Board Thread:Speculation House/@comment-69.66.169.227-20130802171349/@comment-5869016-20130912130736

Force X Distance = Joules required

If the mass of her and her scythe is 80kg, Gravitational force is 800N (Assuming net gravitational acceleration to be 10 m/s^2). Assuming 810N force applied.

810N X 20 meters (Reasonable height) = 16200 Joules

Anyways, she hacked through a meter of a solid tree trunk with ease, technically you won't know how much force is required, because it is unknown how durable the bird is (with its INNARDS surviving explosions from Yang). Logically, Blake's swings as she ran on the bird would be impossible as well, because completing a full swing would imply that the flesh is cut.

Since it's established that we don't know how strong Ruby is, the point about the bird is irrelevant.