s3.3质点系的角动量定理和角动量守恒定律 复习 质点角动量:L=FX(m)=FxD 力矩:=F×F 质点角动量定理: dL M=L at 0 L,,=Mdt 质点角动量守恒定律:若:M=0,则:L=恒矢量§3.3 质点系的角动量定理和角动量守恒定律 复习 质点角动量: L r mv r p      = ( ) =  a r m v O L  力矩: M r F    =  a o r  F  M  d F⊥  dt dL M L    = = • − =  2 2 1 1 t L L t Mdt    质点角动量定理: 质点角动量守恒定律: 若 : M  0,则: L = 恒矢量.  