In the experiment to study the effect of a net force applied to an object on its motion, the two other measurements that the students should take in each trial, alongside the applied net force, are mass and acceleration.
This is because according to Newton's second law of motion (F = ma), the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Measuring mass will provide the necessary information to calculate acceleration based on the net force applied.