问题 实验题

针对“斜面的倾斜程度与斜面的机械效率有怎样的关系?”这个问题,某同学利用同一木板,搭成不同倾角的斜面,将同一小车沿斜面匀速拉动,记录实验数据如下表。   

实验

次数

斜面倾

斜程度

小车重

G/N

小车上升

高度h/m

沿斜面

拉力F/N

小车移动

距离S/m

有用功

W/J

总功W/J机械

效率η

1较缓4.00.20.91.20.81.0874%
2较陡4.00.31.21.21.21.4483%
3最陡4.00.41.51.21.6  
(1)请你将该同学第3次的实验数据填入表格中。(4分)

(2)分析实验数据可知,在粗糙程度相同的情况下,斜面的省力情况与斜面倾斜程度的关系是:                                                     。(2分)

(3)分析实验数据可知:在粗糙程度相同的情况下,斜面的机械效率与斜面倾斜程度的关系是:                                                   。(2分)

(4)如果该同学还要进一步探究“斜面的机械效率与物重的关系”,实验时应控制小车移动的距离、                                         不变。(2分)

答案

(1)1.80(或1.8)    89%;(各2分)

(2)斜面越陡越费力(2分)(3)斜面越陡机械效率越高(2分)

(4)斜面的粗糙程度   斜面的高度(或斜面的倾角)(各1分)

分析:(1)根据W=FS求出总功,然后根据η= 求出机械效率;

(2)分析1、2、3三次实验数据,在斜面倾斜程度不同的情况下拉力的大小关系得出结论;

(3)分析1、2、3三次实验数据,在斜面倾斜程度不同的情况下机械效率的大小关系得出结论;

(4)要分析斜面机械效率和物重的关系,就要采用控制变量法控制斜面的粗糙程度和斜面的倾斜程度一定.

解答:解:(1)实验次数3的总功W=FS=1.5N×1.2m=1.80J;实验次数3的机械效率η=≈89%;

(2)分析1、2、3次的实验数据可以发现,在小车重力一定时,斜面的倾斜程度越大,越费力;

(3)分析1、2、3次的实验数据可以发现,在斜面粗糙程度一定时,斜面倾斜程度越大,机械效率越高;

(4)影响斜面机械效率的因素有两个:斜面的粗糙程度和斜面的倾斜程度,要探究斜面机械效率和物重的关系,就要控制斜面的粗糙程度和斜面的倾斜程度一定.

故答案为:

(1)

实验次数斜面倾斜程度小车重力G/N小车上升高度h/m沿斜面拉力F/N小车移动距离S/m有用功W/J 总功W/J机械效率η
1较缓4.00.20.91.20.81.0874%
2较陡4.00.31.21.21.21.4483%
3最陡4.00.41.51.21.61.80  89%
(2)斜面越陡越费力;

(3)斜面越陡机械效率越高;

(4)斜面的粗糙程度   斜面的高度(或斜面的倾角)

完形填空
It was an early morning in summer. In the streets, sleepy-eyed people were moving quickly, heading towards their    . This was the beginning of another      day in New York City.      this day was to be different.
Waiting     the crowded streets, on top of a       110 stories high, was Philippe Petit. This daring Frenchman was about to     a tightrope (绷索) between the two towers of the World Trade Center.
Philippe took his first      with great care.  The wire held. Now he was     he could do it.     only a balancing pole, Philippe walked his way across, a      of 131 feet.
 Soon the rush-hour     began to notice. What a      ! There, 131 feet above the street, a      figure was walking on air.
 Philippe made seven      , back and forth (来回). He wasn't satisfied with just      . At times, he would turn, sit down, and     go on his knees. Once, he had the astonishing     to lie down on the thin thread. And thousands of      watchers stared with their hearts beating fast.
 After the forty-five-minute     , Philippe was taken to the police station.  He was asked     he did it. Philippe shrugged (耸肩) and said, "When I see two tall buildings, I walk."
小题1:
A.jobsB.homesC.busesD.offices
小题2:
A.workingB.hotC.sameD.ordinary
小题3:
A.AndB.SoC.ButD.Thus
小题4:
A.forB.inC.byD.above
小题5:
A.roofB.positionC.wallD.building
小题6:
A.throwB.walkC.climbD.fix
小题7:
A.actB.landingC.stepD.trip
小题8:
A.sureB.uncertainC.gladD.nervous
小题9:
A.ThroughB.AgainstC.WithD.On
小题10:
A.distanceB.heightC.spaceD.rope
小题11:
A.streetsB.crowdsC.passengersD.city
小题12:
A.heightB.pleasureC.wonderD.danger
小题13:
A.greatB.strangeC.publicD.tiny
小题14:
A.experimentsB.circlesC.tripsD.movements
小题15:
A.walkingB.stayingC.actingD.showing
小题16:
A.almostB.evenC.oftenD.rather
小题17:
A.spiritB.resultC.strengthD.courage
小题18:
A.patientB.terrifiedC.pleasedD.enjoyable
小题19:
A.showB.trickC.tryD.program
小题20:
A.howB.whyC.whetherD.when
问答题 简答题