大声点。，lewin：，So, speak, up。，我们可以尝试用，机械能守恒定律吗？，这样用有什么问题吗？

LEWIN Shall we try the conservation of mechanical energy Is there anything wrong with that?

youdao

大声点。，lewin：，So, speak, up。，我们可以尝试用，机械能守恒定律吗？，这样用有什么问题吗？

LEWIN Shall we try the conservation of mechanical energy Is there anything wrong with that?

youdao