/sci/ - Science & Math » Thread #11622446

1MiB, 2848x1356, 20200430_173531.jpg

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Statics

Anonymous Fri 01 May 00:59:46 2020 No.11622446 View Reply Original Report

Quoted By: >>11622540

Hey nerdboys/gals, is this correct? F2 is influenced by a resistance band so as it stretches the force increases.

Anonymous

Anonymous Fri 01 May 2020 01:31:32 No.11622540 Report

Quoted By:

>>11622446
how about you upload the problem itself? Can you draw out the FBD you used to relate N and F2?
Its not really clear how you related them.

Anonymous

Anonymous Fri 01 May 2020 01:36:52 No.11622554 Report

Quoted By: >>11622617

Unfortunately there is no homework problem, this is a real life project where I'm trying to understand the forces involved.

So I believe that since F2 is created by a resistance band stretching, the equation of F2 should be F2=(distance)(strength of band in lbs/in)

N = strength of the resistance band in lbs/in

Anonymous

Anonymous Fri 01 May 2020 01:45:53 No.11622594 Report

Quoted By:

No dude, you need to figure out the state of stress in the beam and then apply hook's law (for shear AND normal stress).

Anonymous

View Same Google iqdb SauceNAO sketch.jpg, 17KiB, 665x308

Anonymous Fri 01 May 2020 01:50:19 No.11622617 Report

Quoted By: >>11622626

>>11622554
ok I see, so your system is like this?

It would be helpful to just draw the resistance band as a spring in your model.

Anonymous

Anonymous Fri 01 May 2020 01:53:59 No.11622626 Report

Quoted By: >>11622666

>>11622617
Yep thats correct. Sorry man I'm an accountant, this statics stuff is a little new to me

Anonymous

Anonymous Fri 01 May 2020 02:05:29 No.11622666 Report

Quoted By: >>11622684

>>11622626
ok so here is the issue,
a spring force is caused by a deformation in the spring.
F2 = NX, where X is the amount the spring has contracted/extended.
F2 = Nd is not correct since d is not the deformation of the spring.

Anonymous

Anonymous Fri 01 May 2020 02:12:31 No.11622684 Report

Quoted By: >>11622726

>>11622666
Ok cool, so to find X can I use X = Tan28*L2?

And then substitute that into the function so that:
F2 = N*L2*tan28

Is this correct?

Anonymous

Anonymous Fri 01 May 2020 02:28:37 No.11622726 Report

Quoted By: >>11622768

>>11622684
No since in this model we are working with tan28L2 is just a distance and not the deformation of the spring.

you either start off knowing how much your resistance band has deformed and use that to define F2 and then solve for F1. Or you know what F1 is, use that to Solve for F2 and then find out how much the resistance band has deformed.

can you explain more exactly what you are trying to analyze and I can try to help you make a better model.

Anonymous

View Same Google iqdb SauceNAO 20200430_193735.jpg, 1MiB, 2848x1356

Anonymous Fri 01 May 2020 02:42:52 No.11622768 Report

Quoted By: >>11622832

>>11622726
This is what it is. My friend made this hand strengthener and Im trying to see how much force Im producing on it.

I guess by knowing for X you can figure out what the deformation of the band is. It has a total internal circumference of 5.5 inches at rest. Prior to having any additional force acted upon it.

So would the deformation of the band be 5.5 inches + distance X*2 (2 times because it is wrapped around the end?)

Anonymous

View Same Google iqdb SauceNAO sketch2.jpg, 34KiB, 746x330

Anonymous Fri 01 May 2020 03:03:09 No.11622832 Report

Quoted By: >>11622847

>>11622768
ok so here is what to do.

keep in mind the straighter the band is the more accurate your result will be and this is only an approximation since we are modeling it as if there are independent bands on each side.

measure the normal length of the band as shown in the photo
and then measure the length of it after you grip it.
so now X = (the length after you apply your force)-(the normal length of the band)
F2 = 2*N*X and then solve it with your other equation of equilibrium.

Anonymous

Anonymous Fri 01 May 2020 03:07:08 No.11622847 Report

Quoted By: >>11622911

>>11622832
Ok legit.

So we could say:
F1 =L2*(2*N*X))/L1

Right?

Also thank you for the help

Anonymous

Anonymous Fri 01 May 2020 03:23:06 No.11622911 Report

Quoted By: >>11622950

>>11622847
yup
exactly the same as your original answer. my bad on the initial confusion.

Anonymous

Anonymous Fri 01 May 2020 03:32:04 No.11622950 Report

Quoted By:

>>11622911
You provided more clarity on it and I got something out of this. Definitely helped a lot. Thank you

Now I can make it more complicated by moving the bands around towards the fulcrum and figure the change in length of the resistance bands

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