根据理解，完成阅读
With the help of the Internet, shopping is becoming an easy job. You don't need to go to the street, looking for things from shop to shop. You just click the mouse to choose the things you like at any time or any places you like. And in a few minutes, the shopping is over. And the next three to seven days, the thing you buy online will come to your house.
It sounds fun, easy and quick. But sometimes you may meet something bad from online shopping. If you are not careful enough, you may buy some fakes. They are cheap copy things. And you want to give them back. But the owner of the shop online may not keep in touch with you. If you give them Chaping, They may do something bad to you. We often read this kind of news on the newspaper. It is terrible. And if you want to be different, it is a good idea not to buy clothes online. Once you put on the coat and go out. You will find many people wear the same clothes in the street. You may feel uncomfortable. But the next example will make you mad. According to the survey of March 15th Party this year, many kinds of Japanese food, such as Japanese Calbee and Xinxie Rice, is dangerous. After eating them, you may have a bad body.
。现将重物向下拉
，然后放手，则在刚释放的瞬间，重物加速度的大小是（
=
）