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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: 游客未登录  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 expressed i0zh,.cwr3ala; dj m,i n 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 systdx, f9jkop* lbq o2zfb dd8/+0em 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 har5slp 2 oz-z:fw j3e9qkd against a stationary brick wall, the amount of work you ds kwo 5e z:3pl2f-q9zjo

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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 lifuc;f n )3 g0ph+j;wl43*x5vvmzr qtpoted 2.0 m vertically and is being held there. How much work is being done in holding the box o)0f3crvwp ;q u5n ht;+pjzm l 4x3vg*in this position?

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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 forward at a /xoy5, 0whp emhfa 3z3constant velocity carrying a 10-N object, the amount of work you do ispho 3/xe5 a0,yfmhz3w

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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 g( x1ld( mrn.jnj)r /, :dhghxvertically 3.0 m then returned to its original position. If them dnx :)/.g,hnhj grdj((1xrl total weight 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 thm 9lhjr+f f;x/8/u7sjqh3gvue object?

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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. Comq *4-bhv (yboijxnfz 16ymb/2 pare the sign of the work done by gravity while the ball goes up with the sign of the work done b*bi2fvo-q1 j4m hx(bnby 6y/zy 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 versus position (F vs. x-e6rij sybwb04e /t6k ) graph, representsy-tiseb j 0/ 64w6ekbr

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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), what represents the woor; nkowok( (i .co7z2rk done by the forcr. oioo2zk wk(c7 (no;e 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 p/lsi q/6+ aanli3d1 cpositive, then the object'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 on an object is negative, then the object's kinetic energx ytxgn9nyd, l-39 l)gy

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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 objecto/7psyi; pzh2 is zero, then 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 speed of the ipb ;/8dyv/pkcar. Which statement is true about the truck's kini pd bv8y/pk;/etic energy 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, a6lr7qv+ j+v+br jht acp7vi .:nd car J has half the mass of car K. The kinetic ene7 qhrb.a+ji:lj6 +vp vt7v rc+rgy of car J, compared to 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 wiy(a46sd r vqn7th half of its original speed. What is the ratio ofq7aysd (n4vr6 the final kinetic energy to the initial kinetic 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 3 m/s and a pebble is mu,+gl a+ oi o2rav3ao)*ah6ww3key+loving at a speed of 5 m/s. If bl,a hw wr3e+* aoloaogky36a++) 2uiv oth objects have the same kinetic energy, what is the ratio of the brick's mass to the 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 m/s. A 1.0-kg mass is moving wi2,)mou pgojmh b5) vk5th speed 4.0 m/s. Both objects encounter the same constant brakm2 b)g)pvjumo5 5, hoking 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 yoxx1 x :v;(nzwl5pqj440d qsf9 :es grdur car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same coq: l pfn: ; v9sx4qzxrx 5w1j(e04sdgdnditions?

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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. 1 6a4 x8qf(s gafu6ixxNeglecting any friction effects, what happens to the planet's ki4fi6gx8 xqsx16(a uaf netic 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 prsmcx d ag0ly*:8hl pu/1r3zo5inciple.
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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 negepqvxjs m i3g;)a+g9-ative potential 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;,x4wxu-hf k*ub th(c rest a height h above the ground. A second object with four times the mass of the first if released from the same height.(*c wh,f4;x-kbhu tux 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 5.9jo21bm j:z)idp 9d qv0 cm. If another 0.200-kg mass is added to the spring, the potenb m99)j 2v:pqjzodd 1itial 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 energy of a mz-dpr1/ a sv5system

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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. Compare its kinetic energy K, to its potente4a8 yllk;x8tx r)ly; ial energy U. a ;)yxle88l;ryxklt4

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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 car drivbub1yxz.uo u 6y/zp +-ing 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 spe0o1fy dz wdd-1eds along a level frictionless sur1-d df1zwd0yo face. They both 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 z9rg)b 2w exg,w +7mll$m_{1}$ 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 conservanpm b;*goei** o /rh2ttive forcesm ;b n2ioo r*ge**/hpt.
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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 by0lg6l 3rjj5:t k 8ywzee,xh x)(t)sof 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 x))y:tl,s(j6y eetg0wjz3hrb k5 lx8 (U) at the top of the building?

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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 n7yy2onzmvbz0+ 0i2 p air resistance. How much gravitational potenbi om02ynn2 0z7yz vp+tial energy did the ball lose?

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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 of gravitational pm2bww hk)3k(l . hk2kvs.b4jgotential energy. Do not ignor 2) 3mh w.ghkwk4jbl2vbk(s.ke air resistance. How much kinetic energy 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 ent zro*rvjc(b4 3rd9 8d gq.7soergy.
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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 isn)t(rujg w)o7

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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 power expressebgg2(/k/ p;orpd pnb +d 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 unit of power?3*ziyr zr*yj 5u(xx/h

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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 )92ku kzy 7gnxin one-third the time. To do so, unkzg9 )xyk 72your power output 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 at a constant.km9vr a;hx48k k4v;lhbnt*( qcq fw; 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 a(4n.pb* z; td i(bsiobnd held there. If the object weighs 90 N, how much work was done in lifting it?;b(4ti pnbs*zi do(b.

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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 physics book up in the air a distan0:at,lxmazyp69: hl) waw4 un ce of 1.0 m, at a constant velocity of 0.50 m/spaw : :a9wxzahymln0tl)u6 ,4 . 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*yw ocg 2+x0 d zi(.v.wissiile7)wiqrgr+4 3 pulled upward with a constant force of 5500 N for a distance of 50.o+diic( +xli *3wwqw .sv2zri s4 0 gy)7ei.rg0 m. What is the work done by 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 force of 5500k.k)i *plr 8;hmi3fec N for a distance ofrk8h;* m ci3f lk)eip. 50.0 m. What is the work done by the weight of the 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 ux yx 3,ej)l0lupward with a constant force of 5500 N for a distance of 50.0 m. What is the net work done on the elevae uj03lyx)lx,tor?

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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 l+c0ejonu:lawi7 mc9 n5b af;iiz8 .;6.0 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 8.0 m down a ramp, inclined at:kzv6utf 2lfncz5 vffc)09b: $30^{\circ}$ 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 sister Sarah in cj1 c:k jf-ba-/suj*q a sled on an icy surface (assume no friction), with a force of 60. :jja/kcs-uqf1 -cb* j0 N 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 in the direction of the force.g qz 6ynl dlofkgof7)kg2(55uvk 3,* u The graph in Fig. 6-1 shows the force versus t7z uu)( gkl6dvy5qf5fokn3 o *glg2,khe 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 the force. Thedo4/+vzvrd9goem 7* xy : pt.i graph in Fig. 6-1 shows the force versus the object's position. mpzv:y*+ 9ivt4r. doxe/od7gFind the work done when the object moves from 2.0 to 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 in Fig. 6-1bcu q( chr38+a shows the force versus the object's position. (b+u c3qa8c rh Find the 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 force. The graph in Fig. 6-1 sdn(i*stm4 9mshows the force versus the object's position. Find the work done when ns4im 9st *dm(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 (inipe-qx 5gylve, no;x 1;tially at rest) across a 10 m level surface. -; y, qnxeeglvp1x5o;What is the final kinetic energy of the cart?

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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 (i)m.9s7fn(un7uzq 45gwiu kxpnitially at rest) across a 10 m level surface. What is the final speed of thx(g 9sz7nuqu5. 4k7w nfm )puie 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 speed of 5.0 m/s. How much work is required t k;ox pk7.0quvo stop the m0ukx.op ;qv7kass?

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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 initially moving at 25 m/s, what distfs/xd0:etg2vzi p;t1cjs* mmsc5rx45h2 qo7ance is required to stop a car movi z52r*tqs1/7m2 sxc :xsvgmch tef0;4pioj5dng at 50 m/s under the same condition?

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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 by82jn)0 hjnrqc.mvw u1 exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the1jh 8qu.vm nrn0c2w)j 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 horizontwz3(*ich fs 154rtr dval component of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the flod (zf3wt1c ir* 5hsr4vor. 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 horizontallanb xpgac55zd4 kq )05y into a bale of hay, striking the hay with a velocity 5 0 5x5kn4zgacbpqad) of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping 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 to a h;p1m 2) ns*cm6k 6x;riiwhlwl eight of 13.0 m above the floor. What is the change in gravitatirl;imcsm2 )1 h ;n6wkx*pl6w ional 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 inclined plane. The plane is 4.0 m long and risex ve;lvc ),83b5szpn vs 2.0 m. If the plane is frictionless, how m3e;vx svplc v) nzb5,8uch 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 sprinh(fqx:q,u)nt v :si8p g, causes the spring to stretch 2.0 cm. What is the spring constant?sip :(nfuxt, :8)vh qq

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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/m. How much potecbvrt/ah+l( 2 s t ,nit4zt7 (uhu*l.kntial energy +autus(bc .lk(z lth742,*t r/tvhn idoes it store, when 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 required to compress an initially uncompressed spring with a 4eivuo7d:;lp spring constant of 4oeup7dlv ;i: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 spryclec 9h, /0ating of spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position ist /hyla c,9ce0 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 constafxp 3w:-c hjt,nt of 15 N/m is initially compressed by 3.0 cm. How much work is required to compress the c fw3,pxth: -jspring 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 fc+7tl w4a kf0nrom the top of a 50-m high slope. What is the speed of the skier on reaching thea04c+tw kln7 f bottom of the slope? (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 initia-ljrrk;2 rru slj776 pl speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 m u2- lr ks r767jplr;rjin 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 inclined plane. At the +gy1+llh.z rgbcgp: / bottom, it has a speed of 9.1 g+ z/ycgpl+h:g.brl80 m/s. What is the vertical height of the 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 0.70 m ab m sy r4+-j inxdyz3gpx)mr6- ,g(ths(ove the floor, its potential energy exactly equals ir, gzpjmtr6x- ssdiy(3 x)ygn-4m+h (ts kinetic 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 -y( bsy. qpgng3sf n7*ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what verti7*.y fy-np3ng(sqg bscal height does it rise?

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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 kinetic energy of 220 J)l79x*fx6 3*md xcfkjue7ez z . At the highest poizxz7 9 k 7) *mecxjl36fd*xefunt in its trajectory, its kinetic energy is 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 rez* *;6au.vf4l49n0 ( gzhzhnzcyegyj st at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the s4u4vfel6n z j(z 0ng*hhz*ayg ;.z9ycpeed of the roller coaster at the top of the 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 staripu ,xu 4:5gbq/s3wchts with a speed of 5.0 m/s 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 the next slope, whichshuq bp35ig: 4/u,w xc 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 above the bom6v;ke+ mn q i,t*hz,bttom of a dip with a speed of 25 m/s (See Fig. 6-2). 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,q*; nmvk,t +eb 6mhzi dip?


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78#
 
  What is the minimum speed of tlh :nqt i2oawf7n8u6frn1 5z :he ball at the 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 2-kg pendulum of length 50 cm is pu(d rpgofv+ * ng.ge6/zlled 0.27 m away from the vertical axis and released from rest. What will be its speed at the bottom of gr*np+og6v g./f z(edits 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 uncompr0,hkgs 1nu(7, h ge*px5ate tsessed horizontal spring withs xg*t, t(n 517euks,hep agh0 spring 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) gp)k2*/o h hall(rmy down her 2000 kg car to stop for a red light. What work is done by the friction force again*o2khr ya)l/ hgmp(l)st 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 friction force between a 60.0-kg object ann2rdamtmf3w 3 1h2*wi t :8omud a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what di 3 ofmt38au1mnmwht*dw r2:2istance 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 movb4(ht7k* h22drikh tking on a rough, level surface. It has 24 J of kinetic energy. Ti2ht72khkrk *tb4(h dhe friction force on it is a constant 0.50 N. How far will 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 horizontalu,erdso( 02a ai1,ms nly to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If,ms(aor2e1 0dunia s, the mass is moved a distance of 10 m, what is the change 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 re;zllq4jdh1 nhc z e ;b6ei,y81st from the top of a 50-m high slope. If the work done by frl,z6 e 4jhbd ie;18 zqnh;yc1liction 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 4.0 m lonqf5.;(ksm .zx nndlc;g and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. m.cxnq zl.n (5 ;k;sdfWhat was the magnitude of the average friction 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 plane incl. e f4a9n uts,jf85dehined 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 mass aftf9e,8 hn5taj 4 suef.der 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 ofku 8wos:t+(gg e+lvo/ 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air friction acts og+uv+sgt l(:w8o/ke 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 byi iqv -sm51l t9w-+hgoy using energy when he runs up a flight of stairs 10.0-m higiw g+-v5 1tmqsi9h-lyh, 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/sx0 jjm 0)vhsq2. What power must be delivered ts0jq j)hm v0x2o 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 runs for 1.1*63ldp0 k 2rqzczdcu0 hr? (1 hp ldk2czz6 rcu31q d0*p = 746 W)

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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 of 500 W while ridin*63q ahplg erm:lv82s g. How much force does her foot push wig 38e2hallrs:6 v*qp mth 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 accelerates from 0 to 25 m/s in 7.0 s. Whf * qo9x5db9dbat is the average power dq5fdox* bd9b 9elivered by the engine? (1 hp = 746 W)

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