Grade 9 Test on Mechanics 20241217 - 无忧得胜-网上国际课程 (5edu.win)

1#

单选题 ( 1.0 分) 切至整卷模式 eid: 4094 对错数 0:0 难度: *****

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A new car manufacturer advertises that ud uah6,5gyu 4their car can go "from zero to sixty in 8 s". This is a de 6a ,uuyud5g4hscription of

A. average speed.

B. instantaneous speed.

C. average acceleration.

D. instantaneous acceleration.

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2#

单选题 ( 1.0 分) 切至整卷模式 eid: 4095 对错数 0:0 难度: *****

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Suppose that a car travelingz dtn2b(4dsu:e r:tc1 to the East (+x direction) begins to slow down as it approachu bstcn(e4 zd:2:r dt1es a traffic light. Make a statement concerning its acceleration.

A. The car is decelerating, and its acceleration is positive.

B. The car is decelerating, and its acceleration is negative.

C. The acceleration is zero.

D. A statement cannot be made using the information given.

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3#

单选题 ( 1.0 分) 切至整卷模式 eid: 4096 对错数 0:0 难度: *****

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If the velocity of an0vstb4 .hc r-:qd 7ank,.pn 8vyym3xq object is zero, does it mean that the acceleration is zero? Support your answer with an c7bmd-h yr kyt8vns4 ..n 0q,3q:ax pvexample.

A. no, and an example would be an object starting from rest

B. no, and an example would be an object coming to a stop

C. yes, because of the way in which velocity is defined

D. yes, because of the way in which acceleration is defined

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4#

单选题 ( 1.0 分) 切至整卷模式 eid: 4097 对错数 0:0 难度: *****

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Objects A and B both start at rest. They both accelerate at the samcctbu3y3mfe j )y+ e ,+*pg,hme rate. However, object A accelerates for twice the time as object B. What is the fi+yhf g+) *c mjm,buectp, 33yenal speed of object A compared to that of object B?

A. the same speed

B. twice as fast

C. three times as fast

D. four times as fast

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5#

单选题 ( 1.0 分) 切至整卷模式 eid: 4098 对错数 0:0 难度: *****

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Suppose a ball is thrown straight up. Make a statem)2or pue04pfient about the velocity and the acceleration when the bau0p4p rf2)e ioll reaches the highest point.

A. Both its velocity and its acceleration are zero.

B. Its velocity is zero and its acceleration is not zero.

C. Its velocity is not zero and its acceleration is zero.

D. Neither its velocity nor its acceleration is zero.

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6#

单选题 ( 1.0 分) 切至整卷模式 eid: 4099 对错数 0:0 难度: *****

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Ball A is dropped from the top of a building. x(cuvh n4lo0 k z)5(ijs-0ft i One second later, ball B is dropped from the same building. c5 s)ohv(f0(-40ki zutjl xi nAs time progresses, the difference in their speeds

A. increases.

B. remains constant.

C. decreases.

D. cannot be determined from the information given.

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7#

单选题 ( 1.0 分) 切至整卷模式 eid: 4100 对错数 0:0 难度: *****

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A cart starts from rest and accelerates abk+fdn)a )9nps7 nb5gt $4.0 \; m/s^2$ 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. 20 m/s

B. 16 m/s

C. 12 m/s

D. 10 m/s

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8#

单选题 ( 1.0 分) 切至整卷模式 eid: 4101 对错数 0:0 难度: *****

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A cart with an initial velocity of 5.0 m/s experiences a constant accem+ 7lix unoo4 t 8;bbo 8s.qdcoax(:)nleration of;7(suo oxnbtal +icqo.8bd4):n o8 xm $2.0 \; m/s^2$. What is the cart's displacement during the first 6.0 s of its motion?

A. $10 \; m$

B. $55 \; m$

C. $66 \; m$

D. $80 \; m$

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9#

单选题 ( 1.0 分) 切至整卷模式 eid: 4102 对错数 0:0 难度: *****

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An object is thrown upward with a speed of v 67c1higxfb .*l5u8hr +:mc goo ii.x15 m/s on the surface of planet X where the acceleration due to gravity ibi *x86cmi5ol of.+7xhcvig g ru:. h1s $2.5 \; m/s^2$. How long does it take for the object to return to where it is thrown?

A. $6.0 \; s$

B. $8.0 \; s$

C. $10 \; s$

D. $12 \; s$

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10#

填空题 ( 3.0 分) 切至整卷模式 eid: 4103 对错数 0:0 难度: *****

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A ball is thrown straight up with a speedr2 ,: jc7* 6(ejq bht(ran,u yqf)ijvr of 30 m/s. (only fill in numerical value in hj:r, e7(26ujyi qn v)b*(rcqt fj,rathe 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?    $m/s$

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11#

单选题 ( 1.0 分) 切至整卷模式 eid: 4104 对错数 0:0 难度: *****

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In Fig. 2-1, what is thefp apn7yn*s (0 velocity at t = 5.5 s?

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A. 0

B. 10 m/s

C. 20 m/s

D. -40 m/s

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12#

单选题 ( 1.0 分) 切至整卷模式 eid: 4105 对错数 0:0 难度: *****

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In Fig. 2-2, what is the acceleration at :/efylfhqn ,sm25y n .p2 ;gwf1.0 s?

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A. 0

B. $2.0 \; m/s^2$

C. $-2.5 \; m/s^2$

D. $10 \; m/s^2$

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13#

单选题 ( 1.0 分) 切至整卷模式 eid: 4106 对错数 0:0 难度: *****

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When you sit on a chai - bxzs wpy9;b.qn(*yoo3g er/4rph2wr, the resultant force on you is

A. zero.

B. up.

C. down.

D. depending on your weight.

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14#

单选题 ( 1.0 分) 切至整卷模式 eid: 4107 对错数 0:0 难度: *****

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In the absence of an external force, a moving objec)4,. np qgrz6udb vmnx*do,,v t will

A. stop immediately.

B. slow down and eventually come to a stop.

C. go faster and faster.

D. move with constant velocity.

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15#

单选题 ( 1.0 分) 切至整卷模式 eid: 4108 对错数 0:0 难度: *****

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When the rocket engines on the starship NO-PAIN-NO-GAIN are supq/mb,3.4 ax p b7qrpzddenly turned off, while traveling in empty, rqbpq3paz m.7/x b4p space, the starship will

A. stop immediately.

B. slowly slow down, and then stop.

C. go faster and faster.

D. move with constant speed.

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16#

单选题 ( 1.0 分) 切至整卷模式 eid: 4109 对错数 0:0 难度: *****

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A net force F acts on a mass m and produces an accelerazkogt7n (t1 z//tr,zhtion a. What acceleration results if a net foz/,1zg t7zthr ok/(ntrce 2F acts on mass 4m?

A. $a/2$

B. $8 \; a$

C. $4 \; a$

D. $2 \; a$

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17#

单选题 ( 1.0 分) 切至整卷模式 eid: 4110 对错数 0:0 难度: *****

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A 20-ton truck collides with a 1500-lb i/n*i-h 5acps-jlst5car and causes a lot of damage to the car. Since a lot of damage is donp5n5*jhs/ai -c- l stie on the car

A. the force on the truck is greater then the force on the car.

B. the force on the truck is equal to the force on the car.

C. the force on the truck is smaller than the force on the car.

D. the truck did not slow down during the collision.

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18#

单选题 ( 1.0 分) 切至整卷模式 eid: 4111 对错数 0:0 难度: *****

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An object of mass m sits on a flat table. The Earth pulls on this objecwj6t2 t o38nzd)s(grwoso+x (t with force mg, which we will d(3oj2 gttwno8(s o+s6z)wxrcall the action force. What is the reaction force?

A. The table pushing up on the object with force mg.

B. The object pushing down on the table with force mg.

C. The table pushing down on the floor with force mg.

D. The object pulling upward on the Earth with force mg.

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19#

单选题 ( 1.0 分) 切至整卷模式 eid: 4112 对错数 0:0 难度: *****

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A brick and a feather fall to the earth at their respective terminal veekt+.i,d -( iimbsthi1( hkbmh.; lrqq4 w4v :locities. Which o4q:4r(;hl ivh b.sbqi(1,tei -d kwk.h itm+m bject experiences the greater force of air friction?

A. the feather

B. the brick

C. Neither, both experience the same amount of air friction.

D. It cannot be determined because there is not enough information given.

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20#

单选题 ( 1.0 分) 切至整卷模式 eid: 4113 对错数 0:0 难度: *****

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An object of mass m is hanging by a string from the ceiling of an9zwh8 +tdx1jd elevator. The elevator is moving upward, but slowing down. What is t9wddj1xtz +h8he tension in the string?

A. less than mg

B. exactly mg

C. greater than mg

D. zero

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21#

单选题 ( 1.0 分) 切至整卷模式 eid: 4114 对错数 0:0 难度: *****

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A packing crate slides down an inclined ramp at constant velociu eazj-rc+ ;k9ty. Thus we can deduce jkr;+c- e9 auzthat

A. a frictional force is acting on it.

B. a net downward force is acting on it.

C. it may be accelerating.

D. it is not acted on by appreciable gravitational force.

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22#

单选题 ( 1.0 分) 切至整卷模式 eid: 4115 对错数 0:0 难度: *****

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A person of weight 480 N stands on a scale in aj2du pa;;(du tn elevator. What will the scale be reading when the elevator is accelerating downward at( jdt ap;2u;du $4.00 \; m/s^2$?

A. $196 \; N$

B. $284 \; N$

C. $676 \; N$

D. $480 \; N$

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23#

单选题 ( 1.0 分) 切至整卷模式 eid: 4116 对错数 0:0 难度: *****

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In the Atwood machine shown in Fig. 4-1, if M = 0.60 kg and autzha5x(19n ih d61 tm = 0.40 kg, what is the magnitude of the acceleration of the s5x( dn1ih1 u 6tatzah9ystem? (Ignore friction and the mass of the pulley.)

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A. $5.3 \; m/s^2$

B. $3.9 \; m/s^2$

C. $2.0 \; m/s^2$

D. $0.98 \; m/s^2$

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24#

单选题 ( 1.0 分) 切至整卷模式 eid: 4117 对错数 0:0 难度: *****

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A student pulls a box of books on a smix), yzky)8h fzjj ,0zooth horizontal floor with a force of 100 N in a direction of 8 yyhzjx,ik0f)j z,)z $37^{\circ}$ above the horizontal. If the mass of the box and the books is 40.0 kg, what is the acceleration of the box?

A. $1.5 \; m/s^2$

B. $1.9 \; m/s^2$

C. $2.0 \; m/s^2$

D. $3.3 \; m/s^2$

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25#

单选题 ( 1.0 分) 切至整卷模式 eid: 4118 对错数 0:0 难度: *****

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A traffic light of weight 100 N is supported by two ropes d+zv-xi rz7aasb:lh:6j ()bk0 ekr8uas shown in Fig. 4-2. What are the tensions jkb 8i 7 0x-u:h:rv6bszdz ar+()aelkin the ropes?

本题所包含的其它图片:

A. $50 \; N$

B. $63 \; N$

C. $66 \; N$

D. $83 \; N$

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26#

单选题 ( 1.0 分) 切至整卷模式 eid: 4119 对错数 0:0 难度: *****

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Two boxes of masses m andor4suh0b3h+ b+ x.9 9of o+rek5vvugv3 oea w/ 2m are in contact with each other on a frictionless surface. (See Fig. 4-3.) What is the acceleration of the moru/se+hka 4 buo3 .9oeo5 o++wh brvv9vg0fxr 3e massive box?

本题所包含的其它图片:

A. $F/m$

B. $F/(2m)$

C. $F/(3m)$

D. $F/(4m)$

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27#

单选题 ( 1.0 分) 切至整卷模式 eid: 4120 对错数 0:0 难度: *****

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A horizontal force of 5.0 N accelerates a 4.0-kg mass, fr,zvy kb;ma 6i+om rest, at a rate of $0.50 \; m/s^2$ in the positive direction. What friction force acts on the mass?

A. $2.0 \; N$

B. $3.0 \; N$

C. $4.0 \; N$

D. $5.0 \; N$

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28#

单选题 ( 1.0 分) 切至整卷模式 eid: 4121 对错数 0:0 难度: *****

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An object is on a frib+));p/ hdra *plja ybx g6zr6ctionless inclined plane. The plane is inclined at an angle of*6 yajh;/)blrr )p d ga6bz+px $30^{\circ}$ with the horizontal. What is the object's acceleration?

A. $0.50 \; g$

B. $0.56 \; g$

C. $0.87 \; g$

D. $1.0 \; g$

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29#

单选题 ( 1.0 分) 切至整卷模式 eid: 4123 对错数 0:0 难度: *****

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If you push twice as hard against t m v.d4egw)ti.f:t4ca stationary brick wall, the amount of work youeittt. d m4)v.c4:fw g do

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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30#

单选题 ( 1.0 分) 切至整卷模式 eid: 4124 对错数 0:0 难度: *****

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If you walk 5.0 m horizontally forward at a coh 3jqtvt/z,5bn ( xkk(nstant velocity carrying a 10-N object, (k3zt v5bnqtxkjh,( / the amount of work you do is

A. more than 50 J.

B. equal to 50 J.

C. less than 50 J, but more than 0 J.

D. zero.

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31#

单选题 ( 1.0 分) 切至整卷模式 eid: 4125 对错数 0:0 难度: *****

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You throw a ball straight up. Compare the sign of the work done by gre)w 4fr(s3 c8 djzl*lgavity while the ball goes ue) *z84(rllscwgd jf3 p with the sign of the work done by gravity while it goes down.

A. Work is + on the way up and + on the way down.

B. Work is + on the way up and - on the way down.

C. Work is - on the way up and + on the way down.

D. Work is - on the way up and - on the way down.

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32#

单选题 ( 1.0 分) 切至整卷模式 eid: 4126 对错数 0:0 难度: *****

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A truck weighs twice as much as a car, anu /zki u9s:i ;q,*m 7ipxi ps)samb71w9dg5bs d is moving at twice the speed of the car. Which statement is true about the truck's kinetiip w:b usp9qm)u/17d 5misxk7ii;*gs s9, bazc energy compared to that of the car?

A. All that can be said is that the truck has more kinetic energy.

B. The truck has twice the kinetic energy of the car.

C. The truck has 4 times the kinetic energy of the car.

D. The truck has 8 times the kinetic energy of the car.

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33#

单选题 ( 1.0 分) 切至整卷模式 eid: 4127 对错数 0:0 难度: *****

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A 4.0-kg mass is moving with speed 5qm0yvptj *x*4 + aife2.0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same const0 m*j*+yixetvap5 fq4ant braking force, and are brought to rest. Which object travels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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34#

单选题 ( 1.0 分) 切至整卷模式 eid: 4128 对错数 0:0 难度: *****

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Is it possible for a system to have negativee9 ao) tz9ur-xzia )7j potential energy?

A. Yes, as long as the total energy is positive.

B. Yes, since the choice of the zero of potential energy is arbitrary.

C. No, because the kinetic energy of a system must equal its potential energy.

D. No, because this would have no physical meaning.

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35#

单选题 ( 1.0 分) 切至整卷模式 eid: 4129 对错数 0:0 难度: *****

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An acorn falls from a tree. 52k j9bhrc e7zCompare its kinetic energy K, to its potential energy U.7 ehrzkc5j 9b2

A. K increases and U decreases.

B. K decreases and U decreases.

C. K increases and U increases.

D. K decreases and U increases.

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36#

单选题 ( 1.0 分) 切至整卷模式 eid: 4130 对错数 0:0 难度: *****

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Compared to yesterday, you did 3 times the work in one-third the time. e/m,pkgn02x3jijpi ju :3 eb5 To do so, your power output must have bee3p: j0e 5i3 mgpui/jjn ,xe2bkn

A. the same as yesterday's power output.

B. one-third of yesterday's power output.

C. 3 times yesterday's power output.

D. 9 times yesterday's power output.

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37#

单选题 ( 1.0 分) 切至整卷模式 eid: 4131 对错数 0:0 难度: *****

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If it takes 50 m to stop izetig n; ha l+:q2)t;wjwf3(a car initially moving at 25 m/s, what distance is required to stop a car moving at 50 ei jinl t:2a;h);gq3t+ ww(fz m/s under the same condition?

A. $50 \; m$

B. $100 \; m$

C. $200 \; m$

D. $400 \; m$

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38#

单选题 ( 1.0 分) 切至整卷模式 eid: 4132 对错数 0:0 难度: *****

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A skier, of mass 40 kg, pushes off the top of a hill with an initial speed oygat:xs ugy/uio.4oim /tim 07 53u5k f 4.0 m/s. Neglecting frictionu7/om 503g: xogauki t5imysit. /4 uy, how fast will she be moving after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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39#

单选题 ( 1.0 分) 切至整卷模式 eid: 4133 对错数 0:0 难度: *****

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A toy rocket, weighing 10 N, blasts straight up from ground level with a kinem3-s0zswj- la tic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J-3slmj zs0a -w. To what vertical height does it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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40#

单选题 ( 1.0 分) 切至整卷模式 eid: 4134 对错数 0:0 难度: *****

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A roller coaster starts from rest at a point 45 m above the bo d(qh+:i7n 4b z82casysejh)attom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster ae) 4zqh8hj(a cn:+ssy2di7abt the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 17 m/s

C. 24 m/s

D. 30 m/s

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41#

单选题 ( 1.0 分) 切至整卷模式 eid: 4135 对错数 0:0 难度: *****

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A roller coaster starts at a point 30 m above the bottom of a dip wit3r1ekig zbrd,9(x)t +ue6fxd h a speed of 25 m/s (See Fig. 6-2). 396(e dbx1z+egfkri,ud) xt r Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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42#

单选题 ( 1.0 分) 切至整卷模式 eid: 4136 对错数 0:0 难度: *****

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A 10-N force is neede) d)c0n/m:fw 9hupyftblu :)ed to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by th):l:ce )0m)u /fbunph9dtwy fe force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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