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

1#

What is the correct unit of ,9nxp 1;ar (yr a+qebgwork 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 there is no motion6lsdl*a ll22b.;o6 +ys 4h*aweczgga ?

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 station5wxqoy 2o.qqc(ap)0d ary brick wall, the amount of work you d 50 o (ayoq)2pqxc.wqdo

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 vertiro)i 6pb+sq k,6ijah +cally and is being held there. How much work is being done in ho soii6+pb,ajh +rkq )6lding 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 horizonta3w2p+imel-f7d0)) sna oyrdblly forward at a constant velocity carrying a 10-N object, the amount of work yo- d230e7nsw)fpm abo)ri+ ydlu 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 jeptewg-:j. 5 3.0 m then returned to its original position. If the total wei.ew5eg-p: jtj ght 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:g sl e1 yf.jkmkc//j1 force 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 done by gravity w xqyg4v-4fghwqiz+ o+jg9be +1q,1)dw9 m lgbhile the ball goes up with the sign of the wor4 9q)+-, gjqx9+y1 dgoegg ibqv hzfl14m+wbw k 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, reprtnc7o0 u 1k/i -j:gjkrpvgo2*j-*k rresents- -v0r 7gjg* ok1rpnkikc *:2tj/u ojr

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 work done by t9 i g do; lj(m/+8flrw:kailg0he force F?i mo /(l :kdr;jga 80lflig+w9

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 atp t-o5d fzus3( n,.h.spu ).rkw ,;1 ksuqozan object is positive, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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13#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an m4,4,z bp+ 0my l: ddgehkz qqmfoa0,(object is negative, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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14#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is zero, then the object's kinetic enerb7s--f v-n-uy w5ahs xgy

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 isb4 qzzy 7o.f)s moving at twice the speed of the car. Which statement is true abouz y7ob.)q zf4st 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 halq jsq.w1o-4n kf the mass of car K. The kinetic energy of car J, qoq 4jw k1n-.scompared 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 bounx7ehb.qgb g0)ces back with half of its original speed. What is the rg)be h0xbqg.7atio 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 apetjz4 cssv9:;c ai37dy97op speed of 3 m/s and a pebble is moving at a speed of 5 m/s. If both objects have the same kinetic ener;97 vd co:9p4tzc7is 3j apseygy, 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 movin vb*q)ej-shk7y2qwbp4q0 d (xg with speed 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 thbq2v* 4x q-dwejs p7qhb)yk(0e 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+qg-;/ef ;,jo +jl acw)sv5j shz p)e/h9dfih of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car have skidded, under the same conditi9 ; hj;zq/lhahdw5 ) jfj)eps +si+vfg-e,/coons?

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 Sulb24(etn ha ;tn in an elliptical orbit. Neglecting any friction effects, what ha42blna t(; ehtppens 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 priniw )t nsyz)4imeiwz7k3z2+h6 ciple.

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 tql89wcdplg3;zpu :dr 6o3q,zo 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 rest0tlc 4noxj8j+.lwn x xm;y-ac0/xq9 p a height h above the ground. A second object with four times the mass of the first if released from the same height. The potential energy+4ao 0jx8l -x/pxny t cxlc0.;m q9jwn of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the end of a spring causes it jz bvm57kypo71.n3zm to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potevmm zz o.3jp57ynk1b 7ntial 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 energ3vo6 v1p/ltxj7y2amvm1 n 2cdy 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 enek6 +3wj 8frycbrgy K, to its potential energy U3yr j kc+b6fw8.

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 d ujah-6,1cf juqf85y. q;fcua 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 7uhn. iwc 7 fx svmr;q*62kagh1q qu1,object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a gf2qhux qc671h;iuqa.kr w m7s*g, n1v reater 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 p pji v9n dir24gj0 82wmq0r8y$m_{1}$ 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 mechanvt pr; *nu7y)pical energy for conservative forces *nyvp);r7 utp.

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 buildin:,k9fllvz/o1w3fwhj sve )7gq10r pp g, through the air (air friction is present), to th wv7gp/k1 qfp 9f,w z)eh srv:l13olj0e 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?

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 energyb(ur 51 sxjq,*1 mzdaq. Do not ignore air resistance. Hoqjm uqa*r, d11b(zsx5w 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 30 J of gravitational rt;8r2iv1h 7u9ft u nepotential energy. Do not ignore air resistance. How much kinetic energy df 2ttv7h9ur;eu r in81id 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 of energy. /jyav:0a /wby

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 isa /(sz 0.ikvmg3yc1x v x3svk7

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 S +:piyk d7a;;)g4u9zz zu-sx)vqof gkI 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 vh,v ck(lb9 e7i5 nt)g8somp;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 i fjmpbf/e lxd0, i4+eqy/g/-3 times the work in one-third the time. To do so, your power ouqedge0y//m+/4i ,bj-f f p xiltput 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 acceleration, the car's engine musthhi/ 566u p5(bhoup 57zchqy wqdf k;ex6 u/m6

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 objlupwj30k6 xxl ;hzp3kpny896ect weighs 90 N, how much work was lpkz6yn hp3pkl xw6ux308;9j 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 iwch 1h nu9,m19falt 8rn the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is1uh n9fc8,rwm19l aht 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 upwatw6uo 9oi(yj (rd with a constant force of 5500 N for a distance of 50.0 m. What is the work done byy(o(o69tiw uj 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 con by2r;k(5qe am4 gkq:ostant force of 5500 N for a distance of 50.0 m. What is the work done by theqe(bka: gr;y4q5mo k 2 weight of the elevator?

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

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

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

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

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47#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5500 N for a j h fu dd:0jl xog5j.hl9:6 (84-kddhc 9giatedistance of 50.0 m. What is the net work done on t6od (0 xhi5jh-ec4ld h9l.gu t 8kdf g9:ad:jjhe 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 alontvdlkgqc:*k;ya5wyu-: 7 9 uxid;9 ym g 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 9gjha m/ 5fuwhw +9 (f/e,hgaf8.0 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 anmc0z16y9 r)pgzj3im f icy surface (assume no friction), with a force of 6yc)m zgm9i0fzpjr31 6 0.0 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.hf(u+ 9pc6 zfh The graph in Fig. 6-1 shows the force versus the objehf+9fuz 6hc( pct's position. 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 force. Theagwe o/1l:*it graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 2.0 to olt1e*a w/: ig4.0 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 the5;y qa2vws qc- force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4.0 tqv c5-ywq;as 2o 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 graph in Fig.9zd9bsp12rb n 6-1 shows the force versusbd9z 2r1 bnsp9 the object'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 cart (initially6ns-an dn y7/l at rest) across a 10 m level surface. What is the final kinetic energy7nlns6dya/ -n 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 af,lf cuxoi:g 2pg1 9zi7i6 gs0pplied to move a 55-kg cart (initially at rest) across a 1xi szoi7l9c2g0 1:,f gfgpui60 m level 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 requiree / 4k*mgd).p c4offtrd to stop the mass.fr g/ oft*m 4ckd4ep)?

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+; s9mho w qcwh3qry(5 at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same condw c +3shoqrh;m5y9(qwition?

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(m )doj y4.( sxqfl.+s tnx7lz by exerting a force of 20dsf joqlml n.7( 4(ts)xz .+yx 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 componen)bl3r novx nw + *a1eo1ez)i (3jf;ttbn4b1pnt of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the floor. Whv b1nfr)tj n onb)ee 4xoaizw (1l*13;n3tpb+at is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g is shot horizontally inz ggo:2 jy4;grto a bale of hay, striking the hay with a velocity of 60 m j:y2g ;z4gogr/s. It penetrates a depth 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 sct a(jj7rf.u ( 6jr1-j4m.6g xo rhvis g1/kffloor to a height of 13.0 tga1jfo r(mr( 6 vcxsjgh/4u6ki j1.fr7. s-jm 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 up an inclined pl;u p3-*dp jgx4 kmv:enane. The plane is 4.0 m long and rises 2.0 m. If the plane is frve*m jp3;-n x udk4:gpictionless, 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 sz rq* aw 71w4iiqs3l5zeia p3hgt (j. vz*:m0a spring, causes the spring to stretch 2.0 cm. What is the springgw 3 a z1s*.h( izeq0z:jis rvw tpia547l*q3m 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. H4r:(: vld/ qg hekn1ywow much potential energy does it store,hy41 rwg:(vknl:e qd/ 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 compress an initially uncompre;h9;zok5 alzessed spring with a sp zz9h;ka oel;5ring constant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring ncvqc*j8r)l(y d b;6yfp26 u xawd1bko x,6 )uof spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position is ataxuo))6f ,uycj*d plqb6rn8cxdbkv;6 1(2 yw x = 0.)

A. $0.45 \; J$

B. $0.80 \; J$

C. $1.3 \; J$

D. $0.050 \; J$

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68#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring with a spring constant of 15 N/m is initially compressed byx)k2iy*d py 4t 3.0 cm. How much work2y 4*kxidty)p 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 508kdd(;ddm1h b 9agbb0-m high slope. What is the speed of the slier on reach1ad; d ghd8b90kdmb b(ing 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 of a hill with an initial speed oft +iyql2v 8 (3n qr5t6nua,rip 4.0 m/s. Neglectinir28luayq 63 (,+vtrp t5 nqing 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. Avj***k6 o 3soyrlit3mt the bottom, it has a speed of 9.80 m/s. What is the vertical heigs*k3 j**6 iytvlm 3rooht 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 it is 0.70ov68sg t ioc yj*8ij5( m above the floor, its potential energy exactly equals its kineticv ooyijg8j s8* i6c5t( 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 up from grou1ut(f lmv 2m6zfk9pg- nd level with a kinetic energy of 40 J. At the exact top of its trajectorl12m -6fumfk9 tp(zgv y, its total mechanical energy is 140 J. To what vertical height does it rise?

A. $1.0 \; m$

B. $10 \; m$

C. $14 \; m$

D. $24 \; m$

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74#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A projectile of mass m leaves the ground with a kinetic energyul vz7ne 1wcs ay;u(g*, h ta0ft926xn of 220 J. At the highest point in its trajectory, its kinetic energyc hw a n*atu v;x6tfe2 slyun(7g91,z0 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 thetkpx + /b/.fxm bottom of a dip (See Fig. 6-2). Neglect fric./mxk/fb+tpx tion, 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 starts with a speed of 5.0 m/s at a poi4+ 7p1g l*5smy t j(czkj 5az(ybefmt1nt 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 30 m aboa ( y74pt m5k1+zf5z1jl*g(jseymtc bve 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 startmpvo w78 ak0z*s at a point 30 m above the bottom of a dip with a speed of 25 m/s (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at the top of the next slope, which is 45 m above thzva7w op0*8 kme 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 s4dygafsm .m4mft n0 .n1 ;cbq;wing (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 q*m/pyc d6ir e*v4wp/ cm is pulled 30 cm away from the vertical axis and released from res i w4c/d*pe* qrmvy/p6t. 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 initialsna +w7wux:e0,e liu*av2ei4 fy6v7yly uncompressed horizontal spring wx2vi4wfus 7 e:, +l yyev*67uw na0ieaith spring constant of $2.0 \times 10^6 \; N/m$. What is the maximum compression of the spring? (Neglect the mass of the spring.)

A. $0.17 \; m$

B. $0.34 \; m$

C. $0.51 \; m$

D. $0.68 \; m$

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83#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A driver, traveling at 22 m/s, slows down her 2000 kg car to stop for a red lighwyh1 ,vhq )6xkt. What work is done by the friction 1y)hvxqkw ,h6 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 horizontalxdah)r5+0v-djxrs3br3 +2 uotvy)uo surface is 50.0 N. If the initial speed of the object is 25.0 m/s, y-orx+vuo)u 3a3dr hj5)d v0rbxt s+2 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, uqd63;pm;edmdkv+y - level surface. It has 24 J of kinetic energy. The friction force on it is a constant mqm;63kvudd dep+; y-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 onftowjl, ls* o+m-kn 77 a level surface. The coefficient of kinetic friction between th 7o mlo-s7 fw,k+j*tnle 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 resa8ps 6w-zg+6 4 teanhlwvq67wt from the top of a 50-m high slope. If the work do-n7v6qe+apt 6lz8 4sw a6gwwhne by friction 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 pushed3kt t)wzfu80jhrw,:v z/r + ba up an inclined plane. The 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 frictionjzua)z:+8 0vwh3 t tk/r,bwfr 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 inclined at 20e a74,bga g).-lb- lf au gkz ggh*it08izbove horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What w0)iftl ,bkhg.l8 zgb-a-*z7 gg iaug4ill 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 height 6kol g/08cldp*tnp4l of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air fri4pnl pk/l6od t* cl0g8ction 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 hf s :c41cnj2bee runs up a flight of stairs 10.0-e:2 41cbnfjscm high, in
8.00 s?

A. $75.0 \; W$

B. $735 \; W$

C. $4.80 \; kW$

D. $48 \; W$

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92#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. :*qhjeg8hsq 0 What pow :q0g j*shh8eqer must be delivered to the object by the force?

A. $0.50 \; W$

B. $1.0 \; W$

C. $50 \; W$

D. $100 \; W$

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93#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

How many joules of energy are used by a 1.0 hp motor that runs for 1.0 hr? (1 hf-mbl3t)-dsoj ih fw g* 8o6w,p =owdf *6wmgjbl8io t3-fhs- ), 746 W)

A. $3.6 \times 10^{3} \; J$

B. $2.7 \times 10^{6} \; J$

C. $4.5 \times 10^{4} \; J$

D. $4.8 \; J$

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94#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A cyclist does work at the rate of 500 W while riding. How much forc.3i siq w.4nub:izdq 7q.u1xee does her foot push with when sqeuu.iqsx. :34 d.1b7inqz w ihe is traveling at 8.0 m/s?

A. $31 \; N$

B. $63 \; N$

C. $80 \; N$

D. $4000 \; N$

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95#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car accelerates from 0 to 25 m/s i2( j ;fg/ l:ib7d 1f9jkbmv iwz/cexq0n 7.0 s. What is the average power dz2 7gjiqiekj 0/f/vx:cm 9fl(bbd 1 w;elivered by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95