Physics in Relation to Barbell Length & Plate Density

[HomeschoolMom]

I am trying to understand physics, aerodynamics, and density, and their effect on load and force. I have a variety of barbells and plates. The barbells vary in length (4ft - 5 ft) and the plates vary in density. I recently purchased the Les Mills barbell and plate set, and those plates are larger and sand-filled versus my other plates which are smaller and solid iron(?). I loaded both barbells to the same weight, even tested on a scale. There was a 1.4 pound difference, but the larger, less dense plates "felt" significantly lighter to lift than the smaller more dense plates. I also notice than when the same weight is loaded on a longer barbell and the weight is distributed further apart, the load seems easier to lift. My question is whether the force my muscles use to lift the weight is less since the weight "feels" lighter, despite the actual scale weight being the same. So are muscles worked to the same degree if the weight being used is the same, but the load feels easier do to the aerodynamics and density? I notice the same thing with two different sets of 8# dumbbells. One is coated and shaped slightly smaller and the other is iron hexagon. In this case, the iron hexagon feel lighter since it is 1.75" longer.

 

[jldx2in2000]

I am not a scientist by any means (unless watching Big Bang Theory counts). I would imagine this has more to do with leverage than aerodynamics.

I did find some information on this in a powerlifting program I have. It discusses the "whip" of the bar which is the bars ability to bend (even if we do not see it) and that thicker plates move the force of the weight towards the end of the bar increasing the "whip" and making it feel easier to lift. I would assume the same idea would apply to a longer bar in that it moves the weight farther away from you and could potentially have a greater "whip" potential.

Someone with a science background can probably do a better job of explaining why this is.

 

[MommaPew]

With regard to the 8# dumbbells the coated ones may feel heavier as they usually have a thicker handle so you might feel the need to fist your hand more and therefore your forearms feel tired faster. Hope I'm making sense.

 

[Cafelattee]

I'm guessing it also has to do with weight distribution. I can curl heavier using a barbell then dumbbells. I have all iron plates for barbell and solid iron dumbbells but spreading the weight across the bar allows me to add weights

 

[loneswaneast]

I am trying to understand physics, aerodynamics, and density, and their effect on load and force. I have a variety of barbells and plates. The barbells vary in length (4ft - 5 ft) and the plates vary in density. I recently purchased the Les Mills barbell and plate set, and those plates are larger and sand-filled versus my other plates which are smaller and solid iron(?). I loaded both barbells to the same weight, even tested on a scale. There was a 1.4 pound difference, but the larger, less dense plates "felt" significantly lighter to lift than the smaller more dense plates. I also notice than when the same weight is loaded on a longer barbell and the weight is distributed further apart, the load seems easier to lift. My question is whether the force my muscles use to lift the weight is less since the weight "feels" lighter, despite the actual scale weight being the same. So are muscles worked to the same degree if the weight being used is the same, but the load feels easier do to the aerodynamics and density? I notice the same thing with two different sets of 8# dumbbells. One is coated and shaped slightly smaller and the other is iron hexagon. In this case, the iron hexagon feel lighter since it is 1.75" longer.

Interesting question and one I often have when working out. My question, however, has more to do with compound exercise and its affect on each body part being worked. If one is doing a squat into a shoulder press, does the push from the legs transfer to the shoulder press, making it less effective?