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

1#

What is the correct unit of work expressed in S ;:+ei -hxfssy f zad3r;vg14lI 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 mob plbkx0t3+4 6myu,setion?

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 amouno ,ac o(.bai+ dwxx 2uypjea41 f)n(g)t of work yox4a cu +w)nd2(y e)j .baixoao,1pgf(u 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 li/djl )p xn. ( pnjmxx/-6pth3tfted 2.0 m vertically and is being held there. How much work is being -j /)tn3.6ppnxthlx m/x(pdjdone in 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 at a constant velocity carryingkv 1tu adm -ff4e. y:osne0+5c a 10-N object, the amount of w ut f-0seok4:acfm1+.ye 5dvnork 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 :( t ow,lbjbt13.0 m then returned to its original position. If the total weight is 30 N,wj1,bltt(b :o how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on the object?p;:by itpow8+np4ps +

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

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

C. No, because the object has constant speed.

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

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8#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You throw a ball straight up. Compare the sign of the work done by gravity whilc-pm 1 mtjq2marf75 o*e the ball goes75p-frm*cam2 q oj m1t up with the 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) n *gcrth +g//zgraph, represents rn+chz/g /g*t

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 po3vm dj/i*ln .m7o ja1osition (F vs. x), what represents the work done by the force 1.*/n3 ivajlo mmj7odF?

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 yn-it(qv:5ndadj6hy5w ; (ej the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is negative, then thckzx2t/q6p s9 ,tas:h 5b x3kye 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 zerffkse( +hvebh5- n;4 g6e mm.ao, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice as much as a car, and is moving at twice thenn8 zw 9i7t*+mbdy s.z speed of the car. Which statement is true about the truck's kinetic energy compared to tha*wns7.d +z89b myn itzt 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)(*y2zn3ejt l6ft0eve o vi/u (mv2esf the mass of car K. The kinetic energy of car J, compaf *j0tv e6(l(soz n 2e3t/vuy2ei)emvred 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 om6 :x3v 2j q iqg.4fld9meh,) vwbjf w-r7qaw,f its original speed. What is the ratio of the final kinetic energl-b j2x3w94i mmvr wv,dqa.q7qffwj 6:,g eh )y 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 me ; k/s1a ivmwv;9p3h)n4z4cxmih6j loving at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratio of the brick's mass to the ra/1jw 3xvsn4mhi;m9z4 le;v ph ci6k)ock's mass?

A. 25 to 9

B. 5 to 3

C. 12.5 to 4.5

D. 3 to 5

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.0-kg mass is moving with speed 2.0 m/s. A 1ce7qk2dy) c6f.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Whickc267 qd yfe)ch 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 brakb fsew ;twx:,z6b0v0qes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car havee0w xqbwzt60b f;:,sv 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 mki*qtm ;n8 7 rbfz/hgx v0np)7ass orbits the Sun in an elliptical orbit. Neglecting any friction effects, what happens to the planet'q0mpgk *;8 h7n7brvn x/zt)i fs 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 princwls4suar/a): 94b ucwn q/7ax iple.

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 negatijmk3ppjx40i y 2r6bb91wrph1ve 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 groo v k5fddnmhll3tz tdo682wj (kf fd52-,yn48 und. A second object with four times them4tt8 d35w zlj 2 lfv,-2oh8nfk6oddnd 5(fy k mass of the first if released from the same height. The potential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the end of a spring causes it to uy ntj(nftway r; b8m :n5(zdfd4n.9;stretch 5.0 cm. If another 0.200-kg mass is added to thed 4nut(mbjy;5 :a fn yr(ndwfzn 8t.;9 spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical energy of a system0n am3k9 34sqf.,- flnoxru na

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. Cq 5 oj(y::s1ch f2r y;mcrcs5tompare its kinetic energy K, to its potential energy c;s yhqtyoj:5s (mr1:rc5cf2 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 carx( 3eibhfmya,+ o ;aq3k(b+se 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 equaldib6s)kr4n 3w speeds along a level friction3b4 srkdw6)i nless surface. They both slide up the same 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 zxc9 68kllf;tj49jka$m_{1}$ 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 conservatm : /bhw*e yv(,.fdlpfive forcesev.bwfl yh(f mp ,*d:/.

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 buildingi)7rszidtoaoj c) 2 5)-j,ky w, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U)2j ) )rii7jyw5)oa oz,t-dcsk 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 igse7n+ r;t qid(kb0 9ysnore air resistance. How much gravitational potenr t sd (0qbkse+;9n7iytial 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 gravitat. oo63bk1dmmceimjl 6h0dxu)s .** r uional potential energy. Do not ignore air resistance. How much kinetic energy 13 0mu ohd xk)6lb*rmsej .dcmiu6 .o*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 conservation of energy.r +9do4fhp rr8

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 ismtm*7 rys, n7u

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 powerf5ygngm as3 ,,63nrm l 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, whjxed(g dq7wgw 2v ,a2.ich is not 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 the work in one-thirdj1,z-te(qg0knk:a5l t t 2vh.bl;hid the time. To do so, 50;tj ( :n2iagl1e kl-,q ktdzv. bhhtyour 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 enginkeipuc: o/ h22 z*o/5yyya4a+uds da/e 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 N lk+*o,xf+p0up jp .bv, how mub*uv p.px +pkl,+f 0joch 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 u,ahzw9 fo3s7/ c+cav19lsgh distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight of thevg7/u 9wcfashh9l ocz a,s 1+3 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 for8 i q94tpyzy s;):b n0jn:hnprce of 5500 N for a distance of 50.0pnt4jpn ;yb )h0s8ziy9rn q:: 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 cod14fzhaqcy 26 nstant force of 5500 N for a distance of 50.0 m. What is the work done by the weigq y64d2h1fcaz ht 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 hs 4z be(nz*kyq*s4irja79 -u N for a distance of 50.0 m. What is the net work done on the4-4*jiaez(s*nz s 7khq y9rbu elevator?

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

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

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

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

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulled 6.0 m c,,xbhvhl, e .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 )6sj,q:ho 1;nohqk a8 p8ira p-rdib n6s78iqm down 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 littlerdq0f*kk/9h;u vm.q18phok m sister Sarah in a sled on an icy surface (assume no friction),m vq q k9*fh1;hdkpo/.ur08km with a force of 60.0 N at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the -n4tnhgn h(wi5rj9 nmomm,( (direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the objoh mgrwn95m(tj-ni4n, h m((nect moves from 0 to 2.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the directzljvasg * 658 ( f d4rj+kml8izaq8dw)ion of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to 4.8kqag ld8zi +)*jrwdl65s4vf8zjam(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 directi1p9f5bo.kyvi on of the force. The graph in Fig. 6-1 shows the force versus the object's position. Fifvp1o5yib 9 k.nd 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 object in the dwax8/dmzo 4 i+irection of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the workwia+/8xz 4m do 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 01)o xti+ynhu b5qyesbi8ixr e,*3n3 applied to move a 55-kg cart (initially at rest) acrosnsir5 x31)x bi,ytebh8*+ 3u yneiqo0s 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 appwyr3hb 45ssrgqy *-/qlied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speeh r4/*q5-gqwsy3bys rd 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 m93z) zkcmf:a s/s. How much work is required to stop thz)m9 f k:3azsce 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 movin3sva:kqm8cd* dqhi fl6daiv s6 8e-:8 g at 25 m/s, what distance is required to st83k 8dismivfld:a6v :86sq -h*c qedaop a car moving at 50 m/s under the same condition?

A. $50 \; m$

B. $100 \; m$

C. $200 \; m$

D. $400 \; m$

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59#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring-driven dart gun propels a 10-g dart. Ifw(rw z snufpd*6 ws/my-8m:.t 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, asms (.n:8-/fmys wfww*udp6zr suming 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(thov y -hxf r5ifjpa-xvp,ev(1: )t . of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 mxhotp aef 1 (ix-)-j(t .p5rvy: vhvf, 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 9rg(f 0ouw wkqq6r*j3m0d/n l horizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm befoj/*lngdwqo9kf0 um0r3r (w6 qre 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 moved from a height of 7.00 m z31ptwu p8.z)n s42ipkgxdo /above a floor to a height of 13.0 m above the floor. What is the change i sn x p)1u8.k4p2t/dpoizw3 zgn gravitational 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 plan g.qo yb4fb*e7i/jvl5 e is 4.0 m long and rises 2.0 m. If the plane is frictionless, vo7ylbiq5 f*4e./ jgbhow 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 /6pz6tmxf *ti a spring, causes the spring to stretch 2.0 cm. What is the szx/66i *tt pmfpring 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 Naq 2 cv2roh3a1/m. How much potential enc 3ovar1a qh22ergy does it 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 required to compress an initially uncompressed spring with a( 8tudmp*jaot0;xd8o spr 0;88otduam xo( jd*pting constant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring of 0k2 /goevyp:(7fy;m nneyw p6spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position is at x = y0nwo/ 7p (6n ym2keg;:fepyv0.)

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 cof1, ;c /lor5rla+ dili*dzse-mpressed by 3.0 cm. How much work is required to compres/e5zdd ;o -1*i+crlfll,rais s 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 from rest from thdpqcjme,q - l1xp9a s40h 4bp0m pjcyic-/6d 9e top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Neglect fr4p1im ,ja hc6c0q 9/ d0cysjmpe 9d-p lb4xpq-iction.)

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 h b)ffiy)mj-hou(9b9,m8 rr ggill with an initial speed of 4.0 m/s. Neglecting friction, how fas)hjgby (f,r)oigu98 m9 -rbfmt 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 oywz8kim a)h8l/3 i4 khas a speed of 9.80 m/ )li /i4z3ykahwmo 8k8s. What is the vertical height of the plane?

A. $19.6 \; m$

B. $9.80 \; m$

C. $4.90 \; m$

D. $2.45 \; m$

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72#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1.0-kg ball falls to the floor. When it is 0.70 m above the floor, .p/zibrhqtm:96/ 4vnrw1t jy its potential energy exactly e. t1vzwqnp6 hbyrt:ji 9m4r// quals its kinetic energy. How fast is it moving?

A. 3.7 m/s

B. 6.9 m/s

C. 14 m/s

D. 45 m/s

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73#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A toy rocket, weighing 10 N, blasts stra afxw0d;2zd 6cight up from ground level with a kinetic energy of 40d xw;fa c6z0d2 J. At the 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 m leaves the ground with m )ht/f qq bd(ty)1wa2zapn53 a kinetic energy of 220 J. At the highest point in its trajtwd1bp5ty()hna2/ z)3aqf m qectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise?

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

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

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

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts frkhe;9g* ni w*2no+2vxapb n 7jom rest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above 92o * np7jw2n +vkie;ng xha*bthe 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 witqe8v zjgjoh80d;pw1 / ur5 6pfh a speed of 5.0 m/s at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m above the oprz06/w e1qg 8d8hj5pfuv j;bottom of the dip?

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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 poinq r1i) o6 d)g/w,5-c uqpzhuf53txjau t 30 m above the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, w/u6jw-5oqgqhud5 i ftup xra) ,13) czhat will be the speed of the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip?

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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 sm(: :/j c*cfosfr3beqpeed 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 verticalzl c2luc6- 6ii7v8uq /*q rgd u5,gsus axis and released from rest. What will be its speed at the botg* g2qrlus uiulz v76ud/c5,i-8 cq 6stom 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 initially uncompressed horizontag 1pqu6w 9qxwb27)hlel spring with spring constant ow)7q12x9 u bwgehlq6pf $2.0 \times 10^6 \; N/m$. 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 adwmqgqr4o1 5n 4(ex o) red ligh r4qom51we4qg xdn ()ot. What 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 objecd.q/7jfb*m kj z( se;)xyxhu .t and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what distance will it slide before coming to ax;hzfy7sb. *jk xu(m/) qd.e j 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 7glsh p 0 xack*n) t83iyry9g.24 J of kinetic energy. The friction force 8*axi9ks0 gl3ncyt)y h 7 .rgpon it 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 applidw:6wp g7 jf5ted horizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the change in its kinetic en:tgf 67wjdpw 5ergy?

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 wtkzmym jp. jmon+f-4(3wl), h ork done by friction ism) jm pl-kf+hy,3m. z n(4wjot $-6.0 \times 10^{3} \; J$, 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 ply,2 tykyuzs-+ dtnoni/ 40(kxane. The 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 on the box?-4,y y0sk +notx (ukt/dni 2yz

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 20e abovjbw vg,kv:,(t30 9azevvgdm*5p l2dqe horizontal. The coefficient of kinetic friction between the mas0,ajqvb*zvdgm vtp2,: 9 (3v ekwgd5ls 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 height of 10.0 m, ang s(rh/e i0j(kd strikes the ground with a velocity of 7.00 m/s. What average force of air fri/g (j0(kih resction 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 upvwl8 9v;,e ;xr- dww hencgw-( a flight of stairs 10.0-m dw;xr9wl een-8w -( hvvwcg,;high, 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 t *zya4tz5omlhh4 m+l5o move an object with a constant velocity of 5.0 m/s. What power must be4tha45z lmm5 *+ohzl y delivered 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 energyivcyt4eeoez;6 (m p - x83nq9w are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp =mye c;8-p e 3t(vxwo9e6n 4qzi 746 W)

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

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

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

D. $4.8 \; J$

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94#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A cyclist does work at the rate of 500 W while riding. H4)w,j6,u uzmdhq8h ozow much force does her foot push with when she is traveling at 8.0,dhqmhu uo,6zwzj 48) 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 s. What ixkz9i8i1 q5 hgs the average power delivered by the engin z815xkq g9ihie? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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