
(b) a = -8.0 $m/s^2$    m

Show that the equationu ..b8yaqf0p7j6 xocn 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 nv-a; u*./qrzj5:t i0o die tjm/s on the highway. The car’s driver looks for an opportunity to pass, guessi0vzn/-j:quj5r ota eidit ;.*ng 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 lesat9u*-c579 1bo *hvlldf fx hws than 30.0 min. After exactly 27.0 min, there are still 1100 m to go. The runner mustfa 17vlxf t-9col9 h*5dbw*hu 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 as the o.zcgjk i g9:;n9j5 cwtraffic 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 th;k:.5w zc o9gc9ngjij e 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 clifg3a, 2;jr8b3b j 2f chd.swyo8tb)rrif. It hits the ground below after 3.25 s. How hf3b tjai2jcwd;) 8s 2orr.rb83yb h,gigh is the cliff?    m

  If a car rolls gently+x(-6hyb4z6z(kbb oa/ xwqcs ($v_0\,=\,0$) 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-+z 4el ejbnpx* hy3zu/ui-n7 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 thbq +;jy4x dha6 e,v.36pjqkbwrowing it vertically upward. With what speed dixhk6 p we+,djbvy 3.4 aq;q6jbd he throw it, and what height did it reach?    m/s (Round to the nearest integer)    m

An object starts from rest and falls undcm,uhbp g0eac/ cj(0ho1+vk0er the influence of gravity. Draw graphs of (a) its,a 0m10ecvcgh/bu ck j(o0+ ph 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 spef0 gb3acdhno: i5ct1+ed of 5.20 m/s. At a height of 125 m aboa0fcn+3h1cidotbg:5 ve 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 =__ s

For an object falling freely from rest, show that the distance kf4zke n6 a,n-traveled during each successive second increases in the ratio of successive odd integers (1, 3, 5nefkz k-a n6,4, etc.). This was first shown by Galileo. See Figs. 2–18 and 2–21.

If air resistance is neglected, show (algebrj aest12hb* 5iguq kqnf 950f6aically) that a ball thrown vertically upward wi n f95 g26hq0utqfasej ik*1b5th 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 u:tw5t1eu2ezbyqzeqpl 6glr+, / yv 39 pward 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 number on9uabknj zn3( +i8m ;tmwi3u*f photoflashes per second). Assume the+nmi3(injz *3 ; 9mu k8tawunb 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. 2–3v6c i v:*:-pv- zqgnch2). From whvh:c*gqn cvi- v-: zp6at height above the top of the window did the stone fall?    m

  A rock is dropped from a sea cliff, and the sv0.w* o3umy0qr etqv2ound of it striking the ocean is heard 3.2 s later. If the speed of soundrv q00u3t *mvwyoe q2. is 340 m/s , how high is the cliff? H =    m

  Suppose you adjust your garden hose nozzle fou8x ftnar)cpuu.,o fsww;9 v -oh,g3(r a hard stream of water. You point the nozzle vertically upward at a height of 1.5 m above the ground (Fig. 2–33). When you quickly move the nozzle away from the vertical, you hear the water strikingt)o,xag r8;fu,wvuc(u wo.-3fn h 9s p 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(; w 5uv:uqrtm the edge of a cliff 70.0 m high (Fig. 2–34).u uw:v(m;t 5qr
(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 t k06ub / -jnhlkpz5q,the street with a vertical speed of 13 m/s If the ball was thrownhl,nj5 ktu0 -q/6bpzk 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 of0epx0;o.zqm/h ff7 y,;f*tfr gvggg4)lc, r g a train as a function of time. (a) At what time was its velocity greatest? (b) During what fqg 0gg; f eo4xy0.g,ctrrp; zgv,hf7f* )m/lperiods, if any, was the velocity constant? (c) During what periods, if any, was the acceleration constant? (d) When was the magnitude of the acceleration greatest?

  The position of a rabbit along a straight tunnel as a function of ti 3z.grnt-ry dl5 tn68dme is plotted in Fig. 2–28. What is i6.rytg rd5 8lnz3d-ntts 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 acce6fq 6dcx, i , l:mkul(n21ppwjlerate approximately as shown in the velocity–time graph op 6:,dq2 ,xk jllfi6m 1wpncu(f 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 in the previous Pu1-4x+ hfidpn,fnw v9 roblem (Fig. 2–35) whev9f+uw 41ninxph-fd,n 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 traveled during stek4f 8y+5i-3cmg o m
(a) the first minute,   
(b) the second minute.    m

Construct the vs. t graph for the objec;z8 x eorrg(trke2(* pt whose displacement as a function of time is giveno 2egk (*8zxr(rp;ert by Fig. 2–28.

Figure 2–36 is a position versus time graph for thedn( jfp t1sa;8jc ;v:hlcgh0euf2cs0pt/ ;g- motion of an object along the x axis. Consider the time interval from A to B. (a) Is the object moving in the positive or negative direction? (b) Is the object speeding up or slowing down? (c) Is the acceleration of the object positive or negative? Now consider the time interval from D to E. (d) Is the obje2 aj01tvnh:8jc ;cf t psg- dp gl/(ch0f;es;uct 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 lmd m e 95qsv+z+b tk;-,xxw/ufirefighter’s safety net. The survivor stretches the net 1.0 m before coming to re+m5kd9 vb+q/,x-x ; mulzt wsest, Fig. 2–37.
(a) What was the average deceleration experienced by the survivor when she was slowed to rest by the net?    $m/s^2$
(b) What would you do to make it “safer” (that is, to generate a smaller deceleration): would you stiffen or loosen the net? Explain.  ----待选择----stiffen loosen 

The acceleration due to gravity on the Moon is about ozvp+3+ coiyf0ne-sixth what it is on Earth. If an object is thrown vertically upward on the Moon, how many times higher will it go tha iy+pcv+f0o3 zn it would on Earth, assuming the same initial velocity?

  A person who is properly constraineq(lu ikeainq/+vj1y 90 c8e)hd by an over-the-shoulder seat belt has a good chance of surviving a car collision if the kcl9 a1e/nij iu8+ h)(qeqv y0deceleration 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 bridgepjsa;)o -u wl0, 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 sl) oap-j;w0um 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 itw1p:l996vdjwak4n d fs cars for front-end collisions by hauling td9 6w :kfpa4 91wvjnldhem up on a crane and dropping them from a certain height.
(a) Show that the speed just before a car hits the ground, after falling from rest a vertical distance H, is given by $\sqrt{2gH}$ . What height corresponds to a collision at
(b) 60 km/h ? $\approx$    m (Round to the nearest integer)
(c) 100 km/h ? $\approx$    m (Round to the nearest integer)

  Every year the Earth travels 4 u8 /8*e)rpj jnjdodsabout $10^9\,km$ as it orbits the Sun. What is Earth’s average speed in km/h?    $ \times10^{ 5}\,km/h $

  A 95-m-long train begi ,;6kfl* a hnqc0lc1i-frhj1t ns uniform 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 of the train started. What will be the speed of the last car as it passes the worker? (See Fig. a 10thf;nkc 6- cq1rlfjl,* ih2–38.)    m/s

  A person jumps off a diving board 4.0 m above the water.rq)l),o / ig;rdmr(/fr6jybaba +0q qr y0hf’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 wh +)h0b l/yrji q)bfq;yr/g0r rraa, (f.qmdo6ile under the water. $\approx$    $m/s^2$ (Round to the nearest integer)

  In the design of a rapid transit system, it is necessarg9 opwla* 6 arsz;g4nh+6nvv -y to balance the average speed of a train against the distance between stops. The more stops there are, the slower the train’s average speed. To get an idea of this problem, calculate the time it takes a train to make a 9.096z4poga * +snh-g;vnlw 6v ra-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 m9sj5q .8rmnxand free fall straight down when diving for fish. Suppose a pelican starts its diqs 8.5m9 jrmnxve 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? Assume the fish is at the surface of the water.    m

  In putting, the force with which a golfer strikes a ball is planne8moo8io 1 gzr1d so that the ball will stop within some small distance of th18o8 i rozom1ge cup, say, 1.0 m long or short, in case the putt is missed. Accomplishing this from an uphill lie (that is, putting downhill, see Fig. 2–39) is more difficult than from a downhill lie. To see why, assume that on a particular green the ball decelerates constantly at $20 m/s^2$ going downhill, and constantly at $3.0 m/s^2$ going uphill. Suppose we have an uphill lie 7.0 m from the cup. Calculate the allowable range of initial velocities we may impart to the ball so that it stops in the range 1.0 m short to 1.0 m long of the cup.    m/s to    m/sDo the same for a downhill lie 7.0 m from the cup.    m/s to    m/sWhat in your results suggests that the downhill putt is more difficult?

  A fugitive tries to hop on yom pkghe;( ..a freight train traveling at a constant speed of 6.0 m/s Just as an empty box car passes him, theh. py.me ;ogk( fugitive starts from rest and accelerates at $a\,=\,4.0 m/s^2$ to his maximum speed of 8.0 m/s
(a) How long does it take him to catch up to the empty box car?    s
(b) What is the distance traveled to reach the box car?    m

  A stone is dropped from the roof of a high building. A second stone is dropped q 3arz1lynvj1/e o *0t1.50 s later. How far apart are the stones whe ve1jz1lryo0*3 a/qt nn 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 ew h;qdt3; 4,s hf/pzmof a time trial lasting ten laps. If the first nine laps were done at 198.0 km/h . what average speed must be maintained fordmz/3;,s w;efhh4t qp the last lap?    km/h

  A bicyclist in the Tour de France crests a mounnn dh ji93,dkgo98q:ntain pass as he moves at 18 km/h . At the bottom, 4.0 km farther, his speed is 75 km/h . What was his average acceleratioo,j3q9 g8:hdnd nkn9i n (in $m/s^2$) while riding down the mountain?    $m/s^2$

  Two children are playing on two trampoline8u ycz0l92envd8ba o +uy x1l5s. The first child can bounce up one-and-a-half times higher than the second childbv9 xanl1uy88lu d025 ycoe+z. 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 pu5b mt*b3dc:a 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 the res53tdc*mubb:p ults 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 o+rm(dr* jye 3 uyb(fr4f 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 thdry(e+uy43 rmr jb(f*e throwing motion.    $m/s^2$

  A rocket rises vertically, from rest, with an acceleration off ehd ah+gb(3cai 3tbk+q c5e ,)da.4e $3.2 m/s^2$ 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. E * rp2)zr)qn)qqnc;,p tpy4nbach intersection has a traffic signal, and the speed limit is 50 km/s . Suppose you are driving from the west at the speed limit. When you are 10 m from the first intersection, all the lights turn grez bq*t,;2)py nprrqpqc4n)n )en. 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 15nmzt i(:ix . v(pmgel8l+41pz: h bjb20 km/h takes off in hot pursuit. The police officer catches up to the speeder ib8+: l bm:zpvii(tl en. g1m5xz( pjh4n 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 buildbx,:l3m kc-m oing; 2.00 s after that, a second stone is thrown straight down with an initial speed ox,-mb :kc om3lf 25.0 m/s and the two stones land at the same time.
(a) How long did it take the first stone to reach the ground? $t_1$ =    s
(b) How high is the building?    m
(c) What are the speeds of the two stones just before they hit the ground? #1    m/s #2    m/s

  Two stones are thrown vertically up at the same time. The first stone is throw44q ,mvb5o ddpn with an initial velocity of 11.0 m/s from a 12th-floor balcony of a buildinp4dvd,4ob qm5g 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 resi h s2m zmt*2m1e*,xsqqstance, how long would it take a free-falling parachutist to fall from a plane at 3200 m to an altitude of 350 m, where she will pull her ripcord? q*h1xmmze m 2,s2qts* 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 burgersm+k sm2az)jy h()sp x m1+v,lv through a grilling machine. If the grilling m m1ypv ,)m 2has sx+k+zl)m(vjachine is 1.1 m long and the burgers require 2.5 min to cook, how fast must the conveyor belt travel? If the burgers are spaced 15 cm apart, what is the rate of burger production (in burgers/min)?
   m/min
   $\frac{burgers}{min}$

  Bill can throw a ball vertically at a speed 1.5 times fhh/woji5-x-i0r,kd(noo5m :xb j zh ,aster than Joe can. How many times higher will Bo0z(5jm: 5i -jhd i,x w nk/obh,-roxhill’s ball go than Joe’s? $\approx$ =    (retain one decimal places)

  You stand at the top of a cliff while your frien1l4s.qfl+xm n7i:8u ci- ai xnd stands on the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such that it just comes to rest in your hand. What is the speed with which y7. :+ clqlixfnixui1nmas4- 8 our friend threw the ball?    m/s

  Two students are asked to find the height o/3ej *ir zen 1(ualq6wf 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 difference does the 0.3 s make for the estimates of the building’s hnl(e 1jzqurwa e/*i 63eight?    m

Figure 2–43 shows the position vs. time graph for two bicycles, A and B. (a) Ir n6-;ckxz;kjvo)+iu k), zsys there any instant at which the two c-y )zkjkn6vr; );sxuzok+i ,bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicycle has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?