This is a simple activity that I use as an introduction both to Newton's Laws as well as free fall problems in kinematics (depending on the class level). Its main purpose is to guide the students to the conclusion by experience and observation that all objects fall with the same acceleration, neglecting air resistance.
There is no math involved in this activity- it is ALL observation based. I think it would be suitable for younger students as well as the high school classes in which I have used it. It typically takes 20 -30 minutes, depending on class level and class size. I make it a graded, "every man for himself" type of exercise.