问题 实验题

某同学设计了如图所示的装置以探究加速度与力的关系。弹簧秤固定在一合适的木板上,桌面的右边缘固定一支表面光滑的铅笔以代替定滑轮,细绳的两端分别与弹簧秤的挂钩和矿泉水瓶连接。在桌面上画出两条平行线MN,PQ,并测出间距d。开始时将木板置于MN处,现缓慢向瓶中加水,直到木板刚刚开始运动为止,记下弹簧秤的示数F0,以此表示滑动摩擦力的大小。再将木板放回原处并按住,继续向瓶中加水后,记下弹簧秤的示数F1,然后释放木板,并用秒表记下木板运动到PQ处的时间t。则

(1)木板的加速度为a=___(用d,t表示);

(2)改变瓶中水的质量重复实验,确定加速度a与弹簧秤示数F1的关系,下列图象中能表示该同学实验结果的是___。

答案

(1)

(2)C

阅读理解

阅读理解。

     When Mr Black looked out of the window, he saw two armed men running towards his house. One was

short and the other was rather thin and tall.

     Having closed the window quietly, Mr. Black gave his pistol (手枪) to his son and said, "We are surrounded

by the robbers now," He pointed to the kitchen and his son went in there quickly.

     Mr Black went to the front door with nothing in his hand. He was very good at ju-do (柔道), and lungful. 

     The tall man entered the room with a sharp sword in his hand. He didn't see Mr. Black who stood just

behind the door. He fell onto the floor as Mr. Black attacked. Unfortunately the short man with a pistol jumped

into the room after he had broken the window. He shot Mr. Black in the arm and tied him to a chair. The two

men went out through the kitchen with money they had taken in Mr. Back's bedroom. Suddenly two shots

were heard and the two men fell down. Mr. Black's son had shot them. When the police arrived after they

received the boy's telephone, they took Mr. Black and the two robbers to hospital.

1. When Mr. Black saw two armed men running towards his house, _____. [ ]

A. he was very much frightened

B. he told his son get away at once

C. he closed all the windows and doors to keep the robbers off

D. he was calm and had an idea to fight them

2. How did Mr. Black know the two men when he first saw them? [ ]

A. They carried weapons with them.

B. Mr. Black had seen them before.

C. They were both running towards the house.

D. Mr. black had never seen them before.

3. Mr. Black fought the tall man _____. [ ]

A. with a sharp sword

B. with his hand

C. with a pistol

D. with a broom he found behind the door

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