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

1#

What is the correct unit of work ex dnh- *j, 0flburz63 0phh2cdm(c o8wgpressed 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 mop93zi tmh2-,tt;c 5mci0i/e ufpf 9tption?

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 starc )s.ox+n m3ttionary brick wall, the amount of work you do3 . rxsc)n+tom

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 he.q3p tfpdu +e;ld there. How much work is being done in hpe +tpu ;.3qdfolding 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 constant velocity carryilfz56 )fabri 6ng a 10-N object, the amount o bra)ffil 6z56f 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 re*op21pwa )cjab ,)lnh turned to its original position. If the total weight is 30 N, how much work was doc*ja,) woppn )lh 1ab2ne?

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 work on : 9cxn(q/wjfs ii6sg, y,2maqthe 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 soi;hu*u mw.8 work done by gravity while the ball goes up with t.u ;*8muihsow he sign of the work done by gravity 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 (F vs. x) graph, ( i/upe9f e1x:+:ghbz , ngrsarepresentse eg:i bf/x9 a+h1ug( ,:srnzp

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 rxw a f38t0hf7wwu5)va epresents the work done by the force F8a vwha fwtx5) f73wu0?

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 ob .n:8,h i ph)amyvs15cpn8t ipject'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 t/6tfu v(9)3-qeqx c wk7ioyf ohe 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 obje :tpc1h v .jryo s5eqlo0;d.s0ct 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 caru3 3*rmtjy3,dioh4v t, and is moving at twice the speed of the car. Which statement is true abo 3rum 334 ,vtjdy*tihout 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 cqdcuw v:.zrf 8tju*i 228t 3ssar J has half the mass of car K. The kinetic energy of car J, co:u* ti8 dz2 rj.u8f2s3qsctvwmpared 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 ha w 9w0.x6i5g dxsac/tylf of its original speed. What is the ratio of the final kinetic ener/x9 yia60wx st 5.dcwggy 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 movinmr u 8t l7s-,cc14 vh-mu4b4gepb /zbqg at a speed of 5 m/s. If both objecsv7mgm4t-lbz4u /bb4hq8r cu c,-1epts have the same kinetic 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 spewfkwio-: g)n 1ed 2.0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same co :)iwo1gnw-k fnstant braking force, and are brought 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 certain distl g4rpu),pm v5qpdo :kd.q2 h)ance on a strai :,q go.vm4lru25d pp)pqk )dhght, level road. If you had been 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 orbits the Sunit.g:y:a ye2c it39 qv in an elliptical orbit. Neglecting any friction effects, what happens to the planet's kinetic entqvaict93i:yge : .y2 ergy?

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 prx/3u cjly-he 9q)y6bz/shd v 5inciple.

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 c lkks iz aseh2 6:bm/:lwtf7n5*-mo*system to have negative 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 qq9tln;bj d1lm ho-4;above the ground. A second object with four times the mass on ldt9h -;bq;1ljmq4of 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 endz *i 2sfw5iigx;72pwa of a spring causes it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the sz272f*;ii5 as pgwwixpring 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*-ri;+uk4 te o ya)tfw 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. :2- n mjt73u ;bqw3td,jyamwm Compare its kinetic energy K, to its potential ener; -mw37:,tjja mt 2uymbw3ndqgy 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 car driving up a *q* xq:sdqfj6gn c)b65fn n3ehill.

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 v0nlr x i 4*mv8nhj9eh)ery heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which0emh9)i xjvr48l n*nh 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 oq8v66/, :h q q(pa,gkbz;zfy5tvaxl$m_{1}$ 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 conse 6c11d 9zuvkcurvation of mechanical energy for conservative forces.u 61czud1cv9k

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 (air frictivw;vwq7ph +1 lon is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to thevw +p;1v7 qwlh 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 ofs))cu ;nssk6l kinetic energy. Do not ignore air resistance. Hownlk)sc; s6 u)s much gravitational 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 gravitapnj)h /bq:p7; ebfk; ttional potential energy. Do not ignore air resistance. How much kinetic enebbqtehp ;:;/7pnjkf) rgy 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 conser mlhej:l1ddi ,i+o77 zvation 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 isiq6pwb .b1 ekh;/z 5wj

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 nsyx qsw,t626 of 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 of poqduw*(alrz ,fa0m 9q, wer?

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-thpl. g.;pky 5pj kei62vird the time. To do so, your power output must haveeij.. pkp6 ; lpkv5gy2 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 conag5oaicyb c cj w8c 3p( cm5a/cdjird 4,-e+55stant acceleration, the car'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 b;sg r4-,jqll+*ky hzr3 et p+m and held there. If the object weighs 90 N, how mu43rgkl;-s+ bl,*ph+zy terqjch 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 air a distance of 1.0 m, vs4jbrzdy9 1 rczbae+/lx/0 -at a constant velocity of 0.50 m/s. What is the work done by the wei dl 0cazz1y/srv /r9bb4jx+- eght 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 foriln ( kq 04 ;/(f(ps/tfce4eibtej;khce of 5500 N for a distance of 50.0 m. What is the work( nkk0(b/q; etipl e;jti4s4eh f/ (fc 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 wits/sq4zo .7 nwqh a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the wos.z/ s4q 7nqelevator?

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+8 (xupn fx )alk(zfco05k-ms for a distance of 50.0 m. What is the net work done on the elev0f u8 xl+f-pm)a(s zoc5xknk(ator?

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 h7kmms* m9 2 kyml1oohv4(l/b6.0 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, cthu+py n**13:p*dp vbp0 bmt 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 (s 39*xm c+v uh1vjw4k2hbt+wyassume no friction), with a force of 60.0 N at an angleb 2 vxs41w3huk cjy+ t*+9hmwv 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 indaf-fb( a ((0ozbom7 n the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done wh(a((bo-b7fd o fnm 0zaen 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 s mrbq0qn*qa)g 930zg in the direction of the force. The graph in Fig. 6-1 shows the force versu9 s rg0q agqm*b0nz3)qs the 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. The graph in Fig. 6-1 sgdxmj +:57c. hedg (zjhows the force versus the object's position. Find the work done when the object 5 .e(h:+mgczdxjgd7j 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 the force. The graph in Fig. 6- ikrsog4-d*kb)k g;v81 shows the force versus the object's posikkr4ogd-vk b*gi) ;8s tion. 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 9:v a0kyzufp4t+rz9 9jymzl* to move a 55-kg cart (initially at rest) acrorz 4*:ltkyy9vzu9pf+aj0 z9 mss a 10 m level surface. What is the final kinetic 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 200 N is applied to move a 55-kg cart (initially at r t+(vw(b*cj ylw9-i soest) across a 10- 9l (wywcst*bi(j+ov m level surface. What is the 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 i r9dw0k-za;pn4o; /zog wn -tds required to stop the maknn ;o /owz9-w0dtzpg;-4ard ss?

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 ae0lzi; u: ysf.s.7d2: vu5zveclyy-u car initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same conditie.::eu z d2 zsu5ly-ycif0l. 7vys;u von?

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 fo2wpc6g.4xj e1tz(ccjk,n m: fppp; p( rce of 20 N over a distance of 5.0 cm. With what2cj xg6( tf zec,p:p1k. c4(pmwnp;pj 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 gts *bmgu*z9 ci5y66p80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along thtc 56b *m69gs iyzgup*e 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, strikinp+a0k)z ,d ifvg the hay wi+ akfdp ),iv0zth a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. 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 m/ ns/dc6jjhylh cqu/-(1l4 npoved 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 /( hs 6n-lq4 c1j/dnc hlpyju/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 plane. The plane is 4.0 m long and rise9gtu-3whez , rs 2.0 m. If the plane is friction ewr -g,t39uzhless, 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, causes the spring tocw :lu:y z r,y9mv66tlkog(2q stretch 2.0 cm. What is tcyuol(6vyw :: 6l, mqzt29r gkhe 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 l( bin7;ow/ rvkohcim p5 5k,8constant of 60 N/m. How much potential energy does it store, when str7r 5;co i p5ki wl8/hvmkn(,boetched 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 togg 8m o:ivjodm 1*5+ r)i9ttkp compress an initially uncompressed spring with a spring constant of 2*)gi+ gtmo kdjtrop:v918im55 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 st7xqch1*wzb .r ix2 gg3retch a spring of spring constant 40 N/m from x = 0.20 m to 0.b.g x 3ic qg71x2zr*hw25 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. h 6nxjleo*z(hc+fu* 5 How m*h z eocunx56(* jl+fhuch work is required to compress the spring 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 fro6,i6ww ebhyn -m rest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Negl -iye6w,bn 6whect 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 s*oxyf-dmvg;f( -n. kkz4kar:m)n5xa hill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after 4ym 5n :rxk vmk(af gz*sdk;.-n -xof)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 friction1d7s al2khkz, less inclined plane. At the bottom, it has a speed of 9.80 mhlkz72ks ,ad1 /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 theg7 yz3m)rmhz ; floor. When it is 0.70 m above the floor, its potential energy exactly equals its kinehr3zm ymz )7;gtic 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, weighio 09ymp9m fovk zwx81;ng 10 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top of its0fmw1ovxmpo 99 zk8y; 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 llu ;uzr 86b(uxeaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic enerzblu8ru6;xu ( gy 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 ro )mfavl6kl*1 th (r 2s.uh+irest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, k*l 6 sr.2 a)uolv+1mfhtri h(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 ato/qrz 1h7 i(;cao :b phsy-za* a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be*:zp (hh /q-yrza 1aic s7obo; 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 b mmsm8)(rmz t98k2 wavottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed mt()9msmvkwaz 28 8mrof the roller coaster at 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 sx9epbtg17m j)x st(bi)v3)b mpeed of the ball at the bottom of its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

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 verticala* *mn.f3 sbfebr;k8l axis and released from rest. What will be its speed at the bottom of its swin3kb;** .lrs b8me fafng?

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 initially uncompressed horizontal spri7v +yg l 0(*w0f vg.v/ovnla t.ajs6/cz9g kleng with sprin/nv7 z+ (y.wllv0 tl eg vfokaacg96.sj*v g/0g 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 2000 kg car to stop for l gjnjbhp;5:q)o/ 0 jfw+a(ksa red light. What work is donel;n )jk (:oq +f jwpsbj5hag/0 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 vzaqod6 50deh+1f4oc l/t *inkx(c/mand a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what de 0 /xok4 o/6a+ f (idlhztn5q*cmdvc1istance 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)h2 9 sye;0hmwr(zgy c. It has 24 J of kinetic energy. The friction force on ie (rcm 9s;zh0wg2y hy)t is a constant 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 tbva674ali k/ to a 2.0-kg mass on a level surface. The coefficient of kinetic friction betweit/67 vlakab4 en 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 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 t gpvqn-l v 3qk;yc*93the work done by friction qy-*3c;gvpn9vtkq l3 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 4.0t499oxip9 lcuh)f 5pk m long and rises 2.0 m. It requires 3200 lcotiuf 4k9ph59x )9p 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*qo*z fu+(k,k 2 o490oujwue0ibg cfk top of 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 after sliding 4.0 m along the plane9 4cug2uk(+*uo0okbf jw 0qz*ek ,ifo?

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 ayy1,s*hry* i v2rex3g/y/ r yc height of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air friction acts oy hv yycxey3r1/* g/2 sy,irr*n 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 a f jpij)uo bve.pa d3dpfwm5y13)(0y(v light of stairs 10.0-m higyd1uppv w odjy(f.bei 3(a)mv3p 0 )5jh, 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 -wqxlsg94trmgcb6k+ 8 qgqr5i xp2y*p* b0f7move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by thei*pcrsrxq645gqb+ m-xw qfyt2g*7g 8kl 0 9 bp 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 runs for ar, qr++te x h,i0dhr/1.0 hr? (1 hp = 746 h+/a0rr, hqi, +d txerW)

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 th.u hu3e5kub /d.i6 tcifv m/c;e rate of 500 W while riding. How much force does her foot push with when she is travef3ei5/u ; ibh .ud./mut c6cvkling 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 t))9* vwt wehmjo 25 m/s in 7.0 s. What is the average power delivered by the engine? (1 hp = 746 m )twe9 h)w*jvW)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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