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

1#

What is the correct unit of w((lzxj) b3zq a*lzjs,ork 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 ishxvsgkb))hwgo 9j8+owuv - hc,4b /0 z 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 mi0o,+lgmc ;hwall, the amount of work you dh gm cl,oi0m;+o

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 vertfb uq3/ui-y wy0ut52jically and is being held there. How much work is being done in holding t0ityqfb3-5uj uy/u 2 whe 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 horizontall:ir,s c+rofu 9y forward at a constant velocity carrying a 10-N objer :io c9s,u+rfct, 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 lifted vertically 3.0 m then returned to its orige4).j;fkhkdw n.cp0)v5zpp +sjyg m ) inal position. If the total wkjgdvpzmphjn)e p45; k).0 y+cwf )s.eight 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 obz*6nvkp wifq ).7a s+gject?

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 w2tq 2ybj*de4m hile the ball 2 ytm4e bq2*jdgoes up with the sign of the work done by gravity while it goes down.

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

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

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

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

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9#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The area under the curve, on a Force versus position (F vs. x) graph, cf,t.jnr5osl76 d r /+lpez k(represents(fkre .or7/ 5njlptsl c,+zd6

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;i artma)bj cd dh;v e3a.k26( vs. x), what represents the work done by the foec )ra;jivhd.dam(b2a ;kt 63rce F?

A. the slope of the curve

B. the length of the curve

C. the area under the curve

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

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11#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

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

A. the kinetic energy of the object.

B. the potential energy of the object.

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

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

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12#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

If the net work done on an object is positive, tye3 o0i uzy/*rhen 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, then the object's kinetic energ;q/. nztc4ng:k cp3mry

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 obj;q:zmj/1a aau ect 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 a; lk hy.w5ikfct*d-/x s much as a car, and is moving at twice the speed of the car. Wc*-xw5 ./yfhkkdi tl; hich statement is true about the truck's kinetic energy compared to that of the car?

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

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

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

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

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16#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Car J moves twice as fast as car K, and car J has half th zzz;dy.tu,(t4b9 a2q ewmyh,e mass of car K. The kinetic energy of car J, cdyytzz;b9w(t. zu m4hq,2ae ,ompared to car K is

A. the same.

B. 2 to 1.

C. 4 to 1.

D. 1 to 2.

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17#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An object hits a wall and bounces back with half of its original n.8r0 rr: lyraspeed. What is the ratio of the final kinetic energy to the r r:8r0.yalnr initial kinetic energy?

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

B. 1/4

C. 2

D. 4

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18#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A brick is moving at a speed of 3 m/s and a pebble is moving at a speed of 5 m/s:ji-26f6x1a 7zty hoz2m dbq k. If both objects have the same kinetic energy, what is the ratio of the brick's mass to thy:fz671b mk ixotq22a6h dz-je 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 28 g eezb;ry*u.rrh56v.0 m/s. A 1.0-kg mass is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and .h8 vu;g*zry b5r6ereare 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, an4 k5vf,uwy blk3 q)4ked skid a certain distance on a straight, level road. Ikku534lf)e4,kb wyvq f you had been traveling twice as fast, what distance would the car have skidded, under the same conditions?

A. It would have skidded 4 times farther.

B. It would have skidded twice as far.

C. It would have skidded 1.4 times farther.

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

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21#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A planet of constant mass orbits the Sun in an elliptical orbit. Neglecl+d 78qe0u kehting any friction effects, what happens to the planetuqk0e8+edl 7h'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;j)(gh3:po ggtqa (t s principle.

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 poten7coc 8:aa dah8tial 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 groumrg *j 6(v pime.a.i7)pi) wggnd. A second object with four times the mass of the first if released from the same height. The potential energyj irepai* .(i. ggmw)p6mv7g) 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 spnnf2pfq2 m(2ixmu t 76ring causes it to stretch 5.0 cm. If anoxnupm2f7i2t2f q m n6(ther 0.200-kg mass is added to the spring, the potential energy of the spring will be

A. the same.

B. twice as much.

C. 3 times as much.

D. 4 times as much.

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28#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

The total mechanical energy of at3pz(/qmr. .1ty b5aq ohkwt6 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 kinetic2 )o y7c:5x8cmkofcwj energy K, to its potential energycoyo j wc: 2)fk78m5cx 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 drivi3z ai2tb9x (eo;x ei 9;fhifz*ng 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 ar8+t w/bpiuex/wex.c puj 9,d5 e sliding with equal speeds along a level frictionless surfaxup 9ibw .wxec5dup t/8e+,j/ce. 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 zd1crbpqkf u-no+7zdw ;.os3/p0c3 s$m_{1}$ 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 fu8uvz 3s6/ fdworces.zw8fuds v6 3u/

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 3s3txjjl*4 o0 :uth goa building, through the air (air friction is present), to the gro uo33:sjhog*x0jt4 tlund below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building?

A. K is equal to U.

B. K is greater than U.

C. K is less than U.

D. It is impossible to tell.

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35#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance jx1id3e i6:j-gyc .k zand gains 30 J of kinetic energy. Do not ignore air resistae.z3- xjgyi d:jcki61nce. How much gravitational potential energy did the ball lose?

A. more than 30 J

B. exactly 30 J

C. less than 30 J

D. cannot be determined from the information given

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36#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A ball drops some distance and loses 30 J of gravitational potential e s3hv ww,deg3kd7- s0- j ozq:qdihi35nergy. Do not ignore air resistance. How much kinetic energy did the ball gao-diwqh3gh -s :wk7q3d5 0z, jives3 din?

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 conservaam,qr1icg(cl- 1*8o po. j rhntion 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 isq g6hegw*csw9 fa3* 5oxb5cw 2

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 un7v +yc o:zu-i 9f 9.eacafzf3uit of power expressed in SI units?

A. $kg m/s^2$

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

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

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

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40#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Of the following, which is not a unit o9 0ehi i-ud 9ucm(9*)veohjjk f 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 yesterdayafb7kjb5i uhcv ,k8:9qa7 xv:o 57ytt, you did 3 times the work in one-third the time. To do so, y87abcq5:,kivt h 7 9jbfato 75:vuy xkour power output must have been

A. the same as yesterday's power output.

B. one-third of yesterday's power output.

C. 3 times yesterday's power output.

D. 9 times yesterday's power output.

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42#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

To accelerate your car at a constant acceleration, the car's engine mustrt1yz,eal1 :5j, +s6ajnoh ci

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 mm*kyl ruz(ys2oa3 i- 8 and held there. If the object weighs 90 N, 3zal2 oyk(8sr iym-*u how much 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 m, at a g-(7uh40nkjgdfo3i9 fgmcl0 hvh 3, c constant velocity of 0-f fg,(0cl 3mncgdk i34ou7hjg0 hhv9.50 m/s. What is the work done by the weight of the book?

A. +10 J

B. -10 J

C. +5.0 J

D. -5.0 J

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45#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a cons.;ajg ;t38 mrxuv agch(n*7adtant force of 5500 N for a distance of 50.0 m. What is tua aa 8grnhvj* ;73x. ;m(cgdthe work done by the 5500 N force?

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

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

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

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

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46#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 500-kg elevator is pulled upward with a constant force of 5500 N for a di gld/moc.ja7ovnb t.77a85lgstance of 50.0 m. What is the work done by the weit/..abn7 8vj57a7glmoodclg ght 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 5t k6-8mue(.xvt +xsb/l skk a8o3tgo4 500 N for a distance of 50.0 m. What is the net wos3x t+ otgk86xv 8eo 4/k(-b.muakl tsrk done on the elevator?

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

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

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

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

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48#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 30-N box is pulled 6.0 w3+ cm77gto vpm up 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 slid4tqgrix09zh,i vvg1r )*snf 6 es 8.0 m down a ramp, inclined at $30^{\circ}$ from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box?

A. $157 \; J$

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

C. $78.4 \; J$

D. $-78.4 \; J$

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50#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Matthew pulls his li.9mh gcm5ok- 13hsqz lttle sister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 N at1g. s-lhzc9mqh5o m 3k 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 fohxa,0get rd ;3rce. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done ;r at dg,e0h3xwhen 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 th3fvhb+4 v7l5 ou1 zs(v,hklrwe force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done 5 vuf3( v1lvs4+z l 7hkwhor,bwhen 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 objec jw grh0.vyv0w/t+mh/ t in the direction of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the tww0/h v.g/0myh+ jvr 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 direc+(m qj:qg +p+ ksby7ohtion of the force. The graph in Fig. 6-1 shows the force versus the object's position. Find the work done when the object moves fb 7+hk+jyo q+mqgp:s( rom 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 (initi3et1w ce be13g.eg: m:-)u.smfo lqjgally at rest) across a 10 m level surface. What is the final kinetic energy of the cbq lu1-1moc 3mfj s weeg:g e)t.:g.3eart?

A. $1.0 \times 10^{3} \; J$

B. $2.0 \times 10^{3} \; J$

C. $2.7 \times 10^{3} \; J$

D. $4.0 \times 10^{3} \; J$

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56#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A horizontal force of 200 N is applied to move a 55-kg car:y 0*df0 f/1psr pqetdt (initially at rest) across a 10dtp/d fef0sp1yrq 0*: m level surface. What is the final speed of the cart?

A. 73 m/s

B. 36 m/s

C. 8.5 m/s

D. 6.0 m/s

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57#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 10-kg mass is moving with a speepaaj 33 unm,d.:wil)kd of 5.0 m/s. How much work is required to stop .:udanw3a3 lmj)i,kpthe 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 carvg ,ck9hwn0e m6m 2s7v initially moving at 25 m/s, what distance is required to stop a car moving at 50 m/s under thc,6m79mk g nv2e0vsw he 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 ny04c 2 6 f pp(*(zlj(vkwxondif1wm5k.s8t na 10-g dart. It is cocked by exerting a force of 20 N over a distance 5kmjik.(f o1(dfz8t n*64p xw2(pnl wy vns0 cof 5.0 cm. With what speed will the dart leave the gun, assuming the spring has negligible mass?

A. 10 m/s

B. 14 m/s

C. 17 m/s

D. 20 m/s

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60#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A 100-N force has a horizontal component of 80 N and a +(sh. 0tqe pzh e(l*wgnt8uf/ vertical component of 60 N. ((/ph*wttq zf0u leh +n8s.eg 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 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 zf ikumq1-r; cs* 4ims 1bb6p0a bale of hay, striking the hay with a velocity of 60 m/s. I0kcsu z1b - b*srqp4 1iimf6;mt 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 olw 1p f3g+6ey+llw)v nf 7.00 m above a floor to a height of 13.0 m above the floor. What is the change in gravitational potential ene yegw nv)l+ flp31wl6+rgy?

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 plad*rhxmse,nc vv )7lzs4r-. f 7mz k4:une is 4.0 m long and rises 2.0 m. If tvl rhr7,.z:fzv7 ndms ke*)4msx-4cuhe plane is frictionless, 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 spring to stretch .p ro 0 xlhax :.q65.5my30enrelftch 2.0 cm. What is the spring cc x tqmp5 loeyxl6n. hr.e:0a3r0.5f honstant?

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 constantb, xgfw61n1 ruc1f2gr of 60 N/m. How much potential enerr ,1 uxng6r21wf g1cfbgy does it store, when stretched by 1.0 cm?

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

B. $0.30 \; J$

C. $60 \; J$

D. $600 \; J$

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66#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

Calculate the work requiro /l:,83 .kakm nbpv1-hphibted to compress an initially uncompressed spring with a spring,lbh3mt pbo:p./n v 1 -akih8k constant of 25 N/m by 10 cm.

A. $0.10 \; J$

B. $0.13 \; J$

C. $0.17 \; J$

D. $0.25 \; J$

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67#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

What work is required to stretch a spring of spring conna ;lyh rm3,l, 1l3qld 11ejlgstant 40 N/m from x = 0.20 m to 0.25 m? (Assume the unstretched position is at h 1lmln1,,l e313drg;qalyjlx = 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 initl,kpbz;( e n/+8 qr0ebipvh01 txzr9kially compressed by 3.0 cm. How much work is req / n8r 9t+hkrbk0x0zep,ibvq(e1 ;p zluired 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 fro ,na mgvx*dx aw0r1:o-m rest from the top of a 50-m high slope. What is the speed of the slier on reaching the odm , 0:r nx1xa-*wgvabottom of the slope? (Neglect friction.)

A. 22 m/s

B. 31 m/s

C. 9.8 m/s

D. 41 m/s

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70#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A skier, of mass 40 kg, pushes off the top of a hill with an i-tvl8)l) unbhg a ti+z o;c:o9nitial speed of 4.0 m/s. Neglecting friction, how fast will she be moving after droppihc igno; 9zt :-))b8tll avou+ng 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 fri- m13tyq7xzn 7cibk 8octionless inclined plane. At the bottom, it has a speed of 9.80 m/s. What is the vertical height of the plan -c7 int1zob8y7km3xqe?

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 in3w;-px4a/ w tigoi 8xs 0.70 m above the floor, its potential energy exactly equals its kinetia;w/xxn3gi p w8 -4tioc 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 ground level wi yr8kt* /,fk7rzj*c2ap52x gutz/jupgkd ;)rth a kinetic energy of 40 J. At the exact top of its trajectory, its total mechanical ecj 2apykt/z;)fu75rrgputjkz*2 k 8x,g* /rdnergy 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 lke9po ;j(nufrj f,ez70* r0k oeaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relj*7r;e0oprf 0 (n9 ujkz oe,kfative to its launch point, did it rise?

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

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

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

D. Impossible to determine without knowing the angle of launch

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75#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

A roller coaster starts from rest at a point 45 m above thepxj wwrpt+b+, q ;(+-m d9mglng re-2f bottom of a dip (See Fig. 6-2). Neglect friction, what will be the speed of the roller l(r w-x, r +++;9emptgmjgbfwpq2nd-coaster at the top of the next slope, which is 30 m above the bottom of the dip?

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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 syb.9kpajbhmvi, yi g6579c;)dej7c bpeed 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 the top of the next slope, which is 30 m above the b79pjykb5vb6;gjb iame ch y) .7c9id,ottom 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 30nfy o+47xz 3 f0mc9oar m above the bottom of a dip with a speed of 25 m/s (See Fignfoxocr 39fm7+ a04zy . 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 the dip?

本题所包含的其它图片:

A. 14 m/s

B. 16 m/s

C. 18 m/s

D. 20 m/s

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78#

( 1.0 分) 切至整卷模式搜藏此题

What is the minimum speed of the ball at the bottom of its swing (p-.x33d u oxxrxoint

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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 pull*4oxz gmfg bl3w4)/eled 30 cm away from the vertical axis and released from rest. What wio*e /wlbgg34 zmx)4f lll 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 25jagf,* y)y 8cb) jsv60uni ic5 m/s hits an initially uncompressed horizontal spring with spring constant ofv ag5cyi,b*un f))j 6 j8yis0c $2.0 \times 10^6 \; N/m$. 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 hebc ,rt5, sc;ksr 2000 kg car to stop for a red lighr5,kc;cs ts ,bt. What work is done 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-k;icmk ado h;.7g object and a horizontal surface is 50.0 N. If the initial speed of the object is 25.0 mh;;. oadmck i7/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 uyu* p5we6 ph,z2ap tx.qv 6a,of kinetic energy. The friction force on it is a constant 0.50 N. How xz 2a6u 6ha,5yu *.pp,ptvqwefar 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 mayd3( /:iaydigkc0 g t9ss on a level surface. The coefficient of kinetic friction between the mass and the surface is iak0 ( 3d9tg/c :gydyi0.20. 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 f8nkydvhttm oj*9yf4v 6f41t -xy.2re rom rest from the top of a 50-m high slope. If the work done by fricvf8* y 6ef -.y hjty4dx rt9k2tom14nvtion is $-6.0 \times 10^{3} \; J$, what is the speed of the skier on reaching the bottom of the slope?

A. 17 m/s

B. 24 m/s

C. 34 m/s

D. 31 m/s

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88#

单选题 ( 1.0 分) 切至整卷模式搜藏此题

An 800-N box is pushed up an inclined plane. The plane is 4.0 m long and rise-3ijym.9ezd qs 2.0 m. It requires 3200 J of work to get the box to the top of .ejdyq mi9 z-3the 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 the top of a plane inclined at rh s-r3rqci 1020e above horizontal. The coefficient of kis30riqhr1c r-netic 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 10.0 m, and strikes t,cvtzkc eal3w)ov k5. )n v4-ihe ground with a velocity of 7.00 m/s .i 3)c ,ncvkvk )otla45zevw-. 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 boyl6u.ugrtl f28-v , c74mfgzsv using energy when he runs up a flight of stairs 10.c4.gf,lv7fvmut l62-u8s grz0-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 needed to move an objesqq:xl5m /9pg,7hn9pylvss3 ct with a constant velocity of 5.0 m/s. What power m97sn9m sxs l,q p3qhlg5vy:/ pust 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 ark0 +zux))c. cbtgkjx4 0i/vj 1.0 hp motor that runs for 1.0 hr? (1 hp = 746 W)x+ j j.kcur/kibg 0vc)0xt4)z

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. H7g g ybttpy;u-9zy345 vpxjq5ow much force does her foot push withvt3tu jyx b5yg q45 7ygzpp9-; 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 xh)0f6uiim 6b1rhn) jthe average power delivered by theh6r01m6 )n)jhx iufb i engine? (1 hp = 746 W)

A. $60 \; hp$

B. $70 \; hp$

C. $80 \; hp$

D. $90 \; hp$

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