Advantages: Rubber grip the pedal, lubricant can loose the rusty screw, Roller can help object to move easily, Disadvantages: Rough surface can wear out shoe sole, Amir injured after fall off the bike, Drill produce loud sound and cause sound pollution,

Effect of Frictional Force

排行榜

視覺風格

選項

切換範本

恢復自動保存: ?