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

1#

What is the correct unit ol)v o* py8c+pgf 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 if ther n2j .5hz5tyvue 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 h g+se85pm :lztg ae:(hard against a stationary brick wall, the amount of work yoee+gpa :z5 ltgms:8(hu 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. Ho+/,u qgk+fy k/k-mmzc 16lsonw much work is being done in holding k1gsfz6m/,o n+cml /uyk+k q-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 ag,69/ hibh**a qndtyzt a constant velocity carrying a 10-N objec6zgtniqhha, 9**y / dbt, 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,enuoxm0 1i; w then returned to its original position. If the t0iumxen;o,1w otal 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 for 0ix;+hi ua1cfce 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 the work don:1tmjle1:-dx;aq pe ;ggrvih25 2tq re by gravity while the ball goes up with the sign of the work done by gravitg d5q;;2hi:: q mex11tjlaver 2p g-try 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 v6npu,l(shqv+ ersus position (F vs. x) graph, represents hpnv+q ,lsu(6

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 ,y-hhh)ao l 3b(F vs. x), what represents the work done by the forceb3, yaho)-hh l 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 object is positive, then the object's kinet8 ;n7( nlhnbgle7i k0fic 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 the objecop lv )cwmwn y2-u4toky )q5-(t'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 object's kinetic en+ d wrjtid3 li(fv43/nergy

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 ptng 6,1xw7uc z(y74 /t2og jmrytixcu6z, b3a car, and is moving at twice the speed of the car. Which statement is true about the truck's kinetic energy compared to that of the cao6txzgimt2 774jcn /3( buy rgu1pt,z yc6xw,r?

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 hm1)o rdqxzj6 x8gw2 kh./x ,t1y uva8a ff:z6aas half the mass of car K. The kinetic energy of car J, compared to car K iazz88a.y jufho rg:6 26,/atmxd )qxx1f1wvks

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 2y;u6 o 9avirj2)u(uovk+nb+4 rmqn pbounces back with half of its original speed. What is the ratio of the final kinetic energy to the initial )o+r2 o(r;v6mv4upk iun +n29bauyqjkinetic 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 movx4,zag3fnoi /:qqeb8zwol:e5 *j h b 1ing at a speed of 5 m/s. If both objfqi ge 43lj,8bw qb :*x5/azoon:eh1zects have the same 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 sp,fi25 ;.mvc +odb hojxeed 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 the gv fbm2c.o5,o h+ jd;ixreater 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 certa l/v q 2gtsyl6/j2cr1h1)paex in distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skiddedjl)12/xgqr2eyca / vlh t1s6 p, 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 h(o 2lzoumw:us;2zr1 orbits the Sun in an elliptical orbit. Neglecting any friction effecom2 wlsuuzorh :21( z;ts, 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 .av+vd taesd5*q5 * dhprinciple.

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 energyyc-,od 0f6k ktl)h+1 )cs bt fkup/i)i?

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 abvir2/x3kv-c , c)jy oxove the ground. A second object with four times the mass of the first if released from the same height. r)xci/2 3v-okjv ycx, 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 spr9 f8,yz02xnhreqs 3 2usv 8nmwing causes it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential en 2 n shyez,8nmrwv032qus98x fergy 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 ener zdjbten*7 6th/pb07pge 5 lq3gy 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 potential ene;i f8yvf :0cs2vj jyy38 *+quthaxgx6rgy y8qa83jv c2 0*x v:jfstxu fy6; hyi+gU.

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 8qzb5pa6iw 0n driving up a hill.

A. entirely kinetic

B. entirely potential

C. both kinetic and potential

D. gravitational

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31#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A lightweight object and a very heavy object are sliding +yv;me-u * w wc 6iru(;exk.ymwith equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a ymu;-vw*(6 cu+eem xr; kiyw.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 lgw db,9yrlpsa,*5 -f$m_{1}$ 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 energv 0*p6udikaw t5lt .;ay for conservative forces*tt6u dl5;kvi0 aw p.a.

该题自我估分: (必填) (满分:1.0分)

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34#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball falls from the top of a building, through th:st-hyh,l)sr xem9/g i+i9fxj he9u0e 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+e9yghuii0st) le/- mxxs,hr :j9 9hf ) at the top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and gains 30 J of kinetic energy. Do not ignu +z6pv(ti 6tpore air resistance. How muc(v zp66uptit+h 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 distance and loses 30 J of gravitational pqu)k7 xxzkt0 h:c )*ceotential energy. Do not ignore air resistance. How much kinetqh: k)xt)*u0kccx7 ezic 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 ocwm,fe8ejs1 bxo) 1p ;f 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 istqm5 rlpa9e .6

A. the kinetic energy of the object.

B. the potential energy of the object.

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

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

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39#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What is the correct unit of power expressed in SI unity.qog90+f xu zs?

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 noxomz al d6vesi 8,k;i2j-d4 (nqe ,s2rt a unit of power?

A. watt/second

B. newton-meter/second

C. joule/second

D. watt

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41#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Compared to yesterday, you did 3 times the work in one-third the time. To do sga f-b1gy8ixqrp lac45c 921 go, yar acb4 1-cpl2x 59ifqggg1y8our power output must have been

A. the same as yesterday's power output.

B. one-third of yesterday's power output.

C. 3 times yesterday's power output.

D. 9 times yesterday's power output.

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42#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

To accelerate your car at a constant acceler,tvwjh4gpz 9 q+;9/, xstnpmzation, 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. Ij+:tte2,ms*9f thsv g6mxz t+f the object weighs 90 N, how much workm2+xt* v 9fj st6,: gmth+setz was done in lifting it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You lift a 10-N physics book up in the air a distance of 1.0 m, at a constant vepfrgio r3klucv7 m5: ymo-23)locitpuvc:o33mo) rr f-i g5 7mk2lyy of 0.50 m/s. What is the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5500:: kkrj2wnnh sr/ c/x. N for a distance of 50.0 m. What is the work dorc x: kn.//s hw2kn:rjne 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 upwardffde 8- i3 p2zdc xwk9qyj-(:z with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the elec9jdx-:( zw8eq2 k d pyziff-3vator?

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 kok4jp2n6ueme3,qew3x-wk 9di bm.h a constant force of 5500 N for a distance of 50.0 m. mi.9 64x2w4kpeqk3 w3 j-d,meub k oneWhat 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 upr/ 73nhd w.+d0wslkwx 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 e9 rsc *ve tuv957af55e04jiwbk 8f nt8.0 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 (ass(ynkw;3m m g7eume no frictkm; mgen(y37 wion), with a force of 60.0 N at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of thvhw88vc -pla,e 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 2.0 ,pcv8wv8-alh 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 objech8w2f 5f hqa6ot in the direction of the force. The graph in Fig. 6-1 shows the force versus the object'sf q6 ohfh85w2a 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(h-j+- k2 kl f 55hxbzrxp,hkyhe direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find tkh,-hbkf h-y jx rzk(px55l2+ he work done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the force. The uyxpqk7:k q no(xb:y v91-e0 amffk+:graph in Fig. 6-1 shows the force versus the objep u 0be-fkqy km+qo:7kxax9::yn(f1vct's position. 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 55-kg c,lyn .lmyp-,ujx 1(g cart (initially at rest) across a 10 m level surface. What is the final kinetic ,(-plj xlgy c,n.1myuenergy 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 2cw:oyzwexku6y/jt2 1.-ik v 900 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final spo ki9k2jwe w /cytuz.-6v: y1xeed 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 is requirfwsqw* 9)xwe8 ed to stop the masfwxs)w9 we8q *s?

A. $50 \; J$

B. $75 \; J$

C. $100 \; J$

D. $125 \; J$

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58#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If it takes 50 m to stop a car initially moving at 25 m/s, what distance isl*y cw8+mykaht9a0r5 (musf- required to stop a car moving at 50 m/s c h8yt(al9 m5*usrfawk0m-+ y 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 exerting a for u( ux+b*q lm(ti otvi5(5*5gdhhfw-tce of 20 N over a distance of 5.0 cm. With what speed will the dart leghiu b*dt*(to 5(v+u(t l -xmf5i5wqhave 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 80 N and a ff7:vsu2 pr.z*qyc g 5vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally a.y *qs25uzv7f c fr:gplong 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 horizontac . x zorx7/;*zz2gxnilly into 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 stopp./ roi;z 7*x2xz czgnxing 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 flo9j q9 ito4h nl3-2qmfuor to a height of 13.0 f- ouqh9t2l4 ni93m jqm above the floor. 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 ux x0dz:0iv1 ucp an inclined plane. The plane is 4.0 m long and rises 2.0 m. If the plan 0zxi1:cx du0ve 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,*9 ;tvenyav2g causes the spring to stretch 2.0 cm. What is the spring constant?n2egv *at v9y;

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 constaytb4zc h2;u o+o+a8c int of 60 N/m. How much potential energy does it store, when stretched by 1.02ya4bc+o t;z8hcui+o cm?

A. $3.0 \times 10^{-3} \; J$

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Calculate the work required to compress an initially uncomprdfbg i ss5+2;pessed spring with a spring constant of 25 N/m by 10 cm.;2 sf5bgspid+

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 consv95b+ j- g -cxg4jlx2v-wh c;.4rp0qbgysuydtant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched pos4dxs0+cc-bj- g;yuw.y vr-9 qgvj5hg4xpb2 lition 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 cons)dr 1gpaf7cn/v7k 8a ytant of 15 N/m is initially compressed by 3.0 cm. How much work is required to compress the spring an additioncnpda 77va1fyg/)r8 kal 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. Wha+oa 3gw4i oa+mvlmzf;j24c s-t is the speed of the slier on reac+-4oom if3gajvm+cw2 4 asl;z hing 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 th rr+4n;we nb8ee top of a hill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she bw4r+n8ne ;bre e moving after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a frictionless inclined plane. 3+,gx rtyed+a 1ex9tz At the bottom, it has a speed of 9.80 m/s. What is the vertical height oe3+9+, zxty1dtg rx aef 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 aboves uomf;:zyt rnri2v/4.x 0bf * the floor, its potential /fozuxry2b; .tnv:mis*fr04 energy 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 10 N, blav ,*+nqqo-h sasts straight up from ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J. To what vertical height does it a+h oqnq,-s*v 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 220 J. Ap3lc4yc 8v3 fat the highest poay 43 lc83cfpvint 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 of a dip bn: rpi yog,:0(See Fig. 6-2). Neglect frogn i:by0p: ,riction, 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?

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 star vwgrqwop n1 :,rx5n*lu5oau/58cv i+ts 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, what will be the speed of thp5r/uw qo rvi 5gc15vx8,nal*+n: woue 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. 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 atpa*sa*tqk 6;)6bx3qcy ,cc s speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of ty3x66csk);cabat s* qq,* tcphe 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 bal4 qxmq;1t +kcvl 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 vert.f1 :q/n5houbvun5+wo1 ydk bical axis and released from res:uqbb1o5w fn+n1uk ov5./ dhyt. What will be its speed at 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 hits an initially uadc uq -6m7f-wncompressed horizontal spring with spuwc dm6 qfa-7-ring 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 kg6ff ll -u0th+f car to stop for a red light. What work is done by the friction force aga-ult6 fl+ hff0inst the wheels?

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

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

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

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

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force between a 60.0-kg objexuosry q.4 16l l3/m:y71rnh, ntemlect and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what dis oyu:36/entxrl,l.eml ryh qs1n41m7tance 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 kd.e/w.ybi qyb l2 nlsa k8r.hwh0190 surface. It has 24 J of kinetic energy. The friction force on k .ky.e2widhh8 1ql9y a0bwn0s /rl.bit 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 sp/xpga *e v+nyf d3n:*urface. The coefficient of kinetic friction betweef*e p n*ngd/vp:a3 xy+n 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 rest from the top of a 5vy,rw d 8 2yhzc.8q kp3+lfim;0-m high slope. If the work done by frictckpyqv2ml+8 hy,.rz w 3f;i8dion 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 goc+ zg /q0p 3hjas bk+h/q1y1plane is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the planhh y 1qo1+qagkcbg 0s//z3j+p e. 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 the top of a plabow o zv s.qou(d/9t22ne inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20v.2sb(dqut2zwo o 9o/ . 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 droppedq, t/, jvnivglxp l0*4 from a height of 10.0 m, and strikes the ground with a velocit*il/q, ,p lv0tv xgnj4y of 7.00 m/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 when he runs up a fligz un6c;y-8 n1q(eas 0fv sts.bht of stairs 10.0-m high, ifcbz-q;s t(s vy e8s1n60an.u n
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 aw 7heu;1 nms0 bxe1oi89iwzw.n object with a constant velocity of 5.0 m/s. What power must be delivbn.ox1 uhiw 8z9wew1 m7i;s0eered 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 us*:kw-qh9 f9 7hhqbjz fed by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 7469k97j:q- b hf*zqh fhw 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 wa1*tax/xyroj, r nk+ 4hile riding. How much force does her foot push with when she is traveling a,a x+* 4yj1 txrnkor/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 l4je4r;8nnm6ewr,5 nilec:q s. What is the average power de5 4l 8 ;n:w ,rler6niqen4ejmclivered by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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