问题 探究题

小婧同学在研究滑动摩擦力的大小与哪些因素有关时,她猜想滑动摩擦力的大小与接触面积的大小有关。现有以下器材:带钩的长方体木块(六面光滑程度相同),表面平整的长木板。请你帮小婧同学,设计一个实验,对此猜想进行验证。

(1)为了完成实验还需要什么器材:________________

(2)简述实验步骤:

(a)将木板放在水平桌面上

(b)_______________________________________________

(c)______________________________________________

(3)比较(b )、(c )结果得出结论: _________________________________

答案

(1)弹簧测力计

(2)

将长方体木块平放在木板上,用弹簧测力计水平匀速拉动,记下其示数为F1

将长方体木块侧放在木板上,用弹簧测力计水平匀速拉动,记下其示数为F2

(3)

若F1=F2,滑动摩擦力的大小与接触面积的大小无关;

若F1≠F2,滑动摩擦力的大小与接触面积的大小有关。

单项选择题
单项选择题

A little boy invited his mother to attend his school’s first teacher-parent meeting. To the little boy’s (1) , she said she would go. This (2) be the first time that his classmates and teacher (3) his mother and he felt (4) of her appearance. Although she was a beautiful woman, there was a severe sear (疤痕) that (5) nearly the entire right side of her face. The boy never wanted to (6) why or how she got the sear.At the meeting, the people were (7) by the kindness and natural beauty of his mother (8) the sear, but the little boy was still embarrassed (尴尬) and (9) himself from everyone. He did, however, get within (10) of a conversation between his mother and his teacher.The teacher asked (11) ," How did you get the scar on your face"The mother replied, " (12) my son was a baby, he was in a room that caught fire. Everyone was (13) afraid to go in because the fire was (14) , so I went in. As I was running toward his bed, I saw a long piece of wood coming down and I placed myself over him trying to protect him. I was knocked (15) but fortunately, a fireman came in and saved both of us. " She (16) the burned side of her face. "This scar will be (17) , but to this day, I have never (18) what I did. "At this moment, the little boy came out running toward his mother with tears in his eyes. He held her in his arms and felt a great (19) of the sacrifice (牺牲) that his mother had made for him. He held her hand (20) for the rest of the day.

第(16)空应选择()

A.pointed 

B.showed 

C.wiped 

D.touched