Suggested topics for discussion include whether France should have integration contracts for immigrants applying for citizenship and whether students should be required to sing the French national anthem.

VOA: standard.2009.12.30

That means the force you're applying is cancelled by another force, which has got to be the force of friction.

意味着你施加在物体上的力被另一个力抵消了,这个力就是摩擦力

耶鲁公开课 - 基础物理课程节选