“投石”用英语怎么说？

投石入静水中,看到微波荡漾成圈.Throw a stone into still water and watch the ripples spread in rings.它会以投石运动的反作用晃动起来.It lurches from a standstill in a reaction to the movement of the outgoing rock.投石机: 古代投掷物体之发射器,用作发射长箭或重型球状物.Ballista: ...