道德的含义是什么？

如何维护保养制动器？

如图6-1-14，质量分别为m_A、m_B的木块叠放在光滑的水平面上，在A上施加水平恒力F，使两木块从静止开始做匀加速运动，A、B无相对滑动，则经过t s，木块A所受的合外力的冲量为_______，木块B的动量的增量Δp为_______.

调压室水位波动稳定条件和重要假定各是什么？

按要求改写句子。

1. I'm shorter than he is. (改为一般疑问句)

    _____ _____ shorter than _____ _____?

2. This book is not as interesting as that one. (改为同义句） 

    That book is ____ _____ _____ this one.

3. Tom is thinner than Sam. (同上)

    Sam is _____  as _____ _____ Tom.

4. I'm athletic. He is athletic, too. (合为一句)

    I am _____ _____ _____ he is.

5. He likes swimming. She likes it, too. (同上)

    They _____ _____ doing _____ _____ thing.

磨损按磨损的破坏机理分为粘着磨损、磨料磨损、表面疲劳磨损、腐蚀磨损。