Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
물체가 충격량을 받을 때, 그 속도가 변할 수 있다.mulchega chung-gyeognyangeul bad-eul ttae, geu sokdoga byeonhal su itda.When an object receives an impulse, its speed can change.