A limb with a mass 14 kg falls out of a tree from a height of 3.5 m. How much mechanical energy does the limv have just before it hits the ground? (Assume there is no air resistance.)

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