The forces acting on a child sitting in a seat are described by the free-body diagram shown. a free body diagram with 2 force vectors. the first vector is pointing downward, labeled f subscript g baseline = negative 100 n. the second vector is pointing upward, labeled f subscript n baseline = 100 n. the vectors are the same length. what is the net force acting on the child?

The net force acting on the child is zero [N]

Explanation:

We can understand this problem better by using the attached image, where we can see a free body diagram.

In the y-axis are located the forces acting on the child, the first force is acting downward and his value is 100 [N] or - 100[N], the minus sign means that the force is downward.

The second force is the normal force exerted by the surface of the seat acting upward. The value of this force is 100 [N], which is positive because is acting opposite to the downward force.

This is called static equilibrium and it is defined by the third law of Newton.

In more explicit terms: the third law states that for every force that acts on a body, it realizes a force of equal intensity and direction but of opposite sense on the body that produced it.