Impulse/force in pounds for the time frame

[Dale]

Hi waynexk8,

After you read the links try the following problems:
1) 100 lb * 5 ft =
2) 20 ft*lb / (2 ft) =
3) 32 ft/s² * 10 s =
4) 5 ft/s * 320 lb / (32 ft/s²) =

Do not rush or hurry this, make sure that you get the units correct. This is important.

 

[waynexk8]

No, 90 lb for 10 s is 900 lb*s, not 900 lb!

Yes, that is what I said 900lbs not 900lb all I left out is the s, 900lb = 900lb + 900lbs = 900lbs, they are both the same 900lbs = 900lbs, 900lb = 900lb. It’s the same as 1 stone = 1 stone or 1 stones = 1 stones, there is no difference between 9 stone and 9 stones. 9 stone = 9 stone and 9 stones = 9 stones. How can you say 9 stone and 9 stones = different ?

No, no.
100 lb * 5 s = 500 lb*s
80 lb * 5 s = 400 lb*s

That’s what I said; 100 x 5 = 500, and 80 x 5 = 400. We both said the same thing ?

While it is true that
400 lb + 500 lb = 900 lb

it is completely irrelevant to the problem. What is relevant to the problem is:
400 lb*s + 500 lb*s = 900 lb*s[/quote]

Sorry, not sure what you are getting at, 900lbs = 900, 900lb = 900, what are you saying thinking is different ?

Please read those links I gave you very carefully and ask questions. It is clear that you do not get the units, and this is very important in physics.

Yes I will, but 100 or what ever = 100s unless you state otherwise. How can a 100lb = more than a 100lbs ?

Look at the units I bolded. Pounds and seconds are different types of quantities. One is a unit of force and the other is a unit of time. There is simply no way whatsoever to make any number of pounds equal to any number of seconds.

What do you mean ? If I use 1 pound of force for 1 second, and the use 1 pound of force for 3 seconds, of “course” I have used the same amount of force for longer, as in 1 second first, then 2 seconds.

Look, if I use 1 pound of force for 1 second, then use 1 pound of force for 100 seconds, of course I have used more force, or the same force for a longer time frame. How can you think different ? I

We need to stay on the above until you get the units of force (lb), time (s), and impulse (lb*s) straightened out. Again, please read those links and come back with questions.

Yes will read them.

But I don’t understand you, I use 1 pound of force for 1 second, its more than using 1 pound of force for half a second, how can you think different ?

PS you may think that this is being overly picky, but it is not. I still remember it vividly. My very first lecture of my very first physics class, the professor spent the entire class going over units and emphasizing the importance of always correctly handling the units. He claimed that checking your units was the easiest way to catch the large majority of physics mistakes, and my decades of physics experience since has proven him right again and again. I cannot overemphasize the importance of correct units if you want to do physics at all.

I totally agree with you, but not sure what you are getting at, if you explain, I might see you point.
But if you use or try and use 80 pounds of force for 6 seconds and I use or try and use 100 pounds of force for 6 seconds both moving 80% of the maximum force we can move, HOW can you think or say that 80 = 100 ?

Wayne

 

[waynexk8]

Hi waynexk8,

After you read the links try the following problems:
1) 100 lb * 5 ft =
2) 20 ft*lb / (2 ft) =
3) 32 ft/s² * 10 s =
4) 5 ft/s * 320 lb / (32 ft/s²) =

Do not rush or hurry this, make sure that you get the units correct. This is important.

Not sure what your symbols mean.

Does a 100 lb * 5 ft = 100 lb x 5 ft ? But what does that mean or say ?
Does 20 ft*lb / (2 ft) mean 20 ft*lb divided by (2 ft) ? and what does that mean ?
Does 32 ft/s² * 10 s = mean 32 ft/s² x 10 s and what does that mean ?
Does 5 ft/s * 320 lb / (32 ft/s²) = 5 ft/s x 320 lb / (32 ft/s²) and what does that mean ?


All I am saying is, I try and use 100 pounds of force moving 80 pounds for 6 seconds, the fast, and then you try and use 80 pounds of force moving 80 pounds for 6 seconds the slow, we both agree on this, then you try and turn around and say you used 80 pounds of force for 6 seconds, but your 780 pounds of force somehow = 100 pounds of force ? To me this does and cannot make sense, how can 80 pounds of force used for 6 seconds = 100 pounds of force used for 6 secounds ?

Wayne

 

[Dale]

Not sure what your symbols mean.

Does a 100 lb * 5 ft = 100 lb x 5 ft ?

Yes. Since x is often used as a variable the general practice is to use * for multiplication. So 100 lb * 5 ft means 100 pounds multiplied by 5 feet.

Given that explanation and given the links I posted, please go back and work the problems in 332. Don't worry about what they mean, just see if you can get the right answers.

 

[Dale]

Yes, that is what I said 900lbs not 900lb all I left out is the s, 900lb = 900lb + 900lbs = 900lbs, they are both the same 900lbs = 900lbs, 900lb = 900lb. It’s the same as 1 stone = 1 stone or 1 stones = 1 stones, there is no difference between 9 stone and 9 stones. 9 stone = 9 stone and 9 stones = 9 stones. How can you say 9 stone and 9 stones = different ?

No, you are completely missing the point and consistently getting the units wrong "lb*s" is not the plural of pound (a unit of force), it is a unit of impulse, the "pound second". It is literally 1 pound times 1 second. Your answers above are all wrong because of this critical mistake. 10 lb*s is not at all the same as 10 lb. They are incompatible units. Please read the links and work the problems.

That’s what I said; 100 x 5 = 500, and 80 x 5 = 400. We both said the same thing ?

No, we said very different things. Your units were all wrong. We did not say the same thing any more than 10 miles is the same thing as 10 days.

Do you understand the difference between miles and days? That is the difference between lb and lb*s. They are different units.

Sorry, not sure what you are getting at, 900lbs = 900, 900lb = 900, what are you saying thinking is different ?

The units are different. 900 lb is almost half a ton, it weighs a lot. 900 is a pure number, it weighs nothing. 900 lb ≠ 900.

How can you possibly think that a pure number is the same thing as nearly half a ton? Have you ever heard the expression "comparing apples and oranges"? That is what you are doing wrong, and you are doing it very consistently wrong. We really need to address this before proceeding.

 

[waynexk8]

No, you are completely missing the point and consistently getting the units wrong "lb*s" is not the plural of pound (a unit of force), it is a unit of impulse, the "pound second". It is literally 1 pound times 1 second. Your answers above are all wrong because of this critical mistake. 10 lb*s is not at all the same as 10 lb. They are incompatible units. Please read the links and work the problems.

“RIGHT” get you now, it’s not the plural, it’s the pound second, will rewrite and reanswer the post for you later, and thx, don’t think I have enough time now.

No, we said very different things. Your units were all wrong. We did not say the same thing any more than 10 miles is the same thing as 10 days.

Do you understand the difference between miles and days? That is the difference between lb and lb*s. They are different units.

The units are different. 900 lb is almost half a ton, it weighs a lot. 900 is a pure number, it weighs nothing. 900 lb ≠ 900.

How can you possibly think that a pure number is the same thing as nearly half a ton? Have you ever heard the expression "comparing apples and oranges"? That is what you are doing wrong, and you are doing it very consistently wrong. We really need to address this before proceeding.

So let’s get this right for later, when you ask me something, and you say 100lb*s you mean you have applied a force of 100lb for 1 second ?

Wayne

 

[Dale]

So let’s get this right for later, when you ask me something, and you say 100lb*s you mean you have applied a force of 100lb for 1 second ?

What we mean is that we have applied an impulse of 100 lb*s. That could be a force of 100 lb for 1 s as you said, or it could be a force of 50 lb for 2 s or a force of 25 lb for 4 s or a force of 10 lb for 10 s ...

 

[waynexk8]

One quick one please, for all.

If I hold the 80lb half way up {forget the acceleration/force it took to get there, say someone handed it to me.} for 6 seconds, are you all saying I used the same impulse/force ? As you might or might not know, if you did a fast, then slow rep, and the static hold all the momentary muscular failure, you would be able to hold the weight stationery far far far longer.

Wayne

 

[sophiecentaur]

Do you mean force or do you mean impulse? What "man of Science" would ignore the distinction? This is ridiculous.
You do not "use" a force. You apply a force. When you do it with your muscles, it involves energy expenditure. When you rest the weight on a table, no energy is involved. A table never gets tired, does it?
Muscle failure is not a Physics phenomenon. It's a physiological thing.

 

[waynexk8]

DaleSpam wrote; if you exert a constant 100 lb for 10 s then you have exerted an impulse of 1000 lb*s. And if you exert a constant 80 lb for 10 s then you have exerted an impulse of 800 lb*s.

With the above, its seems you are saying that the fast rep = an impulse of 1000lb*s, slow rep = an impulse of 800lb*s. But then you say no, and that I/that is not right and S. and D. are ?

The only problem in the above, is that the slow may exerted a constant {lets just say constant for now, as its quite close}force for say 80% of the rep, say 10% for acceleration, and 10% for deceleration. However the fast will accelerate for say 80% and decelerate for 20%

Also we have “still” left out the force “on” the muscles from the transition from negative to positive, as in the above we have only worked out the force exerted by the muscles.


1,
Fast rep = 100 force x 10 seconds = 1000lb * 10s.

2,
Slow rep = 80 force x 10 seconds = 800lb * 10s.

Wayne

 

[Dale]

If I hold the 80lb half way up {forget the acceleration/force it took to get there, say someone handed it to me.} for 6 seconds, are you all saying I used the same impulse/force ?

If you hold 80 lb stationary for 6 s then you have exerted an impulse of 480 lb*s. That is the same impulse as 40 lb for 12 s or 160 lb for 3 s.

 

[waynexk8]

Hi waynexk8,

After you read the links try the following problems:
1) 100 lb * 5 ft =
2) 20 ft*lb / (2 ft) =
3) 32 ft/s² * 10 s =
4) 5 ft/s * 320 lb / (32 ft/s²) =

Do not rush or hurry this, make sure that you get the units correct. This is important.

Right, I have/am having a go of this, but I think it could be best if you did one calculation, as I am not sure what I am supposed to be calculating, on 1, it can be 100 x 5 = 500, and if you put 100 lb * 5 ft = on Google, it gives you, 69.1274772 m kg, but I don’t know if that’s right or how it came to that, will have another read and think, but thought best post this now.

Wayne

 

[waynexk8]

Going to have to come back to the other.

If you hold 80 lb stationary for 6 s then you have exerted an impulse of 480 lb*s. That is the same impulse as 40 lb for 12 s or 160 lb for 3 s.

Ok, so could you say the following please, all with 80 pounds for 6 seconds. But please remember the person/machine can use up too 100 pounds or force anytime. And “please add in the forces on the muscles, as you did say that the rep stating with an eccentric going into the concentric gives out a higher force/impulse

1,
Static hold = 480lb*s.

2,
Fast reps =

3,
Slow rep =

As what I would say is; impulse is the integral of a force with respect to time. A small force applied for a long time can produce the same momentum/momentum change as a large force applied briefly, because it is the product of the force and the time for which it is applied that is important.

But what you 3 seem to be saying; A small force applied for the same time can produce the same momentum/momentum change as a large force applied for the same time.

Wayne

 

[douglis]

Going to have to come back to the other.

Ok, so could you say the following please, all with 80 pounds for 6 seconds. But please remember the person/machine can use up too 100 pounds or force anytime. And “please add in the forces on the muscles, as you did say that the rep stating with an eccentric going into the concentric gives out a higher force/impulse

1,
Static hold = 480lb*s.

2,
Fast reps =

3,
Slow rep =


Wayne

1,
Static hold = 480lb*s.

2,
Fast reps = 480lb*s.

3,
Slow rep = 480lb*s.

In all three cases the change in momentum is zero hence the average muscle force is equal with the weight.Impulse equals average force X time.In all cases is equal with 480lb*s.

The last five years you've been explained that half a billion of times by at least twenty different people.Even if you had started from an absolute zero physics level you could have become a physics professor by now...if you only had shut up and listen to them.
But no...you're not here to learn.Your obsession kept you to the absolute zero level.What a waste of time...

 

[waynexk8]

1,
Static hold = 480lb*s.

2,
Fast reps = 480lb*s.

3,
Slow rep = 480lb*s.

In all three cases the change in momentum is zero hence the average muscle force is equal with the weight.Impulse equals average force X time.In all cases is equal with 480lb*s.

I thought you were going to say that.

What do you mean the momentum/movement is zero, its zero in the start hold, but with the slow there is 2m of momentum/movement, and the fast there is 12m momentum/movement.

Say I just repped up 1m would you still say there was zero momentum/movement ? And if so why ?

Why do you not answer questions that puts your little theory as wrong ? Like the below ? Why when you stated yourself the only way to sort this out is EMG, then when EMG states you wrong, you think paper equations written on paper are better, It’s like saying you said we can’t get Men to the Moon, I than go and send Men to the Moon, but you still say I am wrong, even thou I send Men to the Moon ?

Don’t you understand that when muscles are at accelerations, and have to be using more force, that they are under more strain, TENSIONS? And the only way your slower lower force reps can make up this stain, is if they do the reps for longer than the faster reps, this IS proved in that I fail 50% faster, I fail faster because I HAVE put more tension on the muscles per unit of time, thus I have put out more force per unit of time.

I NEED to explain that better tonight, and I don’t think you or the physicists are seeing this.

Let me ask another question please all.

1,
Static hold done for 5 seconds, force used ? =

2,
Static hold done for 10 seconds force used ? =

3,
Fast reps done for 5 seconds, force used ? =

4,
Fast reps done for 10 seconds, force used ? =

5,
Slow reps done for 5 seconds, force used ? =

6,
Slow reps done for 10 seconds, force used ? =

The last five years you've been explained that half a billion of times by at least twenty different people.Even if you had started from an absolute zero physics level you could have become a physics professor by now...if you only had shut up and listen to them.
But no...you're not here to learn.Your obsession kept you to the absolute zero level.What a waste of time...

IF you “think” you are right, you need to answer, address and then “try” and counter when real world experiments prove you little theory wrong, as of yet you have not, a “theory” and that’s “all” you have, “NEEDS” to be proven with real World practical experiments/tests, like I have done, as of yet you have not, you hold no ground at the moment, all you have is a theory on paper, which has by me “^” times be proven “WRONG”.

1,
As I said, the EMG proved me right,

2,
Moving the weight 10m more in the same time frame proved me right,

3,
Using more energy in the fast proved me right,

4,
As you fail with the fast 50% faster proved me right,

5,
I used 100 force moving 80 for 6 seconds, you used 80 force moving 80 for 6 seconds, 100 is more than 80, the 100 = 20 more than 80, 100 = 25% more than 80, that proved me right.

I could go on.

Wayne

 

[douglis]

I thought you were going to say that.

What do you mean the momentum/movement is zero, its zero in the start hold, but with the slow there is 2m of momentum/movement, and the fast there is 12m momentum/movement.

Say I just repped up 1m would you still say there was zero momentum/movement ? And if so why ?

Wayne

Not zero momentum...zero CHANGE in momentum.That's what the impulse represents.

For all the rest I don't have the patience.Just read carefully DaleSpam posts.

 

[Dale]

Right, I have/am having a go of this, but I think it could be best if you did one calculation, as I am not sure what I am supposed to be calculating

OK, here is a step-by-step detailed example of how to calculate a quantity with units in physics:
5 s * 64 lb / (32 ft/s) =
(5 * 64/32) * (s*lb/(ft/s)) =
(5 * 2) * (s*lb*s/ft) =
10 lb*s²/ft

 

[Dale]

As what I would say is; impulse is the integral of a force with respect to time. A small force applied for a long time can produce the same momentum/momentum change as a large force applied briefly, because it is the product of the force and the time for which it is applied that is important.

This is correct.

But what you 3 seem to be saying; A small force applied for the same time can produce the same momentum/momentum change as a large force applied for the same time.

None of us have ever said this. The reason that you believe that we have said it is because of a misunderstanding you have of impulse for time-varying forces and/or a misunderstanding of the forces over a fast vs a slow rep. That is what I am trying to teach you, but we have not gotten to the time-varying part yet.

It would be helpful if you would just focus on the new questions I have asked of you recently instead of repeating your old questions every couple of posts. I am well aware of your old questions, and I am trying to get you to the point where you will understand the answers as quickly as possible. Please focus on making forward progress rather than continually looking back and rehashing the scenario. It is a waste of your time since it provides no new information to me and prevents you from taking the time to learn from what I have already posted.

 

[waynexk8]

Back later to answer the post/s.

Let me try and convince you this way that you are wrong, or that your equations work on paper, but not in practice.

I am going to lift 90% of my 1RM, in this case my 1RM = 100 pounds. So 90% = 90 pounds, you’re going to try and lift 90% of your 1RM which is also a 100 pounds.

1,
I apply my 1RM force, as this is a fast rep, I lift the 90 pounds up and down say 3 times in 6 seconds, I have applied 100 pounds of force for 6 seconds, well not quite that much as my force will have been diminishing But I have overcome gravity for 6 seconds lifting the 90 pounds

2,
You apply 80% or your 1RM as this is a slow, you cannot lift the weight at all, in 6 seconds you have applied 80 pounds of force only. You have not overcome gravity in the 6 seconds, and you have not lifted the weight.

3,
I lifted the weight 3 times in 6 seconds, I thus used more {nearly said it again, the total/overall force, but let’s be correct.} impulse than you in 6 seconds as I overcome gravity and lifted the weight up and down 3 times. THUS putting MORE tensions on the muscles.

Or do you think you put the same tensions on the muscles not lifting a weight as you have not, are not used enough force ?

Wayne

 

[Dale]

This scenario is not in dispute. We all agree that the impulse is greater for 1 than for 2.

 

[Redbelly98]

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