Query weightlifting plates

swimming in a sea

Hi,

Just a query, don't know if this come up before, but the other night the gym was very busy and I was doing my squats. It was very hard to get heavy weights to put on the bar, to make up 120kg I had put a load of 10kgs and 5kgs, so the plates nearly touched the end, I found this lift much harder than when I simply had 25kg plates.

Is there some link to working this out, I didn't do applied maths in school but I think it was this sort of thing they looked into.

Thud

it's all in your head...unless you added the weights up incorrectly

RidleyRider

Definitely in your head. Id you added the weights up correctly the lift should be the same difficulty.

Alf Veedersane

swimming in a sea wrote: »

Hi,

Just a query, don't know if this come up before, but the other night the gym was very busy and I was doing my squats. It was very hard to get heavy weights to put on the bar, to make up 120kg I had put a load of 10kgs and 5kgs, so the plates nearly touched the end, I found this lift much harder than when I simply had 25kg plates.

Is there some link to working this out, I didn't do applied maths in school but I think it was this sort of thing they looked into.

Maybe you added up the weight incorrectly and you had more than 120kg on the plate.

Or it's in your head.

Mr. Manager

Did it occur to you that it might be in your head?

I'm not sure it's been said before but you might have put the weights on incorrectly.

runawaybishop

swimming in a sea wrote: »

Hi,

Just a query, don't know if this come up before, but the other night the gym was very busy and I was doing my squats. It was very hard to get heavy weights to put on the bar, to make up 120kg I had put a load of 10kgs and 5kgs, so the plates nearly touched the end, I found this lift much harder than when I simply had 25kg plates.

Is there some link to working this out, I didn't do applied maths in school but I think it was this sort of thing they looked into.

You are talking about leverage, but that wont make a difference as you are lifting the entire bar.

Donnelly117

swimming in a sea wrote: »

Hi,


Is there some link to working this out, I didn't do applied maths in school but I think it was this sort of thing they looked into.

I dont get this bit...Are you asking if the added distance of the weights which were further out along the bar make it harder? It weighs the same regardless. Applied maths is the maths behind engineering and physics...weight on a bar is just adding.
Of course it may be a mental thing, if the bar looks heavier as it has more plates on it I guess you could fool yourself into thinking its heavier?

swimming in a sea

Yes it probably is all in my head, no I've been doing lifting to long to make a mistake on adding up the weights, just thought I'd ask.

I though it may have been the opposite of using a crowbar, but as above poster said I'm lifting the whole bar so leverage does not come into it.

Thud

runawaybishop wrote: »

You are talking about leverage, but that wont make a difference as you are lifting the entire bar.

agreed.
It might make a tiny difference for something like a one arm barbell shoulder press but it would be negligible

DM-BM

Every one here is assuming that the weight plates actually weigh what they are supposed to.

I have seen plates out by as much as 1.5kg when weighed.

There is no way you can be sure that the bar weighed 120kg on both occasions.

SeaDaily

Donnelly117 wrote: »

I dont get this bit...Are you asking if the added distance of the weights which were further out along the bar make it harder? It weighs the same regardless. Applied maths is the maths behind engineering and physics...weight on a bar is just adding.
Of course it may be a mental thing, if the bar looks heavier as it has more plates on it I guess you could fool yourself into thinking its heavier?

I'd have to disagree with you. I think op has a point. The further the weights are from the fulcrum (which is in this case the point where the bar rests on your back for squats) the greater the turning forces are which act around the fulcrum and so the weight will appear to increase. Imagine you had a 3 meter long bar and you loaded it up with the same weights as a normal bar; it would be far more difficult to lift the same amount of weight.

I think you over-simplified the concept as this can certainly said to be related to physics. Why do you think it is the done thing that the smaller weights are on the outside of the bar?

runawaybishop

SeaDaily wrote: »

I'd have to disagree with you. I think op has a point. The further the weights are from the fulcrum (which is in this case the point where the bar rests on your back for squats) the greater the turning forces are which act around the fulcrum and so the weight will appear to increase. Imagine you had a 3 meter long bar and you loaded it up with the same weights as a normal bar; it would be far more difficult to lift the same amount of weight.

I think you over-simplified the concept as this can certainly said to be related to physics. Why do you think it is the done thing that the smaller weights are on the outside of the bar?

The weight will not appear to increase, its balanced.

SeaDaily

runawaybishop wrote: »

The weight will not appear to increase, its balanced.

So the bar can become infinitely long and it won't make a difference? Sorry that's just incorrect. The bar will never be perfectly balanced on someone's shoulder and the further the weights from the centre the more difficult the lift. Admittedly this will largely be negligible on standard bars but if you were to have a 3m bar as i said it my last post it would most certainly be noticeable.

runawaybishop

SeaDaily wrote: »

So the bar can become infinitely long and it won't make a difference? Sorry that's just incorrect. The bar will never be perfectly balanced on someone's shoulder and the further the weights from the centre the more difficult the lift. Admittedly this will largely be negligible on standard bars but if you were to have a 3m bar as i said it my last post it would most certainly be noticeable.

Ah here, would you get out of it. That's not how physics works. The only weight increase will come from the fact that a 3 meter bar weighs more than a 2 meter bar.

SeaDaily

runawaybishop wrote: »

Ah here, would you get out of it. That's not how physics works. The only weight increase will come from the fact that a 3 meter bar weighs more than a 2 meter bar.

No, you're just wrong. That is exactly how it works. Even if the 3m bar was the exact same weight it would be far more difficult to complete a squat with it compared with a normal bar.

runawaybishop

SeaDaily wrote: »

No, you're just wrong. That is exactly how it works. Even if the 3m bar was the exact same weight it would be far more difficult to complete a squat with it compared with a normal bar.

Except its not? Squatting using a 5 foot bar and a 7 foot bar is no different.

SeaDaily

runawaybishop wrote: »

Except its not? Squatting using a 5 foot bar and a 7 foot bar is no different.

It is different, it is just that the difference is largely negligible. If as I have said several times now, you had a ridiculously long bar you would most certainly notice a difference.

runawaybishop

SeaDaily wrote: »

It is different, it is just that the difference is largely negligible. If as I have said several times now, you had a ridiculously long bar you would most certainly notice a difference.

Difference in what? Thee will be no difference in the weight overall.

SeaDaily

runawaybishop wrote: »

Difference in what? Thee will be no difference in the weight overall.

For god's sake man are you even reading my posts. I said the weights dont actually increase but the lift will be more difficult as the weight appears to be greater.

Alf Veedersane

Talking about longer bars isn't relevant here. If you think there's a difference using the same bar with the same weight on it but one that has the weight extended out further, then you're talking about differences of a scale that people won't notice when they're lifting. There would be a case between different length bars but between the same bar with the same weight? Now you're waiting for Dom to ape you.

SeaDaily

Alf Veedersane wrote: »

Talking about longer bars isn't relevant here. If you think there's a difference using the same bar with the same weight on it but one that has the weight extended out further, then you're talking about differences of a scale that people won't notice when they're lifting.

I did say on several occasions that the difference would probably be negligible in this case.

Alf Veedersane wrote: »

Now you're waiting for Dom to ape you.

No idea what you mean by that btw.

runawaybishop

SeaDaily wrote: »

For god's sake man are you even reading my posts. I said the weights dont actually increase but the lift will be more difficult as the weight appears to be greater.

The weight appears to be more how?

Alf Veedersane

Why is there a 3m long bar being involved in this? The bar is the same length in both cases. The moment of the force is balanced even if it's further and any difference made by the weights going further down the bar will be negligible.

SeaDaily

Alf Veedersane wrote: »

Why is there a 3m long bar being involved in this? The bar is the same length in both cases. The moment of the force is balanced even if it's further and any difference made by the weights going further down the bar will be negligible.

Where you're making the mistake is assuming that the moment of the force is balanced. In the case of a barbell on someones back the moment will not be balanced as the fulcrum wont be right in the middle of the bar.

Donnelly117

SeaDaily wrote: »

For god's sake man are you even reading my posts. I said the weights dont actually increase but the lift will be more difficult as the weight appears to be greater.

I dont see how a weight can appear to be greater. 10 kg weighs 10kg. Theres no point in bringing turning forces into the equation as they cancel each other out when there is equal weight on both sides...

runawaybishop

SeaDaily wrote: »

Where you're making the mistake is assuming that the moment of the force is balanced. In the case of a barbell on someones back the moment will not be balanced as the fulcrum wont be right in the middle of the bar.

The mistake you are making is in thinking the fulcrum is a single point.The bar is braced over the shoulders with stabilisation from the arms over about 2.5-3 foot.

Why wouldn't the fulcrum be in the middle anyway? The fulcrum will only move away from the middle of the weights are uneven on each side, which is not the case here.

SeaDaily

runawaybishop wrote: »

The mistake you are making is in thinking the fulcrum is a single point.The bar is braced over the shoulders with stabilisation from the arms over about 2.5-3 foot.

Why wouldn't the fulcrum be in the middle anyway? The fulcrum will only move away from the middle of the weights are uneven on each side, which is not the case here.

The fulcrum would move away from the middle if the middle of the bar isn't in the middle of your back.

Alf Veedersane

SeaDaily wrote: »

Where you're making the mistake is assuming that the moment of the force is balanced. In the case of a barbell on someones back the moment will not be balanced as the fulcrum wont be right in the middle of the bar.

The plates used on both sides are the same. Or are you basing your whole argument on different plates being used on both sides of the bar?

Donnelly117

SeaDaily wrote: »

The fulcrum would move away from the middle if the middle of the bar isn't in the middle of your back.

The fulcrum of the BAR is in the same place whether its on your back or sitting on the floor. Once there is equal weight on both sides the fulcrum is in the middle. There is no possible way someone could tell the difference by having the bar an inch to the left or right

SeaDaily

Alf Veedersane wrote: »

The plates used on both sides are the same. Or are you basing your whole argument on different plates being used on both sides of the bar?

No. Im talking about the fact that the bar will not be perfectly in the middle of your back and there will be a slightly uneven load.

SeaDaily

Donnelly117 wrote: »

The fulcrum of the BAR is in the same place whether its on your back or sitting on the floor. Once there is equal weight on both sides the fulcrum is in the middle. There is no possible way someone could tell the difference by having the bar an inch to the left or right

The fulcrum isnt a part of the bar.... Do you even know what a fulcrum is?

runawaybishop

SeaDaily wrote: »

No. Im talking about the fact that the bar will not be perfectly in the middle of your back and there will be a slightly uneven load.

That doesn't make it weigh more, or even appear to weigh more.

Why are you insisting the bar wont be in the middle anyway?

SeaDaily wrote: »

The fulcrum isnt a part of the bar.... Do you even know what a fulcrum is?

Do you even lift, brah?

Thud

give up SeaDaily you've lost this one

Alf Veedersane

SeaDaily wrote: »

No. Im talking about the fact that the bar will not be perfectly in the middle of your back and there will be a slightly uneven load.

So you're basing your argument on unequal weights at either end of the bar or the OP having the bar in a stupid position on their back? If you'd said that in the beginning, I'd have been ok with that rather than being bemused by the amount of nonsense you've wasted your time typing...and the amount of time I've wasted replying.

SeaDaily

runawaybishop wrote: »

Do you even lift, brah?

No, not even slightly.

I still disagree with you all but whatever. Continuing the argument has no further relevance to op question.

Mellor

As the weights move further from the centre of the bar the force about the fulcrum increase, like a greater load would create.
But this is cancelled by the force of the other side of the bar. So it's appears to weigh (what ever that means) exactly the same.

As for the bar being off centre on your back. With a longer barbell the effect is reduced because the same distance of error is less relative to the total length.
So by switching to that point, you got it even more wrong.

Blacktie.

Jesus a simple question turned into a maths exam.

Sangre

Mellor wrote: »

As the weights move further from the centre of the bar the force about the fulcrum increase, like a greater load would create.
But this is cancelled by the force of the other side of the bar. So it's appears to weigh (what ever that means) exactly the same.

As for the bar being off centre on your back. With a longer barbell the effect is reduced because the same distance of error is less relative to the total length.
So by switching to that point, you got it even more wrong.

Is it though? A small difference at centre could translate to a big discrepancy at the end of the bar i.e. if bar left of fulcrum was 1cm lower than right this could translate into several cm at end of the bar causing you to be off balance? No idea though.

Loving this thread!

I think theoretically a longer bar shouldn't make a difference but in pratice it most likely will given imperfections, misplacement and the fact that non-uniform lifting of bar would be amplified.

I did loads of maths, applied maths and pyschics in school but haven't looked at it in 10 years.

Sangre

Surely the only sensible solution is to ask Rubadub to test out the above with a homemade 5m bar. I've no doubt he is already McGuyvering something together.

runawaybishop

Sangre wrote: »

Is it though? A small difference at centre could translate to a big discrepancy at the end of the bar i.e. if bar left of fulcrum was 1cm lower than right this could translate into several cm at end of the bar causing you to be off balance? No idea though.

Loving this thread!

I think theoretically a longer bar shouldn't make a difference but in pratice it most likely will given imperfections, misplacement and the fact that non-uniform lifting of bar would be amplified.

I did loads of maths, applied maths and pyschics in school but haven't looked at it in 10 years.

A long bar will mean momentum at the end becomes more difficult to control, that's about it. It would have to be a looooooooong bar though to make a difference.

In this example the bar isn't even free to pivot around the fulcrum because you are holding it. The stabilisation of your back and both hands impedes any rotation.

stevie_b

runawaybishop wrote: »

In this example the bar isn't even free to pivot around the fulcrum because you are holding it.

Donnelly117

SeaDaily wrote: »

The fulcrum isnt a part of the bar.... Do you even know what a fulcrum is?

No I studied Physics and Engineering for 8 years without ever coming across the term :rolleyes:

I know the fulcrum is not part of the bar Im talking about the fulcrum OF the bar...like I wrote in my post. Take the advise of everyone else and give up on your stupid point... Theres no use in arguing a point you know nothing about

kevpants

"Pivot around the fulcrum!", is going to by new motivational slogan to shout at training partners.

Deise Musashi

So besides looking godawful, would there be any difference in the feel of a lift if one side of a bar was 100kg, made up of five 20kg plates, the other side made up of twenty 5kg plates? The mass is the same for each side, the loading begins the same distance from centre, one side is spread over slightly more distance....

In the interest of science I'd try this myself, but I couldn't move 200kg with a pallet truck! :-)

Mythbusters?

SeaDaily

Donnelly117 wrote: »

No I studied Physics and Engineering for 8 years without ever coming across the term :rolleyes:

I know the fulcrum is not part of the bar Im talking about the fulcrum OF the bar...like I wrote in my post. Take the advise of everyone else and give up on your stupid point... Theres no use in arguing a point you know nothing about

See, on the internet anyone can claim to have done anything and have any number of qualifications because no one can disprove it, so claiming you have studied physics for 8 years means nothing.

Hanley

I think both sides raise valid points.

Donnelly117

SeaDaily wrote: »

See, on the internet anyone can claim to have done anything and have any number of qualifications because no one can disprove it, so claiming you have studied physics for 8 years means nothing.

cool story, at least you've given up on your argument...

imonboard

Most of ye talking about balance on one side balancing out the other side is not relavant. It is equilibrium of translation that counts. It is the force you are exerting upwards that has to balance the load of the plates exerting a downward force.
20kg plate at 1 meter from center(you) = 20nm downward force that you have to lift put a 10kg plate at 2 meters from you = 20 nm too. So in theory it could make a difference but the plates being smaller in weight and diameter would balance some of the distance out. Some calculations would be required.

runawaybishop

imonboard wrote: »

Most of ye talking about balance on one side balancing out the other side is not relavant. It is equilibrium of translation that counts. It is the force you are exerting upwards that has to balance the load of the plates exerting a downward force.
20kg plate at 1 meter from center(you) = 20nm downward force that you have to lift put a 10kg plate at 2 meters from you = 20 nm too. So in theory it could make a difference but the plates being smaller in weight and diameter would balance some of the distance out. Some calculations would be required.

You don't load using different plates though, or different orders of weights, it'll be symmetrical. Apart from that the difference will be negligible due to the stabilisation effect the users hold will have. Remember, this is weight over a 12 inch area at the end of the bar. What's not relevant is talking about infinite bars :pac:

edit: the force down is constant anyway on the lifter.