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

1#

What is the correct unit of work expressedua5rj)lw+-te)eeqc ) 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 motionj+7.yt. v)rqkzlepk ;?

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 statiz84f (jm7z xssonary brick wall, the amount of work yos f j784s(mxzzu 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 held there. How muc,-bn+;sc3 zvrs-em blh work is being done in ho,zms-3-b snbc+ r lve;lding the box in this position?

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 constantw/4 bjg nr.+(szqy :nc velocity carrying a 10-N object, the amount of work y+w /s c4b(gqjnzr. n: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 veepmitz6-, j8 r fu x;,jz,ogo9rtically 3.0 m then returned to its original position. If the total weight is 30 N, how much worjoj8, ,ie6ft ;xrp-,zmz9u ogk 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 on an object do won msq9v :8z,ugvg;hwvum ; h:8ihlc7+ rk 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.1 x9v 7 ybeb1h.a+ujyixib9n3nax p(d6)xgu by gravity while the ball goes up with the sign of the work done by gra9+eb1xx xp.hjn73xgnbu()aayy19dv u bi . 6i vity 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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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 h kul/k-2qsg-nr)b.u zoe5 t k015a b:u 0lnrp(F vs. x) graph, representslsul z-un/pa20 ) 50u1:5o nb-tqkkr .khberg

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. xkho(uv 7ti(ybn)95e8x i )ak m9ozrt*), what represents the work done by the force Fvte r*9(uknto9)am5( kh xo7i bi8y) z?

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 l+4 sj (ugltpxj 3hj:d+txk/: positive, 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 obu:+gq hm,f;i73xq1if*hod,*bp uqrpject is negative, then the object's kinetic 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 on an object is zero, then the object's kinev.vzf :zeu4ad7xc72j,ixn1 9kzt ep8tic 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 muctky3. bb* qwox ;4f1inh as a car, and is moving at twice the speed of the car. Which statement itq i;143wnb.fkyb ox*s true 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 carh.xy)yaq f.tvw, k2 h4 K, and car J has half the mass of car K. The kineti)4 t.yvf2. hxa, qwkhyc energy of car J, 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 bounces back with half of its original speed.b9( kf clxbe-bz195ui What is the ratio l-959 zek ib (x1fcbubof 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 atj2d, gse(:yzf8-sf r) b:o -lrbh 2zsu a speed of 5 m/s. If both objects have the same k:z(ujl:ssfy)sf -, -brbr e g2 h2dz8oinetic energy, what is the ratio of the brick's mass to the rock'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 2.8e.bfoj*sbhl: stw 2bfa 7v *-0 m/s. A 1.0-kg mass is moving 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 bet*s:8 l*7a h2bw.vf-bjobe fsfore 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 c cos9qq id9k) b(-8dtcdm1)u war in a panic, and skid a certain distance on a straight, level road. If you had been cw-dku ib qm(st9c8d)9qd1)otraveling 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 orbf-( 9(oedyolu its the Sun in an elliptical orbit. Neglecting any friction effects, what happee9( foou l-d(yns to 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 princicaq: dz6*u +kd-2hmm sple.

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 nzst u h,4n1si1egative 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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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 above the ground. A second obq63 sc96wcwvv ject with four times the mass of the first if rele9s636qc vv wwcased 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 a spring causes it to stretch 5.0 cm. cqy wnh4pey/,/7 ysnb,ok*g81rda*j If another 0.200-kg mass is added to the spring, the potehygjwy7k*, y n,dn/p1 ero/ s 4qa*c8bntial 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))a jd7 tjym 82o0qh 2nh6jake of 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 tree. Compare its kinetipodb-q(0(n plufw*q e r 4z/8tbc6r(gc energy K, to its potential energ *drp ( /6pn(wbc e84fz-rg(to b0uqlqy 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 a carl 0ha7eecr6v d(r ;rm6 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 ko 9rc- (2x1bi l1ytxnequal speeds along a level frictionless surface. They both slide up the sain1or (1xlt2 bykc-9xme frictionless 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 z7requz1 h/j7 qpij(:$m_{1}$ 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 mechanical energy for conservative tl + ,hjftfr-3 2++ookbynwt,forcesbo,+ r++kf ohyttj tl3wf2n-,.

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 ky p3v.xys,7tthe air (air friction is present), to tvy xskp .t7,y3he ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (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 gains 30 J of kinetic energy. Do not ignore air xuth:4e t(u;hdqia-5 resistance. How much gravitational potential energy-(qhxtue d; ati:5u4h 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 losej 8poc-wjx7+vk cl5) vs 30 J of gravitational potential energy. Do not ignore air resistance. How much kinetic energy did thej+ljkv 8cox-pc) w 57v 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 conset* 66kw0qf zd( cuc,pmrvation 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 isyo:kwc 3ql r)0

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 ;zbkgan *) i08v)ryd cof power expressed 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 unit b1f47k6yds iv j- cpxd6g;x5mof 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, )lgnw z fei0 ;uqq48ss4qbu: 9you did 3 times the work in one-third the time. To do so, gzsbu e lsqq4q04iu:n8;)w9f your power 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 car's enyz;7qr(pjc/n s,2b1av pg.rngine 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 held there. If the object weighs 90 g84v: ohpookp( qh;7 eN, how op(8pe4 vkhhoqg o;7: much work was done in lifting 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 y 3 :efmud;mwp68om :gair a distance of 1.0 m, at a constant velocity of 0.50 m/s. Wha;d 3m68wu:pg o efymm:t 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 pulledk vnhwr 0*7 )1bgoap-dmaq(/l upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by t)kamapdg( qb7v* -1 hr/o ln0whe 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 pulled upward with a constant force of *hr vlocf20 o,jt h.4z5500 N for a distance of 50.0 m. What is the work done by the weof ,c.h24* l zhot0vrjight 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 constan 3iizntt 9n2*tt force of 5500 N for a distance of 50.0 m. What is *izt3in9 ntt 2the net work done on 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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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulledxvt(of2-+roq f8 cn +v i/l-nb 6.0 m 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 ramp, i1 cg7h02,bhs rgint:gtm1m-)mqv05 jar(vcj nclined 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 kl jqz+ wb,cb* 3qu7x*897nb o;dimcion an icy surface (assume no friction), with a force of 60.0 N 3m ;cblxnijb 7kwz* di c, 8uq+q9*7obat 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 direction of the force. The graph nm1ml3 z,pkfx5sdrd4r5o- - g in Fig. 6-1 shows the force versus the object's posi d,p15o5-d4m s krlx-fn 3gmrztion. 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 thgk+8gsxuv4 7 izd s86(zvbg a8e direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the objeuks8+ d48zb(7 z8v xiva6gsgg ct 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 directh /66wa+x f x7vpr6 jgmsqq,6oion of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the wgqqx/jmso6 6v 6 r+wpx,hf76aork 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 t8cl*m m,u mp 4go1pl7mx4 mpk2,s/p clhe direction of the force. The graph in Fig. 6-1 shows the force versus the object's positio,o*s4lp 27 m8lpkcclup, /mxg 14mmp mn. 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 is applied to move a 55-kg cart (/n*e3mb cfwy rq xz.56+ o7rdtinitially at rest) across a 10 m level surface. What is the final kinetic energy of the 5wr./mc 7qxdy3f 6obretz n+* 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 i ,vnskkf(5cwyh 0 61.lpd8aj move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speed of the cart (5ha6idkfnj0s,p .wck8 y1vl?

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 d;q9 eqdl1,pcm/s. How much work is required to stop t1d9pcd qe q;l,he 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 cark1 dg orsx 1e7f6tb31l initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under l1xr1 dgst 761eo3bfkthe 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)kyii ln4;h(xc.i) qw propels a 10-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 h4n.)cyq )likix ;(whi as 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 a vertical compo) tg-.1 mlibi/3qs ju n9ftnj;nent of 60 N. The force is applied to a box whic-jbijmnft;g/l.s 913n i) tquh rests on a level frictionless floor. The cart starts from rest, 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 the h,d (yhgz;jdqn o- z36oay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopp-oohnzd;gy3j 6,q z( ding. What 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 moveddk(llg/ v 7vte5sh3u ) from a height of 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitational potential entk/glu(v)evl7 5 hsd3ergy?

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 plane. The plane is 4.0 m long and rises :orv h/ njb kqnvxw5/h(;f4(p * bv*hl2.0 m. If the plane in(*bwh/vr; q :4n/v fho (blp hv*jxk5s frictionless, how much work 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-4p aff6j3 9ar0txgsb k3itzev0i63 w, causes the spring to stretch 2.0 cm. What is the spring constant?t069a-3bzsi3 v3 fkapw0 tj4eirf g6x

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 u1ap8rdb m4m2of 60 N/m. How much potential energy does i2b1 4 u8padrmmt store, when stretched 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 require6 4qt /tgaraav 9-u*xqd to compress an initially uncompressed spring with a spring constant of 2v*a/aug-a 4rqq9x6t t5 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 sd( 7epa)jp3o0tjd rmz0qc+e6pring of spring constant 40 N/m from x = 0.20 m07j6madc+ez odt e(p0rj3p) q to 0.25 m? (Assume the unstretched 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 cm. Hz; aqclqe6z . 96ibws1ow much work is required to compress the spring an addiisbe6 qqz ;9cl6w1az. tional 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 high slope. What is y.hb59 f0sm9pb r/oya the speed of the slier on reaching the bottomh/oys5 b9fr0 ya9bp m. of the slope? (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 the top of a hill with an initial spe54d jls sa: 6cmrpikfzs2l 8hq -16m)ved of 4.0 m/s:f-)aqihr25 mlp lsd 866 k4zs1jv msc. Neglecting friction, 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 s a/2dzp +s: yydm k.ya45ns4mqpeed of 9.80 m/s. ya5n.dmsza/m4:y qkps4dy + 2What 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 0.70 m above the floor,r5yl0uki/,7141zs n co wcyug its potential energy exactly equals its kinetic energy. How fast is it movins,zk14iou cw51ng/0 7rly cuy g?

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 withvzf1b p82bf.i a kinetic energy of 40 J. At the exact top .bp bzfv12fi8of its trajectory, its total mechanical energy is 140 J. To 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 2 yvdd8oo8q-t2 0hqck7.y n x+n20 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, d7-2 qnhd0qvy.knox 8y8 +tcorelative 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 dip (Sn*a pqinrz id q* a7nv*37;k(bee Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m aboveab*q(ni k77*q vzipn* 3a;dnr 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 g4 uje3dnjdnu *531pp5dont 9of 5.0 m/s at a point 45 m above the bottom of a 13oe4ngd 5t5j du3j* dnnu9ppdip (See Fig. 6-2). Neglect friction, what will be the 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. 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 a dip with a speedc - w,)qqq.ky ;re )ivmw1u8ib of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top 1vre-.cqki wwq uq) im)yb 8,;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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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the b;lzmm -,1 hrenottom 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 vh1wm1f b:qcz- hnv3ox oj04+ hmj8 lzw,my:3eertical axis and released fr:jm 8- vhenw lmhz14x3oo0wz :hjc,my+b1f 3qom rest. What will be its speed 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 f0a 6/:gqgfzb 25 m/s hits an initially uncompressed horizontal spring with springg/bgfq0:fa6z 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 22 m/s, slows down her(f19qi.wx*i ymgs2i s 6.rfgb 2000 kg car to stop for a red light. What work isg bwm 12i.*rxg.fifyqsi(6s 9 done by 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-r1l9oqi b39xh1s5 5i5 re aaphkg object and a horizontal surface is 50.0 N. If the initial 39i5ehqoa s5p51rrhxl1ai b9 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 movinmp+7 .i nin)yc4n rfb +0j)oamg on a rough, level surface. It has 24 J of kinetic energy. The friction force on it is a conj4 b+m0opnarf+n mci) 7y)n.istant 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 su ,cn+:0 fvy eqnmc-trb+hm4b1 rface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10+fmcb,b:4c yqn+m vt hnre01- m, what is the change in its kinetic 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. If the work hr5e.,e85 x dis jhpy/e-fsl. doi hhlje/5y85sp d -s.,f.e rexne by friction 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 m long and ritv t;krud6n .hzd b :tjbjf60 :1d))tvses 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude o;tvv ufbhj61b)kttn)d dz 6rjd:: t.0f 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 amvw9hj) 0q 1bra2xlk i1(h )jthe top of a plane inclined at 20e above horizontal. The coefficient of kinetic friction bejw2ba)h (m1kqrvx1 hl9)0 iaj tween the mass and the plane is 0.20. What will be the speed of the mass after 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 heig ) ij,8yja.vl unj)x+ta:ob- lht of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air frictiontu8)l jl. )iyn xojjb,v+-a a: 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 rucxwn7) cx pl--ns up a flight of stairs 10.0-m hig 7nw- cpcxl)-xh, in
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 to move an object with a /x d;*vcn)roe constant velocity of 5.0 m/s. What power must be deliveredne dv )/o;*cxr to the object by the 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 9h61h c7liy kr pavpxy+i- -j)runs for 1.0 hr? (1 hp = 746 vy cyra6--k97p h)+1ijh lxipW)

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 formq zf/1p lu +sdkax- 8-0g hw-y):nrkoce does her fopk)08kdf1sgny:+ho- - muwqa- l/xrz ot push 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 accelerates from 0 to 25 m/s in 7.0)983x uwbyiw l+9s osi s. What is the average power delivered wos8)+s 9 x3wli9yibu by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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