ガクンとsuddenly, with a jerk

急(きゅう)ブレーキで車(くるま)がガクンと止(と)まった。

The car stopped suddenly with a jerk due to the abrupt braking. {suddenly, with a jerk}

膝(ひざ)カックンをされて膝(ひざ)がガクンとなりました。

My knee was jerked suddenly and it became wobbly. {suddenly, with a jerk}

インフルエンザが流行(りゅうこう)したせいで客足(きゃくあし)がガクンと減(へ)った。

Due to the outbreak of the flu, the number of customers suddenly dropped drastically. {suddenly, with a jerk}

売(う)り上(あ)げがガクンと落(お)ちれば、従業(じゅうぎょう)員(いん)のボーナスも減(へ)るだろう。

If sales suddenly drop, the employees' bonuses will probably decrease as well. {suddenly, with a jerk}

バスがガクンと止(と)まり、乗客(じょうきゃく)たちの体(からだ)が一斉(いっせい)に前(まえ)へ放(ほう)り投(な)げ出(だ)された。

The bus stopped suddenly with a jerk, and all the passengers' bodies were thrown forward at once. {suddenly, with a jerk}