某同学设计了一个测量物体质量的装置,如图所示,其中P为光滑水平面,K是轻质弹簧,A是质量为M的带夹子的标准质量金属块,Q是待测质量的物体, 已知该装置的弹簧振子做简谐运动的周期为T= 2π ,其中,m是振子的质量,k是与弹簧的劲度系数有关的常数,当只有A时,测得其振动周期为T₁,将待测物体Q固定在A上后振动周期为T₂,则待测物体的质量为多大?

    Have you ever been sad because of failure? Please remember, for quite often achieving what you set out to do is not the most important thing.

    A boy decided to dig a deep hole behind his house. As he was working, a couple of older boys stopped by to watch. “What are you doing?” asked one of the visitors. “I want to dig a hole all the way through the earth!” the boy answered excitedly. The older boys began to laugh, telling him that digging a hole all the way through the earth was impossible. After a while, the boy picked up a jar. He showed it to the visitors. It was full of all kinds of stones and insects. Then he said calmly and confidently, “Maybe I can't finish digging all the way through the earth, but look at what I've found during this period!”

    The boy's goal was far too difficult, but it did cause him to go on. And that is what a goal is for－to cause us to move in the direction we have chosen, in other words, to cause us to keep working!

    Not every goal will be fully achieved. Not every job will end up with a success. Not every dream will come true. But when you fall short of your aim, maybe you can say, “Yes, but look at what I've found along the way! There are so many wonderful things having come into my life because I tried to do something!” It is in the digging that life is lived. It is the unexpected joy on the journey that really makes sense.