问题 多选题

沿X轴正向传播的一列简谐横波在t=0时刻的波形如图所示,M为介质中的一个质点,该波的传播速度为40m/s,则t=

1
40
s时(  )

A.质点M对平衡位置的位移一定为负值

B.质点M的速度方向与对平衡位置的位移方向相同

C.质点M的加速度方向与速度方向一定相同

D.质点M的加速度与对平衡位置的位移方向相反

答案

A、由图知,λ=4m,则周期T=

λ
T
=
4
40
s=0.1s,波沿x轴正向传播,质点M的速度方向向上,则经过t=0.025s=
1
4
T,质点M位于平衡位置上方,质点M对平衡位置的位移一定为正值.故A错误.

B、质点M的速度方向向下,对平衡位置的位移方向向上,两者相反,故B错误.

C、质点M的加速度方向与位移方向相反,方向向下,速度方向也向下,故C正确.

D、质点M的加速度方向与对平衡位置的位移相反.故D正确.

故选:CD.

完形填空
Being on the road at 3:15 a. m. to drive 450 kms wasn’t in my plans for the weekend. I had been looking forward to a couple of  ____ days to prepare myself for the following busy  ___ .
My son, Simon, and his good friends were heading for the ___ . Due to the last- minute issue with transportation, I __  my car to ensure that everyone could get to the   point so that they could get together and enjoy their week’s ____ by snowboarding and skiing.
The only thing that  ____ to me on my journey was that no sooner had I ____ and said goodbye than I would make the trip ____,in total, a round trip of 900 kms in just 10 hours. Such a long drive in one day was frightening, __  as I was looking forward to relaxation
Simon and I ___,on our way,a little about his break and a whole lot of his school subjects. It was great to have this time with him as we ____ spent five continuous hours together,other than when we played Saturday cricket (板球).
On my return trip, I ____a strange sense of loneliness in some heavy morning ____. Within an hour it ____. I spent the next four hours listening to some CDs and enjoying the scenery. Surprisingly, after my long trip home I was    refreshed and energized even though I was physically exhausted. And I knew that I would have a(n) ____ sleep that evening.
A change ____ your environment, no matter how great, can provide you with the opportunity to _ something from different angles, as well as to be refreshed and energized
Now I’m looking forward to my next     event and many more opportunities to spend quality time with those who are important to me and make my life more rewarding.
小题1:
A.surprisingB.excitingC.movingD.relaxing
小题2:
A.hourB.weekC.dayD.month
小题3:
A.hotelB.beachC.snowfieldD.school
小题4:
A. fueledB.offeredC.parkedD.lent
小题5:
A.drop-offB.kick-offC.get-offD.take-off
小题6:
A.freedomB.breakC.adventureD.excitement
小题7:
A.occurredB.happenedC.appearedD.appealed
小题8:
A.restedB.startedC.arrivedD.left
小题9:
A.backB.forwardC.outD.away
小题10:
A.evenB.justC.particularlyD.mostly
小题11:
A.talkedB.quarreledC.complainedD.argued
小题12:
A.constantlyB.rarelyC.frequentlyD.usually
小题13:
A.developedB.showedC.lostD.kept
小题14:
A.smokeB.dustC.fogD.snow
小题15:
A.turnedB.shoneC.frozeD.cleared
小题16:
A.greatlyB.mentallyC.immediatelyD.completely
小题17:
A.soundB.uneasyC.uncomfortableD.light
小题18:
A.aboutB.fromC.inD.for
小题19:
A.give upB.look atC.find outD.carry on
小题20:
A.plannedB.discussedC.preparedD.unexpected
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