First we must assume that as the limb falls from a tree, then it was initially in repose.
For that moment the mechanical energy will be equal to the potential energy of the object, which will be given by:
E = m * g * h
where,
m = mass
g = gravity
h = height
Substituting the values:
E = m * g * h
E = (14) * (9.8) * (3.5) = 480.2
E = 480.2J
Then, for conservation of energy. the mechanical energy before touching the ground, it is the same mechanical energy that it had when it started to fall
E = 480.2J
answer
the mechanical energy is E = 480.2J
