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

1#

What is the correct ucp-ne9:a 3 yiin6l cln9d,z )znit of work expressed in SI units?

A. $kg m/s^2$

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

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

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

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2#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Can work be done on a system if there is no motionhn37;w.op nsv ?

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, the amount of work yv 1u;p6ga3 3)gq0 f ziro;bru.4rckqgou g3uki .aob4 )r ;f g0c1p;vr6rqzguq 3do

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 verticall2s/gjeip jw(z530;awsvf6r q y and is being held there. How much work is being done in holding t3rw5vswq;60i gjf/2z (epsjahe 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 hori20.*ey3 v esuf x 3hf+vet,wvczontally forward at a constant velocity carrying a 10-N objecvvy+0svef3ch .u *e,e 32f wxtt, the amount of work you do is

A. more than 50 J.

B. equal to 50 J.

C. less than 50 J, but more than 0 J.

D. zero.

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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A container of water is lyu)j vmx;n(h+l1a2ao ifted vertically 3.0 m then returned to its original poam21hjxvnl+; y )a(u osition. If the total weight is 30 N, how much work was done?

A. $45 \; J$

B. $90 \; J$

C. $180 \; J$

D. No work was done.

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7#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Does the centripetal force acting on an object do work on the objecx9z 7gmb9 4xeut?

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 agyf4fk0d +y5 work done by gravity while the ball goes up wit g5f4ay0y fdk+h 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) grapha ot71m,fp et.(m hv:s, representshm(m p1e:tstoaf, 7.v

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 workg/rduo qp+f-ssjr5 14 /lp)n c done by the ff /)uo c s4nq1g-sjpl/pr+d5rorce 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 o5vdz79f f-v6jz*gc b jwmr)s+bject 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 object is negative, thel*hu eq+n6ptvh:n 18 yn 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 enedf x,fxvzvi67w ):w fs-0p1g ergy

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 twi/ * b-(rn:q5xk,m+eim rbkwhwce the speed of the car. Which statement is true about the truck's kinetic energy compared to that of the e *,h(mn+ w-/rm: wbxk5qrbikcar?

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*;uzyeifct*bdt60rq pe+ )6b. The kinetep*fi 60z*;bd+t6u )qbrt ecy ic 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 fdawo (hfqp0 5bv:9m/ bounces back with half of its original speed. What is the ratio o5 po0 h(m/fwa:db vq9ff 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 a8j0d tbq )r(6covgx :34zmejl speed of 5 m/s. If both objects have the same kinetic b) mvzt:c o(40rqgjedx6lj38energy, 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. gepgks ej,6 j6s4-mri.4g,(r 9qn a lewk12wd0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, en2mrw ks.g(ajqk6 ji9,re6ds 4w,e41-l gpgand 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 certain distanccl;r 3iqut/;re on a straight, level road. If you had been traveling twice as fasi;t;lqrc / 3rut, 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 ak t9f5i .8qmw +ii ntv0gryg2gy,-, vmass orbits the Sun in an elliptical orbit. Neglecting any friction effects, wi t59yk vqmv atn8yrigi0g-+2f.,g w,hat happens to the planet's kinetic energy?

A. It remains constant.

B. It increases continually.

C. It decreases continually.

D. It increases when the planet approaches the Sun, and decreases when it moves farther away.

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22#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the work-energy p;+4xg)/by -pwy uplf hrinciple.

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 -hf( x +dlfrf nt.oz:7s ze05ito 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 frov/qfhh.7cx e 6:l/kf.w vuj k.m rest a height h above the ground. A second object with four times the mass of the first if released from the sax .7 hh:/.ejlwkk.vfc 6u/vfq me 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 endr+wz 7.wed9wx w3wd7 hffbp+6;bz s x9 of a spring causes it to stretch 5.0 cm. If another 0.200-kg mass is added to the spring, the potential enew3f9 .+ d7 w+dsw9pxz xrbbfhwe 7z6w;rgy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical energy :k( *pcxs o39;v ugvvbof 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 q-ii 5. th0b:jnb5 sfga tree. Compare its kinetic energy K, to its potential energy :ih-fbn jsb0i5 .tgq5 U.

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 hils (p b1hk.u-o.e2 l0osc)thjq 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 object aheq/ 3(yh wz2gre sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless e y3(g hqzh2w/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 7 f c7qy6g3zta19 4uak wyw9vk$m_{1}$ 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 mechandas- m 3 nh6n9gp,q /2unw*rkptmf)r4ical energy for conservative forcesd3k2asn r9 m 6wh p- nng/rqpmf)4,tu*.

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 topfievr5t615ig3aq t h3 of a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at ttiih55qa6 13eft3 r gvhe top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and gains 30 J of kinetic energy. xn9 yaq+h;fk-*u4r ut Do not ignore air resistance. How much gravitational potentikyu* 9t-a;fqrnh4 +ux al 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(yr wnh0 kq*y5fdl(x 2 J of gravitational potential energy. Do not ignore qyyf0 (x5 hkl*r d(n2wair resistance. How much kinetic energy did the ball gain?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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37#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the law of conservation of enebss+ba,5a: -r2qmpkg rgy.

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 is ts 8tt150ebyg

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 powerp8 *hek.bgqv .ud9hj:z3 i/lb expressed in SI units?

A. $kg m/s^2$

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

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

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

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which is not a unit of p+ujzjin+,fm: eka8 ovuce8, 1ower?

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, y wbo a/d igtwcs74p)u4:7mke.a 5;ahsou did 3 times the work in one-third the time. To do so, your power output7 :wio; /bsha)tdse .m75wc 4k agaup4 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 carwvp0cpy9 w0u f4p +b i-j1uss2'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 object weighs 90 N,op/1 iw -i7dqi6,pgvbymh3v 4 how much work was done in liftinoqdi ywi3h4p6 -m,bivgp1v 7/ g 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 slwf /+ki+6vv (zgrx04)dvr g the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by tiv )6+0gzrvw +dk(/rvs4xgf lhe 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 550w25 vd4pt ngb.0 N for a distance of 50.0 m. What is the work done b25d 4pv.gnbtwy 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 consw,q9u(mib( 0sbf2 pvv tant force of 5500 N for a distance of 50.0 m. What i w vvpi2fub(m 90qb(,ss the work 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 N for a distan jj,.yta9k:+pn0,aaef ; reunce of 50.0 m. What is the net work done ueajr.,p0eya;jnak+ n9f t,: 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 a(wp/gvp0f n 0zlong 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, it,*xwtmcv;x 0(ydm +wnclined 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 7eo xc9 .eznqx *9/pbu958vcswex8fgsister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 N at an angle ofwepc x9bq./59e7u*xxc8e 9szfno 8v g $37^{\circ}$ 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 forcemfq1 w3bxu vymnjh 5++m +l0z2. The graph in Fig. 6-1 shows thmn3w1xjz bl umh0q ++m2+y 5fve force versus the object'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. The graph inux*iswy/du,82 vt s, su -t.n/ynb2ct Fig. 6-1 shows the force versus the obj.ss/tc bv2d-, yty8*/x,t n wnu siu2uect'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 Fd.pp ).zsk. v5zjjc2 uig. 6-1 shows the force versus the object's position. Find the work done when the object moves from 4.0 to 6.0 .2.jkjs)ppv.z5u c dzm.

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 obj +u;zepo9 ke;mect in the direction of the force. The graph in Fig. 6-1 shows the forcez+pe;em uk9o; versus 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 zpq p-,wx3d ng4tjx-amj3h6c .(ug9 m cart (initially at rest) across a 10 m lev4x - j uq3m gcg(athpx dw-m.nzp69,3jel surface. What is the 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 to mo(fwf p ashqv 2 0j(p:xkn-p(/zve a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speed of the c(p s(f/kxz -jnp(pq20hfwav :art?

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 hi fn1p 3(x.akspeed of 5.0 m/s. How much work is required to stokhx (1fp ai.3np the 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 inz y jek2b9.up7itially moving at 25 m/s, what distance is required to stop a car mkbzej y2.u7p9oving at 50 m/s under the same condition?

A. $50 \; m$

B. $100 \; m$

C. $200 \; m$

D. $400 \; m$

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59#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A spring-driven dart gun pr5pxqv8 dy uxoq : )vf474bd2bhc5iv i1opels a 10-g dart. 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 spring haxp8 4d:vi quv5vyb5c x2bfi1dohq 74)s negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80k;9yvtlr5z, or8fe: a N and a vertical component of 60 N. The forcr :f 85y,oa9e ztr;lvke 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. What is the cart's final kinetic energy?

A. $200 \; J$

B. $160 \; J$

C. $120 \; J$

D. zero

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61#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An arrow of mass 20 g is shot horizontally into a balj9+py9 njej;ae of hay, striking the hay with a velocity of 60 m/s. It penetrates a deptjj9 ;epy9 a+njh 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 hei6fca ;im 1i,hcf2vc3tght of 13.0 m above the floor. What is the change in gravitational potential ene cii1t6fcav 2c m;fh,3rgy?

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 vyz) gwebex(9t u61 e)long and rises 2.0 m. If the plane is frictiont6ew9 )xzv)e u(1gyeb less, how much work was done by the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass, hung onto a spring, cause5 oaagww 2 p*/+aze)dbs the spring to stretch 2.0 cm. What is the spring consta5ow+a)/ bza adgp ew*2nt?

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 ofelnl(el(; rfual*7vrnh m /3- 60 N/m. How much potential energy does it(- re*aull f /(h7vlnr 3e;mnl 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 compress ) 6qh,u y99opxfsdm*9kgmmf9gpz ; 0o an initially uncompressed spring with a spring constant of 25pm h*;mg ,fgz u9d0 99q yxks9)fopmo6 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 stretchhn8ibf.q y5 bsy4/wf1 a spring of spring constant 40 N/m from x = 0.20 m to 0.25 m? (Assum1wsiyyn fq58hbb f. /4e 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 initially compx y1t3n(b 4y39s jlmvfressed by 3.0 cm. How much work is required to compress the sprinlb(f9xnty34jy1 m3v sg 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 745gh3d,ij, w-/az dyw - rzpve )nnmtrest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Neglect fri)wmjw,za,h v4d p5e d tn/7igzn3-ry-ction.)

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 k:b;urz)(v a vg3*wh1f mjr n5xg, pushes off the top of a hill with an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 m ir g: ) 5v1nzaxfvhb(u *3mwrj;n 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 f uerpu y8 kwcq -5 b2)acxf5zaeq7)70xrictionless inclined plane. At the bottom, it has a speed of 9.80 m/s. What is q)w2k-q x xyueb5aeprc7 zfcu a70)58 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 it is 0.70 m above the +sb6v;r(4snxhd y)sp floor, its potential energy exactly equals i ;x6h ss+dsvb )4rp(nyts 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 up froms3,hbdskx s pe0v0yj gb 94i-3 ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 J.,sb3d3gb04 9xj -yie shpvsk0 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 th:hxea6w c )u8hk:k6lme ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what verticalel :kuh6 6mwcxak8h: ) 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 po .+62*gpv1q pa:hpedqchq1tx int 45 m above the bottom of a dip (See Fig. 6-2). Neglect frictio 1 d1pv+qgheqh * :pa2tqx.c6pn, 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 starts9 v :,cfesuu3n with a speed of 5.0 m/s at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, whatuv :e f9u3,cns 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. 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 abo 2k6l ecmrd(dt)y y5x7ve 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 the bottom of tdrct7)yey kdml6x2( 5he 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:hzn g.x8:m-.fugi gy7ky6 h b its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertical axis and relk dm/ha37wy(leased from reslmy hdw/k73( at. What will be its speed at the bottom of its swing?

A. 0.50 m/s

B. 0.79 m/s

C. 1.2 m/s

D. 1.4 m/s

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82#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 1500-kg car moving at 25 m/s hits an initially uncompresxs, sq6fqzkbr r.x86 f56un4nsed horizontal spring withf4 z6.xu8s6x5fkrnb qnr6, qs 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 pp x *.ctv7mo7a red light. What work is donemxopc7t *7p.v by the friction force against the wheels?

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

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

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

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

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84#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The kinetic friction force between a 60.0-rz,q: e4aepl+a w)c1gkg object and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what distance will it sr )eqaz4c1,g:awlp+ elide 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 yn /.igwxq4 k4 dhbj(nu72(s2-jsfun has 24 J of kinetic energy. The friction force on it is a 2h wsxy4 djbnfq4 ug2(jnnku/(. si7-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 onxgw o.r:( ei *xbv-8cyu co+e+ a level surface. The coefficien:b+x ov*yowc8euc (g.i -+e xrt of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the change in its kinetic energy?

A. $20 \; J$

B. $39 \; J$

C. $46 \; J$

D. $61 \; J$

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87#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of z1 ik9tivq.7 1j -vwera 50-m high slope. If the work done by frictiqi1z -k.v9 jwe7rt vi1on 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 yyxz+wect: 9(i1b-xr 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. wrc xxyzy(it9 -+:1beWhat was the magnitude of the average friction force on the box?

A. $0 \; N$

B. non-zero, but less than 400 N

C. $400 \; N$

D. greater than 400 N

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89#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 2.0-kg mass is released from rest at the top of a plane inclined at 2mjqe 2,d6-eutq5z u ;pz+e *n1mnslb30e 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 4.0 m along the pla u-* n3qmzb m6;zudel2,5jspn+teqe1 ne?

A. 2.2 m/s

B. 3.0 m/s

C. 3.5 m/s

D. 5.2 m/s

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90#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30.0-N stone is dropped from a height of 10.0 m, a y.a(ff*du1 yo6aq1 iznd strikes the ground with a velocity of 7.0a1i.d (1fy6azfyo* qu0 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 ogk5yul t8bp 11f stairs 10.0-m high, 1k58l bytpu1g 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 l uz0; load90mm/s. What power must be delivered to thelo9a0m0u;z l d 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 energ pvif7-v xjv 1n)-igd2y are used by a 1.0 hp motor that runs for 1.0 hr? (1 hp =n i1xv7)vj -g2-p vifd 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 forcrgc)dn5u vc) 3x)i j5tr)u(xie does her foot pushc3x v gxi t5(i)rnud5)uj))rc with when she 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 bxbf2wve;-a/ nl ,rk88 7uo spfrom 0 to 25 m/s in 7.0 s. What is the average power deliv 8oe2w; ,k8fn7l x-rbpbauv/sered by the engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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