Physics Unit6: Work and Energy - 51fly国际课程 (51fly.win)

1#

What is the correct unit 0tabo4se m2 kd.hv yls(:8a 3cof work expressed in SI units?

A. $kg m/s^2$

B. $kg m^{2}/s$

C. $kg m^{2}/s^2$

D. $kg^2 m/s^2$

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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 system if there is no w .az5axn0c(vmotion?

A. Yes, if an outside force is provided.

B. Yes, since motion is only relative.

C. No, since a system which is not moving has no energy.

D. No, because of the way work is defined.

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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,ln1ecq):e rv;n3+wg z the amount of work youe+e3 w )l:g;n rzc1nqv do

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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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 vertically and is being i2iz8rjf h e,:b-bly:held there. How much work is being done in holding the box in this positb: f8 e -hl:i2ri,zybjion?

A. more than 100 J

B. 100 J

C. less than 100 J, but more than 0 J

D. 0 J

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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 constant velocity car,;4rjpr;s)bhzv vn+pr 08o8c;qwv * v- ivdozrying a 10-N object,z;wzr c q opo vpns;hrjr-v+v ivd*)v84b0;,8 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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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A container of water is lifted vj-l8*wjlr/;vy :xu pcertically 3.0 m then returned to its original position. If the total weig lcwu/j y8-pl:*;rj xvht is 30 N, how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No 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 onpfktz*lx g 51:,8jsjvtm8fo. an object do work on the object?

A. Yes, since a force acts and the object moves, and work is force times distance.

B. Yes, since it takes energy to turn an object.

C. No, because the object has constant speed.

D. No, because the force and the displacement of the object are perpendicular.

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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 done by gravity whis5kd(i2eylbwkk7 :4 cle the ball goes up with the sign of the work done by gravity while it goes dodk54c7 kye k:s(w2 bilwn.

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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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 veryw: t 5e/633wgczg gthsus position (F vs. x) graph, represents wet3yg36c t:g g/5zhw

A. work.

B. kinetic energy.

C. power.

D. potential energy.

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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 work done by tflv( i c8-.k,jay-btevg6l3 the fojv-te abg8c(,lvfy 6 -kli. t3rce F?

A. the slope of the curve

B. the length of the curve

C. the area under the curve

D. the product of the maximum force times the maximum x

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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

A. the kinetic energy of the object.

B. the potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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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 posi4zz5:rqdm yvg39mdzcc 3 :hj: tive, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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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 kv pgv,7+qh*+rcku6ya inetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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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 onkdtoj ;u1c*ifeg33d - an object is zero, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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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, as xrb q n1e7c3lglln3 6d6k5ydm,zuj ux:,2b 9nd is moving at twice the speed of the car. Which statement is trnlme 6335q71u,kln9r yx d 2sxludbz:cb6 j g,ue about the truck's kinetic 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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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 half the mass of car K. Thb/ wqhexnzl(kj888t 2 e kinetic energy of car J88(j lzh t/qbn8e2kw x, compared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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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 bou5 flq4lsabock,5 ,+1lsdg en65f rouqxj ,z)/nces back with half of its original speed. What is the rau o)+jezqxk ,qn 4l1or5,g6lcls bsa5 f5fd, /tio of the final kinetic energy to the initial kinetic energy?

A. \frac{1}{2} \;

B. 1/4

C. 2

D. 4

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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 moving at q gqy8w*ka/;m 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 akym/g; wq q*8rock's mass?

A. 25 to 9

B. 5 to 3

C. 12.5 to 4.5

D. 3 to 5

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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 c6v8fw y*8dh jmoving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance wcd 86hvf*jy8 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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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 skie(.qpl1 ,y 1x ykbb/ p:qxmey5d a certain distance on a straight, level road. If you had bx:kx 1l b,. e51qepy(m/yqpbyeen traveling twice as fast, what distance would the car have skidded, under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

D. It is impossible to tell from the information given.

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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 orin:v4* 4tccc lbits the Sun in an elliptical orbit. Neglecting any friction effects, what happens toltccc v4n:*4 i the planet's kinetic energy?

A. It remains constant.

B. It increases continually.

C. It decreases continually.

D. It increases when the planet approaches the Sun, and decreases when it moves farther away.

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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 princ8) h7-snnju dl+tg6k z .kn2qhiple.

该题自我估分: (必填) (满分:1.0分)

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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

A. the kinetic energy of the object.

B. the gravitational potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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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

A. the kinetic energy of the object.

B. the elastic potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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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 potential energy-qfgi3u7 5rg z ,:fbgq- pjym:?

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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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is released from rtkiv: kod.y6e: em*:c est a height h above the ground. A second object with four 6ki:y *:toe:v ck.me dtimes the mass of the first if released from the same height. The potential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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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 g iosb bu:6qbn1 cl;5,a spring causes it to stretch 5.0 cm. If 6bs 5cq,nou;b1il:bg another 0.200-kg mass is added to the spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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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 ofk,nc z66/wwj*zd+ yflp eq g4- a system

A. is equally divided between kinetic energy and potential energy.

B. is either all kinetic energy or all potential energy, at any one instant.

C. can never be negative.

D. is constant, only if conservative forces act.

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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 trq.m)b *4r2. zgaubuisf; b.aqee. Compare its kinetic energy K, to its potential energa2gqr4ubiu.; as bbz. qm.)* fy U.

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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30#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Describe the energy of amvrz-i h fpp/w ;3d;-h car driving up a hill.

A. entirely kinetic

B. entirely potential

C. both kinetic and potential

D. gravitational

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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 spee.j)wm 45ag dme2qjl:s/ah:e rds along a level frictionless surface. They both slide up the same friqm):jg .d 4meraas52wlej:h /ctionless hill. Which rises to a greater height?

A. The heavy object, because it has greater kinetic energy.

B. The lightweight object, because it weighs less.

C. They both slide to the same height.

D. cannot be determined from the information given

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32#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Consider two masses 1ykf2 )be15-qrnue3w /ig prm$m_{1}$ 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?

A. $m_{1}$

B. $m_{2}$

C. They both are going the same speed.

D. cannot be determined without knowing the masses

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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/8jp o,rd(ass+b xc t:v),rt c mechanical energy for conservative forcesaxod+ j/ts) p,cc:, (rrt s8vb.

该题自我估分: (必填) (满分:1.0分)

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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 a building, through the air (r1;s3*h bp lbh nkt6- fth c*h*v-ilf*air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential enef*bc-snlr-3 il6tbp v*kf **h;t1 hhhrgy (U) at the top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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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/n f7nvvlz78j; my u6k gains 30 J of kinetic energy. Do not ignore air resistance. How much gravitational potential energyvzjukfm678 /l7v n;ny did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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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 potential eneojqsz t)ug /;vg)tg k1)(k1a grgy. Do not ignore air gsg)k1(gt; /tva)kug)1 ojqz resistance. How much kinetic energy did the ball gain?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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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 conservationnvwm f v/ r14n9r1:qy) fcckr* of energy.

该题自我估分: (必填) (满分:1.0分)

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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 isv gl;w rvn, .do+u-d8i

A. the kinetic energy of the object.

B. the potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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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 eod u06ol8 nl5axpressed in SI units?

A. $kg m/s^2$

B. $kg m^{2}/s^2$

C. $kg m^{2}/s^3$

D. $kg^2 m/s^2$

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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 uni/ge/m(m 7cf+e-se,ao9zda 1t ;eli wpt of power?

A. watt/second

B. newton-meter/second

C. joule/second

D. watt

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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.4l : g,adv ::b 2nt*mjec:omjmghhx-- To do so, your power , 2jnmm-je xt:h*:-ld:mab4o:c g hgv output must have been

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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42#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

To accelerate your car at a constant acceleration, the ca/o7znvcx, d2ge 5+pukpu w nb9qx89q)r's engine must

A. maintain a constant power output.

B. develop ever-decreasing power.

C. develop ever-increasing power.

D. maintain a constant turning speed.

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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 and hel5rs sus7(px2w d there. If the object weighs 90 N, how much work was done in liftings5 s7 r2s(xpuw it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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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 distance of 1.0 fvl)z h k6fp 06u6vvau985 thum, at a constant velociv6 ukzfhh)t u 06a95lvv 68ufpty of 0.50 m/s. What is the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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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 for a xbd9i 1 f/vne5:;5lm g*riuph5sj+ lr93cyywdistance of 50.0 m. Wmhyfrr9 iy 5gpe53wixds5/lc;9 *n l v :+ubj1hat is the work done by the 5500 N force?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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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 pulb* qdag zgebe9,,e5b 4led upward with a constant force of 5500 N for a distance of 50.0b *4edg95abg, bqze,e m. What is the work done by the weight of the elevator?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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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 consta66li ig-p/ ibr5o4 9i iiuzzw+e-x2n jnt force of 5500 N for a distance of 50.0 m. What is the net work done on tinzi up w6jril bo/ix9-i4-2+6ze i5 ghe elevator?

A. $2.75 \times 10^{5} \; J$

B. $-2.45 \times 10^{5} \; J$

C. $3.00 \times 10^{4} \; J$

D. $-5.20 \times 10^{5} \; J$

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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 m 3s;gog58h9 hntk) mmbf5.rbvczq6;h up along a $37^{\circ}$ inclined plane. What is the work done by the weight (gravitational force) of the box?

A. $-11 \; J$

B. $-1.1 \times 10^{2} \; J$

C. $-1.4 \times 10^{2} \; J$

D. $-1.8 \times 10^{2} \; J$

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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 0q(gl, epa( eh 2).bdox:zvaxramp, 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?

A. $157 \; J$

B. $-157 \; J + 78.4 \; J$

C. $78.4 \; J$

D. $-78.4 \; J$

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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 a sled on an icy sgni-:i(j fobl 6 2vn4uurface (assume no friction), wituov6n 4-bnl2i(g i f:jh a force of 60.0 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?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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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 dira0j3g+ep hco ,ection of the force. The graph in Fig. 6-1 shows the force versus the object's position, goa+3hejp c0. Find the work done when the object moves from 0 to 2.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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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. The graph d.s gxbb dzo+(-n sk9+in Fig. 6-1 shows the force versus the object's position. Find the sk +-bxdbz .9sod(+ng work done when the object moves from 2.0 to 4.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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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. 6-1l7c1n xig01bcfwb bhg,8uxs0k18ll/ shows the force versus the object's position. Find the bux7c1ws x, 80i1 b/nggklcllhb0 1f8work done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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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 (1eha6anxc 0mn a98 awthe force. The graph in Fig. 6-1 shows the force versus the object's positin(8 6mnawcx1e9ha aa 0on. Find the work done when the object moves from 0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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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:t7ygu hx08u a is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic enxh a g7:0yu8tuergy of the cart?

A. $1.0 \times 10^{3} \; J$

B. $2.0 \times 10^{3} \; J$

C. $2.7 \times 10^{3} \; J$

D. $4.0 \times 10^{3} \; J$

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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 (wpe010. uod/qd 7j)gs7nh u6 hkyyf u0initially at rest) across a 10 m level surface. What is thewof yg. /01u )n7dj0hhq spkye6d0u 7u final speed of the cart?

A. 73 m/s

B. 36 m/s

C. 8.5 m/s

D. 6.0 m/s

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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 z 6 *ic7/v-k cpyt1hyqf6twf3 is required to stf 6-cz6f3/c1k vy pyhq* wt7itop the mass?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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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 na- bu0mqvs 7f)8q io36rsll/at 25 m/s, what distance is required to sn-q 3s s oirbl)8muv7qa/6l0ftop a car moving at 50 m/s under the same condition?

A. $50 \; m$

B. $100 \; m$

C. $200 \; m$

D. $400 \; m$

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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 1cl xh /l)kj6o60-g dart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the spring k)x l6/c6jlohhas negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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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 6ba9-pra vn :uzfwm;cct d,7h)l9wj :a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from revn9) r -p 9dhza:t;:jcb6 wa wm,c7lfust, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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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 horizontally into a bale of hay, striking th3x 5)nhq iw:stw qt32je hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. Wwt323)hijq xst q :nw5hat is the average stopping force acting on the arrow?

A. $45 \; N$

B. $90 \; N$

C. $180 \; N$

D. $360 \; N$

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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 abovu,e.;r:i7iw5q h ssgie a floor to a height of 13.0 m above the floor. What is the change in grav. qi:wui,isg r seh75;itational potential energy?

A. zero

B. 1030 J

C. 1176 J

D. 1910 J

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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 pph4 k8u) mye ycy.rhr15 ;vs6tlane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much wortyh us m46 hp18 c)rv5ke.yy;rk was done by the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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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. What ict 7jt.)gtvp,s the sp7t.pj),tgct vring constant?

A. $4.9 \times 10^{3} \; N/m$

B. $5.0 \times 10^{3} \; N/m$

C. 20 N/m

D. 2.0 N/m

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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 pl xvt ;tpv8t9jbr:k:2 otential energy does it store, when str2t 9t:tbxkjv8 ;p:vl retched by 1.0 cm?

A. $3.0 \times 10^{-3} \; J$

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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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 initia3 2 wuiq54+plng+yngklly uncompressed spring with a sprin4 +g3qi p kwyul5gnn+2g constant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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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 constrnlmdzn,u qb)o9 e(75 6qlpo+ant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstrelbo,z)unmpl9q( d+r 6no5q7etched position is at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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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 of 15 N/m is initially compressed by 3.0 cmyara5 wsabsgf+d.c7 ye6 0/h7. How much work is required to compress the spri chswegra0+7bsy df. 7ay5a/6 ng an additional 4.0 cm?

A. $0.0068 \; J$

B. $0.012 \; J$

C. $0.024 \; J$

D. $0.030 \; J$

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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 higpld+ j oc;5r2h2yb 5bj.gc* lch slope. What is the speed of the slier on reaching the bottom of the slope?l5j h2l5.c*rc;y+2gdop j cbb (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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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 u:i(3 cic6dw ki. rlm;the top of a hill with an initial speed of 4.0 m/s. Neglecting friction, 6( irciwm:k.duc 3;il 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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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 bottom, it has a sj6q4mz; q.gghtj mfc)/j k-s5 peed of .gj hcz4fkq5 m- jt jq6gs;)/m9.80 m/s. What is the vertical height of the plane?

A. $19.6 \; m$

B. $9.80 \; m$

C. $4.90 \; m$

D. $2.45 \; m$

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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 0.7b8 g6a3)saraqnz6v ns x-:m*b0 m above the floor, its potential energy exactly equals itssr q-aznaxna* s6b6 :v38 )mbg kinetic energy. How fast is it moving?

A. 3.7 m/s

B. 6.9 m/s

C. 14 m/s

D. 45 m/s

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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 level with8skv/ ;pm ede 38l0lrp a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. Topme388;d lr e lpvs0/k what vertical height does it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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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 220pa44d.f bof fvec 2v3l4av4 u9 J. At the high boevfd 4p4af9 f43vuc2.v al4est point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise?

A. $\frac{220}{mg} \; m$

B. $\frac{120}{mg} \; m$

C. $\frac{100}{mg} \; m$

D. Impossible to determine without knowing the angle of launch

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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 rest at a point 45 m above the bottom of a l yf .j)t+e;w bjx4s0ldip (See Fig. 6-2). Neglect friction, what will be j4e0wl.f;sj xl)y b +tthe speed of the roller coaster at 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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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 a point 45 p lno.j vx+5h;m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at ;.lo5 p +nvhxjthe 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. 12 m/s

B. 14 m/s

C. 16 m/s

D. 18 m/s

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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 bottom of yt3w)4u v*mu pa 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 botto*4wtvuy) pm3u m 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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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the bag ckn -xe(5msn70r qy43ppo ad:7.exjll 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

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

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 the vertical w/ ,xjsvin0iit ; j:4oaxis and released from rest. What will be its spt:sj vw o,i;xin4j /0ieed at the bottom of its swing?

A. 0.50 m/s

B. 0.79 m/s

C. 1.2 m/s

D. 1.4 m/s

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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/e59nd; lj7lumlrrp5:0w lc(p s hits an initially uncompressed horizontal spring with 7d9:l;w5u0erlpp r(n5lclj m spring constant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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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 22c(vduk) :mk( q m/s, slows down her 2000 kg car to stop for a red light. What work is done by v:ckq m(k)ud( the friction force against the wheels?

A. $-2.2 \times 10^{4} \; J$

B. $-4.4 \times 10^{4} \; J$

C. $-4.84 \times 10^{5} \; J$

D. $-9.68 \times 10^{5} \; J$

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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 and a horizontaupj w-e;b ,jvfs6k; 69us,2jfsrqu +pl surface is fwv ks;-uu 2b,9jqsre6f +j psj,p6;u50.0 N. If the initial speed of the object is 25.0 m/s, what distance will it slide before coming to a stop?

A. $15.0 \; m$

B. $30.0 \; m$

C. $375 \; m$

D. $750 \; m$

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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 jzugd+r1zinhc3 ;e0ebl )8 2bsurface. It has 24 J of kinetic energy. The friction force on it is a constant 3dbh+ 8cezg ub10rijz;en2)l 0.50 N. How far will it slide?

A. $2.0 \; m$

B. $12 \; m$

C. $24 \; m$

D. $48 \; m$

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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 to a 2.0-kg mass on a level n ,qid6 x+xn+ wi;2tcesurface. 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 change in its kinetic i cn2wne,d+xx6 +tqi;energy?

A. $20 \; J$

B. $39 \; J$

C. $46 \; J$

D. $61 \; J$

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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.(7 1sao6,u kdc ta6nxy If the work done by fric6da7,(nau6yk cos x1 ttion is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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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 g * u/2o /ymwqo:r*aepm long and rises 2.0 m. It requires ug*a om*q: w /2o/pery3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force on the box?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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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 o7z chv4c3u )jvf a plane 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 mass a4)cuh vv7c 3jzfter sliding 4.0 m along the plane?

A. 2.2 m/s

B. 3.0 m/s

C. 3.5 m/s

D. 5.2 m/s

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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 10.0 m, and strb8xh v 9wg36flzup7jy)ko t88ikes the ground with a velocity of 7.00 m/s.6 3htgvko88pybjw9uzlf )x8 7 What average force of air friction acts on it as it falls?

A. $22.5 \; N$

B. $75.0 \; N$

C. $225 \; N$

D. $293 \; N$

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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 ua3z0x;-v +i a9elgcyox5) cy fp a flight of stairs 10.0-m high, ig3zcafa )0;xxe y vyoi9cl -5+n
8.00 s?

A. $75.0 \; W$

B. $735 \; W$

C. $4.80 \; kW$

D. $48 \; W$

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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 tgm 9j9 ;:t(vs 5* ppdsk8sdczko move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the vpg dds9*ks;p9 jzt5 msk(:8c force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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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 rcvzcdc5j 8 pz. s(9hg*p:nu/ vuns for 1.0 hr? (1 hp =vj*/chc dz8c spugn9 zpv5:. ( 746 W)

A. $3.6 \times 10^{3} \; J$

B. $2.7 \times 10^{6} \; J$

C. $4.5 \times 10^{4} \; J$

D. $4.8 \; J$

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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 riding. How much force does 23ul 9p eosn+fher foot pus+e9l2 n 3fuspoh with when she is traveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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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 accelerat5amqoe 4ud*e9ggm*qeje.;bir i zrg9 u*e(/-es from 0 to 25 m/s in 7.0 s. What is the average power delivered by the engine? (1 h-i *r rq umm4ea g;9zugie.*(e9j bgeeq/do* 5p = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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