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

1#

What is the correct unit of work f8x;4z zm5e9h+u aisu;ba0v d 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 nolzzai gtm*bc:-wvkbs56 as..*rg h6 7 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 ha3 yknykbkb/asi,rf00s b2 cw* c(8)kdrd against a stationary brick wall, the amount of work you dbb,kc nfsk*a(2 wr0/ikc b0kd8)syy 3o

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-N object was lifted 2.0 m vertically and is being held there. How much wor nxz1a, rj,9-8h m9 y1goh:8 wqjgiarmk is being done in holding the box in this positi ryqz8hgi1mgm w ,- 1j9:,a8a xnroj9hon?

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 horizontalle 58n(*fa58 p-yglruu: swouhy forward at a constant velocity carrying a 10-N object, the amount of work : sn5lf8gyuw8u*-h p( oreu5ayou 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 returqo m1dm5r9,e2 7fwr hr*y0jb*ebbb;qned to its original position. If the to0be2r9m* rh 1q bwd 5o,fmyq;e bb7r*jtal weight is 30 N, how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on the objecsn21sgh5* ( 0gpew1lv:eh hew t?

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 sibkc lsv316 di8gn of the work done by gravity while the ball goes up with the sign of v8 1bl6ik3dc sthe 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 ver 8dxj+t 3*cg2 fwz7wvfsus position (F vs. x) graph, representst3gc ffj*w z27+dwv8x

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 repw3c kqv4pa)2z resents the work done by the pwkva3 2)4 cqzforce 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 o+ 5zl7d8zcjsebject is positive, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an obj,cjf w-9 )pmne+pnn8 ject is negative, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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14#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on awnx q:93es,byh;yi1j(-e6 fikxs +fdn 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 twicefzj q7-:u4bq dx qgb7eb:)1 ht as much as a car, and is moving at twice the speed of the car. Which statement is true about the truck's kineticz77b1 xe:gbftq-h q q)u :b4dj 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 q*7 5nxiq-gzccar J has half the mass of car K. The kinetic energy ofcqn7q*-i5 gz x car J, compared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with half of its original speed. What :eatnb4rfi)/(w)is2h gyb 4 vis sb4wyne: 2v/h(a)ib) gitrf4the ratio of the final kinetic energy to the initial kinetic energy?

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

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed of 5 mu(txxq739mkmer g+-n /s. If both objects have the same kinetic energy, what is the ratio of the x(mqm97rku+ten x g3-brick's mass to the rock's mass?

A. 25 to 9

B. 5 to 3

C. 12.5 to 4.5

D. 3 to 5

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.0-kg mass is moving with speed 2.0 m/s. A 1.0-kg mass is moving with speed uso1 v0o3auy hdfj9de*e47 rbvt7 x0. 4.0 m/s. Both objects encounter the same constant braking force, 0s9duyjoe 7o74b u evh x*0f1 ad3.vrtand 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 +2o tw;t.nqm wfc/f 2oa certain distance on a straight, level road. If you had been traveling 2m2 w;/oo.wf+ct tfnq 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 Sun in an elliptical orbit. Neglectina:wh whgtd9 25ga-nc s8z: hs;g any friction effechw:h:8gh2tn z-s95aadw ;g c sts, what happens 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 prin b(gz5*y.f ijd9i1 pigciple.

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 ha/oi6k7c4 jdej c; bnx(,f z:apve 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 above the ym/cte; h1n.(lwury:mzg o, (ground. A second object with four times the mass of the first if released from the same height. The potential energy of the second o(nwo / mce: u;tlhm1y(,ygrz.bject 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 it1ex65/ hbbw h(p;zajy to stretch 5.0 cm. If another 0.200-kg mass is ab;pb5yhjzw6h1x /( e added to the spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical energyq- x(ynwi-.jz m 3tw0c of a system

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

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

C. can never be negative.

D. is constant, only if conservative forces act.

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29#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An acorn falls from a tree. Compare its ki.e:pv;u4ciu;is f6n pnetic energy K, to its potential energ6fpu ;p sun ii:4c.;evy 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 drrz ,2v.jybfxbfu -gc5ol ;8ahlqw 76;iving up a hill.

A. entirely kinetic

B. entirely potential

C. both kinetic and potential

D. gravitational

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31#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A lightweight object and a very heavy object are sliding with equal speed7qf3n d -a/x27dk:bhf:inlub vl9 zd /s along a level frictionless surface. They both /7 nddib2 /az7bufq ldv:hxfl93- :kn 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 9pygku10n+4nahy j( t $m_{1}$ 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 consegazg4ofr : 6k)rvation of mechanical energy for conservative forces:a4k of) 6grzg.

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 (h e)r9 jh,rz9bair friction is present), to the ground below. How does the kinetic energj,r)r z9bh9h ey (K) just before striking the ground compare to the potential energy (U) at the top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and gains 3mrg j2io1 il d)/p;x 0oyxkm/90 J of kinetic energy. Do not ignore air resistance. How much gravitational potential enerxm/ip1o m;xkr02/o 9gl)dyij gy 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 g-9 ,vowwbayf c5m(scw- eg+q5ravitational potential energy. Do not ignore air resistance. How much kinetic en9byc,vw+m5e-aq w o (c-5 sfwgergy 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 conserv -xf65bys*crn 8rm.f aation 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 is9nxmfeq:(vgn jcf /:)

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 nq1l7 qq58 rktoi78dhf x. cz ;*bymr;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 uneb2k0bme0 pm/oyk.sq 5)dlpz37cy )pit of power?

A. watt/second

B. newton-meter/second

C. joule/second

D. watt

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41#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Compared to yesterday, you did 3 times the work in one-third the time;;i+e k82ae gpjn4lqf. To do so, your power output muse eg8fijp 4; 2k+nlq;at 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 cahgl-eo6 wdo9mc0- x +xr at a constant 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 m and held there. If the object weighsgxz+rg1ql ;qw-dkat hw ,37h1 90 N, hx+h dz w,k-7h w r3tgqlg1;qa1ow much work was done in lifting it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You lift a 10-N physics book up in the air a distance of 1.0 m, at a cd0.bx oo2xmf ,y0 l+yeonstant velocity of 0.50 m00yoybf,m +. x deoxl2/s. What is the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward witu;g:y7ay aw;ef m) jck/iu44rh a constant force of 5500 N for a distance of 50.uc7)j /i;ra ey g uw4:;yfkm4a0 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 puls3 xsrkl5ii(/ led upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the iksx5 3(s/rliweight 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 cox:n uyn:qwo 19nstant force of 5500 N for a distance oq: 9ow1:xnuynf 50.0 m. What is the net work done on the elevator?

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

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

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

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

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulled 6.0 m up along a nk ;85k hli+h0zb(y uh$37^{\circ}$ 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, q1ls4k6g c0lcinclined 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 lit7,nyg tb:8(f cnpu:igtle sister Sarah in a sled on an icy surface (assume no friction), with a force of f: 8,:7(bnug picgny t60.0 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 direction of the force. Tot q;ikp0:mu ;he graph in Fig. 6-1 shows the force versus the object's positim ;0q;o t:kpuion. Find the work done when the object moves from 0 to 2.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the force. The graphaw-es,s0tz f8 p uw+d. zbx-o: in Fig. 6-1 shows ,te +:xs8.z dofb -w0zp-u swathe force versus 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 d py v2g8bd-edb9+c ;d,c8n chthe force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the objecy cd2vdhgd8p- 89bebd c+,;n ct 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 flf. q*o:o /(hxkqb7mj+b c5 ithe direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the objecth(x /qf7b* c+mb:ofi j oq.l5k 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 i78xi:fj b n56boqjk:ap*v(pr s applied to move a 55-kg cart (initially at rest) across a 10 m vb*:fqa i7px o :n(jbr58kpj6 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 4 )u)jie .ruw1)nryuv N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is thiej)y)r 4rvuu)n 1.uwe 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 mnl,x 20 d43 wvvcb)ma rk1inx5/s. How much work is required to stop therv 102kc4bnidwvm xaln35) x, mass?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If it takes 50 m to stop a car initially moving at 25 m/s, what distanceogb83.ao sv;of8 pb: cgv+yp: is required to stop a car movi.p bgfopv 88;c:+y3 g:booasvng 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 10s 2+ ml8n4engl-g dart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, al8 4lm2ne gs+nssuming 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 comh0ho vntjp 6mob 6ui1j wr+/,-ponent of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless fl +tp orvj,1oh jmu0-iwbn/6h6oor. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g is shot hj ery*bw(q 79tl. pyeylzm:vv6f9 1)q orizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It pwvqjly* fve:yq 7(m rtl9y . 96)pzbe1enetrates 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 moved from a height of 7.00 m above a floor to a height of0/h2vfmolp)- 2o k.cht3yz gg 13.0 m above the floor. What is the change in gravitational potef0l h2c-o2h3y/.t g)g kpzmov ntial 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 iv)u39dn0 la m 06trkvts 4.0 m long and rises 2.0 m. If the plane is frictionl3vmd6av0r0t ult )nk 9ess, 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 y nlb 5+cep86z8vghgv,:wm -e spring to stretch 2.0 cm. What is the spz8yhec :-ve 8nplwggmb,+6 v5ring 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 tnnskll5vp) fps 5 h8gri0q:4y )7fh5much potential energy does it storris 5fnqshvn)8k:ht plgyp5 0)f7 l54 e, 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 inig ;mbqd.b.z9nwy;*ts tially uncompressed spring with a spr *bs q..9;z;gwt bymnding constant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring of spring constant 40 ;y.rcxh7 g5 3h5c*apmsbyt a9 N/m from x = 0.20 m to 0.25 m? (Assume the unstret3b my9rh .cay hapc7 stx5*;5gched 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 hrb2-3f z5r /zvt:bky 3.0 cm. How much work is b:3rtb f25y/vzhz-rkrequired 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 from rest from the top of a 50-m high slope. y7w,al 8q mc5h What is the speed of the slier on reaching the bot amyl7w q8ch,5tom of the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top of a hbloj7nou mprh4gev,79 , ( d,nill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she d,(pg nl,77eu9nbvor 4hmjo, 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 b0d0(g xk 8 1f pi48*thselavzkottom, it has a speed of 9.80 m/s. il(daspgh 0ez*x81t8 4f vkk0What 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 ab8x :3aq +sn:efrvjzf, az0e u3ove the floor, its potential energy exactly equals its kinetic energy.z+u aqf ,ez3rf:v: js03 xa8en 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, blc /2gqg-l8 -uwg. bx/frbotp0-n,b;r vg lk c-asts straight up from ground level with a kinetic enwb-c.pglb,g tkro 8qb/2cgn ux;l-/-frv- g0ergy of 40 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 g+ cgk ib(/o1 (ol5-ok:zevmzzround with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J.1gz(ioo+kkv-z b 5olm: ( /cez 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+kowd) *jg 6ho 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 bottom of the dip? jhd)o*ko6+wg

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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 t ek;s0cfbaw+f9 /fo s4he 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 the dibw+sse/ a 4 9k0fco;ffp?

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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 pointc xn)(qf6is5t 30 m above the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what willifx)q 6nt(s5c be the speed of 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 speed of the ball at the bottom of its swiopo yt09 1 fic( ngcb):92gwvyng (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;:w cs.+apmn7 uh8b (ih3oixa released from rest. What will be its speed at the botumbs a(hp8:. whicx;o7ni +a3tom 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 ho cb1l)-li yug1s) ta,a) 0kwfcrizontal spring with spring constant c, y0 alb1fwi)slc gt -au1k))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 dofmcz h x) 50*kf8dzn*iwn her 2000 kg car to stop for a red light. What *0nz 8 xfzd5f)hk*c imwork 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 fob4 i/-s6x f.9nid mlivr1jmm )rce between a 60.0-kg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what disf9/4m mv x)ndiil i61r .-jbmstance 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 oxsgb3 )/ zu7 *ew8txbvn a rough, level surface. It has 24 J of kinetic enerbux/t*3vw)sz8 g x7eb gy. The friction force on 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 appl)jb9q wwnx:- vied 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 10bq xn9w)- j:vw 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 g /2)h7k(eqg3 lapmnotop of a 50-m high slope. If the work done by frictionm37k 2p( g)qglhoae/n 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. 6+rfgt phtkx.,2 br,bf k0d5k The plane is 4.0 m long and rises 2.0 m.2 6kt b+5,rb fp0rgdhkftk ,.x 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?

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 r4nrf6 ttv )r.qg ar22deehj* 6est at the top of a plane inclined at 20e above horizontal. The coefficient ofe2e6j*ha 4.tqnvfrt )dg r26r 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 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 10.7,21hwe nryl(yq t7 my0 m, and strikes the ground with a velocity of 7.00 m/s. What a7y2ehm7 wly,r n qy(1tverage force of air friction acts on it as it falls?

A. $22.5 \; N$

B. $75.0 \; N$

C. $225 \; N$

D. $293 \; N$

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91#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

At what rate is a 60.0-kg boy using energy w8c *c khc )m:q-5rt*4ombnot rhen he runs up a flight of stairs 10.0-m high, q*m occkoc)*4r5tb mr-n:ht8 in
8.00 s?

A. $75.0 \; W$

B. $735 \; W$

C. $4.80 \; kW$

D. $48 \; W$

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92#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-N force is needed to move afj7hutm.(xg a1qd5b7 n object with a constant velocity of 5.0 m/s. What power must be delivered ttd71b.7g f q (uhm5jaxo the object by the force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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93#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

How many joules of energy are used by a 1.0 hp motor that runs for 1.zg.z 8k2(8ssvbwiok n3e4 ajc;1 cq1w;hfax*0 hr? (1 hp = 746 b; zi8q1 soha*f4;w8c(cx2k3navg 1 kes z.jwW)

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 501s hv7ehvpto .31nnm;0 W while riding. How much force does her foot 7 m1 .ontvn1s ;vh3hpepush with when she is traveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the average powxu y f-+tvf)5ttyqyp- /;zsj7 er delivered by the engine?zp5+-uyf j)7-yytq tv;ftx s/ (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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