问题 计算题

(8分)某种类型的飞机起飞滑行时,从静止开始匀加速运动,加速度大小是4 m/s2,经历20s时,突然接到停止起飞命令,若飞机起飞最小速度为82m/s,问:

(1) 飞机此时速度多大,是否已经离地?

(2) 飞机已经滑行了多远?

答案

(1) 没有离地(2) 800m

题目分析:(1)由 Vt=V0+at     …………3分

可得  Vt=80m/s     Vt="80m/s" < 82m/s  所以没有离地 ………… 1分

(2) 由S=vot+at2        …………3分

得  S=800m         ………… 1分

点评:本题难度较小,飞机只有达到82m/s时才能起飞,因此根据匀变速直线运动的速度和位移公式求解即可

阅读理解

New findings suggest that brainy card games such as contract bridge may temporarily(临时地) raise production of a key blood cell including in fighting off illness. After 90 minutes of play, bridge players had increased levels of immune(免疫) cells, according to the research reported last week.

A researcher, Diamond, studied bridge players from a women’s bridge club. She chose bridge players because the game includes skills stimulating(刺激) a part of the brain called the dorsolateral cortex. Earlier animal research suggests that this part of the brain may play a role in the immune system.

The findings are based on blood samples drawn from 12 women players. Their blood samples showed a rise in levels of white blood cells called T cells after they played bridge for 90 minutes. T cells are produced by the thymus gland(胸腺) and used by the immune system against diseases.

The T cell count jumped significantly in eight of the bridge players, and slightly in the other four. The findings contribute to the field of neuroimmunology(神经免疫学), whose name reflects the fact that the nervous system and the immune system are not considered separate and isolated(独立的) systems. What isn’t clear is whether the help to the immune system from an activity like contract bridge is lasting or temporary. It is also not clear whether the increase in T cells could finally be targeted against special illnesses.

小题1:Playing bridge can help one to fight off diseases because it can _______.

A.raise production of a key blood cell

B.make people joyful

C.aid digestion

D.make break away from the bad habits小题2:Diamond chose to study bridge players for the research because _______.

A.the players are good friends of hers

B.she loves playing bridge

C.this game stimulates a part of the brain that has something to do with immune system

D.she is a clever manager, who operates her bridge club well小题3:A T cell is _______ cell.

A.a brain

B.a white blood

C.a red blood

D.a kind of dangerous blood小题4:Which of the following is true according to this article?

A.The immune system and the brain system used to be considered separate and isolated systems.

B.The help to the immune system that is brought about by playing bridge can last for a long time.

C.Cortex is a kind of blood cell.

D.The new findings are impossible.

单项选择题