He says they actually use dental floss to slowly saw away at the metal, adding tooth powder to increase the friction.
但是犯人们总能找到办法弄到。现在他们用牙线慢慢钜金属，抹上牙粉增加摩擦力。
2
So you saw in a striking example of where friction helped us to balance, and now I want to discuss an object that is hanging and that can freely swing due to gravity.