20:["$","div",null,{"className":"mt-6 border-t border-border pt-6 sm:mt-8 sm:pt-8","children":[["$","div",null,{"className":"rounded-xl bg-success-soft/80 px-4 py-3.5 ring-1 ring-success/15 sm:px-5 sm:py-4","children":[["$","h2",null,{"className":"text-xs font-medium tracking-wide text-success sm:text-sm","children":"参考答案"}],["$","p",null,{"className":"mt-1.5 min-w-0 break-words text-2xl font-semibold leading-none tracking-tight text-success sm:text-3xl","children":"A"}]]}],["$","section",null,{"className":"mt-5 sm:mt-6","children":[["$","h2",null,{"className":"mb-2.5 text-sm font-semibold text-foreground sm:mb-3 sm:text-base","children":"参考解析"}],["$","div",null,{"className":"min-w-0 break-words text-sm leading-relaxed text-slate-700 sm:text-base","children":["$","div",null,{"className":"rich-html min-w-0 max-w-full break-words text-base leading-relaxed text-slate-800","dangerouslySetInnerHTML":{"__html":"

曲率为零时涡丝本身不运动（ $K4-60$ ）。

"}}]}]]}]]}]

直线涡丝自身诱导运动的速度是

参考答案

参考解析