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

1#

What is the correct unit ed *+67ln+s9cza onak of work 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;da8vh+vn sgw ( v8z7q 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 stationary bric6 t -c .(tyfxb0z9m0ld5jvuw tk wall, the amount of work youj 9m00zwv5 b.xftly c(tdt-6u 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. Howazhz1yu lpx7f:2gr 6 - much work is being done iu6zfla: p y1h- x7rgz2n holding the box in this position?

A. more than 100 J

B. 100 J

C. less than 100 J, but more than 0 J

D. 0 J

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5#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you walk 5.0 m horizontally forward at a constant velocity ca* rn6w5q gm-,pv6bb ydrrying a 10-N object, the amoud 5rq wb6,v-*gbm6 ynpnt 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 2kwlhw gr*faj3l -p+0dkbg,0 to its original position. If f0- l*jkwap0 gd2r+3k,wbhlg the total 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 forcejyh yvn lh4*r. :z,+og acting 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 sign of th1q)rlnwf) k,6xz ryb7 e work done by gravity while the ball goes up with the sign of the work done by gravity w,6 fkwrxn)brlz y7)q 1hile 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 voymzf;-f1 0ein) gu7y -f/sdbersus position (F vs. x) graph, represents7f/n) buge-fi1ysmy ;o 0dfz -

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), whz10j; p.ufvyc k6ge4- wsjm9 p:+hb ruat represents the work done by the force ujfy +1wuz4g6hsbp:c jm;r .0pvk-e9 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 /q mko+sy0 u(q*eimf /object 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 -q73 :rj)s nej cd5mbnobject 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 object is zeron1*dn,p ju ujb2f+xt., then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice as much as a car, and is moving b3 *6vr,nfhytat twice the speed of the car. Which statement is true about the truck's kinetic ener h3v*nyb6f,rt gy 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 car J has half the mm)nmai8 ra4j1ass of car K. The kinetic energy of car J, compared to car K is r1 ajinm4m)a8

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 halfcn2 uupb0ys )7tp1r4q of its original speed. What is the ratio of the final kinetic energy to the initial ki t2140prups)n qu ycb7netic 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 m/ j w0cm5zag:-kj ctc(.s. If both objects have the same kinetic energytwkgcc05j .a :j-(zmc, 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 s:me6 gp h+zyu3peed 2.0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels tpu+z3g: m6eyhhe 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 pani8 6-jpn)eu azdc, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under thjeaudz-p)n 6 8e 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 *s0gi uu qc2.qorbits the Sun in an elliptical orbit. Neglecting any friction ef q*0sug 2ci.uqfects, 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 priaxvny a5pr0,) c5oa 5rnciple.

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 todkc vq/- q54z1igafw7 have negative potential energy?

A. Yes, as long as the total energy is positive.

B. Yes, since the choice of the zero of potential energy is arbitrary.

C. No, because the kinetic energy of a system must equal its potential energy.

D. No, because this would have no physical meaning.

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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is released froe1k mir17loiuo76 ,zqm rest a height h above the ground. A second object with four times e k 7zuil11orq ,o67imthe mass of the first if released from the same height. The potential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to c(7g8wngowy2 the end of a spring causes it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, to 7n2(wcg8w yghe potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical energy of a system 0x0 rq:aa( pom;kyes:lh5,pj

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. Comgx lt3ka;+qx hey3u 8.pare its kinetic energy K, to its potential energy U.y+g h3 q8xe;talku .3x

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 drivk8-k1ep. tcwsing 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 sxijsn pwe:dev/ ./6 68nz5tboliding with equal speeds along a level frictionless surface. They both slide up t.dtwzpe:v8 eb /x5on6i6sjn/ he 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 376a9m7nwn u6blx7;ij yu) mytijaw4 $m_{1}$ 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 of0ad: e0 p.lg pw3jnmr9 conservation of mechanical energy for conservative forces..pnp gdam: we309rj0l

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 o1ub oj 2smn+2yf a 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 enemo u2+nbsj1 2yrgy (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 of kinetic enerm07 7bw9lxwtj:xwwg as *)+ ilgy. Do not ignore air resistance. How much g:t+l9g*m l)7w7ws0 bjaxxw wiravitational 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 pox9l-uss ,-mt4l ykya:tential energy. Do t yu4-- mx,lss l:ay9knot ignore air resistance. 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 conservation;e/xz ryu.z- o 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 isdn2ls 0r()of+x 1ygfa+ q:qfr4ah v9e

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 ofk9g 7/s6f cd xkt.f9qg power expressed in SI units?

A. $kg m/s^2$

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

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

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

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which is not a unit of ph npi: i eq-x/0*:djqeower?

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 dm-r s/ bat h+pws1s33in one-third the time. To do so, your power outps/ d3hamtrs-sw 3+ 1pbut 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 accelerca8fode h g 21qjm7qkus03z :;ation, 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 thez5qbp7p 1 vq k6d,hm) cl*8gsw 0q/tbe object weighs 90 N, how much wor s8z01)v5 q hbqg6*bpq/te,cw lmkp7dk 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,e+;0p ; yp5vmz7jgofl at a constant velocity of 0.50 m/s. What is the work 7z ey p+5j0l;;pfovgmdone 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 pulledzgai*8+dw 5tiv ;cjuhw .,1pf upward with a constant force of 5500 N for a distance of 50.0 m. What is the work doncivup;+hg*tw wa 1d.jfz5 i, 8e 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 is7 mi97 y.5mka2x 0zqf5myhrgh pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work dimrhy5a2qyk7079 mxgz hf. m5 one 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 fobwm z8q k .lb63h1ont6p2na+s8udk;o no l9+s r a distance of 50.0 m. What is the net work done on the ;usn ot38+l9wda hskl+2 bqkn6n.o8b1 zp 6omelevator?

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 v 7 ium,(otlnw;asy z-s8o8us;* kcf4 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 slide; 4em yy(xhl5-e +pyoys 8.0 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 icy surface (assume no f0b*i6-,pj.qt vwl. /cjt(nexwidg/ triction), with a force of 60.0 N at an angle* (wtjtq ./ x-0b p6n lciw/tv.,igjde 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 tlszh:tk1np.t 2 ybcs64cq6q ;he force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the o61zt6hbt2qskyc c:4np q l.s;bject 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 in Fig.i/a:x *b;1owxpm7- hulv y0wk 6-1 shows the p0* bw-h:x7 ;lm/uk xw1aoyiv 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 t.5sy ub eov(e3he direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the wor(3be.y5o v uesk done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the for pezy135u(njpce. The graph in Fig. 6-1 shows the force versus the object's positioeup3p1n zyj (5n. Find the work done when the object moves from 0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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55#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55s)wvvbv .+.nzow qk ehu+u:zp739v t c 2b5qm--kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy q7n c5:+wk2qvz9wbohusv .pv3)ue -+btz v.mof 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 q d*a +5uo ka:jfzcpffy 0u1vv-,46yz200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the fiyvca-uj5vk1 , * dofzf4ay+ 0f6:zpuqnal 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. Hojf, gym.8m4 gen.p- xlh+ndt9w much work is required to stop the mant8.l-d 4gj egh.,nfy x9pm m+ss?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If it takes 50 m to stop a car initially movinp)) wl q0v /ot:yfieq,g at 25 m/s, what distance is requv/l yifw, toeq:)q0 p)ired to 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 4j/udfab +*bh by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the spring hadbu4haf/*b j+s 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 component of6kl5a/e)iwty i a*ts/2 v:w vm 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, a i* ts/wea 6akmtv/w25l:) iyvnd 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 int krr0q ./yn,zto a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What is the average sttnkrz .yr,q0/opping 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 tos0xau+x 5.ijm t) s:eq a height of 13.0 m above the floor. What is the change in gravitational potential energy? 0.um x:sti ej)+ax5sq

A. zero

B. 1030 J

C. 1176 J

D. 1910 J

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63#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 400-N box is pushed up an inclined plane. The plane is 4.0 m long and ris0 cqkz(qx qk/2z75* kh9k ckaaes 2.0 m. If the plane is frictionless, how much work was done by the k2kzk9 qaxh0a 5 7c(qzk/c k*qpush?

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 ont) k(o(mx g jpp;w0do8qo a spring, causes the spring to stretch 2.0 cm. What is tmoko( 8(0pdgpw q; x)jhe 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 sr7 eh6rxy (: ft.:*ixlp na+gepring constant of 60 N/m. How much potential energy does it store, when stretched by 1.0 cm *.ynrf eix (+t7hlpa6g: :erx?

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 requ9 a50vb x5kmgknenjonu5 u3.zs t:.1fired to compress an initially uncompressed spring with a spring constanvsmbnot 5 g3j.fkz9ak n5 01uu.: 5xnet 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 lyy;jr10 0m yr40 N/m from x = 0.20 m to 0.25 m? (Assume the umrjr0; yy01lynstretched 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 15h hyo;h +u77ra N/m is initially compressed by 3.0 cm. How much work is required to r ;+a7 7hoyhuhcompress 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 p c gb2-uao3 .s:xtpbd(;lvu1 from rest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottomgdp1 x2avt. (s-cob u3l;:ubp 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 hillltgwra*z+ b9i 8nc o fk35)ey0 with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be movi)3tf+8 05wg9a ykcr n*bzeilong after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a frictionless inclined plane. At the bottom, it h m-x/g( 8kknfmas a speed of 9.80 m/s. What is n/k( -mfmx kg8the 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 flo nv 666stqr7cbt c9-fvaxp;:ror. When it is 0.70 m above the floor, its potential energy exactly equals its kinetic energy. How fast is iq ar6n;p-:rcv 7fbvcs6t9xt6 t moving?

A. 3.7 m/s

B. 6.9 m/s

C. 14 m/s

D. 45 m/s

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73#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A toy rocket, weighing 10 N, blasts straight up from ground level with a kinetvcv852p* f9z:d h,xndj8aiwaic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what vertical height dfvaji c 9xw2,dpnzdv8:8*h5a oes it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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74#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A projectile of mass m leaves the ground with a kinetic energy of 2i)9 8yqei0v auc: .atc20 J. At the highest pivt e:i)u0cac 9aq.8yoint in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise?

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

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

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

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 m above the bottom ofkpje0ee 4t4n9h ltom(1ii. s ; a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of thtkee41n0p h4e;lm jo.i is 9t(e 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 starts with a speed of 5.0 m/s at a point 45 m above the3/d( jbuj+ey1 6ssmtf5usj.b.w836 ravjcuk 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. e/j3j6v+ mu6 jtw sb8.bsju(31sca kurfdy5?

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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 abov*r y-c 3u lmlws5fni13e the bottom of a dip with a speed of 25 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 abov w1yf5 n-ilml33 scr*ue 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 b;o 0 *sat0rf)gkbtaun gp;a20all at the bottom of its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertical axisjun-wq+:je:ek (cvx/xt0 h 3q and released from rest. What will be its speed at th03n+ x veh(/qetux:qjcj:-w ke 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 hits an initie13ttnb3 ewu7db lfekr.c0 z-h9xq/;ally uncompressed horizontal spring with sprin/ntf .th -bxlze1ru 03 c;7wed3k 9qebg constant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for a rednv i6 nhfgorhtz,scm6/ 9,s)6 light. Whm6 6f/,szsrt,6 hno) ig 9vnchat work is done by the friction force against the wheels?

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

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

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

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

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force between a 60swbqg 4 rg3*6q a/yag:.0-kg object and a horizontal surface is 50.0 N. qqg rwa*a6:4b3gy/ gs If the initial speed of the object is 25.0 m/s, 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, level surface. It has 1ug;y knl:- kofgy:l2 24 J of kinetic energy. u o; g-kn fyl1k2:l:gyThe 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 applied horizontally to a 2.0vedn yq.(c/;p-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 dist dp(.veqny/;cance 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 t0j 5ienomgz4 yr49 zhg)xtcuq*8m;m(op of a 50-m high slope. If the work done by friction is ;it c0(*eh49jozmm q4nu)m 5r8gxy zg$-6.0 \times 10^{3} \; J$, 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 lt wm7mj9*ip2t ong and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force owp7tmt 9mj*i 2n the box?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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89#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass is released from rest at the top of a plane inclined at 20e q:mz mccz.8c )xlw1)e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass c:qw8)l c ze)z1.mxcmafter 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 strikes the ground oyhhh;g he:+40b1 ha)e7sye jwith a velocity of 7.00 m/s. What average fha7yy4e jso0be ghhh;:h+1e)orce 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 when he runs up a flight of stairs 10 xxeqz,x ccuyv:29c)8.0-m high, in8zx9qyxcu,e ) ccvx2:
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 constant velocity of k+lfc32ftj+xm/s7 zyh 66evy 5.0 m/s. What power jfs6vh+3z6fl m7 tcy/y 2+ kxemust 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 -irvn8d :rew *;xkt68 ifmhg/ hp motor that runs for 1.0 hr? (1 hp gdmf6ve/ 8irxwk: t-h8 ;rni* = 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 ridnto(+4;dvga rhiy 6 5ming. How much force does her foot push with when she is 64nt mv(h +r go;idya5traveling 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. pkeahw ) efltkyr*9+ . d b)m-2aqp1.kWhat is the average power deld)qt 2kfpek1l9 )ap kr+mbhy -*..e awivered by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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