问题 计算题

两个完全相同的物块A、B,质量均为m=0.8kg,在同一粗糙水平面上以相同的初速度从同一位置开始运动,图中的两条直线分别表示A物块受到水平拉力F作用和B物块不受拉力作用的v-t图像,求:

(1)物块A所受拉力F的大小;

(2)8s末物块A、B之间的距离s。

答案

解:(1)设A、B两物块的加速度分别为a1、a2

由v-t图可得:-1.5m/s2,负号表示加速度方向与初速度方向相反

对A、B两物块分别由牛顿第二定律得;F-Ff=ma1,Ff=ma2

由各式可得:F=1.8N

(2)设A、B两物块8s内的位移分别为x1、x2

由图像得:

所以s=x1-x2=60m

阅读理解

One day my teacher said, “ Life is a game of chess, and the other player is time.” From that moment, I knew I had to enjoy my life.Do not waste time, because, you know, time will not come back.You cannot buy it.It is one of those things in life that you must really, really value.

When you see an opportunity, take it.You might not get it back.Never let an opportunity pass.And if it is too hard, remember that in the middle of every difficulty lies an opportunity.

Remember, you cannot choose how you' re going to die, or when.You can only decide how you' re going to live.Study as if you were going to live forever; live as if you were going to die tomorrow.Don' t just think of the present, but also think of your future. Your future is yet another chapter in your life and another way to live it.

Every single living thing has a purpose in life."The purpose of life is a life of purpose," said Robert Byre.

Learn to use time wisely, take opportunities, and enjoy life.We can discover the meaning of life in three different ways: (1) by doing a deed; (2) by experiencing a value; (3) by suffering.Life.

56.小题1:The underlined part suggests that___________.

A.If life is a game of chess, time is also a game of chess

B.If life is a game of chess, both you and time are the players

C.If life is one player in a game of chess, time is the other player

D.If time is a game of chess, both life and you are the players57.小题2:According to the author, what can you decide?

A.How you die.

B.When you die.

C.How you live.

D.When you succeed.58.小题3:This article is most probably from__________.

A.an explanation of time in the universe

B.an essay about time and life

C.an argument that time is the most important thing in life

D.a description of an important class

单项选择题