If a 50 n weight is sitting motionless on a table, what is the net force acting on the object?
a. 0 n
b. -50 n
c. +50 n
d. +100 n

A net force is a sum of all forces acting on an object.
F net = F 1 + F 2 + ... + F n
If the net force acting on an object is zero ( 0 ), then the object is in a state of equilibrium. In this case, weight is balanced out by table`s support force (/ or the normal force ):
F net = - 50 N + 50 N = 0 N
A. 0 N.