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

1#

What is the correct unit of wo2xzx+)gdege6 y bl.hp9u 1 su4rk 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 thup p:(m .ql:d2ci/ p8ml v9bgcere 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 brick wall, (igf;yk/(ph8w qog 8cthe amount of work you dg8hk/f8wyp co q ;g((io

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-N object was lifted 2.0 m vertically and is being held there. How mutf;vic ui:dz- ivbxyi .8(l4(ch work is beini: cb(xvd4izv;8i y-utl.fi(g done in 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 forwsshs9 s55 *w3anzhm2tard at a constant velocity carrying a 10-N object, the amount of work yon w2hs mh5zs39a*sst 5u 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 to its b9q /cht:)yvy-tlsh ,original position. If the total weight is 30 N, how much/ys)c qlh, b9-: ttvyh work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on the o.q p-mkd5r*nrbject?

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 thewdy(. /fo oyp,9j- x. inwa/sc work done by gravity while the ball goes up with the sign of the work done b ypwsfx c .ji/9no,d-o.aw y/(y gravity while it goes down.

A. Work is + on the way up and + on the way down.

B. Work is + on the way up and - on the way down.

C. Work is - on the way up and + on the way down.

D. Work is - on the way up and - on the way down.

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9#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The area under the curve, on a Force versus position qn/8b-z p*rkb;cm;jb (F vs. x) graph, represents*b/mbq8 bzk;j pcn; r-

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 wcte4fb b55 3ohork done by the for bto3f4hce5b 5ce 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 .t-gp4lv(y*7lx vkssthe 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 object is negative, then the object's kinetic ;zsw53ucu a xv/wthen60rp/1 eqzi3* 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 kinetickl:wv 6jh f)3e 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 twic)f7 , d9mg( eazw-taque the speed of the car. Which statement is true about the truck'sqw,a( ag-7 dztm)9fue 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 a;h;yc ;tm* 7z4swk7doapm4t k s car K, and car J has half the mass of car K. The kinetic energy of car J, compared to car K ;k oa4mm *;4kscd zwyt7p;ht7 is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with half of mie i2gx1pk5cs9b- ob vc8;c* its original speed. What is the ra9obmg1 cecc2x5k-8s ipv*bi;tio of the final kinetic energy to the initial kinetic energy?

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

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed of 5 m/sw5 m+h *(apoeq. If both objectaew*op( hmq +5s 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 speed 2.0 m/s. A 1.0-kg mass is mr +;3-lw;szi wqqjc z5oving with speed 4.0 m/s. Both objects encounter the same cqswcz-ql;w 3 iz+5 ;jronstant braking force, and are brought to rest. Which object travels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in a panic, and skid a cert+,. (z5kxc eia ecnq-uain distance on a straight, level road. If you had been traveling twice as fast,kzxic (-, qena .ceu+5 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 orbitt92ifq fab3:n9m y iu-s the Sun in an elliptical orbit. Neglecting any friction effects, what happens to the plane9anyftqi2im 9:bf u 3-t'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 pcf 0w/ to8vpko/q .8sprinciple.

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 potenti3ctq.fprr h/v tv 0p7(al energy?

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

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

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

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

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26#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is released from rest a height h above the ground. A second objecsqk3 al v2jl:+w -.wi;iatmu:t with four tim u:-aa+s3vkwm. l l ;:qjw2iites the 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 the end of a s ,t1wus 68wbgxpring causes it to stretch 5.0 cm. If another 0.200-kg mass is added 1,ubs6g wx8twto the spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical enerzaske3 y-nrrhg.6 ,j2gy 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 ener:lh 1ozgnu4h3q c2ek-gy K, to its potential energy Uu1 z-khn4 3 lgh:oqce2.

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 y;jxuz.k ws sn );ex8,+y sl7ja car 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 veryw(y 4:mx l6r azpy51(g3hvp so heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater ayz((r1hpxpo4g:5 36lwyvm sheight?

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 x2uy.b z.dpe3m5po w/hkw 8:k$m_{1}$ and $m_{2}$ at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which $m_{1}$ sits is at an angle of $30^{\circ}$ with the horizontal, while the plane on which $m_{2}$ sits is at $60^{\circ}$. If the masses are released, which is going faster at the bottom of its plane?

A. $m_{1}$

B. $m_{2}$

C. They both are going the same speed.

D. cannot be determined without knowing the masses

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33#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the principle of conservation of mechanical energy for conservative jbo5p6ph,n 0xzl *0qt forces.hp*noj ,50t z0qpb l6x

该题自我估分: (必填) (满分:1.0分)

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34#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball falls from the top of a building, through the 3(d5-jl ryo hpair (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building-lpjd or35hy (?

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 ignore ax2 xn;(h q3jtair resistance. How muc xq;a xjh3nt(2h 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 potential energ. t /af3i3xhnky. Do not ignore air resistai/3ta nxhk3f. nce. 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 vfrr+lsq 0x84i7sdw7vpz2a57 bl y z8 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 isa0sa c;d lr/x:j7c :2tqw6w,cl ypap9nph/l+

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 p 4. sjx2ctcgl8ph p-(nower 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 c w.g- t1q,yskm 20lwyunit 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 dos )01 4h/ xrhxpb1iadk so, your power output must have 1phsd x0)k1hra/4x bibeen

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 cojgk3uaf h) 5yk+ m:d;qnstant acceleration, the car's engine must

A. maintain a constant power output.

B. develop ever-decreasing power.

C. develop ever-increasing power.

D. maintain a constant turning speed.

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43#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is lifted vertically 2.0 m and held there. If the objeuoi4u.p7,dnj ;7r*uxq oo1lcct weighs 90 N, how muqd.7 7ol ;*jc1u u4rxi npo,uoch work was done in lifting it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You lift a 10-N physics book up in the air+1k8o ijzyaa--x8e f p a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by x1iz a+o a-ekj8pyf8-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 45a(yx, u) ikjg0ikada constant force of 5500 N for a distance of 50.0 m. What is the work ad(ux jia0i)kg4yk, 5done 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 constant force ofo- jq94f dq9bc 5500 N for a distance of 50.0 m. What is the work done byd4cq j fq9-bo9 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 Nzp.i./l8x6 gk *qxwm rv4l4rk for a distance of 50.0 m. What is the netwl *.r4igm. vr/kk 84xzlqx p6 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 alonp8q6( n rpom;dg 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 dop, pr zqr- 6-p,y,kcxhwn 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 surfacx7 2w4 1q- a,fg5e7hg2hstzzlyo. zk ye (assume no friction), with lo7wgz ,-xk2 zy21teq5 h7gafyshz.4 a force of 60.0 N at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the fbqf(9o:koc7dfl 78ino/ -nwd orce. The graph in Fig. 6-1 shows the force versus the object's po(o7 8:k- n7b9iwd qlnc/fofdo sition. Find the work done when the object moves from 0 to 2.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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52#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the forcwwzk 6t(*f2 nhs ufan4ng7: *ee. The graph in Fig. 6-1 shows the for(t*u nkesa42 6 nfw gfzh*:7nwce versus the object's position. Find the work done when the object moves from 2.0 to 4.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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53#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the force. The graph in Fig. 6-1 d. 5hi ng-go.jshows the force versus the object's position. Find the w igjong5h.. d-ork 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 gkp3zte7 (dsj-:2n sx iraph in Fig. 6-1 shows the force versus the object's position. Find the work done whennz 7(d3spe: txjsk-i 2 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 -spv m(s5ejgd*ck1j +N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is vm1pgsck* s+ 5e(jj-dthe final kinetic energy of the cart?

A. $1.0 \times 10^{3} \; J$

B. $2.0 \times 10^{3} \; J$

C. $2.7 \times 10^{3} \; J$

D. $4.0 \times 10^{3} \; J$

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56#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied tohx*9(c pn0kgl move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final9ncxhpk 0 (l*g 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 5cj,ux wj+-piate24dhou6fb7vc ;s 1 5.0 m/s. How much work is required to stop t1,cp as2o5-vd76h4ib;futjc j eu +wxhe 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 fqo5tpk1l j2-5 12htary)wcc:v9p ep 25 m/s, what distance is required to stop a car moving at 50 okp:p)fwr aeh-qj1pcy12v55t l2ct9m/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 j7 0xm jny.bxu-8f *redart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the dart leave the gun, assuming the sp0- r7bxumjn8x jf y.*ering has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80 N and a vertical com l0k8n8izt7 rm,6ruup f6(bxdponent of 60 N. The force is applied to a box which rests on a level frictionless floor. The ca6kx6ui 8(r ,87bmunplf td0zrrt starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g i 5 u.vikb fz6wj0l;wq4s shot horizontally into a bale of hay, striking the hay with a velocity of 60 m/s. It penetrates a .bqz50;kfijluw 4v 6 wdepth of 20 cm before stopping. What is the average stopping force acting on the arrow?

A. $45 \; N$

B. $90 \; N$

C. $180 \; N$

D. $360 \; N$

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62#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 15.0-kg object is moved from a height of 7.00 m above a floor to a he cdhv.,7cex, cight of 13.0 m above the floor. What is the change in gravitationc,,echd cv .7xal potential energy?

A. zero

B. 1030 J

C. 1176 J

D. 1910 J

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63#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 400-N box is pushed up an inclined plane. The plane is 4.0 m long and rnhgegm: ;lg-.ks2l pbw o5 *0geadv++ ises 2.0 m. If the plane is frictionless, how much wo5ggdheel;vgl+.-+s o:m pk g2b* a0nw rk was done by the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass, hung onto a spring, causes the spring to stretch 2.0 cqc6xk j1fg 4m8m. What is the sprik c6qfmj41xg8 ng constant?

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

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

C. 20 N/m

D. 2.0 N/m

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65#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring is characterized by a spring constant of 60 N/m. How much potential lv)d++.ppq ycenergy does it store, when stretched by 1.pp)cvq ld ++y.0 cm?

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

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Calculate the work required to compress an inia-lfw 2dkt0 )ytially uncompressed spring with a spring constant of 25 N/m by 10 cml2 wa0f y-dkt).

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 consta,v *a wr76d.3bijvwofedi; )w;ws)nent 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position is at x,wvr d)).ws*ve in 36a 7 webi;dfwoj; = 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 spri ;*vwfkc +xraim)rh0:2 ktkvhwk7:+bng constant of 15 N/m is initially compressed by 3.0 cm. How much work is required to kr irw+2hhbvmxkk:w* +0:af 7ct );vkcompress 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 f8b2z 5a dng r.q mrcj)pjb9i. 2pi4yo5rom the top of a 50-m high slope. What is the speed of the slier on reaching the9).iqo 2 4b.crd2zpg nj bm yr55jpia8 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 top of a hill jukg9sm/jz ., with an initial speed of 4.0 m/s. Neglecting friction, how fast w9 /g,jk.msuj zill 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 frictionless incl gyc4)cp*x o35mhbjpy 2 jplw u/fm,(9ined plane. At the bottom, it has a speed of 9.w9cjbp/p f g3m2xoh jpc (*y,45 myul)80 m/s. What is the vertical height of the plane?

A. $19.6 \; m$

B. $9.80 \; m$

C. $4.90 \; m$

D. $2.45 \; m$

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72#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1.0-kg ball falls to the floor. When ):xiv kt;txlg v 2)edcx+(k1fit is 0.70 m above the floor, its potential energy exactly equals its kinetittx fkgvd)(likx ;+1): 2e vcxc 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, blastsop9j q r-t- n;sy5ckq; 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 vero5ytr ; qcpn9k; --sqjtical 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 with a kinetic energy of 220 J. At vv)nyyb7f q)4 the highest point in ivf4y y7)qvn)b ts 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 49hthcrvwm vdv2py1(4 10(mow zq*ac- 5 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaow1(vh1h9v- (vrw 4pc m0*yt2z camqdster at the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 17 m/s

C. 24 m/s

D. 30 m/s

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76#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts with a speed of 5.0 m/s at a point 45 m abovetvj6gf0a8 o2-z ft.)vhf;rf p the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at thfa6ht-. 0g)vfzrf;vofj8 p2t e 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 a speed cv ,52)ugqfad9u+ p wxof 25 m/s (See Fig. 6-2). Neglect friction, what will beguacwvu+ x , )dfq9p25 the speed of the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the bottom of its swing (p8rr (1*wwcb r/lx(abt oint

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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 cmr3 twyqx,m o7yy :q5*.km2 xgj is pulled 30 cm away from the vertical axis and released fr3,r2x gq*7j yyq.m :omyw5tx kom rest. 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 hi0t8 3,wl usndsts an initially uncompressed horizontal spring with spring constant t ws08 s,dn3luof $2.0 \times 10^6 \; N/m$. 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 2ik6h/ i9nriw3 oibu de3v5..v2 m/s, slows down her 2000 kg car to stop for a red light. What work is done by the friction force against the wheelid3 iiehvi/95wnkru. 6ob3.v s?

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

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

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

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

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force between a 60.0-kg object and a hori vp o4zkbv4q7 s +;etgby80.dwzontal surface is 50.0 N. If the initial speed of.ypwv8q4z v4ebgt7 0 sb+;dok 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 surf4wui vf:4kx 5 sdw/6juace. It has 24 J of kinetic energy. Tdxuw i 5us6k4 f/vwj:4he 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 2.0-kg mass 8(* qflq,w qlor/fd4oon a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of q/ qf(r*w ool4l,d q8f10 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 high sl/5 62lp z8hviwez*k,b bzq-kgope. If the work done by frictio5b-62zvi z gpl*he,bzkw8q k /n is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. Thetu,2 y bxttc*- plane 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 plane. What was the magnitude of the average b* tc2,x-uytt 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 plane inclin 0ylgd v* )ecwm1b9/ived at 20e above horizontal. The coefficient of kinetic friction between the mass lgdbyvi9)cw m*/01ve and the plane is 0.20. What will be the speed of the mass after sliding 4.0 m along the plane?

A. 2.2 m/s

B. 3.0 m/s

C. 3.5 m/s

D. 5.2 m/s

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90#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30.0-N stone is dropped from a .nr,8wg le8wnheight of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air friction acts on it as ir8w8,gnwln .e t 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 ao4 l*6d )pidpwhen he runs up a flight of stairs 10.0-m hipp4 d 6dl*aio)gh, in
8.00 s?

A. $75.0 \; W$

B. $735 \; W$

C. $4.80 \; kW$

D. $48 \; W$

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92#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-N force is needed to move an object with a constant velocity of 5xe 8xn,cm56/ ojrf :pcy)1bba.0 m/s. What power mus6crx )j/f8ypb oxb:cemn 51a,t 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 energd,lon b9bu e;3y are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W neu;bob, l3d9)

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 rata9yzyu7h u z:r;7p-p ye of 500 W while riding. How much force does her foot push with when she is traveling :z;97ayyp uhr -7uyz pat 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 averbgcadw/ d*4g,04g tw oage power deliverct *bgd wd/0g44go,awed by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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