Suppose that an object travels from one point8rhsiq x eg-su)4m(s5 in space to another. Make a comparison between the displacement and the g8 rssie 5u h)-x4qsm(distance traveled.

  When is the average velocity of an object e)f 7vmxx7(qpibd9j i8qual to the instantaneous velocity?

  A new car manufacturer advertises that their car can g clv+/ j,b yv)ng m2euz/*er5qo "from zero to sixty in 8 s". This gvq2em )l,5b/uv+*ycr zj /enis a description of

  An object moving in the +x axis experienvn)jp5d6f r f2ces an acceleration of $2.0 \; m/s^2$. This means the object is

  Suppose that a car traveling to the East (+x direct. hd;ki et( jvo9smt 08bzz1j)ion) begins to slow down as it approaches a traffic light. 1)9ob hziszv8t(jjd;m 0k.e t Make a statement concerning its acceleration.

  Suppose that a car traveling to t+*f)s9jhc7p u ji q.:iu* 3qr6 kqrhov d-pcu0he West (-x direction) begins to slow down as it approaches a .vdup+6-k o)q09 jh7 ccqiju3rfsqihu:p *r* traffic light. Make a statement concerning its acceleration.

  Suppose that an object is moving with a constant velocity. Make a stat4d2ebchlk sl-j 2ec,3 ement concerning its accelera4 3ld 2 bcjksch2-lee,tion.

  If the velocity of an object is zero+d m2 pijie/*c, does it mean that the acceleration is zero? Support y+jd*me2 pi/icour answer with an example.

  Can an object's velocity change direction when its accel(mn.d zc6at.fs6eyvqu2:/qw eration is constant? Support yourc2 /v:zm.qany6. tw qfu6e s(d answer with an example.

  Suppose that an object is 4bl. ie,xcci* u ahq06moving with constant acceleration. Make a statement cob .qc4lch 6 x*aei0u,incerning its motion with respect to time.

  Can an object have increasing speed while its accelerl9mko* unh;,f ation is decreasing? Support youo l9m;h f*,knur answer with an example.

  Suppose a can, after an initial kick, moves up along a smoothg:j jf/wkcty6iha(.9;k rby/ hill of ice. Make a statement concerning its accelera.:kw(6 c yrh;/iyt9jbfj/ kgation.

  Under what condition is average velocity equal to7weqc)8cs0 j f the average of the object's initial and final vwq cj087 e)csfelocity?

  Objects A and B both start at rest. They both accelerate 1kb6 bwb ds 3fnu -c,cuwl80.xat the same rate. However, object A accelerates for s06ck,nb -8ubu w31d.f cwlxbtwice the time as object B. What is the final speed of object A compared to that of object B?

  Objects A and B both start from rest. They buy;gaq+ y14/f qwq zu*oth accelerate at the same rate. How;q+zy/1f quq4w*gy auever, object A accelerates for twice the time as object B. What is the distance traveled by object A compared to that of object B?

  When an object is rel53/ip ikpkht :eased from rest and falls in the absence of friction, which of the following is true concerning itski hki:/ 53tpp motion?

  When an object is released from rest and fga9txt k51 y:x4jud(l)z e9n halls in the absence of friction, which of the followinge )z:( 4xj9kttn gyh9x ald5u1 is true concerning its motion?

  Suppose a ball is thrown straight up. Make a statement f+l j/z(ca,a rfy*j;pabout the velocity and the acceleration when the ball reaches the hyaj(z;jarp /,f+*l cf ighest point.

  Suppose a ball is thrown ,+(bqml-a6jylwfp.c5caro jc m: *1bstraight up. What is its acceleration just before it reaches ib 1f:cm+,ao. q 6-5arp* ccl(wm bjjylts highest point?

  Suppose a ball is thrown straighgd .0:z;o9jppegik4lt up, reaches a maximum height, then falls to its inep zo kgg4.:pdj90i;litial height. Make a statement about the direction of the velocity and acceleration as the ball is going up.

  A ball is thrown straight u)doko.8oz y+dp, reaches a maximum height, then falls to its initial height. Make a statement about the direction of the velocity and acceleration as the ball is com+)z okd.dy8oo ing down.

  Suppose a ball is thrown downward :cn9-x in sa31r mdtxlr 8-ir8in the absence of air resistance. Make a statement concern r8dn38 -9axrmlinx1si- c:tring its acceleration.

  Suppose a skydiver jui/5 g3uifa rqdwt3) ql iz483c/w: hbmmps from a high-flying plane. What is her acceleration when she she reaches ter8fm:r4wu5itzic d3 /b3qagw /liq) 3hminal velocity?

  A ball is thrown vertically upward with a speed v. An identical second ballz dg .*7buzazua25kv1 is thrown upward with a speed 2v (twice as fast). What is t2z*.zbda5 v1k z7uugahe ratio of the maximum height of the second ball to that of the first ball? (How many times higher does the second ball go than the first ball?)

  Ball A is dropped from the top of a building. One second late+nue:,c.yy xjh h4+ epr, ball B is dropped from the same building. As time progresses, the disy+c . xey+hen4:pjh u,tance between them

  Ball A is dropped from the top1)mrtsi mgn lr8 ln*14 of a building. One second later, ball B is dropped from the same building. As time progresses, the difference in their speel1nn)sgr1imlm r4*8tds

  Two objects are thrown faoyqq p49t6v ,j(an hi57- bkkrom the top of a tall building. One is thrown up, and the other ,anika-q65h( j7ktpo9 4bvy qis thrown down, both with the same initial speed. What are their speeds when they hit the street?

  A brick is dropped from the top of a builu86ntx7q b0 jc4*uquyding. A second brick is thrown straight down from the same building. They are released at the same time. Neglect air resistance. Compare the accelerations onyx7 uq q4u0jt*u cb68f the two bricks.

  An object is moving with constanty+3,lr sqiet-8lu 4c f non-zero velocity in the +x axis. The position versus timrlfyc i-t,+ q3use 84le graph of this object is

  An object is moving with constant non-zero accelrtpl1q7p+b5l,l 2 wvceration in the +x axis. The position versus time grap+tlb2 r 7pl1pw,cvlq5h of this object is

  An object is moving with constant non-zero velocity in the +x ax;q g u)s1e-ase2n qpn kh.upwgdj8* (+is. The velocity versusppgq u8as *d);sw1+g(neq h2 jeu-kn. time graph of this object is

  An object is moving with constant non-zero accelera;d6weuufmn 57 tion in the +x axis. The velocity versus time graph of this object i6u ;fwuendm75 s

  The slope of a position velw o: zd5r/kq/vx5r0 yrsus time graph gives

  The slope of a velocity vn ;,egi1afi5 qersus time graph gives

  The area under a curve in an z 3lz5 w(y0ol8;ls s9yrn:jybi.fx)t acceleration versus time graph gives

  The area under a curve in a velocity versus time 9qm8 :d-i )ctlw8++rnjfj savhv2 xme5,zra)graph gives

  If the position versus time graph of an object is a hob kfjfp p;f(gr s03-7xrizontal line, the object ir-s3g7bfp k0(f ;xfpjs

  If the position versus time graph of an oba8d7r oxvtd )9ject is a vertical line, the object isto)9 vdx8ard7

  If the velocity versus time graph of an objemdlphisva: (di*g7 ke4x44 c 4ct is a horizontal line, the object isah4 id44vg *i(p:d k7xs4mce l

  If the velocity versus time graph of an object is a straik:e r* /qm4grxght line making an angle of 30 d mr rgqkex*/:4egrees with the time axis, the object is

  An object moves 15.0 m north and then 11.0 m south. ) nym bu5wrme :0r*a-yFind both the distance traveled and the magnitude of m*r5erub:w m0a)yyn -the displacement vector.

  A boat can move at 30 km/h in still water. How long will iteddnt20 /ap g6 take to move 12 km upstream 6apt dgend02/in a river flowing 6.0 km/h?

  55 mi/h is how many j . ca,28n47p;(vekk rqdyvibm/s? (1 mi = 1609 m)

  What must be your average speed in 8h .xw39, kjzflpweep)gx8tww, tw 76order to travel 350 km in 5.15 h?

  A runner ran the marw+wk2(gp -t frathon (approximately 42.0 km) in 2 hours and 57 min. What is the average speed of the rt2+ rkw-gfpw (unner in m/s?

  A car travels 90 km/h. How long dme x za3/) 0u 6ojfhbwwg,-mm/k1 +hgcoes it take for it to travel 400 km?

  A ly (light year) is. f my+v ;ob8til8hl-jd1jooub 4q90 b the distance that light travels in one year. The speed of lightyb-to .1hvl;qf0 4ldbjubmi+ 9jo8o8 is $3.00 \times 10^8 \; m/s$. How many miles are there in a light year? (1 mi = 1609 m, 1 yr = 365 d.)

  If you are driving 72 km/h a a(1fy*fiv y.hbw-t 9f1ec+xulong a straight road and you look to the side for 4.0 s, how far do you travel during this inattentive periu yvw*1(+byfae ff1h-9. xcti od?

  If you run a complete loop around an outdoor track (400,av hab9khu x(wh-3:j m), in 100 s, your avera-w :kv9x aujha,h 3bh(ge velocity is

  A polar bear starts at /moq/en 3v9+kspvx0 0kghs2lthe North Pole. It travels 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km west to return to its starting point. This trip takes 45 min. What was the bear's averahp2mn x3 9v/sog+ 0ke0s lkqv/ge speed?

  A polar bear starts at the Northx5on6ru w: yb1 Pole. It travels 1.0 km south, then 1.0 km east, then 1.0 km north, then 1.0 km won1 rxyb6w5 u:est to return to its starting point. This trip takes 45 min. What was the bear's average velocity?

  You are driving home on a weekend from school at 55 m ujtu2d.xv 2s82q ggx-i/h for 110 miles. It then starts to snow v2dut22g ug.-sxq x8jand you slow to 35 mi/h. You arrive home after driving 4 hours and 15 minutes. How far is your hometown from school?

  A motorist travels 160 km a9iiizx5j (ro z,//buf t 80 km/h and 160 km at 100 km/h. What is the average speed of thfz z/b, uo(ixi/j 9r5ie motorist for this trip?

  A motorist travels for 3.0 h at 80 km/6mj7nvk az m ab(zdmne .e10./h and 2.0 h at 100 km/h. What is her average speed for the tripae(v.m /.nz0 z1makn6me7bdj ?

  An airplane travels at 300 mi/h south for 2.00 h and then at 250 mi/h north fo:l1a5jw8fgb ty a fqmun89/ v-r 750 miles. What is the average speed for abfyfaq w ul95:gv88m -1tn/jthe trip?

  In a 400-m relay raceija,o prw 79;z the anchorman (the person who runs the last 100 m) for team A can run 100 m in 9.8 s. His rival, the anchorman for team B, can cover 100 m in 10.1 s. What is the largest lead the team B runner joa7 pw9,; irzcan have when the team A runner starts the final leg of the race, in order that the team A runner not lose the race?

  A car decelerates uniformly and comes to a stop after 13 s. The car's ave4har+w 9-g6auqs54*f g2k x oq4e fdrsrage velocity during deceleration wa f2ow rqu-45 *rah4d+ xa9gqkg4 ssf6es 35 km/h. What was the car's deceleration while slowing down?

  An airplane increases its s ut*eu4rf-k/v*9 qka*pt vc/f peed from 100 m/s to 160 m/s, at the average rate of k/* -fe q4ru/a*v9upt vfkct*$15 \; m/s^2$. How much time does it take for the complete increase in speed?

  A car traveling 60 km/h accelerates at the rk6 s7p.vqhkthyr :6n-pq.3dy toy 7m5ate of $2.0 \; m/s^2$. How much time is required for the car to reach a speed of 90 km/h?

  A cart starts from re z0se p+/kml.vybw;)gst and accelerates at $4.0 \; m/s^2$ for 5.0 s, then maintain that velocity for 10 s, and then decelerates at the rate of $2.0 \; m/s^2$ for 4.0 s. What is the final speed of the car?

  A car travels at 15 m/s for 10 s. It then speeds up with a constanlr 6qou3t; .vit acceleration ivtl6; r.q3uo of $2.0 \; m/s^2$ for 15 s. At the end of this time, what is its velocity?

  A cart with an initial velocity of 3.4 m/s experiences +dmuuafuf6in2kx7i3 :g(,l g a constant acceleration of 3xfn,iug:uk7d6+(f2lmiag u$2.2 \; m/s^2$. What is the cart's displacement during the first 9.0 s of its motion?

  A bullet moving horizontally to the right (+x direction) with a speed w 8leo7dz2, cw;9q4b ha9mnlmof 516 m/s strikes a sandbag and penetrates a distance of 59.06 cm. What is the av w98me b;o,cl49z hla27wq dmnerage acceleration, in $m/s^2$, of the bullet?

  A jet fighter plane is launched from a on1p58 jnr6bvcatapult on an aircraft carrier. It reaches a speed of 42 m/s at the end of the catapult, and th6p8bn1 norj5 vis requires 2.0 s. Assuming the acceleration is constant, what is the length of the catapult?

  A car starting from rest moves with constant accelera1,h /iqw vbu2nxj,jj8/ +tb o9bq7gwution of $2.0 \; m/s^2$ for 10 s, then travels with constant speed for another 10 s, and then finally slows to a stop with constant acceleration of
-$2.0 \; m/s^2$. How far does it travel?

  A car goes from 40 m/s to 80 mq(39pzg7fdmznb 0f0x1cf m s2/s in a distance of 200 m. What is its average accelermsfgcz2z37(qfxn0p fbm 910 dation?

  An object starts from rest and *d2n s3ifdtn n0c1:afwg7-yw v.z.4b*w blyjundergoes uniform acceleration. During the first second it travels 7.0 m. How far will it travel during the th*d nwy4ya gwb7tvil-3.02 f.wfjn zs*1cbdn :ird second?

  An object is moving in a straight line wix a x9w4p4wfe5fcmm )/th constant acceleration. Initially it is traveling at 16 m/s. Three seconds later it is trave4 x9x5 4/ecf )pamwmwfling at 10 m/s. How far does it move during this time?

  A car starts from rest and8 h1lh8fjzkpi t -3)vr accelerates uniformly at $3.0 \; m/s^2$. A second car starts from rest 6.0 s later at the same point and accelerates uniformly at $5.0 \; m/s^2$. How long does it take the second car to overtake the first car?

  A car with good tires on a dry ro09+en 4otizsuad can decelerate at about $5.0 \; m/s^2$ when braking. Suppose a car is initially traveling at 55 mi/h.
(a.) How much time does it take the car to stop?    $s$ (only input numerical values)
(b.) What is the stopping distance?    $m$ ((only input numerical values)

  At the instant a trad ;svksf ol*j0z, ,)9r+ gnvlcffic light turns green, a car that has been waiting at the intersection starts ahead with a csz0vr;lg9 njs kfv,+ )od,lc*onstant acceleration of $2.00 \; m/s^2$. At that moment a truck traveling with a constant velocity of 15.0 m/s overtakes and passes the car.
(a.) Calculate the time necessary for the car to reach the truck.    $s$ (only fill in numerical values)
(b.) Calculate the distance beyond the traffic light that the car will pass the truck.    $m$ (only fill in numerical values)
(c.) Determine the speed of the car when it passes the truck.    $m/s$ (only fill in numerical values)

  An object is thrown upward with a speed of 12 m/ -t, mt a4;9gkzw5gmvcs on the surface of planet X wherea-;5tmcvtgm4,kz 9wg the acceleration due to gravity is $1.5 \; m/s^2$. What is the maximum height reached by the object?

  An object is thrown upward with a speed of 12 m/s on the surfacehwq+d +vi0/ v).kapt e of planet X where the acceleration dki/ )p +a.vhvd 0tqe+wue to gravity is $1.5 \; m/s^2$. How long does it take for the object to reach the maximum height?

  An object is thrown upward with a speed of 15 m/s on the surfacv/2xjxtkz90ux 21 *inoy5e hje of planet X where the acceleration due to gr1u0 j h2 kt5yixxo2n9/ejvzx *avity is $2.5 \; m/s^2$. How long does it take for the object to return to where it is thrown?

  An object is thrown upward with a speed of tb8bikp- 37 xu14 m/s on the surface of planet X where the acceleration due to gravity xi3bbtk- 7up8is $3.5 \; m/s^2$. What is the speed of the object after 8.0 s?

  Human reaction time is usually greater than (+r3rku.+b x3xzrqj odfd l /50.10 s. If your friend holds a ruler between your fingers and releases it without warning, how d x/b33o+5k+x(ujz .qrrdfl rfar can you expect the ruler to fall before you catch it?

  A ball is thrown upward at a velocit ;yzozf+vo3x)y of 19.6 m/s. What is its velocity after 3.00 zx+ )y;3ov zfos?

  A bullet shot straight up returns to its starting point s hdbk 4n/)*(lvhvd 0zzz6 xd-in 20 s. What is the initial speedh4s kl h(d xz)0z*vznd/-v6b d of the bullet?

  A ball is thrown straight up with a speed of 3 vh si).dx+-hg6.0 m/s. How long does it take to return to i+ -.ihsdxh)vgts starting point?

  A ball is thrown downward from the top /v9a bns b:89w7na diiof a building with an initial speed of 27 m/s. It strikes the groudibs9v 98wa/:ab7n nind after 4.0 s. How high is the building?

  A ball is thrown straightgid vhjz01sm-d 84 e1z up with a speed of 30 m/s. (only fill in numerical value in thh zvi81ddegz0 -s14 jme blanks)
(a.) How long does it take the ball to reach the maximum height?    $s$
(b.) What is the maximum height reached by the ball?    $m$
(c.) What is its speed after 4.2 s?    $m/s$

  A foul ball is hit straight up into the air with a speed of 47.0 m/ 75jy-b7k 7tg3yjd tqr.5 l5uwqu mfl7s. (use $g=10 \; m/s^2$, only fill in numerical value in the blank)
(a.) Calculate the time required for the ball to rise to its maximum height.  (数值)  $s$
(b.) Calculate the time for the ball to fall back to the height at which it was hit.  (数值)  $s$
(c.) Calculate the maximum height reached by the ball.  (数值)  $m$
(d.) Calculate the ball's speed 2 seconds later.  (数值)  $m/s$
(e.) Determine the time at which the ball pass a point 8 m above the point of contact between the bat and ball for the first time.  (数值)  $s$
(f.) Determine the time at which the ball pass a point 8.0 m above the point of contact a second time.  (数值)  $s$

  In Fig. below, what is the velo hew6-t0+inxbrljx2k -4;g4 du rz,bicity at t = 1.0 s?

  In Fig. below, what is the velocite4jt r*qur g5l6 c;e1ny at t = 2.5 s?

  In Fig. below, what is the(jc 4na3 q;hlg velocity at t = 4.0 s?

  In Fig. below, what is tkmw 2.4 4 by,fm1hcxtthe velocity at t = 5.5 s?

  In Fig. below, what is the average*j1:fp 7y; xww+iw) mvt,pkbt velocity from 0 to 4.0 s?

  In Fig. below, what is tynzhd dt6w (t/s+ gc z04hum/6he average velocity from 0 to 6.0 s?

  In Fig. below, what isd/t4++,fhw 2hxfrqrq rn)s 2z the acceleration at 1.0 s?

  In Fig. below, what is the acceleration at 3.0 s:gcxivpa+ d3dh9no(whp3 .s:?

  In Fig. below, what is the average accec m8kren9g m6om,; z*ileration from 0 to 5.0 s?

  In Fig. below, what is the aua 9jcm-u* :rl n30qlcverage acceleration from 0 to 8.0 s?

  In Fig. below, what is the displacement from 0 tkroyk0hr9sk)+sx(3 /ku (; s p+wjva bo 8.0 s?

Does a car speedometer measure speed, velocity? {sp.wo9ja(s kt m(eed|velocity}

  An object can have a varying speed if its velocity is c i6do ii:l/l1c* uknt/onstant.

  The velocity of an obktkzf;r;fh4bqg3gq 5(l2vkql *62 ee5y;pza ject can be negative when its acceleration is positive.

  If one object has a greater speed than a second object, t5fdpscj:ie/ *8p/ mouoj( uz +he first must have a greater acceleratozoci:/f/ u*p5esp( +jdmj8uion.

  Two cars emerge side by side from a tunn2r 3bit.h.hxsel. Car A is traveling with a speed of $60 \; km/h$ and has an acceleration of $40 \; km/h/min$ Car B has a speed of $40 \; km/h$ and has an acceleration of $60 \; km/h/min$ . Can A will pass car B at the instant they come out of the tunnel.

  An object can be increasingviz*n(mq1 drdrx .b,. in speed as its acceleration decreases.

  A baseball player hits a foul ball straight up into 3er- mc8ha;nm k+bs 4cthe air. It leaves the bat with a speed khs;r3m c bmne-8+4acof $120 \; km/h$. In the absence of air resistance, how fast will the ball be traveling when the catcher catches it?    $km/h$ (please only fill in numerical value in the blank)

  As a freely falling object speeds up, what is happening to its acceleration,cf 0 h:sfz5v ouwa)w)8ixe h87pdd 5m1 how does it change if air frictio8xpmihf)c0)zuws dh8 oaw55: 1 7evfdn is ignored?

  As a freely falling object speeds up, what is happening to p;6px+q3cy umits acceleration, how does it change if air friction CAN NOT be x;yc p3+6puq mignored?

  An object that is thrown vertically upward will return to its original pofo4 rdcyi 164 u1a)ldpsition with the same speour yialf614) 4pcd1 ded as it had initially if air resistance is negligible. If air resistance is appreciable, how will this result be altered?

  An object can have zero velocity and nonzero acceleration at thec2 n 8y6zp,zv.cfhz1i same time.

  An object can have nonzero velocity ib-(gaafq7d)zej9 frh o9lv ;9 yr..eand zero acceleration at the same time.

  An elevator moving from tpn:j0yaim,z v r; ,l2ohe second floor to the fifth floor making no stops alon ,m:rp;a2lvo0j,iz nyg the way has zero acceleration all the time.

  A rolling ball moves frv z6yta(c3z- m kw tf562lwyfiz84-vtom $x_1=2.2 \mathrm{~cm}$ to $x_2=-4.7 \mathrm{~cm}$ during the time from $t_1=2.9 \mathrm{~s}$ to $t_2=5.7 \mathrm{~s}$. What is its average velocity?  (数值)  $cm/s$ (only fill in numerical value please)

  A particle at $t_1=-3.2 \mathrm{~s}$ is at $x_1=2.7 \mathrm{~cm}$ and at $t_2=3.2 \mathrm{~s}$ is at $x_2=7.5 \mathrm{~cm}$. What is its average velocity?  (数值)  $cm/s$

  A person jogs eight complet79b.1(q mpxqawjsmlvrv-p y 4 ,3yiy+e laps around a quarter-mile ($1 \; mile = 1609 \; m$) track in a total time of 8.7 min. Calculate (a) the average speed  (数值)  $m/s$ and (b) the average velocity    $m/s$

  A horse canters away from its trainer in a straight line, movin) fw5hn*3d vqwq,ss7 cg 116 m away in 13.8 s. It then turns abruptly and gallops halfway back in 4.6 s. Calculate (a) its * q3d7vch)f,ssw5 qnwaverage speed  (数值)  $m/s$ and (b) its average velocity  (数值)  $m/s$ for the entire trip, using “away from the trainer” as the positive direction.

  A car accelerates fr1 fy33chn.g bo c)8ezg-fj d4aom $10 \; m/s$ to $22 \; m/s$ in 4.5 s. What was its acceleration?  (数值)  $m/s^2$ How far did it travel in this time?  (数值)  $m$ Assume constant acceleration.

  A car slows down from wzzn,u u4*sr 2d bxrb,h+d,1v$21 \; m/s$ to rest in a distance of 60 m. What was its acceleration, assumed constant?  (数值)  $m/s^2$

  A light plane must rea1 ibaobm6x-3a ch a speed of $31 \; m/s$ for takeoff. How long a runway is needed if the (constant) acceleration is $2.7 \; m/s^2$ ?  (数值)  $m$

  A world-class sprinter can burst ou)/ k.mds,0crtrg5ahy rx ;t) qt of the blocks to essentially top speed aboutdr);rmt rhytg.xs5, 0)a qc/k $10.3 \; m/s$ in the first 13.2 m of the race. What is the average acceleration of this sprinter?  (数值)  $m/s^2$ and how long does it take her to reach that speed?  (数值)  $s$

  A car slows down uniformly from z041l kd0 cw;cugie3n a speed of $17 \; m/s$ to rest in 5.83 s. How far did it travel in that time?  (数值)  $m$

  In coming to a stop, a car l4(k5k ain f9n j(nznf9eaves skid marks 92 m long on the highway. Assuming na (kz9ifk(jn9 nn4f5a deceleration of $7.00 \; m/s^2$, estimate the speed of the car just before braking.    $m/s$