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

1#

What is the correct unqgw, qgzo g;shv1it ( ei 1.gvevdv836b-mc-7it of 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 +);vga;xe)4 23dst r tgavcqpno motion?

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, the amount of t9mvir,h 2p:n work you dohr:,in 92 vtpm

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)x* hd tpgv8mxhd ).g1 m vertically and is being held there. How much work is being done vmg*.) d dt h8x1x)hgpin holding 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 at6rg:ll ;kbp w o51ktxc) 2 on2i::ejnj a constant velocity carrying a 10-N object, lk 5e2onjk;b t:plj: )w6o1: 2 cgixnrthe 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 vertically 3.0 m then returned 7m6h8* jhhg t.+ss tlmto its original position. If the total weight is 30 N, how much work wamjt76h sh.s8 thg+m*ls 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 fov 33d kl had10 vco8dw;phzqsh/f4:+x rce acting on 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 straw22 2 ke; kn:hqyds8ybight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. 2;2 hdbkes: qk82nyyw

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 (F vs. x) graph, reqniv m2;w 8q(epresentsqw8em(ni 2;q v

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), wha l/:l /y(-/wpx*3rrvjx rh otat represents the work done by the :r -a/xloy3j/tp h (vl/xrr*w force 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 positive, then the object's k 6h3 :ek/naacbo+qkvrn a;;h9inetic 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 thez5 xg,ozet r(: 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) pu+ogs q7)w l/ska4e on 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 s k )77p98seix1zsjgods9bz0 as a car, and is moving at twice the speed of the car. Which statement is k)s 9bx7 sd8zs9 z1s0eog7 jiptrue 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 hal.w+-bla2 k9q 8vmdizy f the mass of car K. The kinetic energy of car J, compared lm2a9 zd-8y. bqivk+w 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. Wh .m:jx*ngkcw4at is the w.k n:*4jxgm cratio 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 movkxrz3.zp22)xu trwq0p g0cw 2ing at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of thet)30r 2qz.c02wz rkxupwgx2p 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 witi04peq gxmokf 548uq/h speed 2.0 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 brog 4qi0 uqf xpme/58k4ought to rest. Which object travels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in a panic, and skid a cxusym+:c10 rhertain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidduxs 1my+r :ch0ed, 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 mnk 7cd,d4(kaxadg 82uass orbits the Sun in an elliptical orbit. Neglecting any friction effects, what happenskd4d ak (8xa7nugcd2 , 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 princips-t xv18- eh7: iggewule.

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 potentia z,6uk62/rhqi-cs g;usuw z:fl 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 ax+)u+ temgit9 height h above the ground. A second object with four times the mass of the first if released from the same height. The potential eni)+ t9ugt emx+ergy 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 l/,w.d ot yz*5luj yy7aa:w,q 5.0 cm. If another 0.200-kg mass is added to the spring, the poten y.*o 7a/yqa jdwyzulw t,,5l:tial 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 enf ymxu frf1epi1-(cxry* ;g,5ergy 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. Comparya6;i/c/ lzk,0ynnvw e its kinetic energy K, to its potential energy U.lz k0a/6w,iv;n y/ cny

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 car driving up a hill ) x22dy)85leydvs)f.. h 9xwlodnbeijui -t9 .

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 s5ddpnb l7je1 3peeds along a level frictionless surface. They both slide up the same frictiolje p1 53ndd7bnless 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 i/m) 0tja0 jse$m_{1}$ 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 of5x 42-cew;oiexwbs87 avh a-r mechanical energy for conservative forces4- e;hwr5ab7xsxwao-i cv2 8e.

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, thro +3glkpx+ gdk(*) axqejl)mh(ugh the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the grok( a)hjg+ *xp+3gq xldklm) e(und 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 andi ro5 8swhex6, gains 30 J of kinetic energy. Do not ignore air resistance. How much gravitationa6w5r 8i,s ohexl potential energy 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 gravitational6-pjc7) gj fj wwao/(a potential energy. Do not ignore air resistance. How much kinetic energy did tjw7o 6j/w ajpa)( -gfche 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 conservugqj+iof1 j8/o)ouqaep:7 k *ation 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 is-x4x o rwq/*kq-ruaq4

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 expressed in SI unitwtc7 -y kn:9rigexs0 bd)5;mq /n (jdxs?

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 notv2kl uqd;: )yc-x pg9t a unit 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 td 1jp: q+c0//t htgykjhe work in one-third the time. To do so, your power output mg pt q1c/ t/d0khyj+:just 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 cad l 3s;wuiht9ns tzq* xx w-4..grr94ir'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 held there. If w8:z eem(j hs wdbjii-(z6a)0tcu*1 s the object weighs 90 N, how much work *i:t jsah(ijbu1we)6z8d e0zm-wc (s 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 air a distance of 1.0 m, at a anxuny*q+3sx qio4gn 0,)3f l constant velocity of 0.50 m/s. What is the work done by the wq0gan*qo)n+ , 3xyu3inl xs4f eight 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 upw ,*etebh-l2: kn3ugc fhcu n 0m4eq32aard with a constant force of 5500 N for a distance 20- ahe32gec fe,* mtnuqbku43hln: cof 50.0 m. What 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 pulled upward with a constant force of 5500 N for a da zp/f hh 6c*o1t)p, m;br9obzistance of 50.0 z t1b)*appbrmz9;c6 h/fh,oom. 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 constant force of 5500 N for a disuat7)1b 6h u (lgjd.v4k3 gw;lin v+yttance of 50.0 m. What is the net work donejnt3u)lh.v bgv+i1y wlk t4dag;7(6u 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 pulled.o z32hml-rxv 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 dow+lj )w3 f8sucqn a ramp, inclined at $30^{\circ}$ from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?

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 surface (assume no fri8aw7btg/dfr1 :b y)sqction), with a force of 60.y 1bag)b/rwtfs d 87q: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 direvqu gm,2w- p,uction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when ,2w-pvmu,guq 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 obje rw*hl*j7k+j5+ djm/ e.wrudtct in the direction of the force. The graph in Fig. 6-1 shows the force versus /dk.w7 jjr*+ 5lhtw d*+jmeruthe object's position. Find the 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. k2m 7waq(.p8x 0twhpc The graph in Fig. 6-1 shows the force versus thpx h cp8mwwqa2(kt.07e object's position. Find the work 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 objf *(axo gxd/)tect in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Fita*xfo)/d(x gnd 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 as6 p6i/qvym; t 55-kg cart (initially at rest) across a 10 m level surface. What is the final kivps66/i; mq tynetic energy 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 200t7r1bt vn l6zr,6 *avtd bi1,w N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final svivdz,t, b 67nr1 r61abtlw*tpeed 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-,ywu4rgo0rz ( wu) )bt+ i+cxm f0aas much work is required to stop thbgaw+wumz u0 t0 ,(yx-)s )fcr+aor4ie 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 movo (r2 /g n1jyihr-qe5ving at 25 m/s, what distance is required to stop a crroe v1 /inh5q (g-j2yar 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 10-g dart. It is cocked by exerting a forc8 xok2q0s0+ kjapjbd )e of 20 N over a disjsbadp0 k +oj8xkq 20)tance of 5.0 cm. With what speed will the dart leave the gun, assuming the spring has 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 componend /t t2n-i4houn6)bvtt 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 floor. What ivn i-h4) 6/btnuo dt2ts 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 ha; yl ;bytu20i)cn -uuxy with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping force a-tibx0y;l2 )uncyu u;cting 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 ha/i2fb bsk-v9o + 9fupeight of 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitational poten9/ou b aksfbif- vp2+9tial 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 plane. The plane is 4.0 m long a.b+cl)zdxa yw4l +w o/nd rises 2.0 m. If the plane i+xlb )o/w. w cdza+y4ls 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, c)m *g.x61/i scd c;s )wtvbsyfauses the spring to stretch 2.0 cm. What is thes1bcgw6)yxs;fcd s/.*vm ) ti spring 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 potentialmxz/p fblm9) 7 energy does it store, whebf z)plmx9 m/7n 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 required to compress an initially uncompressed spring9(x+vzu-bv akqi4 tu, with a spring constant of 25 N/m by 10 cm.-bk v4(xq,+au vu9zti

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 constant 40 N/m from x =na, t,5bfq 1k sienm12g p5k0v 0.251keqvipb25mg, k t01, nnf as0 m 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 ojp8wddg fo1 5pjg*,3 uf 15 N/m is initially compressed by 3.0 cm. How much work is required to compress the spring an additional 4.0 cm p5 uggpjo*1dwj8d,f3?

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 hi lntn)cyi0;hu (sg1i7gh slope. What is the speed of the slier on reaching the bottom of the slope? (Negli )17nyn;isl0h( uctg ect 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 speed of 4.f 2nebn;w42m v0 m/s. ne bf;24vm w2nNeglecting 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. /q;kw 8fmg+4p oexd)t At the bottom, it has a spqdfe/)ogk+8pwxt; m4 eed of 9.80 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 xkmab;k+pp - s8vu8g ;the floor. When it is 0.70 m above the floor, its potential energy exactly equals kx mpgk;8+u v-;sab p8its 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, blastgy iy i9xgz5iu-8e8 0gs straight up from ground level with a kinetic energy of 40 J. At t80yei-y g9 i 5ziggu8xhe exact top of 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 mt r7 1tyun/kebq 10+zgh80s z.igo+de leaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic enery0+btz e8 1hnsg.t q+zeou01ikg /r d7gy 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 dip (Sexxt 7qddwb6y435r:)rvjbu0io y x/8 w5g/tr fe Fig.t55rrx/xw r7 f 8b6xyd0)b3dojvgyw /u4 t:q i 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. 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 m above hlp o58l;ck,h 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, which is 30 m above the bottom of thepo5h, h8;kcll 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 smhhf u57p/h hn6 z;i4) enuqfifg89q3 peed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster ahn) 7qq z6/5mf gpif3nh9uu4he;i 8hf t the top of the next slope, which is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the bottom of r5v djy +y4ii9its 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 axis and vyxx(-6 6;q*sw ae9vvt4pepa released from rest. What wilv;s6 yea axvp4x9tpqw( 6v*e- l 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 25 m/s hits an initiallyu8yceu3yhk2t1 9z . rj uncompressed horizontal spring with spring co. zu r1h3y8ej2yc u9tknstant 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 2/x *xsb gg4wci8f()sax p:hx9 2 m/s, slows down her 2000 kg car to stop for a red light. Whb:*fcsxhip x g /g4sx(8xw) 9aat work is 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-kg object and a horizontal surfach,qmn:(; kz97vf r yxte is 50.0 N. If the initial speed of the object i,m ;7q: vf(t9hnyzk xrs 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 surface. It has 24 J of kinetic (*p72uitg r)k6bddad energy. The friction force on it is a constant 0.50 N. How far will it t7 id)6b2rdk dgau(p* 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 surf sfw ts+/-/rlevv8q b)ace. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass -)ftq/+sew svr b8lv /is moved a distance of 10 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-,ovb 1 u,e9p:y+uct hhm high slope. If the work done by friction ish yc,e,buvph9+u1 :to $-6.0 \times 10^{3} \; J$, 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. The4 hb c7pqggs+y t*ma*6 plane is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force+ybacqh*46mp *7s gtg 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 of a plane inclined at 2 i- ea-y2gbq2e0e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass after b22e- qeayi g-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 strikes the grouhja v0)7laf 9.zw u-qwnr96 xynd with a velocity of 7.00 m/s. What average force of aia w6uhq .nl z7jfwrya 9-90)xvr 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 up zzmc3 b(2lx-d6c rirm):(ikja flight of stairs 10.0-m high, ii -d):rrckx(6 m(jzb2lmc3zi 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 to m 5 9ojj,rjvmu,ove an object with a constant velocity of 5.0 m/s. What power must be delivered to the object jvjrm ,uj o5,9by 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 ar/ev -h5 cwrdu8e used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 74cd er-w85/h uv6 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 while0m2(3af ughzrjoy ; 9p riding. How much force does her footgarzj;ofyuh(2m09 3p 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 25v o.a4wmxg;,*1dk:kwhc/ ea6fr f18r4 uo jhm m/s in 7.0 s. What is the average power delivere1h.havm okcf:xmf,4k6rw4u wdj1r8 eo*;a g/d by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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