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

1#

What is the correct unit of work expressed in SI uni(sbfi.i1ix 7maacw ;1 ts?

A. $kg m/s^2$

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

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

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

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2#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Can work be done on a system if there isyrr fl-jv90b . 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 stationan tc)c -.;yjkury brick wall, the amount of work you do-tn )jc.y kc;u

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 oe o1j(1cgn2 ql/ c0iy qjgrv::dq28xvertically and is being held there. How much work is bei(d 2noj:c /c1qj8q:r 0g2lqe1goyxvi ng 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 forward j v2 9i9n/ij cerg:7tz56mr1zewi-nn *d1xu a at a constant velocity carrying a 10-N object, the amount of work you do is2t ei7w *n1icxgzmj9 1d j5:9anu-/erv6z in r

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 rx ub6p ,znl0sk- q:c2peturned to its original position. If the total weighk q- xpubslnc0,z: 2p6t is 30 N, how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on 0 .caa,5l8ad ct7lpby 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.t5rte3do u:c1 66ntlhl860ms pqwdl8 Compare the sign of the work done by gravity while the ball g68u1l epl6t:3dtom wt 0rhcn8ql6s d5oes up with the sign of the work done by gravity while it goes down.

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

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

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

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

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9#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The area under the curve, on a Force versus position (F vs. x) graph, repr+6h8b8zso qs a-zvit. esentsbzs+. - qith8v68szoa

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 vsig7,wt2xotodfpt/l to7. (e; . x), what represents the work done by the; 7 tlt o.doeixwgo( fp7,tt/2 force 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 o pmkd4j+x jj6;bject'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 k tt vqv;a,tm(;h.pqje58sl q1k t3 vz14 q+driinetic 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 obje7t7hr+nhh 2tkct is zero, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice as much as a ;wxr l)nsw7(ho6 (:f qv) cvll s);s9qiyqj;h car, and is moving at twice the speed of the c: noyhj);(l c w f ;si qvq79q;xllhs)6v(wrs)ar. Which statement is true about the truck's kinetic energy compared to that of the car?

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

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

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

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

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16#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Car J moves twice as fast as car K, and car J has half the mass of car K. e9x sv1bcc81 eThe ki1v ebc1 se98cxnetic energy of car J, compared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with halr7qo9n;3 nm +re1no9br fg0tva jck. +f of its original speed. What is9nr .+ rqamkf1 bo0e; tc9 vo+ng3njr7 the ratio 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/c2k;j6ydqge ;wh 0 p(qdoz 2w:s. If both objects have the same kinetic ekedo26 zp;(hwyj: 02 ;wgqd cqnergy, 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 movc2ul o7g-rmq5ing with speed 4.0 m/s. Both objects encounter the same constant braking for- mgr5qc7l 2uoce, 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 pa tcgu322(unut9bov) rnic, and skid a certain distance on a straight, level road. If you had 3c9 2vt ogn)rt uuub2(been traveling twice as fast, what distance would the car have skidded, under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

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

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A planet of constant mass orbits the Sun in an elliptical orbit. Neglect,me ewe7.v t9ting any friction effects, what happens .vwete,e9 7tmto 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 pr805az)+ y owvgozo7frinciple.

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 ajv:p -dh;.jv qvg,l4ft5g4y *t3 baua system to 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 from rest a height h above the ground.zhyx .-i)bcz8 xwc;1 i A second object with four times the mass of the first if released from the same height. The potential energy of -b;yzx czi x1wc)8hi.the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the end of a spring ca77vtwtv i .a;vuses it to stretch 5.0 cm. If another 0.200-kg mass v viavtt7w7;.is added to 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 :q+r1eugvj5yu,tee8energy 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 itwd47qoe8a gbvp6.e l 3s kinetic energy K, to its potential energy eepq 4. 36vodlbga 7w8U.

A. K increases and U decreases.

B. K decreases and U decreases.

C. K increases and U increases.

D. K decreases and U increases.

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30#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Describe the energy of a car driving up a hil, vkx w4j2roadc4weto4;n h7/l.

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 o)4 rewz l)hg0zlgp+h6bject are sliding with equal speeds along a level frictionless surface. They both se 6l4ghgr )hz)p0 z+wllide up the same frictionless hill. Which rises to a greater height?

A. The heavy object, because it has greater kinetic energy.

B. The lightweight object, because it weighs less.

C. They both slide to the same height.

D. cannot be determined from the information given

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32#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Consider two masses xgi0ox-o6eksi -r p*n-d w7o .$m_{1}$ 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 ofyw;6f7;9 j0qiim fyf s mechanical energy for conservative forcesffi7fm0swyji6;9q ;y.

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 air (air frictio 3ovih:y/f r8,l (mug5mlx3u wn is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (Uh ug /8u 5yim3 xml(f:vorw,l3) 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 energqeoqu hy3 98i 1gsf7.r+m1qbsik-:rw y. Do not ignore air resistance. Howiqq-rk 3+.y8s qi:bhwu7o1r9 1 fm esg much gravitational potential energy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 3:87 y(nyoeldo 0 J of gravitational potential energy. Do not ignore air resistance. How much kinetic energy did the ball gain:n (o87oyde ly?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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37#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the law of conservation of ene*c p1rp dg1g7kbsjh/4o)se r;rgy.

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38#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity Fd/t is-s.e+/gk froak f(hs;

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 uni. 6h ; *wkezkjf,1zsfdt of 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 ofi6k -hhxvu(5amu+4qi 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 h2mt u:p7 ,mdmdo so, your power output must hm7dt m: ph2u,mave 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 acc2buunrq4( 9d heleration, 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 hel3b v03 p-udw8 m2eknot067pp 2u tcwmnd there. If the object weighs 90 N, how much work was23- 8uptm 7m p ew0vnwb3c2pdon tuk06 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 1vc.nl 7t;r t/0chxdd;*nz x, v.0 m, at a constant vellcdcd*zh ;rn, t;x/.nt7vv 0x ocity 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 N for a d at5 znfg 1ai*cj,(1*vsrvdhh9w9)a mistance of 50.0 m. What is the workwtfda1 n99av g* *c1h(rm)vi5,hzsja done by the 5500 N force?

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

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

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

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

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46#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5t/pikjqzn. ,(wqdx+0 500 N for a distance of 50.0 m. What is the w0 t+ ,/izx.qdpwjn( kqork done by the weight of the elevator?

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

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

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

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

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5500 wh( pm y6p87ruq, 0ndugp2q(eN for a distance of 50.0 m. What is the pqm 6(qgp0dp7n wr2,u uy8e (hnet 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 alo 4i0fdn:kcnpvy/o t*4ng 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 down a ramp, inclol dn3y(2;elvv ,nbv,ined 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 p/-e.is .jevx a sled on an icy surface (assume no fricvs .e.j-eixp/tion), 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 the force. The grap ,ohc:5*n9rqmt7dla t5 sf/a2wr cf )a c4dlp*h in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves froc tr/,)taf ndq2dhclr59lmw4 sa*p:c 7*5afom 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. Th9:u8 mta fr.rre graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves fr r ram89.urft:om 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 die ohh 20.d;nvcf8za5vx ,ke b8 kb0b.v/5atzmrection of the force. The graph in Fig. 6-1 shows the force 88v aknb. o/h200c5dezavzbh5kv t , xmbfe. ;versus the object's position. Find the work done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object i +5xv gm5xcs3hn the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 0 to 6.vhxg5c3 + xm5s0 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 2) iacooc9mx t 9+as/uuy:d87z00 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of9ds iatmuu7 :cy9 zc/o8+xa o) 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 to move a 55-kg cart (initially at ey uz re/er.* qmij4io0 .7mg97unwb5rest) across a 10 m lev eo j5um/n4ug97.i0ebr 7zr ei*qy.wmel surface. What is the final speed of the cart?

A. 73 m/s

B. 36 m/s

C. 8.5 m/s

D. 6.0 m/s

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57#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass is moving with a speed of 5.0 m/s. How much work is requireijp.ikf8+lu1 f zp+ 5bd to stop ti1 kfp++ilpbf5 ju8z.he 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 stok3*n mpe1uyfkfn b21 e6)b a*wp a car initially moving at 25 m/s, what distance is requirk fa*e)e1 *nnuy3 2mf1bbwp6k ed 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 gux3 hs:bz5p6 mun propels a 10-g dart. It is cocked by exerting a force ofu: pzhmxs3b65 20 N over a distance of 5.0 cm. With what speed will the dart leave 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 an5tqup0u6gn0n a k7n8b7o fh;7e j(y pkd a vertical component of 60 N. The force is kfe7oupajnn k;7(7 q50h6ubpg0t8ny applied to a box which rests on a level frictionless floor. The cart 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 is shot horizontallub, a0bm*5m cgy 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 stopping force am,mabu g5bc0 *cting 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 z jg5c:;70bai rxdbu .from a height of 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitation7:0brbd.aicx ugj z;5 al 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 lons)tkyxe* c7(w xv6g-ug and rises 2.0 m. If the plane is frictionless, how much work was done by the pusv6(7xcwk x es-yug*t) h?

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 u/c m -i9ma+lsspring to stretch 2.0 cm. What is the spring cons ic9m-a+um/ lstant?

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 consta 5onksuwl6zvu)) k j3/nt of 60 N/m. How much potential enerv suknjzlo)u w3k)65/gy does it store, when stretched by 1.0 cm?

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

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Calculate the work required to compre)npn;sl7 l0j. 1qm aspss an initially uncompressed spring with a spring co)p 0la1j;ns qnsl.p7mnstant 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 sl qy3ejn+u k8(pring of spring constant 40 N/m from x = 0.20 m to 0.25 m?kny(u+le3jq 8 (Assume the unstretched position is at x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring constant of 15 N/m is wfy8slyd0 0 4ncq+ v-l0tbm ,sinitially compressed by 3.0 cm. How-0m0yl stqc ,df4+b0yn ws8lv much work is required to compress the spring an additional 4.0 cm?

A. $0.0068 \; J$

B. $0.012 \; J$

C. $0.024 \; J$

D. $0.030 \; J$

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69#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50-m h f yixs1 gey(2oy6v0.1 hw-rvfigh slope. What is the speed of the slier on 2 y wxf0 yvv.1e1(rify6ohsg-reaching the bottom of the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top ,vvt iabn:8*.)m sefsof a hill with an initial speed of 4.08 m:v.*s v)ainfetbs, m/s. Neglecting friction, how fast will she be moving after dropping 10 m in elevation?

A. 7.3 m/s

B. 15 m/s

C. 49 m/s

D. 196 m/s

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71#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object slides down a frictionless inclined plane. At the bottom, it hal/s g*n74 ) fpxxm:obns a speed of 9.80 m/s. What is the vertical height og/ pox 7* lfnb:nm4xs)f 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 e qs(9gorz eg8xhi62;the floor. When it is 0.70 m above the floor, its potential energy exactly equaxehi9e (z8rgoq;gs 26ls 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, blasts straight upx1vdj.hm ;6je from ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 1j; .ehm1dj 6xv40 J. To what vertical height does it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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74#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A projectile of mass m leaves the ground with a kinetic e1x6u:a,g z,nz ozcnc/s380hu+r dx x5jqa 6itnergy of 220 J. At the highest poi+: uc/5ijn dohz,t,aan8z13s qc xz6g06r xxunt 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 startsmqeqmrs + ,awp7-o: ;w from rest at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the q7 qsw ,+mmo r:ae;w-proller coaster at the top of the next slope, which is 30 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 17 m/s

C. 24 m/s

D. 30 m/s

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76#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts with a speed of 5.0 m/s at a point)/znk to)me8k wgr 6c; 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at thr)8n kc) tm6o;g/kwzee 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 9rd 8xnxgawf 1.zco 0,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 above the bottom of the1w0,a9 fgn oxz.rdx8 c 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 ic odn9oal4gs+(o p-*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 ve; 6hdzoyk,ld6m1 z x-hf;2avvr- je .vrtical axis and released from rest. What will be its speed at th.;k fv;v y za l 2meohd1x-j,6v6-hzdre 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 io (,jxjeso /8initially uncompressed horizontal spring with spring consts/eoi x(jjo ,8ant 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;4n5roa ,jvuhq3n-k0cv+ yob kg car to stop for a red light. What work is done byaj, bnq-+ y35konc4vv0hrou; 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 60.0-kg object and a horizontal surface isoq 8x ux2y7xir d(yzpwem vwxk ,5;(6rwv3: w- 50.0 N. If the od7ww yrzi :y83-x w6(wvpux (xv,k2q;re5mxinitial 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 24 J osbh6dj6 ba k54f kinetic energy. The friction force on it is a constant 0.50 N. How far 465bd jk6abhs 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 surom6ivu v3 )qf).gkx *fface. The coefficient of kinetic friction between the mass and the surface is 0.20. )*g o ufmqx6v)3vfik .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 xig3gvd g8orrx,jx e 38+3rk ij6v(x/the top of a 50-m high slope. If the work done by fricvx xxx3jkvoje/ r,8+3 6grdii8g(g3rtion is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane is 4.0 m long and rises,dhx20mg oh;p 2.0 m. It requires 3200 J of work to get dp;2h h,xo0mg the box to the top of the plane. What was the magnitude of the average friction force on the box?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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89#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass is released from rest ata4*us ol2ux-1su gp8yy.f 0vx the top of a plane inclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speed of the mass after sliding 4p41 yl vsuy0osfx uxau.-82*g.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 snzvet g3;(52hee34d on fjq (from a height of 10.0 m, and strikes the ground with a velocih( 4; z3onnqfsv3e 2(td5jegety 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 flight of stairs c kz;0(ichn /ges,.e p; bb-he10.0-m hig;/heez,s ; k(n bhcp0gbc.ei -h, 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 constantz:r2(trm1m y t velocity of 5.0 m/s. What power must be delivered to the object by the ftytmr:mr2( z1 orce?

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 enp0 e 5tily l,v.:kd y9uq+vhz5ergy are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W)+vhly .zdyut, 50l 9e k5pq:vi

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 atg )4+ fabcb0b1z9wvzwic94q q the rate of 500 W while riding. How much force does her foot push with when she ibwca z qcgf41z9q90+ i bvbw4)s traveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s in 7.0 s. Wh5xsre vck8w y inm;5uur08 9o.at is the average power delivered bysyv r0xurc8iokenw;895u .m5 the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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