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

1#

What is the correct unit of work expressed in SI unibgsw1 xq cet88 btzm52r ..qt1ts?

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 mobvyir7)t3z bt,b/a d(tion?

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 stationaryap(ax:2 1q9ffl wfqclt j))6b brick wall, the amount of work youjql bfqw lt )a( f216axcp:)9f 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 lijubhoat.x ;t9iy f;4( fted 2.0 m vertically and is being held there. How much work is being done in holding the box in th;ioa(ht.t 9xy4uf ;bjis 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 carryin6+pj ) h(qpm+hr6vi lt6pkfe1g a 10-N objeplpp1mq(6kj 6r+6f)h +tiv hect, the amount of work you do is

A. more than 50 J.

B. equal to 50 J.

C. less than 50 J, but more than 0 J.

D. zero.

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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A container of water is lifted vertically 3.0 m then returned togbo7 n574wj hsirj*d/ its original position. If the total wew*ri74jhobg7n j 5ds/ight 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 actingnn* ot8n rzo8gaz /:lj87p3kv on an object do work on the object?

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

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

C. No, because the object has constant speed.

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

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8#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You throw a ball straight up. Compare the sign2j wapu. (o)jyy zuc;: of the work done by gravity while the ball goes up with thep( ;2az):. ywcjo juuy 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) :0 3pknoun08one pzju72mz b;graph, representsk 78o nun mznz:3j0p2o;b0e up

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 versu2dwz4 h mw*21wm00)xzog v+ goi6hrvxs position (F vs. x), what represents the work done by the force F? +zwvhowm4x wgx vmgdz *2)r06ih01o2

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 objece2p(he3y ycb 0l;g4xmt'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 objec bqat 5f0)dtz3sbykk x:+f7n-t is negative, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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14#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an (z04e(b nst0 o sdy*8uo)psn6sghzj 7 object is zero, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice asp3b +efq m/ i3oh pp9*m8hx4ge much as a car, and is moving at twice the speed of the car. Whihhb/g 3p+ pmo*e84fm pexqi93 ch statement is true about the truck's kinetic energy compared to that of the car?

A. All that can be said is that the truck has more kinetic energy.

B. The truck has twice the kinetic energy of the car.

C. The truck has 4 times the kinetic energy of the car.

D. The truck has 8 times the kinetic energy of the car.

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16#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Car J moves twice as fast as ca,st), phn7y n3olb/ac v uq-8ur K, and car J has half the mass of car K. The kinetic energy of car J, compared to yt8,3 onc-)spba /vl7,q huuncar 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 wal/s7kqyur7re efcy re k 6,q2./l and bounces back with half of its original speed. What is the ratio of the final kinetic en7r7r.eq kk c6e /qrfys,y u/e2ergy 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 moving5ob)advdnl3 9 at a speed of 5 m/s. If both objects have the samb 5l)on d93adve 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 speed 2.0 m/s. A7y3skx ihdc +j+7 o2 s5 *wxy4vfeg)vi 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking foyfxkjw7sey )v7 d2o+i +*x3 h54sigvcrce, 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 distance onydt0i/1h,zd/1j giwc ;cxlv; 2 2p xoz a straight, level road. If you h,xp;zl1it1dov xgy/dz c; hwc2/0ji 2ad 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 Sun in an elliptical orbit. Neglecting any pfwfrhq+h5zv. 5 z:r2 friction effects, whatvf zh5+qhz.2w:f pr5 r 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 princp b/j sslg0ln( aj;:-qiple.

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 negatikiwtcoj )in j:k1f7hx4nzv+ fe a8r,3, wm r4*ve 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 +ci()nb wxixn 1m(lx1from rest a height h above the ground. A second object with four times the mass of the first if released from the same height. The poixc1)i w+m l(nbn(x1xtential 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 causesgmrkd h ,kp,ez :)u*6xa9bsl ; it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the sprd xar,u:mh e6gz,bk;)kl9 *psing 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 syste-y jg*uj5mn+gm

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 kinetg.ryt)xl,z e , 73oedcic energy K, to its potential energy U.,d .e3ge7 c)o z,rytlx

A. K increases and U decreases.

B. K decreases and U decreases.

C. K increases and U increases.

D. K decreases and U increases.

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30#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Describe the energy of a car driving up a hill.pgc ;pow u1mi3q )..tty:/wad

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 objec*, ;r6+ funky9whdnkn t are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater heu 9*nk rndyf;,6+nk hwight?

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 6q:6 z ciz(nvo$m_{1}$ 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 conservattja /7w w:acsyk3j 2*live forcesak3jt wj/wy a *sl2c7:.

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 xa2t r/oj s/puqua,.2:x-qzy building, 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) at the top of the o/ ytpauj :. s2zax /-u2qx,qrbuilding?

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 ignoro7 3+.ruo.n r :ubs4fdwa5 zjl6e9nase air resist:r7e6 n5o9.anau4u lzsfwr od bs .+3jance. How 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 distvz brky-ghfg8 (vm6; ;ance and loses 30 J of gravitational potential energy. Do not ignore air resistance. How much kinetic energy did the ballhgf8r6 gv;mkz;y- b v( 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 energq i5voet3;k8y5 s03yexlo bl 2y.

该题自我估分: (必填) (满分:1.0分)

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38#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity Fd/t is+dwv+h0x mpz9sra 6,v

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 expr 0or276hhylo to +3tsyessed 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 noy:i *)u sdtdxy4+ gre nu04k+xt 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 dido u,mkon7ib 5 dh;o.1z 3 times the work in one-third the time. To do so, your powezmdo1 5.; 7k oibn,huor 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 engine2e r+u y;o3xexwn-tjz 7b6/u 1ha1plf 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+lun23 autu2s 2.0 m and held there. If the object weighs 90 N, how much work was done in liftilu+su a23t2un ng 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 disk1ngqki9 (p7v4xfo1t.e 4ik ttance of 1.0 m, at a constant velocity of 0.50 m/se7f.(k pg9t 1vi tknokxq 4i41. 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 with a constant force of 5500 N for aork v*in8w8cx 6n h:/f distance of 50.0 m. What is the ino/ hr8vk w86* xncf: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 pszsla v+sphfp5*7w55 ulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by5pph5+s 7zsv5a ws*fl the weight of the elevator?

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

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

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

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

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward wit4 1ep9 +vv dmbbhq6o 3*nlgfr5h a constant force of 5500 N for a distance of 50.0 m. What is the net work dh+lb6eb *v g4q13m59vfnorpdone 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 .:7deahme+mv /yw l6a.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 lx edb; :u;cs38.0 m 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 little sister Sarah in a sled on an ick vu11 z, ct; y/k6a3la v2wxv:,tteccy surface (assume no friction), wi3k xte;,zatwuc k t/c l2cv,vya11: 6vth 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 direction of the force. The graph in 9mp)pnvx tp,u*e.2 at Fig. 6-1 shows the force versus the object's positionp 2pavutx.)9,m e*n tp. 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 graph i :m-llndnb(is0-55vwy uosv6h 87bcpn Fig. 6-1 shows the f 8s5b-llv wvo n: mb6pc-0(y5ndisuh 7orce 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 the force. The graph in Fig. 6-1l tq1 gb7no0/lruz9;v shows the force versus the objen/z1t7lg9vl;r uqo b0ct's position. Find the work done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object 75837tzwx .se 1f iny+ dcwxyjin the direction 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 0 to 6.0 1it5xjn8 .y+yc wx3ez7f wds7m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55-kg cart (initially at ivnh:fpe*gf j 8r(/;n rest) fv*gji:nf; e(/ p8rn hacross 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 tz7u4vwm0fb x* o move a 55-kg cart (initially at rest) across a 10 m level surface. Wv7bw 0m 4*zuxfhat 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 in2 ;lne+fy) qbdomrt5r/4 0y b x7ynz9s required to stop the mas dn7entb+ n)ofr4y2yqxlmb/5y r ;9z 0s?

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 , t 2ajni:5a yueyc31gh2j1fk 25 m/s, what distance is required 1ijy2 h :aty3jf,1ngkau ec25to stop 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. It is cocked by exe2- +5fa70tbic+zgwv g.lwlksrting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assu 5+c+ g-wlwiavbtzs k0.f27lg ming the spring has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80 N and a vertical 69 hnv -vm/foecomponent of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, vvh9m6ef- n/oand moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g is shot horizontally into a bale of hay, strikiwdod6 6;qnh1ing the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What q61 niwh;do6d 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 2t-lm 1 gdb.+d eb :g)ybbzb(ha height of 13.0 m above the floor. d g2bdm:1+zh.gb-lb ()ebytb What is the change in 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 plaky6rsm ln8i59* tpviq;+fev7 ne is 4.0 m long and rises 2.0 mm+k p;7qiyrf*lts 6v 5nvi89e. If the plane is frictionless, how much work was done by the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. What i)on3e0,s m)tmf;cd3 s h b0 z)ijp(lfis the spe i d)tnsjch) im0 m;sfb0p3fzl(, o)3ring constant?

A. $4.9 \times 10^{3} \; N/m$

B. $5.0 \times 10^{3} \; N/m$

C. 20 N/m

D. 2.0 N/m

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65#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring is characterized by a spring constant of 60 N/m. How much potential enqhj ln++ dq-14sf n+iz-lvpk :ergy do nl nhvqp1zj+-+4 i:s-lf+dqkes 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 l2i:- twu(yjl an initially uncompressed spring with a spring consta-ulw yt2(il :jnt 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 constantoqoph dw ,/:f5s6jr1j 40 N/m from x = 0.20 m to 0.2/fjd6h:pr w5oos,1j q5 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 compreo a ov p0i2fn-s.b01rsssed by 3.0 cm. How much0b-ao i .nfr 10ossv2p 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 from rest from thczf d,jzq6b1/e top of a 50-m high slope. What is the speed of the slier on reaching the bottom /fz1 ,qdzb 6cjof 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 kv*jlly*0ku1 o4man a)g, pushes off the top of a hill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 m4a*kljvlam)n 0y1uo* in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a frictionless inclined plane q+3:fd1aamy w. At the bottom, it has a speedfw :+qama3yd1 of 9.80 m/s. What is the vertical height of the plane?

A. $19.6 \; m$

B. $9.80 \; m$

C. $4.90 \; m$

D. $2.45 \; m$

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72#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1.0-kg ball falls to the floor. When it is 0.70 m above the floor, its pogl yq5fzh(s 6,tential energ5zs g,6q lfh(yy exactly equals 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 1m9w7sjs a1 p*y.uy8q /y0 bbu*kj.jcq0 N, blasts straight up from ground level with a kinetic energy of 40 J. At the exact top ofp18su 0b yu7qqjw9b/*ycy*j.a m.jsk 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 grouu9whjl-k *5bhao0d )d+sv3*iflt i l2nd with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical heig) juhvl3590l*aso+lw dih *d2-fbkitht, relative to its launch point, did it rise?

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

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

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

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point p +*lcb jckwg 5 fga8* iv+hb).6-swca45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, w.fwjw -)g*aiclk sga +5p+8hbcvb6c* hat 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 speedmit.1vp e ) gidi966vf 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 bottom of the ditipf96 iv1m)v.ei d6g p?

本题所包含的其它图片:

A. 12 m/s

B. 14 m/s

C. 16 m/s

D. 18 m/s

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77#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts at a point 30 m above the bottom of a dip with a speed y9soj -cl0d/(a 4nb juof 25 m/s (See Fig.lscjnoaju0/ 4b- 9(yd 6-2). Neglect friction, what 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?

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 i; 9focwl;8k biq3l4ndv*fo1 tdj sd z m+,d4)mts swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertical axis and rm s6-hg .bm)lxeleased from rest. What will be its speed at xlm)g .6-mbhs the bottom of its swing?

A. 0.50 m/s

B. 0.79 m/s

C. 1.2 m/s

D. 1.4 m/s

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82#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car moving at 25 m/s tvfo4b9 dw6/t4ax nd :hits an initially uncompressed horizontal spring with spring xb9v64/:d4twota dnf 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, s cr*.n -)qhwf(5qfvu(0s lyj mlows down her 2000 kg car to stop for a red light. What work is done by the friction force against the whee0yc*5qf(msjr uhqf.vw ) n- l(ls?

A. $-2.2 \times 10^{4} \; J$

B. $-4.4 \times 10^{4} \; J$

C. $-4.84 \times 10^{5} \; J$

D. $-9.68 \times 10^{5} \; J$

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force between a 60.0-kg object and a horizontal surfa7 tn3 oqfhh-:kwnx*lf7t rd+s+ wi0c :ce is 50.0 N. If the initial speed of the object is 25.0 m/s, what distance wih*so+n:ni:flt-h3trfw 7d7q wck 0x+ll it slide before coming to a stop?

A. $15.0 \; m$

B. $30.0 \; m$

C. $375 \; m$

D. $750 \; m$

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85#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 12-kg object is moving on a rough, level surface. It has 24 J ofbk)ei6rli gzlx8u xa1lrk-: xjp3;8; kinetic energy. The friction fgkl: i ;e 88)p1bxr zlk63i-rxauj;l xorce 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 applied horizontally to a 2.0-kg mass on a level surface:pbblce )qfxy;.5+dd. The coefficient of kinetic ffq: lxdb)+ 5yd. bcp;eriction 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 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 restd55 7cy5tgxo j;te+b(e hjrj 0 from the top of a 50-m high slope. If the work done by friction ist05 x y5+5; eejh7 cgdtjbjor( $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane is 4.0 m long and h-dazu9a* vkgw8r 7n2t z;mw3rises 2.0 m. It requires 3200 J of work to get the box to theu;vw nazt-92w am g387k h*zdr 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 frd;yvdt4b 6l94y/ wjypom rest at the top of a plane inclined at 20e above horizontal. The coefficient of kinp/wyld4b;dyj v9 t 4y6etic 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 10.0 m, and strikesu;u- l;pr ,q ,o8ncjkn(pulhx5c/1ve the ground with a velocity of 7.00 m/ ;e5rn pn oqx k1,p/ul(8c ;,ucjulhv-s. What average 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 z9 w5hk8e -(dzyf4ibs1er1llk; d-j i when he runs up a flight of stairs 10.0-k5 bw-si984- 1ykrh1lfe j e(d;zdlzim 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 to move an object with a conf lv.i;u.h)3 rdp*yeostant velocity of 5.0 m/s. What power must be delivered to the object by the f3 d) pvli.;*.fuyr eohorce?

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 aj 4.gm0v)h ie.3b q;euj gwj(gre used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 74 ;jgv 4whqj) .e.gieg3j 0mu(b6 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. How much force dp4lp 0ns(qeskc58 y :c-s x .wgipf6+voes her foot push with fp-i : gven spy( k spcc6s45l.qx8w0+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.a8yx*n:mh+2g 1yofmybt nu yz: :szz bi 754c00 s. What is the average power delivered by the ena yyzn:yb507n:8*1fzcxym4hgmsu +z:2ib t o gine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95