The motion will follow the path of the stronger force on the object.

Below is a top-view diagram of a box sitting on a floor. Students are asked to describe the path/motion of the box, assuming that the forces remain constant. 

 Correct Answer

Students suffering from this misconception will state that the box travels in a straight line to the right, ignoring the smaller 10 N force acting on the box.

 

Related misconceptions/student difficulties that may arise in the question:

An object with a constant net force will have a constant speed.

A constant force accelerates a body, until the body uses up all the power of the force.

The net force must be in the direction of motion, so objects will travel along a line in that direction.