The experiment you conducted is an exercise in the discipline of Dynamics not Statics. If you wanted to do a Static experiment you would need the force measuring tool pictured in 93rev2sev’s post above. None the less, your experiment results do give validity to my free body diagram. I am not surprised with your results and could give you a series of free body diagrams that would show and explain the forces you were observing during this Dynamic experiment. But this won’t work because it is impossible to explain 2 semesters of fundamental engineering courses over the internet. Now, not only do I recommend you seek someone with intrinsic knowledge of statics to explain my free body diagram to you, have them also explain the results of your experiment to you. The same person can explain both to you, because the Statics instructor also teaches Dynamics.