Dear Dad,
I know you are busy. You have a lot to do in the army (部队), but I am hoping you can help me out anyway. I' m thinking of quitting (离开) the football team, and I want to know your advice.
Don't be surprised. It's just that I have so much homework to do this year. If I play with the football team, I won't have enough time to finish my homework. And I'm the only man of the house while you are away, so I have more housework to do.
On the other hand, I've put in two years on the team. I love football more than any other sport in the world. I' m a really good player. And the coach says I will make captain (队长) soon. So I really don't want to quit.
Dad, what do you think? Should I try something new that will take less time? My friends on the football team are great. We will be friends to the end, but it will be cool (妙极了) to meet some new kids, right?
I miss (想念) you so much! Please write back to me soon.
Paolo
①空沙桶的重力 G=N;小车运动时滑块与小车之间的滑动摩擦力的大小为N;
②在滑块上继续逐个叠放相同的滑块,如图3所示,重复上述实验,将小车运动起来后力传感器的读数记录在如下表格中。分析表中数据可得:
滑块个数 |
1 |
2 |
3 |
4 |
5 |
… |
传感器示数F/N |
3 |
6 |
9 |
12 |
15 |
在接触面材料和粗糙程度等因素相同时,滑动摩擦力大小与压力大小成比(选填正或反);
③小亮又设计了如图4所示的实验,他将一根连有氢气球的绳子系在滑块中央,重复上述实验,当小车运动起来后,力传感器的读数F=1N,则此时滑块对小车的压力大小为N,氢气球通过细绳对滑块向上的拉力为N。
a=15
b=20
a=b
print(a)