曾在办公室或是教室弹射橡皮筋的人都知道，那种一张一弛的感觉其乐无穷。
ANYONE who has fired a rubber band across the office or classroom will know the joy of storing and releasing kinetic energy.
曾在办公室或是教室弹射橡皮筋的人都知道，那种一张一弛的感觉其乐无穷。
ANYONE who has fired a rubber band across the office or classroom will know the joy of storing and releasing kinetic energy.
应用推荐