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Dimentiinal analysis anyone?

FN5.7

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The thrust propelling a rocket is given by the equation
F=nN((sqrt) kRT).
Where R is a gas constant wich for air is 53.35 ft×lbf/(lbm ׺R); k is a dimentionless ratio; T is the air temp (ºR); and N is a dimentionless mach number.

What are the fundamental dimentions of n and what does n physically represent?

This is a glimps of my homework. We solved this in a study group.
I enjoy brain workouts, if you think you can solve this post an answer.

Hint: you will need to convert this in to its fundamental form. ie F=(ML)/t^2
Enjoy.
 

dramad1

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Maximum amount of flow that can pass through and edge. Lol
 

dramad1

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How about 1 newton unit of force??? Ill be honest I'm guessing. Curious though. Lol.
 

rennurx

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I thought this was one of those spam threads when I first read it haha.
 

redarkx

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FN5.7 said:
The thrust propelling a rocket is given by the equation
F=nN((sqrt) kRT).
Where R is a gas constant wich for air is 53.35 ft×lbf/(lbm ׺R); k is a dimentionless ratio; T is the air temp (ºR); and N is a dimentionless mach number.

What are the fundamental dimentions of n and what does n physically represent?

This is a glimps of my homework. We solved this in a study group.
I enjoy brain workouts, if you think you can solve this post an answer.

Hint: you will need to convert this in to its fundamental form. ie F=(ML)/t^2
Enjoy.

I do not miss stuff like this from school. While it was fun at the time, I enjoy working and being done when I leave waaaaaay more.
 

FN5.7

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What do you do for work? This is engineering type classes are you a engineer? Just curious. Im excited to go work and be done with this too but at least its enjoyable unlike algebra.

Nope not 1 newton of force. Im at work now but ill post the work and answer when I get home. Keep working on it.
 

dramad1

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What do you do for work? This is engineering type classes are you a engineer? Just curious. Im excited to go work and be done with this too but at least its enjoyable unlike algebra.

Nope not 1 newton of force. Im at work now but ill post the work and answer when I get home. Keep working on it.

I wish I was an engineer. I'm a union iron worker. Lol. So called" cowboys in the sky", lol.
I always enjoy a good brain exercise. Went to school for a little while doing computer information systems. Pretty much program writing for security systems. I never finished because I had kids and needed to work more to support the family. Plus schooling started to get pretty challenging as far as work that had to be learned and completed. Ill finish one day I hope.
I'm curious now as to what the answer is. I feel like its almost a trick question. Power to you for enjoying it more than algebra. I think I'd be lost or way off track.
 

FN5.7

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You need to figure out what n is in its basic dimentional for. Do you know what dimentional form is?
 

dramad1

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Many physical relationships in engineering and especially fluid mechanics are, by nature, extremely complex. Often a phenomenon is to complicated to, theoretically, derive a formula describing it e.g the forces experienced when an object moves through a fluid. Demensional analysis is then used to identify variables which can be combined in groups which are definitely related. Experiments can then be completed to formulate this relationship and allow determination of the actual performance characteristics of real world systems..
This method derives from the principle that each term in an equation depicting a physical relationship must have the same demension. Non-dementional quantities expressing the relationship among the variables are constructed e.g [ length/ (velocity. Time)] or, [force/(mass/acceleration)]. These are equated and then experiments are completed to determine their functional relationship.
The principles of demensional analysis are developed from the principle of demensional homogeneity which is self evident.
It is characteristic of physical equations that only like quantities, that is those systems having the same demensions, are added or equated.
It is okay to equate forces (5 newtons= 2 newtons + 3 newtons).
It is clearly not okay to equate forces with lengths (5 newtons=2 newtons + 3m)

n= angle. ??????

I'm still trying to pick this up and am trying to Learn so please correct me if I'm am wrong with anything I said. It's just weird to me. Hmmmm.....
 

FN5.7

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Haha.

Still at work. I should be home in an hr or so. Your explination of dimentional analysis sounds right.

Basically your trying to see if all the dimensions in an equations make sense. In other words, you cant subtract apple from oranges.

N and k are dimension less so the equation you are really working with is
F=n ((sqrt) RT).

A fundamental dimention would be length or mass.

What two fundamental dimentions represent and what dose n represent physically.
 
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Gadget

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To be able to calculate the reaction force of a rocket engine you have to factor in the pressure outside of the reaction chamber, or ambient pressure.

This value will change as the ambient pressure changes. As the rocket engine climbs in altitude the rocket engine will produce a greater reactive force and this has to be accounted for to factor in your acceleration curve.

G
 

dpartinvr4

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clearly he's trying to determine the influence zone for surface wave paths
 

FN5.7

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E = mc(vag ina)

correct!

lol
k i will do my best to represent the answer so that it is understandable. please account for mispelled words or accidentally using the wrong words. example (saying physical dimension in stead of fundamental dimension.)

F=nN((sqrt)kRT) sqrt= square root for anyone that might have been confused.

first, N and k are dimentionless so they get dropped. leaving us F=n((sqrt)RT).

now we need to convert to fundamental dimensions. So F(force)= ML/t^2 (mass times length divided by time squared) new equation ML/t^2=n((sqrt)RT

the problem has more given information, R=53.35ftlbf(foot pounds force)/(lbm(pound mass)degR(degree R, my key bord dosnt have a little degree symbol.)53.35 is a number therefore it is dimentionless so it gets dropped. new equation ML/t^2=n((sqrt)ftlbf/((lbm)(degR))T)

the equation also states that degR is represented by T. new equation. ML/t^2=n((sqrt)(ftlbf/((lbm)(T))T)


i have to leave for class. i will finish this when i get back.

the answer is n=M/T(mass over time) so n has fundamental dimensions of mass over time. since mass alone dosnt change over time then n physically represents mass.

We havnt had this graded yet but we feel confident that its correct.

I will finish the work when i get back. Glad to see we have so many math fans on here, not surprising considering its a mechanical/analytical type of forum. haha and call someone else on here a nerd. pot/kettle maybe?
 

FN5.7

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Haha, that is a gun model. The best gun ever for home deffense imo.
 

FN5.7

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here is the rest of the work. sorry it took so long guys.

when we left the equation last we had ML/t^2=n((sqrt)(ftlbf/((lbm)(T))T)

now we can convert ftlbf and lbm to its fundamental dimentions and eliminate like dimentions.giving us a new equation of ML/T^2=n((sqrt)L^2/T^2) remove the radican and we get

ML/T^2=n(L/T)

algebra gives us n=(T/L)(ML/T^2)

now eliminate like terms giving us M/T=n

so we see that n=mass over time. its fundamental dimentions

mass dosnot change over time unless its coupled with another FD(fundamental dimentin) therefore n=mass.

again this hasnt been graded yet but if its wrong i will apologize to ya'll for posting an impossible riddle. who knows it very well could = vagi a
 
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