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

1#

What is the correct unit of work expressed in 8 r gskyb;g4m0SI 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 sp;swq9s, ud re0.c vk .5oxsqf/e2np1 ystem if there is no motion?

A. Yes, if an outside force is provided.

B. Yes, since motion is only relative.

C. No, since a system which is not moving has no energy.

D. No, because of the way work is defined.

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3#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you push twice as hard against a statios 5 lrcmze4./bhl:mx7nary brick wall, the amount of work you5r4xcblm: ms e7lz h/. 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 lifted 2.0 m vertically and is being held there.p-bm0ompr;*bc 6eb,yq d:lcomlr- ; 3 How much work is being done in holding the box in this positioncqd*-;- m; c,o:or lybmeb 3brl6mp0p?

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 hori) m40hd4xixx dzontally forward at a constant velocity carrying a 10-N object, the amount of work you do i0hxxid d4m)x 4s

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 i* kaqi *.w+suxu4sns0x3t v z8s lifted vertically 3.0 m then returned to its original position. If the total weight 8.t3i*4x*v uuznw0a x+sq kssis 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 act6lz5;bb h2egda /mb1zi tm;i4ing 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 hyp1fdx j/oe/lmb3/wo ,4pz6the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes dof6eo hpdy z /43b,l1x wj/p/omwn.

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 versuhmapx,:/3 e zps position (F vs. x) graph, represents:3,/me pah xzp

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 represents the p dbox(,ik *2e6*yq l,,v yzfivs3l4vwork done by the force F*v6 vl di4q* yko2 x,iel3y,sfpzv,(b?

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 l gfk1 sa kt(w1.0et7aobject'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 thi u8gn8 8m,crae 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 zero, then the objecj e xz2;xc/wbz2m ,).fvrjg n1t'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 the speed of t m16dl0vqfdq -he car. Which statfm-6vd1 0qdlqement 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 ax z-rdeunf30mk;73xpw7 ,l ln gn6y e2s car K, and car J has half the mass of car K. The kinetic energy of car J, compared r 6n mdg3-zwn3;f 7 lxn,e2peukl0xy7 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 bounyr m1vm;8a li9zj5x o+-v,qlaces back with half of its original speed. What is the ratio of the final kinetic energa+i jym5vr8 ,z1m9 l; vlaxo-qy 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 si63-q28bve2 uk am epm/s. If both objects have the same kinetic6um bvis qp2akee2-83 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. A 1.0-kg mass is movin i qwbuaii4yz(;(3iaa48ha1fg with speed 4.0 m/s. Both objects encounter the same constant braking force, and are b(1a44wyfi(i aia 8q3;iubza h rought 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 knxch g,eb)+roikz 4;-c8* fhpanic, and skid a certain distance on a shx+-b4e8h kzc)ncg ;o*,f i rktraight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

D. It is impossible to tell from the information given.

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A planet of constant mass orbits the Sun in an elliptical orbit. Neglecting anwhmu y3; tlqu/5j *dh,y friction effects,h,*/udjy 3lh;wmu 5q t 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 princr)w hf4vfu7f0kqjk/4y* nd5riple.

该题自我估分: (必填) (满分:1.0分)

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23#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity mgy is

A. the kinetic energy of the object.

B. the gravitational potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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24#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity $\frac{1}{2} \; kx^2$ is

A. the kinetic energy of the object.

B. the elastic potential energy of the object.

C. the work done on the object by the force.

D. the power supplied to the object by the force.

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25#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Is it possible for a system to have negative potential m:e ava. 3nom9energy?

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 ground. i8q 1 on,ut*gy A second object with four times the mat1u*q,o8g niy ss 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 5v b*(gbutzaef;g wh;cii;3tztr.;p e n(5s,to stretch 5.0 cm. If another 0.200-kg mass is added to p hafti5;(zcw(tun5*i b. ,zvts g ;e ;rbe;g3the 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 enerpw nxd+4sz3)gy (f:mvbv +s0wr (yrh .p)m;jsgy 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 kinetic energy K, to its potenti:f x8c,)tlsdk3y lj- ial energyly )t-clkd f3 i8:s,xj 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 drivw4-o66a-qobtixbd9r yn 1 ow7ing 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 m6z (sr+/msu land a very heavy object are sliding with equal speeds along a level frictionless surfasmz(rm+u 6sl/ ce. 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 c z(9-dnmm -r tojf r6ufzi8*8$m_{1}$ 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 cokb .ieot o/82anservation of mechanical energy for conservative forcestbk ao8/2 oi.e.

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 bui4yis kdj6a/yo 56f rp(0sr-vjlding, through the air (air friction is present), to the ground below. How does the kij(v/r 0r o6a f p45yj-k6dsisynetic energy (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 30 J oflp hqj3ak512k kinetic energy. Do not ignore air resistance. How much 5lpkkjq32 1ahgravitational potential energy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 30 J of gravitational potential ener9t:;c8 d7gkcw/ qebw ogy. Do not ignore air :k /d8b w c9ecgoq;7wtresistance. How much kinetic energy 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 conservation1,q,z(3o: aai-6 zcr o lbizbi 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 isbggbg*a-f2h )

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 expressedce- j,60ila, , je8noc0d kved in SI units?

A. $kg m/s^2$

B. $kg m^{2}/s^2$

C. $kg m^{2}/s^3$

D. $kg^2 m/s^2$

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which is not h8.ufdxi5voy, ev55sx*g*5 hhx nk6sa 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-third the time. To do so, go5 tqcxm.x;s72- noa.3s pag your power output must have 5gma p x.7t x- nco3.gqsa;2sobeen

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 n y+ *jr7 twjlnlyf.;zyi)w0j 8-*houacceleration, 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. Ifoj-h6k bh;f o6g6ysd0sepk;o/;l-ot z n )pt . the object weighs 90 N, how much wo.;jfdkksgsy/6lop6 hh6z)-e o obtp0;o -n t;rk 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 diso3e,g niox i7jl -87mytance of 1.0 m, at a constant velocity of 0.50 m/s. What is the woroino,x37ge j7imy8 l- k 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 a dis+:s- w:s5gln wygh7sjm4w/y ytance of 50.0 m. What is the workshjswyg7l4:s mg :5ww+y y -n/ 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 constaohb6k .qgafol1t - 7,int force of 5500 N for a distance of 50.0 m. hi-76.k t1af,olbogq What is the work done by the weight of the elevator?

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

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

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

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

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5500 N for a distayoblxw26**xw gks //vncev owx6y wgbl/x/k*2 s* of 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 2i *ft:pc:qh. go+btmalong a $37^{\circ}$ inclined plane. What is the work done by the weight (gravitational force) of the box?

A. $-11 \; J$

B. $-1.1 \times 10^{2} \; J$

C. $-1.4 \times 10^{2} \; J$

D. $-1.8 \times 10^{2} \; J$

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49#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.00-kg box of fruit slides 8.0 m do+wx66a xxl1qown 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 ps(k+2ivnj1wicy surface (assume no friction), with a force of 60.0 N n ki+jw 2s(vp1at 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 Fiy8g4 x-hglts tg:f4 zpv 1b77gg. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to gp f: 1gg4 4ztsbvxytgh778l -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) ; j6h8wt4e ym(m: f1qwvjblj direction of the force. The graph in Fig. 6-1 shows the force versus the obm1( jwwt)qf jejm :yvl64hb ;8ject'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 o dwidm r9t3q-/gpi1-. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4 rwi t/m93o1dpq- id-g.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 objectl h)/ozt,qk1z in 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 ok)z,l/z q1th m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55-kg cart (initiall oh0m,gw(fj 6hy at rest) across a 10 m level surface. What is the final kino g0, hmw6hj(fetic 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 o zoi)i-cp -33m 2f qbkfnp;o4tf 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface -fpmo;qtkbz2- i34ocnf) i3p . What is the final speed of the cart?

A. 73 m/s

B. 36 m/s

C. 8.5 m/s

D. 6.0 m/s

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57#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass is moving with a speed of 5.0 m/s. How much wo55ttjg:frh b3)7g6 ywv f+z7tj/nqhwrk is required to stop tf5tz3ty7h +bt)q fgw7ghnr jv/:6j5whe 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, whatw 9, pqgx*e:v3pw+voo distance is required to stopgvxvpe po3 + :*oqww9, 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 dau i- (;lixbs3hrt. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave; -l3uhiis( bx the gun, assuming the spring has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of qsia6::vb;./p.wdkb,n wr 6b b jpc z;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, andbvi;ab q j.cwp/k nwbr ,s:z6:d;.bp6 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, striking th)c7tcd :zcjm(vn o61xe hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average stopping : (7m1cvn z6d toxjcc)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 movr5*9 imudvv 0m9;dey ued from a height of 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravu9e mviudmy9;d* 0 5vritational 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 inxvxg/nu7f d,j ave/fe12,h/,e1izd nclined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much work was done by t nu,dv/fe/ja1ni7vzx g , e,2h d/ef1xhe 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 on6l6ysh .*kqnb a8aqt p+g9f7pto a spring, causes the spring to stretch 2.0 cm. What is thnf.g668ka7s+hqbt*qp ap ly9e spring constant?

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

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

C. 20 N/m

D. 2.0 N/m

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65#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring is characterized by a spring zsxwi/l3b, w;constant of 60 N/m. How much potential energy does it store, when stretcbz w3sw ;xl,/ihed 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 l7pnylg4b k sna6z8ty7f ;9c,compress an initially uncompressed spring with a spring constan8 cp,;n9s67yy zab74ntkl lg ft 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 constancc h9ps0ap) oy3:.umj9ba8;8 zfjgnje 2 wo6yt 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched posit c.8ca9 g0 jp6zo8 a9shfmu: yj32oyn; bje)pwion is at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring constant of 15 N/m is initially compressed by 3.0 cuwe4 j1 d3kt8qm. How mu41tjdke 83qwuch 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 the top of a 50-m high slope. What is tnv;qi +k)f lk7he speed of ki)7nv;lk +q fthe slier on reaching the bottom 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 pi4.9 giwa*cj top of a hill with an initial speed of 4.0 m/s. Neglecting frictia49* pjg w.icion, how fast will she be moving after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a dg:w ia/fo*.q4wep-r c) grb 59jt cd)frictionless inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height of the pladeo. ti wdqg) c gba-cr9j5)4:fr*w p/ne?

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 m,ch+ yfzi2gg41.si x above the floor, its potential energy exactly equals its kinetic energy. How fast is it m f+m4 hzc gy.,isgx21ioving?

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 straight up from grou,;2 oz ivi(ypund level with a kinetic ezo;iyi(2p vu, nergy 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 ground pj-fk-3-1 5*r4ngqzfebmz1uzja l c.with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height-1z rn534e-z l j qcjp*fbkmuf.z1g a-, relative to its launch point, did it rise?

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

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

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

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 m above the bottom o,nd1 1kfq*tf3c*(h0 dwkp vvgf a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster atd(10 3g pkv wvqh dn1*cftkf*, the top of the next slope, which is 30 m above the bottom of the dip?

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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 star r 7 os:o*z/41z(th mb 0ko6gjnk,drpxts with a speed of 5.0 m/s at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, zo,1gso* p:kr 7m(nxkh bj04dzo/tr6what 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?

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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 point 30 m above the bottom of a dip -camwi5bdae8 5;h ed x:j1k3 zwith a speed of 25 ij bhc5ma51xzde:ake3; dw8-m/s (See Fig. 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 2sdnkj jdvlhi)i )q,yp/ 8x40 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 isz50wf69ttm b4 t7rrsp pulled 30 cm away from the vertical axis and released from rest. What will be its speed at the bott9r 7zt5tpwb6tr m 4sf0om 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 initiald/. ( w tpb+pxjx:em,bly uncompressed horizontal spring with s. ,:tdjwe+ / x(pbxpmbpring constant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop focjvwgj97 fu763d70d clfu/q c r a red light. What work is done by the friction force df jdjwg377qfu 96 u/cc0 c7vlagainst 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 ) ;quye1s;w -t7zkrey 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, yr ;q7eyet 1;zuksw-)what distance will it slide before coming to a stop?

A. $15.0 \; m$

B. $30.0 \; m$

C. $375 \; m$

D. $750 \; m$

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85#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 12-kg object is moving on a rough, levele54 -rjly*l nt;bs y.e surface. It has 24 J of kinetic energy. The friction force onjy5yne.l4s*r l-eb; t 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 a+6xw2ufo94o n - rhovepplied 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 movuhr+- 6f2o4 v xewo9oned a distance of 10 m, what is the change in its kinetic energy?

A. $20 \; J$

B. $39 \; J$

C. $46 \; J$

D. $61 \; J$

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87#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50-m pi-qe,auwl cvuei:u ,*1jg:(high slope. If the work done by j,c*g q,e(i: ewiuv u:1u-aplfriction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane is 4.0 m+xe8sv1,k v1ky7 hg hz long and rises 2.0 m. It requires 3200 J of zk1gh+ h 1ke,vxv y7s8work to get the box to the top of the plane. What was the magnitude of the average friction force on the box?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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89#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass is released from rest at thwiniw .a/ 4t1gbak0 fk96.yree top of a plane inclined at 20e above horizontal. The coefficient of kinetic friction b1t./.y4 g eiki 0 r9bwf6akwanetween 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 droppeaf-1lu vrdj0(xq:r t u5dp-6ts nr7w20 lps r-d from a height of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What0- 1rd-s-6rjputw5sf2un:a70 p rdr(ql l xtv 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 usdxlbh3b kd *c,otem;0 1/8 mdhfv8 cm+ing energy when he runs up a flight of stairs 10.0-m ;b/k+m 8c3hf dd,vhm8 x1e mtl*0dbco 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 obpy;k lmqg1z7ak-e 96e*jayt 3ject with a constant velocity of 5.0 m/s. What power maqk9k; -amgz7j* 163ety lpeyust be 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 energy are used by a 1.0 hp motor thau5cho lzu9.8nj6 4nbb: z.qz xt runs for 1.0 hr? (1 hpnz5 zu.9 chxb :.u8 jo46nqzlb = 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. How much force does hel,3mn 7vebn0n4s wt(q+jtq2 mr foo0 4t 3tsnq(m,7lnqb+nmevj w2t push with when she is traveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. What is the averag lteg3( 4p+ghoe power delivered by the engine? (1 hp = o +p(h43eggt l746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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