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习题练习:Physics Unit6: Work and Energy



 作者: admin发布日期: 2022-07-28 12:33   总分: 95分  得分: _____________

答题人: 匿名未登录  开始时间: 22年07月26日 13:45  切换到: 整卷模式

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1#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the correct unit of work epg. jv0 ,v2k raaxc2byn6 2y*oxpressed in SI units?

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2#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Can work be done on a systzp xi/4p 4t)r sqz2tb5em if there is no motion?

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3#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you push twice as hard against a stationary brick wall 1g5 liv-oz(c e;rob(r2oe w) jfp/gp2, the amount of work you doeo(z pp -(;/el 1rfbw)5gi 2co2jorg v

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4#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 50-N object was lifted 2.0 m verticallyas68czgd,w) gj6iph7 and is being held there. How much work is being done in holding the box in this posizagj6s ) ,6ip g8whd7ction?

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5#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If you walk 5.0 m horizontally forwar ozb( 45ewx:vvip/u9vd at a constant velocity carrying a 10-N object, 9v4vx(:i5o buwzev/p the amount of work you do is

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6#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A container of water is lifted vertically 3.0 m then returned to its orig dhq5ly7,n 6l3 nq1yzfinal position. If the total w5lq63dlzf 1qyy,h n7neight is 30 N, how much work was done?

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7#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Does the centripetal force acting on an object do work on the objel k.l 6rtw:rc;ct?

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8#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You throw a ball straight up. Compare the sign of the work dongn9* i waf x(j:nv)gy)e by gravity while the ball goes up with the sign of the work done ) fn)nj: *gv9g(iyax wby gravity while it goes down.

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9#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The area under the curve, on a Force versuewpu- opaml:w+/ei (+r+v 0ers position (F vs. x) graph, representsiwl / v pow+ea:eu(m+r+pre0 -

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10#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  On a plot of Force versus position (F vs. x), wkb3bw a +nn(9ihat represents the work done by the forceni(9w bb3a+kn F?

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11#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The quantity $\frac{1}{2} \; mv^2$ is

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12#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the net work done on an object is positive, then the ob4g4o5fh+ao5q vx-2p7, imdspv b1dd gject's kinetic energy

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13#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the net work done onj d4 6nlm )(m+lmg 2ijywvsv8* an object is negative, then the object's kinetic energy

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14#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If the net work done on an object is zero, t:+9u wv4vpnvg1(z fi *e8d(e ejaqj12+ z mpzkhen the object's kinetic energy

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15#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A truck weighs twice as much as a car, and is moving at twice the tb) c8v )0w, t;s:dy5zkcunku speed of the car. Which statement is true about the truck's kinetic energyuck wd;8 uv),yt)b5c n:0kszt compared to that of the car?

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16#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Car J moves twice as fast as car K, and car J has bqeg wu.4uf, (half the mass of car K. The kinetic energy of car J, compared t f ,w(4eug.qbuo car K is

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17#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An object hits a wall and bounces back with half of its original speed. What is3bw:lp*2vs b6z:a 76 flzhlby the ratio of the final kinetic energy to the initial :fbplayz73 z6hsw6*l 2l:b v bkinetic energy?

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18#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A brick is moving at a speed of 3wg (oy0o p mfndy(v v3* ah(z,y;b79iz m/s and a pebble is moving at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the brick's mass to the ym9adz3hzg((7pf,(0w*ovni ybvyo ; rock's mass?

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19#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 4.0-kg mass is moving with speed 2.0 mu)q,88kbh+j b6 vna2t. j ly53qesybn/s. A 1.0-kg mass is moving with speed 4.0 m/s. .t3n5,8aq6 suylh)2n qkbb y8j jb +evBoth objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

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20#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You slam on the brakes of your car in a panic, and skid a certain distance*+zmuw i 9kk7wl)u8fzx xh-4e on a straight, level road. If you had been traveling twice as fast, what distance would the car have skiwmu k7+-w8z94ze *i x)fxlukhdded, under the same conditions?

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21#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A planet of constant mass orbits the Sun in an elliptical orbit. N t3x64zlfgp9i0q:n7s +qojwu tzhc- (eglecting any friction effects, what happens to j36fp 4n 7 i +gttusz0z-qcwq:o9(x hlthe planet's kinetic energy?

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22#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
State the work-energy pr9s-h;wjlc8aqi7bet at( xs* luc j,..inciple.
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23#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The quantity mgy is

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24#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The quantity $\frac{1}{2} \; kx^2$ is

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25#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Is it possible for a system to have negative potene2rtf4 c6-v b(o9d0- wdyzmzdtial energy?

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26#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An object is released from rest a height h ucky,lht7 dxud*f (h 4f2l r-9o+oa;pabove the ground. A second object with four times the mass of the first if released from the +7o- lpr a , ol9dyxh(cuhkt4*df;2u fsame height. The potential energy of the second object compared to the first is

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27#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 0.200-kg mass attached to the end of a spring causes it to stretch 5.0 cm. y2 ble: 1w83sdln hu4sIf an2 1bs uwsdneh8l3y:l4 other 0.200-kg mass is added to the spring, the potential energy of the spring will be

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28#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The total mechanical energypiu qdd-p qcz+5d zch/(p) *v- of a system

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29#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An acorn falls from a tree.ppp 3oy) .2coh Compare its kinetic energy K, to its potential energy .yc)o php32op U.

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30#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Describe the energy of a caw8r+n lta.hm ,r driving up a hill.

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31#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A lightweight object and a very heavy object are sliding with equal speedkq y;mp3e47 nws along a level frictionless surface. They bo4;p3kqe n 7mwyth slide up the same frictionless hill. Which rises to a greater height?

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32#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Consider two masses cu lyzx:,v)blx-fe/ j7 ;k:zl$m_{1}$ and $m_{2}$ at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which $m_{1}$ sits is at an angle of $30^{\circ}$ with the horizontal, while the plane on which $m_{2}$ sits is at $60^{\circ}$. If the masses are released, which is going faster at the bottom of its plane?

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33#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
State the principle of conservation of mechanical energy for conservat3i we +rqu wu/i5dp(m:ive forces.qei(: + u3md /5wpuriw
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34#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A ball falls from the top of(sgysqaw5r-)pq ojsmc :q;7/ a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the build)qqaqy-p7m 5cg; ows s(:/jsring?

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35#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A ball drops some distance and gains 30 J of kinetic energy. Do not ignore sv0-t )njkl,v air resistance. How much gravitational potential energy did the ball lose?),jvvk snt -0l

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36#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A ball drops some distance and loses 30 J tg vwjl,0 j-0e3rh,sg of gravitational potential energy. Do not ignore air resistance. How much kinetic enw3hjg 0v-,lsj,e0 t rgergy did the ball gain?

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37#
 
问答题 ( 1.0 分) 切至整卷模式 搜藏此题  
State the law of conservation of ener3ye.r iqlgqqw/:8z-agy.
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38#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The quantity Fd/t is,;ktaaqaeh 3ej lws: q,o 0u f)9bd:,i

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39#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What is the correct unit of powy02rui :2wdhn zizh:-er expressed in SI units?

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40#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Of the following, which is not a unipg p/n1 vubhtd)g(6h 9t of power?

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41#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Compared to yesterday, you did 3 times the work in one-third the time.wf oc0:x4e 98 tpcam(yb:a +pa To do so, your power xfc y+0pa:m:eaap4t 9(cbow8output must have been

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42#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  To accelerate your car attyl +98n5vmztg j11li a constant acceleration, the car's engine must

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43#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An object is lifted vertically 2.0 m 2:kcr-.mdp b tand held there. If the object weighs 90 N, ho.tp bd 2-rm:kcw much work was done in lifting it?

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44#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  You lift a 10-N physiw,wn*il;z *o o1ecrp6cs book up in the air a distance of 1.0 m, at a constant velociwrz ioeo;p1c w*n ,l6*ty of 0.50 m/s. What is the work done by the weight of the book?

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45#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 500-kg elevator is pulled upward with a constant force of 5500 N fousv2/x78 1lc s; wokx+wair) wr a distance of 50.0 m. What is the work done bywsowixvau1c8)x ;7 sl +r2kw / the 5500 N force?

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46#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 500-kg elevator is pulled upward with a constant formqyja.va5dqx (p5h 9*ce of 5500 N for a distance of 50.0 m. What is the work done by the weight of the *59yq mada.(vphxq5j elevator?

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47#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 500-kg elevator is pulled upward with a constant force of 5500 N for ag/ rq95g+h+j ncplayn u6o *-n distance of 50.0 m. Whaln+9onhjcq +u5 - *a/gnygr6p t is the net work done on the elevator?

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48#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 30-N box is pulled 6.0 ;z v4wjj:;rdeu vc2.z m up along a $37^{\circ}$ inclined plane. What is the work done by the weight (gravitational force) of the box?

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49#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 4.00-kg box of fruit slides 8o i b-/, s9fcg 2mcilguz)tioqq/ 8(j;.0 m down a ramp, inclined at $30^{\circ}$ from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?

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50#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Matthew pulls his little sist/c 2 te4rt,pkyp;0pig er Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 Npckyt 0i /2 g,r;4petp at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

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51#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A force moves an object i( e.ri kv6)q7a) - ukfu7xphaln the direction of the force. The graph in Fig. 6-1 shows the forceu77 a)-e )urf6qx(av kikl.h p versus the object's position. Find the work done when the object moves from 0 to 2.0 m.


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52#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A force moves an object in the direction of ne;*o gycngdh .89h 2qthe force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to go genqch.hn; 89d*y2 4.0 m.


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53#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A force moves an object in the direction of the force. The graph indrjl83 (ejx2xwk) rs. Fig. 6-1 shows the force versus the object's position. Find j .)xx(d3 rw82sekrljthe work done when the object moves from 4.0 to 6.0 m.


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54#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A force moves an object in the direction of the nb pqf+e6vy4u3 4xh:yforce. The graph in Fig. 6-1 shows the force ver6p+h4vefnu3 yyxb 4q :sus the object's position. Find the work done when the object moves from 0 to 6.0 m.


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55#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A horizontal force of 200 N is applied to move a 55-kg cart (initiax;(-(uq z4fyjvpdd me55pf v 0lly at rest) across a 10 m level surface. What is the final kinetic energy of the car(v(0df xe z 5uvfpd-yq;jpm45 t?

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56#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A horizontal force of 200 N is applied to move a 55-kg cart (ipbf d416 ao- koxztw1rdpc +(9nitially at rest) across a 10 m level su(ro-a+1bc dppf1ok tdz x6w49rface. What is the final speed of the cart?

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57#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 10-kg mass is moving with a s2v4p 6lqsvyu-ikbts- 2r.i4dpeed of 5.0 m/s. How much work is required to stop the m- vpl4d.s 2 rqi2-tks4iv6uybass?

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58#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  If it takes 50 m to stop a car initid2dzbgobvbd*2, 8 /cjally moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same cd c*/bjv,zbgo2 bdd8 2ondition?

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59#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A spring-driven dart gun propels a 10-g dart. It is cocked by exerting a f)xl0w 4dhh lgb +(c*qeorce of 20 N over a distanhbwcl)q+xeh( d04* lgce of 5.0 cm. With what speed will the dart leave the gun, assuming the spring has negligible mass?

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60#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 100-N force has a horizontal component of 80 N and a verzvfb6l)4a i d,tical component of 60 N. The force is applied to a box which rests on a level frictionless floo) azl,fd6b iv4r. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

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61#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An arrow of mass 20 g is shot hb8obap 345q9pux6.9iskm p7oamh8 zporizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopp9.6bxa 7kpuam834p5ozsmb9 i ohp8 qping force acting on the arrow?

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62#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 15.0-kg object is moved from a height of 7.00 m above a floor t/k y z:wzhfa zwwm5+0*o a height of 13.0 /azw+5y* wk f zwhm:z0m above the floor. What is the change in gravitational potential energy?

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63#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 400-N box is pushed up an -v jjoxcrcra,9 .q0 (binclined plane. The plane is 4.0 m long and rises 2.jvo. ,(rc-j0 b9xcqa r0 m. If the plane is frictionless, how much work was done by the push?

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64#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 10-kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. Wh4:tn e4qfz moafa5 0n5at is t:f0za 5af 4q4o5 mnntehe spring constant?

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65#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A spring is characterized by a spring constant of 60 N/0ug8aq1dx7a 7z cqs8zm. How much potential energy does it store, 07u 8a s a8qxcz7qzdg1when stretched by 1.0 cm?

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66#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  Calculate the work requirq7 +dff8c*b*x:dtxfy ed to compress an initially uncompressed spring with a spring constaf**qfc 7dxb8+ x:d fytnt of 25 N/m by 10 cm.

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67#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  What work is required to stretch a spring of spring constant 40 N/m froeexug(j:. m6 mm x = 0.20 m to 0.25 m? (A gem(m.j: 6euxssume the unstretched position is at x = 0.)

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68#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A spring with a spring constant ofe+f9gmtj6 fep .zl qkf)hx,x67ojq58 15 N/m is initially compressed by 3.0 cm. How much work is required to compre,7.mh 6qfl k5e8oe q6fjg)tfp+zjxx9ss the spring an additional 4.0 cm?

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69#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 60-kg skier starts from rest from the top of a 50-m hig( 5z hq+ojmvat)8 o v()qawif)h slope. What is the speed of the slier on reaching the bottom of the sloptqa(z v8)o ))ha fjwov(q5+ ime? (Neglect friction.)

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70#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A skier, of mass 40 kg, pushes off the top of a hill with an initi:skq,z.xt nkb m2wm 87al speed of 4.0 m/s. Neglecting friction, how fast will she be moving after drot sq.8 2bmkw7,mkxnz:pping 10 m in elevation?

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71#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An object slides down a frictionless .m p jbn*m-2sol4jlr4inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height of the jor-s2jmln4.4*lpb m plane?

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72#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 1.0-kg ball falls to the floor. When it is rqr (g/gn99bs abat3, 0.70 m above the floor, its potential energy exactly equals its kirqbnat /b 9ga(s9,g r3netic energy. How fast is it moving?

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73#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A toy rocket, weighing 10 N, blasts straight up from ground l 9 n;cw9isb6vnevel with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what vertical height does it ri s;i6wn9nvc 9bse?

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74#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A projectile of mass m leaves the ground with a qmm. 8. 5md)gof u)o boxb:gq;kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy 5 o bm)o:gqmq u8.)fom.gxd;bis 120 J. To what vertical height, relative to its launch point, did it rise?

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75#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A roller coaster starts from r qw-uet gj3+ fcm23d2xest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of tu-3t2w32jmxqdf e +cghe next slope, which is 30 m above the bottom of the dip?


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76#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A roller coaster starts with a speed of 5.0 m/s at l o;+crr 6-k89hou lffk /auh4rr,hm7 a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the lu+chl,8mu f; ro4-7r/h9a rkrfhko6next slope, which is 30 m above the bottom of the dip?


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77#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A roller coaster starts at a point 30 m abovep.gq)6m c7 xi-oy;hoh the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coasg.7qx6)h i y-pcmoho; ter at the top of the next slope, which is 45 m above the bottom of the dip?


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78#
 
  What is the minimum speed of the ball at the: hh m6tm-v(j)3bl mnz bottom of its swing (point

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79#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A:2.2 m/s

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80#
 
  难度:2

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81#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A pendulum of length 50 cm is pulled 30 cm away from th3d0x b:(ci,4 v2o ntycaf 1rvse vertical axis and released from rest. What will beayi2rvf14 bod3 nc st c(vx,0: its speed at the bottom of its swing?

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82#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 1500-kg car moving at 25 m/s hits an initially uncompressed horizonkkox9:.:5 0 -au wkakbx)a aoftal spring with springfko0aaaxbak -. ) :5ou:kkx w9 constant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

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83#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for ip1 je1jx9 -rca red light. What work is done by the friction force againstjr-ex9 cpi11 j the wheels?

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84#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  The kinetic frictiondu0e3 -ys2e f5opxx, d force between a 60.0-kg object and a horizontal surface is 50.0 N. If the initial spe0deexp,- o 3df xsu2y5ed of the object is 25.0 m/s, what distance will it slide before coming to a stop?

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85#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 12-kg object is moving on a rough, level surface. It has 24 J of kinetic (an 3 io4oh2hhenergy. The friction force on it is a constant 0.50 N. How far will hh(h3 oion4a2 it slide?

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86#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A force of 10 N is applied horizontally tndokj9 y, *-:crfqit8o a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the ch-,d c9krj:if toyqn8*ange in its kinetic energy?

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87#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 60-kg skier starts from rest from the top of a 50-m high slope.zau5 4c t:au8qx3p 38rb.vx uw If the work done u8vca3tx 5bxa3puq.zr8w4:u by friction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

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88#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  An 800-N box is pushed up an inclined plane. The plane is 4x gbarna(+,t ..0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average frict+ a(n xab.r,tgion force on the box?

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89#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 2.0-kg mass is released from rest at the top of a pla0zv l;cs+ xl: (-iz h-tygifo7s*k 64e:utcinne inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the massi0u-c7hx +t: iel-:vn 6*ss;cikft(lo4gy zz after sliding 4.0 m along the plane?

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90#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 30.0-N stone is dropped from a height of 10.0v1i* rd3n ;yl4yv +bxq4 j0)0sozhju u m, and strikes the ground with a velocity of 7.00 m/s. What av jx4q)zndyu+v 1;u 4rb3vo0jsh 0i*ly erage force of air friction acts on it as it falls?

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91#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  At what rate is a 60.0-kg boy using energy when he runs up a flight of sctvs27e6oea-ao4,c 7b ijz k:bosk9 tp+)ed , tairs 10.0--,coe2 )z4ss+ko7a t6t oj 9bdei cvpbaek,:7m high, in
8.00 s?

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92#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. /(o(tnkeam1owb) s xgo :q d0 ab*0,rk What power must be delivereb /,enk:o g(kbs*()qt w1axa00omrodd to the object by the force?

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93#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  How many joules of energy are used by a 1.0 hp motor that run93e zmo buk:j9i t*nv8aj58p9ts wxa5 s for 1.0 hr? (1 hp = 746 ibe:*j8nj os59t pm9uxat a 85z9kvw3W)

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94#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A cyclist does work at the rate oj:wt d ev5,ju;f 500 W while riding. How much force does her footjed 5vu;twj,: push with when she is traveling at 8.0 m/s?

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95#
 
单选题 ( 1.0 分) 切至整卷模式 搜藏此题  
  A 1500-kg car acceleratesa h:v a)nz;vg3 from 0 to 25 m/s in 7.0 s. What is the average power delivered by the engin;:vhgn3za v a)e? (1 hp = 746 W)

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