Impulse/force in pounds for the time frame

sophiecentaur

Nothing more from me until you answer my 'simple' question.

douglis

Everyday you prove that you don't have a clue what everybody is trying to explain to you.

YOU DON'T USE 100% FORCE FOR 30 SECONDS.
You use more force than the weight when you accelerate and less force than the weight when you decelerate.For these 30 seconds....either you lift fast or slow....the average force per second is the weight.

Stop saying nonsense like "average force means nothing in this debate".It's the same average force per second and this answers EVERYTHING everything you asked.
The effect of force over time(which is what you described as "total/overall force") is identical.

douglis

Hi DaleSpam,
he described the "total/overall force" as the effect of force over time so the ∫f(t)dt is exactly what he means.
.....and of course is the same regardless the lifting speed since the average force is the weight in any case.

sophiecentaur

Let's be accurate about this:
∫f(t)dt (a definite integral) is the impulse (change of momentum), which varies, depending which part of the lift cycle your integration extends. There is greatest impulse during sections of the fastest repetitions because the velocity change is greatest.

I wouldn't accept some cranky alternative language from douglis or dalespam so why should I accept it from Wayne?

Some of the published stuff uses terms similar to what he uses but makes it clear that it is only over the lift part. I think Wayne is over / mis interpreting a lot of it because his terminology is so inaccurate that I don't think he can be understanding the true messages.

Funny thing is that I find little to argue with in any of the references I've looked at. Yet he seems to find a great deal of support within the same texts. They obviously steer clear of making non-physics gaffs because they are not interested in Waynes "physics approach". They clearly know the business better than he.

I can see that he reckons he works harder doing faster lifts but I can't see how he can assume that he knows what his muscles are doing whilst he's lifting. That is what the EMG tries to do - but his interpretation of those seems a bit fanciful, to be honest (and polite).

I think his posts must qualify for a record for the consistently long yet vague posts I have read on PF.

DaleSpam

Ah, ok. That is a defined term in physics, called impulse:
http://en.wikipedia.org/wiki/Impulse_(physics)

Edit: I see sophiecentaur already mentioned it.

I just want to point out that impulse does not have units of force, it has units of momentum. Assuming that we are talking about the impulse over one full rep then the change in momentum is 0 so the impulse on the weight is 0.

The only two forces acting on the weight are gravity and the human, so the impulse provided by the human is equal and opposite to the impulse provided by gravity. So, the impulse is equal to the weight times the duration of the rep. Therefore the human provides a larger impulse on a slow rep than on a fast rep.

waynekx8, if by "total force" you mean "impulse" then it is greater for a slow rep than for a fast rep. If you mean some other quantity then please define it explicitly.

douglis

That's the whole point of the discussion and it's been explained to Wayne many times.
Regardless if you lift the weight fast or slow for 30 seconds....the "total/overall" force is always the same and equal with gravity's impulse for that duration.

waynexk8

Well how as a physicist would you define/call it ???

I have said this many times, to move a car 1 mile in 30 minutes, with the force of a Man pushing, you will “have” to use a certain amount of force, right ??? As if you knew the exact amount of force, and you used less force, you would not move the car 1 mile in 30 minutes, so you must be used a certain amount of force for 30 minutes. And if you moved the car 1 mile in 45 minutes, you “would” be using less overall or total force, yes ???

I am not being sarcastic here, but when I do ??? It means I am asking you a question if you agree of not, and it’s very hard for me if you don’t answer, so please if you agree or don’t agree, please state why.

How can we add up total or overall speed. Right, let’s take an easy one, and measure speed by every .1 of a second. The object is moving at a constant speed of 100mps, so we could say JUST for arguments sake, the total or overall speed for 10 seconds = 1000. This is like they do all over the World in powerlifting, weightlifting, bodybuilding and athletics, if they have done a training day on squats and bench press; they say they have moved a certain amount of tonnage or poundage in a day. So if they did 10 x 10 squats and 10 x 10 bench press with 200 pounds, they will say they have moved 4000 poundage in one day, and if they want to get very technical, they will work or the exact amount of time they moved this poundage, and say they moved 4000 in 200 seconds, thus producing more power and force in less time than the week before hopefully.

But speed is a different thing, F = ma. If we work out the forces at work on some objects, it will be by multiplying the weight of the object by the acceleration of the object right.
The force at work on a cart pulled by a horse, the weight of the cart is 400 and an Acceleration of 20m/s to work out the Force pushing the cart is by multiplying the weight by the acceleration, 400 x 20 = 8000N in 1 second, if an acceleration of 40m/s its 400 x 40 = 16000N in 1 second. The more seconds you push the weight, the longer in seconds you will have to use this same force, as you cannot push the same weight for 10m with just using a 1 second push of 1600N can you ??? Seems like some are forgetting to add in the force with respect to time, which equals more distance the weight moved, and longer the force is applied ???

Wayne

DaleSpam

The more seconds you push with a fixed force, the larger the impulse of the push. Therefore a slow rep will have a greater impulse than a fast rep.

douglis

....consequently,when the same average force is applied for the same duration the impulse is always the same regardless if you lift fast or slow or if you do more or less reps.

That's the whole story that took so many pages and so many threads.

sophiecentaur

I'd call it Impulse or Work Done or whatever else I actually meant. Your problem is that you haven't really got beyond the stage of deciding what you really want to know or what you mean. We have all told you answers that could apply for a range of things that you could mean. (Please please don't give us another story to illustrate what you mean - I think I shall run out screaming at another mention of Rep Rate)

You start of talking about a force then you suddenly jump to "overall or total force". That's where the nonsense creeps in. Force is Force and it means just one thing. If the man pushed the car for 30 minutes, then I am assuming this would be at a steady speed on a flat road, just against friction??? What you could say is that the WORK he did was Force times the distance the car traveled.
If he pushed with less force, then the car would not be going as fast and it would cover less distance. The WORK done would be the new force times the new distance.
You seem to have some objection to describing things that way. Why? It's the way that the rest of us talk because it fits in with the rest of Physics.
You would be doing less WORK but your description, involving the word 'force' makes no sense.
I have done that for you.


Here you go again with 'total speed'. What you seem to mean here is that the DISTANCE is 1000 (100m/s for 10s). Speed times time = distance, doesn't it? So "total speed = distance" for you? Not good enough. You want to join the Physics club and get answers. Club rules apply, I'm afraid and you have to use the right terms or no one will understand what you're on about.

No - they did more WORK and possibly in less time. This means more Power. The details of what forces were involved are not included in their statement.

Speed is a different thing, is it? But Maths applies to everything. The word 'total' means adding things together, whether it's cabbages or Joules. Some things just can't be 'added together' and adding speeds-at-different-times is as much forbidden as adding forces-at-different-times. This isn't poetry or stream of consciousness - it's strict and rigorous stuff.

Sorry, the last bit just reads like ramblings. I can't see what you're getting at except to tell me a story in non-technical terms. Why does a horse and cart have to be different from a man and a car? The man and car scenario says it all.

You are getting some damned good value out of all this you know.

DaleSpam

Agreed.

DaleSpam

waynexk8, please try to learn the correct term for the different concepts in physics. If I came to your gym to ask for weightlifting advice you would be right to teach me the difference between a "curl" and a "squat". And if I called a "curl" a "total squat" you would be right to correct me and insist on using the correct language. And if I persisted in calling "curls" by the word "total squats" it would make things confusing, particularly if I began talking about how I am concerned that my knee surgery will interfere with my "total squats":

Me: "But my doctor says I wont be able to bend my knee as far"
You: "So what, curls don't use your knee"
Me: "Yes, but I am talking about total squats, and squats do use your knee"
You: "Yes, squats do use your knee, but you are talking about a different thing. What you call total squats are properly called curls. Curls don't use your knee"
Me: "But squats do use my knee and my doctor says I won't be able to bend my knee as far"
...

waynexk8

Not sure if I am doing the right thing here, going to answer some of the more recent posts, if you all think it’s a bad idea please say. I will get back to the other posts.

Very right of you, I do agree, but please I do find this hard at times, but if you tell me something I said wrong, I will try and remember, but if for some reason I get it wrong of forget, please tell me again and I will make a note. So sorry all, I am trying, but the most annoying is when people do not answer my writings, unless you have, and I have not got to them

Yes see what you mean, could you point me out on the things I am getting wrong please.

Total get your point, and it’s a good one, and I do need to concentrate on this more.

Wayne

sophiecentaur

Perhaps I could suggest, Wayne, that you look up the definition of each of these 'physics' words, write that definition down for reference then only make comments using them as you've written them in your notes.
Don't make me larf!

We spend most of our time telling you where you are using the wrong terms. If you are really so low in intelligence that you cannot recognise that then you will never get any of this. But look up the word 'intransigence'. It describes exactly what I see in your attitude to this problem.
You are very free with your apologies about this but there is no sign that you are actually doing anything about it. "Sorry" means you intend not to do something again. It's not just a get-out-of-gaol-free card.
We could be here till next Christmas and you will not get an answer in your own private made-up terms. Nor will you get it anywhere else.

Tell us, do you write all these put-downs in a book and then relate them to your weight lifting chums for a good giggle? You certainly know how to evoke them. You cause me to become very inventive!

waynexk8

Originally Posted by douglis

....consequently,when the same average force is applied for the same duration the impulse is always the same regardless if you lift fast or slow or if you do more or less reps.

But D. has not stated the average force, and some here are telling me, that there cannot be an overall or/and total force, so “please” where and how do you get this average force from ??? I do not get where you get this from or how you work it out, or from which repetition ???

Here is how I sort of see it, let’s just say I used the following numbers of force in Newton’s, for 1 third of a second each. 7 then 13 then 91, average of the 3 numbers = 37, but the overall and or total of force used in the 1 second would be 111, so where do you get that the average is the same ???

PLEASE, you need to say which repetitions you are talking about. As if you measure the impulse from a weight lifted off the ground, lifted up 1m in .5 of a second, and then lowered down 1m in .5 of a second, and then you measured the impulse from a weight that started at the top, was lowered down 1m in .5 of a second, and then lifted up 1m in .5 of a second. Then there would be more force/impulse needed when lower and then lifting the weight.

As there will be huge deceleration/acceleration peak force from the transition from negative to positive, the MMMTs {momentary Maximum muscle Tensions} and the faster you lower the higher the force/impulse for a Milly second will be.

I would say 99% that you are taking the impulse/force from the weight lifted, and lowered "only" ???

Wayne

sophiecentaur

That statement just demonstrates that you do not know the meaning of the term 'Mean'. You think you can't have a Mean if you can't just add things up? Look up the true definition of the Mean and how it can be calculated. Don't apply your elementary School definition.

waynexk8

Well ok, this is more of the things I need to know, as yes I thought mean/average was adding up the numbers and dividing them, so how else can you get to or have mean/average ???

Wayne