Question

A e limb of mass 12kg falls straight down. If air resistance exerts 27 N of froce on the limb as it falls, what is the net force on the tree limb

Answer 1

During the falling down, two forces are present: gravitational force and air resistance.

So, the net force = mg - f = 12*9.8 - 27 = 90.6 N, the positive sign indicates the direction is pointing towards the center of the earth, which is the same as gravitational force