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

1#

What is the correct unit of work expressed in SI un 9 p6qhfn)elh0its?

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 systeegf(semw 1.w )hc.e5r m if there is no motion?

A. Yes, if an outside force is provided.

B. Yes, since motion is only relative.

C. No, since a system which is not moving has no energy.

D. No, because of the way work is defined.

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3#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you push twice as hard against a stationary brick wall, the amoub:q,nxdm ao54nt of work yox4 m,o qad5b:nu do

A. doubles.

B. is cut in half.

C. remains constant but non-zero.

D. remains constant at zero.

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4#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 50-N object was lifted 2.0 m vertically and is being held there. 7m k9b p4mj:jh How much work is being done in holding:j9k4hpmjb 7m 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 at a constant velocity carrying a 10-jo nj4r2hy4rmt/i1 / sN object, the amount of wor/sn/yj mo 2r4i1 rhj4tk you do is

A. more than 50 J.

B. equal to 50 J.

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

D. zero.

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6#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A container of water is lifted vertically 3.0 m then retu,e4fe4 1wyy 1r.jd0azsq t e*krned to its original position s4q4yazyj*.,wt1 ef0 dk1ere. 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 objecmzqpiwx:i5 b y, -4m.;vquj7 rt 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 dony-bw 3p9m u6xte by gravity while the ball goes up with the sign 3-u6bx p9mywt 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)nx(oginkt n /251s9 6eo hb uu6zzua+: graph, representsuh5a oz6s:biz2x6 (u+ e1tn/gk9ounn

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 don s57 u;e-kk:z 889w-lac dearcki7 b loo*+qfne by the forc o :*z8l5k 7 d9kea-o+na-ewkr siqc8cf b7;ule 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 obzcx*xjopgj. u77 wz4fgb5 m:8ject 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,hzkq,hql 8ud ju,+ x+3 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 *gd rbxvtk 5x(:*tc(han object 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 md 3w)2s*:m:s0 f:hijvidww c iuch as a car, and is moving at twice the speed of the ca: ww*v:sih2mi i 3c:sdjw )fd0r. 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 h-fygn5he0*vzruj 3a *alf the mass of car K. The kinetic energy of car J, compared tn 5vegzf*r3ju* -h ya0o 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 b vy;yxhdp b7(2ack with half of its original speed. What is the ratio of the final kinetic energy to th h(byp 7d2;xvye 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 at yl5 y,-6iu53t 6cg kfw;nnbp pebble is moving at a speed of 5 m/s. If both objects have the same kinetic energy, what is the ratiobl 5ufp5w,t; 6g3yin6nkt cy- 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 m imm; ;wv ;ros/5zb7:,gt fmwl2fbux5 ass is moving with speed 4.0 m/s. t7 gf;mw5 5bbximz;,s om/l w;2uf:vr Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in aiiez/h3 evm422rcup; 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 conditionehmz4ip; rv/32ic ue2s?

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 a /(uw skz9qu9pn elliptical orbit. Neglecting any friction effects, what happens to the planet's kinetic ep(k 9zsuq/w9 unergy?

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 principlec imm kb/lz6.e spi8m*gol.s9r+ 7+id.

该题自我估分: (必填) (满分:1.0分)

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23#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity mgy is

A. the kinetic energy of the object.

B. the gravitational potential energy of the object.

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

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

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24#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity $\frac{1}{2} \; kx^2$ is

A. the kinetic energy of the object.

B. the elastic potential energy of the object.

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

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

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25#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Is it possible for a system to haveq -tft-(/bsbv 56v5q,oe,dh c,m fsn h 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 groundqc8ekd.y0+.z q1 a pbf. A second object with four times the mass of the first if released from the same height. The potential energy of the second object compared c.a ed 1f8qp. 0zbq+kyto 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 to stretch 5.nk9)s8+ d zti2 zz0kqz0 cm. If another 0.200-kg mass is added to the spring, the potential energy of the spz8)kn2z kzi d90q +tzsring 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 of a s tutx4gk;-/+2tjbx out4i( a vystem

A. is equally divided between kinetic energy and potential energy.

B. is either all kinetic energy or all potential energy, at any one instant.

C. can never be negative.

D. is constant, only if conservative forces act.

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29#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An acorn falls from a tree. Compare its kinetic energy K, to its potential ene9vrj k xan/rsp4995y3lyzy y* rgy U.s ly3p*kj 4r v yy/a9nryzx995

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 2nx+ex20 + .lchzhb ecdriving up a hill.

A. entirely kinetic

B. entirely potential

C. both kinetic and potential

D. gravitational

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31#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A lightweight object and a very heavy object are sliding with equal speedsd,l4*wilw( e oz 6ns*i along a level frictionless sur w*(li46szowe,ni d*lface. They both slide 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 +cf t(ww4o:si 5yfiqji cr4+9$m_{1}$ 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 ofl2 xhb5m(x-gwc i fs(5 mechanical energy for conservative forces i-5xwls2(b g(chxm5f.

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 (ml- b l:j0d/ s(z9aixrair friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground com0s xl9 lba:/zmidr-( jpare 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 energy. Do not )nveo d3wmu/bo c5 kr7 :06gl(e(ewmi ignore air resistance. How much gravitational potential 0o)n ugco35dev lb m7:mw/(w6eri(keenergy 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 am: 2vh,a* yzxloses 30 J of gravitational potential energy. Do not ign*am,2 axyh vz:ore air 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 conservationy,-b gy-v;w/gx.qmh tscd/exi/,qnnx w ) /j- of energy.

该题自我估分: (必填) (满分:1.0分)

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38#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity Fd/t ispwvsjy(at s g( e)u6546vmp/t

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 d yluz*a1(6io zf;ox3;0 tiyr 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 u5dvzla;t.cxtjpel c/a +3 +j6t a97ccnit of power?

A. watt/second

B. newton-meter/second

C. joule/second

D. watt

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41#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Compared to yesterday, you did 3 times the work in one-third the time. ,1qdk ok1y )qw(vg3mo To do so, your power output must hav(3vkg1qdq)o w kmy1,o e 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 acce jq+x:otgxb/7e sb *c:e wy44tleration, the car's engine must

A. maintain a constant power output.

B. develop ever-decreasing power.

C. develop ever-increasing power.

D. maintain a constant turning speed.

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43#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object is lifted vertically 2.0 m and held there. p. ig2fgql,b9to*lp: If the object weighs 90 N, how much work was donl29p: bt,fi* q gl.poge 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 b;l h659u qdv tn(rsao0m w mrb7,+5h7i7w ojciook up in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What wlmq+urdnvso 5 cro ,7imh0;9hwtba6j7i 7 (5is 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 disd 3hm7:uy+cce tance of 50.0 m. What is the work done b:ud+h 7yec c3my 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 5500 N for a distan4)ym,a e 8) glkyzxn+m4e j8wkce mx4gkwj aey)k)n4ym z ,+8e8 lof 50.0 m. What is 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 oml/.u, hc 4uq u rudh*wm(2.sN for a distance of 50.0 m. What is the net work sml. ru,.m(/hqc u uod w4h*2udone 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 aloq :lln1w cc1lz7hiami/ 8l 1o,ng 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 r sg /ery7u sfroj4;2yd;j4gr. amp, inclined at $30^{\circ}$ from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?

A. $157 \; J$

B. $-157 \; J + 78.4 \; J$

C. $78.4 \; J$

D. $-78.4 \; J$

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50#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Matthew pulls his little sister Sarah in a sled on an icy surface (assume bz cs0ens gp3v2f. pecqd:yn/5m (t- ;no friction), with a force of 6;ef.-qm 5y s2/gt 0p(b nces3dzvpc:n0.0 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. Thw4 ,2*)fvefa;fxfyole graph in Fig. 6-1 shows the force versus the obj2x, lfevfofway)*4 ;f ect'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 in Fig. 6-1 s*ouyu- cdmxtzk1.9tj92x h +dhows the force versus the object's position. Find the work done when the object moves from 2.9*.djtmhd2z k+ oc xxy91 u-ut0 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 directionnvydh*;6 f+oc of the force. The graph in Fig. 6-1 shows the force versus the object's position. focn +dhv *y6;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 in the direction of the force. The graph in Fig ur)0dqr(k 7qxiyg- -p. 6-1 shows the force versus the object's position. Find the work done when the object moves frg-uqi)0 rpd7x -ykrq(om 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 (initially / ; vu jioee*j52;vfilat rest) across a 10 m level surface. What25 jvfv;;o/l*jeiuie 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 appliedzi1x l 2hairndk )bph8h4)))l to move a 55-kg cart (initially at rest) across a 10 m level surface. What is t)lp)4lz 1rhh )bdii)a n 82khxhe 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 s.f 31u7j)arb9c usp jrpeed of 5.0 m/s. How much work is required to stopu .s puj917crrfb)aj3 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 inikj0qf: ho;ro zzum(-a9 :2gtp tially moving at 25 m/s, what distance is require0ouaf2;tp-kjo:g ( qh mzr z9:d 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 gun propels a 10-g .0aunf+ sqp;k4wt4 dq,c;b q4 bd+owldart. It is cocked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will the darttu4 fbbw0k dla4dn,; q; q++4sow.pcq 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 compo-3 l+ aopn*kubtl37 yvnent of 80 N and a vertical component of 60 N. The force is applied to a box whicvkp 3l+lo y*-a7ub3 nth 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 bale of hay, striking the h.ta ft8 t1qzt;ay with a velocity f8.z tt1aq;tt of 60 m/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 abovexqp/ xnd mx0k/uls2r0s;sv:n.s r 88m a floor to a height of 13.0 m above the floor. What is the change in gravit8 /u qpxs;/sx dx0rs0lr2:n.mnvm sk8 ational 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 u9ym 8:ov1cmqap an inclined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is frictionless, how much work was done oym a1v 9:8cqmby the push?

A. $1600 \; J$

B. $800 \; J$

C. $400 \; J$

D. $100 \; J$

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64#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass, hung onto a spring, causes the spring to sbt*jp:gb qm.2tretch 2.0 cm. What is the sprin jt2*.q bbpgm:g 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 cdffpb -66 lk,jonstant of 60 N/m. How much potential energy does it store, when strf ,l6j6bdf-kpetched 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 l/3v2 hc0i; s jse)vhouncompressed spring with a spring conshj3/vse ); hlois0v2ctant 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 tw6 6agpy-:yen cg t2*jw-o g,qo stretch a spring of spring constant 40 N/m from x = 0.2w qy,n gepg-:ya66w o j-2g*tc0 m to 0.25 m? (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 initially compre /jq/ b2ztvhp0ssed by 3.0 cm. How much b2q0pj zv/th/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 thw7 nll:pda /c: bd04sae top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slolncbd:dpa0 saw4/:7 lpe? (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 of10zk2vc .ow yt*.2qzam5lwvwu 6s w l8 4.0 m/s. Neglecting friction, how fast will she be moving after y6z1luz.c k5l.*m s2v t wv 0wa2qow8wdropping 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 has j82nz1z(t6yl r/yp6y yk1kc ba speed of 9.80 m/s. What i6y(j/kbny26r1yc zyzlt 18kps 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 thes3irrj3+yi cex:;3e jbcntm 0id7z*9 floor. When it is 0.70 m above the floor, its potential energy exactly e zt erres;bmj*y93cx: 3ndi7c+ i0i3jquals 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 up fr(pnc2r x)ogo 7gh,j2d om ground level with a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical energy is 140 ,) gh2pjcdr7oxo 2n(gJ. 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 kin.l*n4lyx8 xv*lq*l t getic energy of 220 J. At the highvtl4n yx8.q*g ll xl**est point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise?

A. $\frac{220}{mg} \; m$

B. $\frac{120}{mg} \; m$

C. $\frac{100}{mg} \; m$

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 ,7(xhav8rid , ywz4lk m above the bottom of a dip (See Fig. 6-2). Neglect fri kxhya 8v( w,drl4i,7zction, 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 speed4ajsk,ac j p,twgju9 i 6bs,we9r 66z2 of 5.0 m/s at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller coaster at theb9rag6,jz ,9k jsai2eu cpt6 6 w,s4jw 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 zan,-;xn+il2*c frms 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 th*;+ s cf2- ia,lnmrxzne speed of the roller coaster at the top of the next slope, which is 45 m above the bottom of the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the botto,tcvco c elw./ln38c /m of its swing (point

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79#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A:2.2 m/s

A. 3.1 m/s

B. 4.4 m/s

C. 4.9 m/s

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80#

( 1.0 分) 切至整卷模式搜藏此题

难度:2

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81#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A pendulum of length 50 cm is pulled 30 cm away from the vertixfc7; 0)zkg:rhx y np+cal axis and released from rest. What will bgyp 7+:c xrfx n0h)k;ze 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 uncompressed hori f-4i;xrebik8zerk)l(t s5t9zontal spring with spring constan;rtikfz9( rbkl5 48-)i sx teet 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 st7s8yb(-b mjxy op for a red light. What work is done by x8(y s-jbb7 mythe 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 andyka2w xz yd8j;)2hu *e a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 m/s, what yxd je;ua8hkw2*y z) 2distance 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 sur +ypy.bzj5 it9o )y nhpwsv4.4m;zfc325a u hgface. It has 24 J of kinetic energy. The friction force on it is a constzp+ 4p2hycbt4)s 9 5 fy j ..yuagmz5vwh;3noiant 0.50 N. How far will it slide?

A. $2.0 \; m$

B. $12 \; m$

C. $24 \; m$

D. $48 \; m$

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86#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force of 10 N is applied horizontally to a 2.0-kg mass on a level surf ) vq x2;b10;mamvsetsace. The coefficient 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 vs m m);bax0;v sqte21in its kinetic energy?

A. $20 \; J$

B. $39 \; J$

C. $46 \; J$

D. $61 \; J$

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87#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50-m high slope. If theie35d+yz c,ss work don5eds3 cz+siy ,e 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 pushed erk:.ci) mda )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 friction ce.m)i:r )dk aforce 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 ftex js,3l 0utr;4:wjinclined at 20e above horizontal. The coefficient of kinetic friction between the mass and the plane is 0.20. What will be the speedxtslet4wu j r,3f: j;0 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 of 10.0 m, and strikes the ground witr0gfzaclj0 - kp/f)5x h a velocity of 7.00 m/s. What average rf lcfzk5 j0-p/axg0) 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 e0) tw85jf vq.bwrgr hz-dky-:nergy when he runs up a flight of stairs 10.0-m high,wk-wqz85:vt ry r .b0 j)ghd-f 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 oblc /q8dzd3y wvs )813.cqto fsject with a constant velocity of 5.0 m/s. Ws cs1dld 38t8 y).vcqf3zwo/qhat power 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 forak3 z ;tkd 8kc8a)pqvj/w;) si 1.0 hr? (1 hp = 746 W) /;q8ti)dk k;3ajcvpz w s)a8k

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.bjua ,hwo )qxvs2hak 7:+ h2+x How much force does her foot pus2hqoxj7ahh2 ku,x va sbw)++:h 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 acceleratonodgz, ys+*+ es from 0 to 25 m/s in 7.0 s. What is the average power delivered by og zn+,*y od+sthe engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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