The net force acting on the block is 80 N plus the magnitude of the frictional force, and its direction is determined by the direction of the frictional force.
The net force acting on the block can be found by adding up all the forces acting on it. In this case, the gravitational force is 40 N and is acting downwards, the normal force is also 40 N and is acting upwards, and the frictional force is given as being exerted to the left. By subtracting the frictional force from the sum of the gravitational force and normal force, we can find the net force.
Net force = Gravitational force + Normal force - Frictional force
Net force = 40 N + 40 N - Frictional force
Since the direction of the frictional force is to the left, we subtract it:
Net force = 40 N + 40 N - (-Frictional force) = 40 N + 40 N + Frictional force
Simplifying, we get:
Net force = 80 N + Frictional force
Therefore, the net force acting on the block is 80 N plus the magnitude of the frictional force, and its direction is determined by the direction of the frictional force.