What is the net force acting on this object?

Question

The forces acting on an object are 39N[N], 13N[S], and 12N[N]. The net force acting on the object is:

a. 38N[N]

b. 64N[S]

c. 64N[N]

d. 14N[N]

e. none of the above

Answer 1

North (N) and South (S) directly oppose each other; think of N as positive and S as negative.

Then we have F_net = 39N - 13N + 12N = 38N

Since the answer is positive, our sign convention tells us the force is North. 38N[N]