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

1#

What is the correct unit of work expressed in SI unit;7bxr fg19k r4i44iutayp 1bj s?

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 th 4pzubmbr;57t 70zetfere 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 sbs h,2th)nj y,tationary brick wall, the amount of work you do2h, snt, ybhj)

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 anc46mc5f g zccf 9k42lwd is being held there. How much work is mc k4z5l9ffccc4w2 6gbeing done in holding the box in this position?

A. more than 100 J

B. 100 J

C. less than 100 J, but more than 0 J

D. 0 J

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5#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If you walk 5.0 m horizontally forward at aafk6li1tnz1 5 constant velocity carrying a 10-N object, the amount of workifzn5atkl11 6 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 vertixld jj*f q.sv8- seyv3urbx(b/n34f: cally 3.0 m then returned to its original position. If the total weight is 30 N, how much 3v: d8jxn x 43sv/j s. qerylf-ufbb*(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 wopps-e 5-2t sw. 4xsxtgrk 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 whi3x7zo vu .5w2xe5t6pg(bmy dele the ball goes up with the siu 5m 2( woxyze.5d bvx7tge63pgn 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 po)g.b 1/nkex)vvsi r+cv.s 0dr r9ns v9sition (F vs. x) graph, representsg.nrnx1/.i+ vs 9esd)v v9cr0kr vb)s

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 pos8qecrkif2 r.j0j63ssition (F vs. x), what represents the work done by the forcece0 s2j8i r6js .3frqk F?

A. the slope of the curve

B. the length of the curve

C. the area under the curve

D. the product of the maximum force times the maximum x

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11#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

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

A. the kinetic energy of the object.

B. the potential energy of the object.

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

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

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12#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object ibrl1zs(+ j+6,9 rsnafw+)dnmba qd2qs 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 oz7bcke0 mqztpbdhj 7ov706q+a8 p 96hbject 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 objedbc zd5gcuk,z c (4a99ct is zero, then the object's kinetic energy

A. decreases.

B. remains the same.

C. increases.

D. is zero.

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15#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A truck weighs twice as much as a carltbwekn*v4 w ;s ju/)c+k)-ys, and is moving at twice the speed of the car. Whic )syb/j- v+n*;twls wck ke4u)h 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 asz6rn l-l1d4kajr5tww5 t iy6 ;s0q+di car K, and car J has half the mass of car K. The kinetic energy of car J, c t-16;4 65+kqrtwnal5wr lidz ysdi j0ompared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces 36mpc 0lkz f1jback with half of its original speed. What is the ratio 6 0f3kcmlz j1pof the final kinetic energy to the initial kinetic energy?

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

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed ;1 deq)t nwy0 -5aswrmof 5 m/s. If both objects have the same kinetic ee 1 smw0dwanr;q5 -yt)nergy, what is the ratio of the brick's mass to the rock's mass?

A. 25 to 9

B. 5 to 3

C. 12.5 to 4.5

D. 3 to 5

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19#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 4.0-kg mass is moving with speed 2.0 m/s. A 1.0-kg mass is moving with speet *p;/ pmgt (cjo 4ed(pzm,/rapn81zmpsd(r2d 4.0 m/s. Both objects encounter the same crz(mtm rt12pco (s* pag; 8jenp(dp,/md zp4/ onstant braking force, and are brought to rest. Which object travels the greater distance before stopping?

A. the 4.0-kg mass

B. the 1.0-kg mass

C. Both travel the same distance.

D. cannot be determined from the information given

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20#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You slam on the brakes of your car in a panic, and s;kkw y:p ucr+)kid a certain distance on a straight, level road. If you had been traveling twice as:kcy;+rpukw ) fast, what distance would the car have skidded, under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

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

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A planet of constant mass orbits thec,6lkt-a r1u n Sun in an elliptical orbit. Neglecting any friction effects, what happensnlurtc6 1a-,k 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 pr e( y)0ee )md+ugh+j2njap3ru inciple.

该题自我估分: (必填) (满分:1.0分)

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23#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The quantity mgy is

A. the kinetic energy of the object.

B. the gravitational potential energy of the object.

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

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

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24#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

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

A. the kinetic energy of the object.

B. the elastic potential energy of the object.

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

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

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25#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Is it possible for a system to have negative potential env siyf+/;qe 295jmxenergy?

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 :2tl8zc o:uvpvob7z9rest a height h above the ground. A second object with four times the mass of the first if released from the same height.cu 97ooz2 bv :zvp:t8l The potential energy of the second object compared to the first is

A. one-fourth as much.

B. one-half as much.

C. twice as much.

D. four times as much.

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27#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 0.200-kg mass attached to the end of a spring causes it to stretch 5.0 cm. .w3 tgpwng w(m2k)/2 x q; y+leo2kigoqav-.sIf another 0.200-kg mass is added to the spring, the poten;av(2xq3meko ypq. wnso- t2/2.gl+) wg gw iktial 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 energy of a;1i6 r gglv6gu 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 energy K, to xk ydb0-vj :6dm5 8u:2rgr ;zj(ixvvvits potential energz:5vgk u vr6-y8jdrxji2 d:b(;v mx 0vy 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 drivinjvh: a7mis u09j1a2v72fy nd/tdqhlk9fdl(6g 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 veryy:t mj2i, l0zwa5a xqt3k;y: y heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hil , a0ayjyxzy5w:;:tiq3l ktm2l. 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 4qj6 s9c .ih9jfkt*kx$m_{1}$ and $m_{2}$ at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which $m_{1}$ sits is at an angle of $30^{\circ}$ with the horizontal, while the plane on which $m_{2}$ sits is at $60^{\circ}$. If the masses are released, which is going faster at the bottom of its plane?

A. $m_{1}$

B. $m_{2}$

C. They both are going the same speed.

D. cannot be determined without knowing the masses

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33#

问答题 ( 1.0 分) 切至整卷模式搜藏此题

State the principle of conservation of mechanical energy for conservative f48(zorcfs(gcw ea :2q34l sz7l4vdeuorces.e :8cr cfw(zqe34a(74zlgsd4 2luosv

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 thew lfd6ubx9rm spa3 m7m24f9 t;h:yvb 0 top 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) dh94y m:s wbrta7v u230p;9 6flmmfx bat 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 kinetik9m8c(9 2a9 (6 jyiatd/e qpsnwf8w iic energy. Do not ignore air resistance. How mucaytw8 mc(f9is w286 q9de(9a/ ijkn pih gravitational potential energy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 30 J of gravitational potential e ktsno6n;,kp *wf k8)fnergy. Do not ignore air resistance. How much kinetic energfkfn p8)nsk*t;k6 w,o y 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 consrq(+b/2t ,oqcvt evhj sz.. /lervation 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 is/dj0r-sk)bg ( gata *8xh01 yxc8sshy

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 exv n t8axm; ox0z-2:l feq.v6hz3pij (hpressed 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 n+kc5i hczs5 ,4cv. r3y4bs jifot a 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 3 times the work in one-third the time.;ro5b r0b4y tu To do so, your power output mu4 rubo5 tb0r;yst 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 accelera2e 7g-r s;1mqzpahibh z54vt;tion, 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. e9oae((ad9-hjki cwq 09mhym bn:)5 jIf the object weighs 90 N, how 09jio(ahmead ) hynckb ew9-(q9 j :5mmuch work was done in lifting it?

A. $360 \; J$

B. $180 \; J$

C. $90 \; J$

D. $0 \; J$

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44#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

You lift a 10-N physics book up in the air a distance of 1.0 myfr* fffu-)sp;f4uh; c6u oi0, at a constant velocity of 0.50 m/s. What is the work done by the weight op;foh6uf*yf ;ff c0)su-i4u rf 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 valc1n8g7 ym6distance of 50.0 m. What is the work done by tc71 mv8yg l6nahe 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 upwar(e iz 1iz*nbw9d with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the elevato *19 iwbn(ezizr?

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 5rs047,39uqrd nxr)zb/rkt zp 500 N for a distance of 50.0 m. What is the net work done on the elekprzq/ r )rdn9rx,u7t bz s034vator?

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 u*2lt/9qf)gjite a865 ivc u) /kxheipx7adq2p along 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, inclin-cmg hqus-jnz k6-*j+ed 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 (assum7 ig;m-kn8pf-m4 r*6sqd y81jmv j7t mp 8ttqke no friction), with a force of 60.0 6g17fvm -t8qkmrdjtm8p;qk *i pj-8s7y t4mn N at an angle of $37^{\circ}$ upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew?

A. $185 \; J$

B. $433 \; J$

C. $575 \; J$

D. $720 \; J$

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51#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the direction of the force. The graph in j6ysnfyz. .56bqa+t-ijs z1 oFig. 6-1 shows the force versus the object's position. Find the work done when thea jyt.sz ib1+66fz.ys jnq- o5 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 directionkajs0k24olftm+9hw 3 of the force. The graph in Fig. 6-1 shows the force versu j4m w+l to9h3fk0ksa2s the object's position. Find the work done when the object moves from 2.0 to 4.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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53#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an objectk6jqfr6ky6 2*pv id)v3l ;a)fu sh-u h in the direction of the force. The graph in Fig. 6-1 shows the force v; 6kv )i qfy-dhhs3v6p2 flua6*)jrukersus the object's position. Find the work done when the object moves from 4.0 to 6.0 m.

本题所包含的其它图片:

A. $20 \; J$

B. $40 \; J$

C. $60 \; J$

D. $80 \; J$

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54#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force moves an object in the c;*zs)5umkk gkc,aaz*2fh wc pjd /*0 direction of the force. The graph in Fig. 6-1 shows the force versus the object's posiz* ah /p,smu*ack)cc jkgw;*2d0 kf z5tion. 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 kqwhh*m4.o b: to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cartohkq4*: mw.hb?

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 movee (vm1(aq+t8h tu.hn avzk1f7qk3 -ya a 55-kg cart (initially at rest) across a 10 m level surface. at81ktnz7ma 3fv kuy+aq( h.1 e( q-vh 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/wknptcrd8e 3c .hl4 0;s. How much work is required to stop the mass?cp4rh e30ntl.dc;w8 k

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 movinp:ek,) z odrk5g at 25 m/s, what distance is required to stop a car moving at 50 m/s under the same con pzod)e,k 5rk:dition?

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 cox/:6w*uuk h)m1nzg xicked by exerting a force of 20 N over a distance of 5.0 cm. With what speed will tigmzx6 un*xh/1ku) : whe 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 horizo.p nf uutc 99hfy2o3-wilz0d /ntal component 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. What is the cart's final kinetic hoz l3i. -yfu/t 29pu9nw c0dfenergy?

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 p di;hac g/qf-*r8vh4 the hay with a velocity of 60 m/s. It penetrates a depth of 20 cm before stopping. What isha8-c/i;pfgh q dv4*r 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 mopvip+n.i-hh f(6;f(s3m nr+h zle cn:ved from a height of 7.00 m above a floor to a height of 13.0 m above the floor. What n6z pf-+i ifmh:+s r ;ev.hl3(chnpn( 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 incb/oo/h 2xme6 clined plane. The plane is 4.0 m long and rises 2.0 m. If the plane is 6xe ho/co/b2mfrictionless, 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, causes the spcp2m+msgvsm5+w. ly rn+v) r(ring to stretch 2.0 cm. What is thepvw m(mn+ mrv ++5ls.y2 rg)sc spring 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 bycq,+w8k26dxhua ow+u x j-qg d1qi)os.5 4wfb a spring constant of 60 N/m. How much potential energy does it store, when stret+qa 2f.ws h)ob-81jw45uudk xgdw+ co 6ixq ,qched 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 :*oza +xk 8fw1+glr zran initially uncompressed spring with a spring constant of 25 N/m by 10 +zor*fa1z+x w8 :lrkgcm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring of spring (s, e3mej. iopw 5,ahyconstant 40 N/m from x = 0.20 m to 0.25 m? (Assume tjo35w h ea,y (ms,pi.ehe 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 compressed by 3.0p z,a;gxz0+ud.pazr4 cm. Ho;p0 .zg+pr4dz,a zxuaw much work is required to compress the spring an additional 4.0 cm?

A. $0.0068 \; J$

B. $0.012 \; J$

C. $0.024 \; J$

D. $0.030 \; J$

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69#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 60-kg skier starts from rest from the top of a 50-m high sloppl ni. )tk*9 y8uckaq.e. What is the speed of the slier on reaching the bottom of the slope? (Neglect friipc a8l*9.knq uk.) ytction.)

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 withi,: x kd6tmxc( an initial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after dropping 10 6(txkdmi:,cx 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 frictionlesk.mlyn4u i d3 7:mvm bj+5dx2as inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertd73m42l5:n ykxib.jm advu+mical 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 f. ap kso: akq4i0)miq0loor. When it is 0.70 m above the floor, its potential eni sq):kpao 4kiq a0.0mergy exactly equals 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 from grq-q2zvphfh 7u0 (6ebe(hm0xgc epv2 5ound level with a kinetic energy of 40 J. At the exact top of its trajectory, its tofe7(220 q0ph5hqxe-hvuce6pgz( m v b tal 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 groubvgx+ 9; d t4;qjwi(ojnd with a kinetic energy of 220 J. At the highest point in its trajectory, its kigv t9bwojd(;jx+ q;4i netic 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 restf4b4h e 372a )7nsrpzh8mkch3b4s xp w at a point 45 m above the bottom of a dip (See Fig. 6-2). Neglect friction, whs 78ebwbp 474) sf4kncmrxzah2p3 3h hat 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 staghennj5zi0vni 8u,cg 1 m q*,6rts 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, what will be the speed of th5*uie6 z1h nvnj8,mcg g0, qnie roller coaster at the top of the next slope, which is 30 m above the bottom of the dip?

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A. 12 m/s

B. 14 m/s

C. 16 m/s

D. 18 m/s

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77#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts at a point 30 m above the bottom of a dip wit w0zj 9ou zzmhmh:x*h4abz- /;h 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 thzzz09h 4 /*w xmahu;zo:h j-mbe dip?

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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 t/k56nynuhqs1 t;pg 6bqz8xb:w d) b* phe ball at the bottom 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 izpupt;q4d4 sekxj ,ps 5/)zl; s pulled 30 cm away from the vertical axis and released from rest. What will be its speed at 5zp) us/ jd xe;4t4kppzq l,;sthe 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 uncompressq.gu 0bs- 2-ip -hpymyed horizontal spring with yi-p0 -2q -hgys.upbmspring 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 d;zt- 5qzh ru(a red light. What work is dord ( qz5-zthu;ne 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-kg object and a horizontal surfacer6xhex(q-m) g jem*x ctne+zt8/ o,4g is 50.0 N. If the initial spee*j4oxq,exgxrnzh/6 mmet(-e c t8g+) d of the object is 25.0 m/s, what distance will it slide before coming to a stop?

A. $15.0 \; m$

B. $30.0 \; m$

C. $375 \; m$

D. $750 \; m$

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85#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 12-kg object is moving on a rough, level surface. It has 24 J of ki0cq8s2k( sracnetic energy. The friction force on it ra 0sc(sc2k q8is a constant 0.50 N. How far will it slide?

A. $2.0 \; m$

B. $12 \; m$

C. $24 \; m$

D. $48 \; m$

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86#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A force of 10 N is applied hor+su. +jq t4 wm2r;ukvoizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.jt q .2rv;o ks4u+m+wu20. 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 a 50-m hizg5n, hn1m7je.md ow9 q4n um1gh slope. If the work done by fr w9qg e,mmmohzn.7 4u5nn1 1djiction is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane9 vu*,rx9fpf t*mmk q. is 4.0 m long and rises 2.0m, k9xvfp*tf.*m9rq u 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 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 thelf3 xyfi*,in+k9 km;x top of a plane inclined at 20e above horizontal. The coefficient knx3 ki9 * xim,ylf;f+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 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 1ag1:k6t1ig p x0.0 m, and strikes the ground with a velocity of 7.00 m/s. What avera gi1a gt1:6xpkge 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 hc)/ o5ao 473ya5 5r cpjr-mci(yq sdbte runs up a flight of stairs 10.0 )5jco5so 7adqcm (t5yra-34p/ rbciy-m 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 needermx:zk(xky b8oq fj6 2f,q90xd to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the forz(0y8xbf kfm2:x6, joq xr kq9ce?

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 b 9tmd+lrxf)2bhb9r)a y a 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W)x brr9 h2+t)dbf9l) am

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 xp/pruyw+wh+k+8dz4g 7bw 0n at the rate of 500 W while riding. How much force does her fooh d8+znb4xp ku0w w+/gwr+7ypt push 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 from 0 to 25 m/s in 7.0 s. What is the k 7bi9wz xto o*,bm k/;gg1e.caverage power delivered by th .bogez 91;/xbom kic *w7kg,te engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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