问题 问答题

某小组同学为了研究物体受力平衡与物体运动状态间的关系,选用了重力大小分别为1牛、2牛的物体在电梯中进行实验研究.同学们观察和记录了电梯静止、匀速上升(或下降)、电梯起动和制动时测力计的示数.经过多次测量,记录数据如下表所示.

实验序号电梯运动状态物体重力

(牛)

测力计示数

(牛)

1静止

1

1
2匀速上升(或下降)1
3电梯向上起动时1.2
4电梯向上运动制动时0.8
5静止

2

2
6匀速上升(或下降)2
7电梯向上起动时2.4
8电梯向上运动制动时1.6
(1)分析比较实验序号1与2或5与6数据及相关条件,可得出的初步结论是:______.

(2)分析比较实验序号______数据及相关条件,可得出的初步结论是:当电梯向上起动或制动时,测力计的示数不等于物体的重力.

(3)进一步综合分析比较表中数据及相关条件,并归纳得出结论.

(a)分析比较实验序号1、2、5和6数据及相关条件,可初步得出:______;

(b)分析比较实验序号3、4、7和8数据及相关条件,可初步得出:______.

答案

(1)由表中实验序号1与2或5与6的实验数据可知,当电梯静止或匀速上升或匀速下降时,弹簧测力计的示数等于物体的重力.

(2)由表中实验序号3与4或7与8的实验数据可知,当电梯向上起动或制动时,测力计的示数不等于物体的重力.

(3)由实验序号1、2、5和6数据及相关条件,可知:当物体静止或匀速直线运动时,物体受到平衡力的作用;

由实验序号3、4、7和8数据及相关条件可知:当物体运动状态发生改变时,物体受到不平衡力的作用.

故答案为:(1)当电梯静止或匀速上升(或下降)时,测力计的示数等于物体的重力.

(2)3与4或7与8.(3)a、当物体静止或匀速直线运动时,物体受到平衡力的作用;

b、当物体运动状态发生改变时,物体受到不平衡力的作用.

选择题
阅读理解

“Wolf!”

Lydia Angiyou's five-year-old nephew Paulussie whispered with alarm as he touched her

arm. At first, she didn't believe him.

Angiyou, Paulussie, her another newphew Lueassie, also five, and her youngest son Jessie,

seven, were walking to her mother's house one night last February. Animals were often sighted

near lvujvik--a village of 274 Inuit on the shore of Hudson Bay--but rarely on its streets.

The 41-year-old teacher and mother of five turned around. Looking behind her into the

darkness, at first she thought that Jessie was the wolf. But a meter behind the boy was 350kg

polar bern -no wolf in sight--standing on the icy road. Jessie turned and saw it, too, then ran,

screaming, to his mother.

Angiyou felt a rush of blood to her brain. "Get as far away as you can!" she shouted to the

boys as she ran towards the bear. She stopped just in front of it, then faced it quiedy. It made a

move to go around her to get to the boys, who must have seemed like the easier meal.

But Angiyou moved with the bear to maintain her position blocking the children. Finally she

got the animal's attention. In response, it rose on its hind legs to its full 2.5m height. The bear

charged, and knocked her into a seated position. The skin under her nose tore. Falling onto her

back, she screamed for help and kicked at the animal in a bicycling motion. She soon passed out.

Sirqualuk Ainalik, a fellow teacher, had been at his brother's house nearby when Jessie

dashed inside for help. Grabing a rifle, the 33-year-old ran to the road, firing a warning shot into

the air. He then aimed his gun at the huge bear.

With two more shots, Ainalik killed the polar bear.

56. Lydia Angiyou and             children went through the adventure.

A. two            B. three           C. four            D. five

57. What's the right order of the following according to the passage?

a. Angiyou passed out.

b. The bear struck Angiyou on the nose.

c. Angiyou went to her mother's home.

d. A fellow teacher killed the bear.

e. Angiyou was warned of a wolf.

A. e c b d a        B. c e d a b          C. c e b a d          D. c e a b d

58. The following are all right except          

A. Lydia Angiyou was in her forties

B. A wolf was finally killed

C. Animals often appeared near the village

D. Angiyou called for help while fighting

59. The story shows that Lydia Angiyou is          

A. strong and clever     B. skilled and careful

C. devoted and fearless    D.cautious and brave