# need help finding a formula for my calc - Hewlett Packard

This is a discussion on need help finding a formula for my calc - Hewlett Packard ; Let's say you have a ball (shpere) that weighs 10 pounds the material is brass which have a density of .305 cubic feet. this is all the information I have. How can I find the diameter of the ball. I ...

# Thread: need help finding a formula for my calc

1. ## need help finding a formula for my calc

Let's say you have a ball (shpere) that weighs 10 pounds the
material is brass which have a density of .305 cubic feet. this is all
the information I have. How can I find the diameter of the ball. I
would like to program the formula on my hp50. thank in advance

2. ## Re: need help finding a formula for my calc

On Mar 24, 6:03 am, gotu...@aol.com wrote:
> Let's say you have a ball (shpere) that weighs 10 pounds the
> material is brass which have a density of .305 cubic feet. this is all
> the information I have. How can I find the diameter of the ball. I
> would like to program the formula on my hp50. thank in advance

Sounds like homework.

Also, density is weight per volume (e.g., pounds per cubic feet).

Also^2, what is the volume of a sphere as a function of its radius?

3. ## Re: need help finding a formula for my calc

"mjc" wrote in message
> On Mar 24, 6:03 am, gotu...@aol.com wrote:
>> Let's say you have a ball (shpere) that weighs 10 pounds the
>> material is brass which have a density of .305 cubic feet. this is all
>> the information I have. How can I find the diameter of the ball. I
>> would like to program the formula on my hp50. thank in advance

>
> Sounds like homework.
>
> Also, density is weight per volume (e.g., pounds per cubic feet).
>
> Also^2, what is the volume of a sphere as a function of its radius?
>

Hardly homework, a very common problem we all wrestle with. Lots of people
have brass balls. Some, like myself, have steel balls. Some people have no
balls at all but they are good at calculating the size of someone else's
balls.

4. ## Re: need help finding a formula for my calc

On Mar 24, 12:12 pm, "Revolvr" wrote:
> "mjc" wrote in message
>
>
> > On Mar 24, 6:03 am, gotu...@aol.com wrote:
> >> Let's say you have a ball (shpere) that weighs 10 pounds the
> >> material is brass which have a density of .305 cubic feet. this is all
> >> the information I have. How can I find the diameter of the ball. I
> >> would like to program the formula on my hp50. thank in advance

>
> > Sounds like homework.

>
> > Also, density is weight per volume (e.g., pounds per cubic feet).

>
> > Also^2, what is the volume of a sphere as a function of its radius?

>
> Hardly homework, a very common problem we all wrestle with. Lots of people
> have brass balls. Some, like myself, have steel balls. Some people have no
> balls at all but they are good at calculating the size of someone else's
> balls.

Sound so gay.

Anyway,

Since you managed to find this site, hopefully my assumption that you
Googled "Volume of a Sphere" was done or you already know the formula.

The question is how to best do this with the calculator. I would enter
NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
diameter or just get the radius and multiply by 2). Simply enter the
value you have into the appropriate field, move cursor to the other
value and solve for that value.

The nice thing is you can save your equation. When you get out of the
screen, the equation you used is saved under the name EQ. Using the
filer, rename it to something you'll remember. Next time you use
NUM.SLV, select CHOOSE and select your renamed equation.

5. ## Re: need help finding a formula for my calc

On Mar 24, 12:12 pm, "Revolvr" wrote:
> "mjc" wrote in message
>
>
> > On Mar 24, 6:03 am, gotu...@aol.com wrote:
> >> Let's say you have a ball (shpere) that weighs 10 pounds the
> >> material is brass which have a density of .305 cubic feet. this is all
> >> the information I have. How can I find the diameter of the ball. I
> >> would like to program the formula on my hp50. thank in advance

>
> > Sounds like homework.

>
> > Also, density is weight per volume (e.g., pounds per cubic feet).

>
> > Also^2, what is the volume of a sphere as a function of its radius?

>
> Hardly homework, a very common problem we all wrestle with. Lots of people
> have brass balls. Some, like myself, have steel balls. Some people have no
> balls at all but they are good at calculating the size of someone else's
> balls.

That sounds so gay.

Anyway,

Since you managed to find this site, hopefully my assumption that you
Googled "Volume of a Sphere" was done or you already knew the formula.

The question is how to best do this with the calculator. I would enter
NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
diameter or just get the radius and multiply by 2). Simply enter the
value you have into the appropriate field, move cursor to the other
value and solve for that value.

The nice thing is you can save your equation. When you get out of the
screen, the equation you used is saved under the name EQ. Using the
filer, rename it to something you'll remember. Next time you use
NUM.SLV, select CHOOSE and select your renamed equation.

6. ## Re: need help finding a formula for my calc

On Mar 24, 9:03 am, gotu...@aol.com wrote:
> Let's say you have a ball (shpere) that weighs 10 pounds the
> material is brass which have a density of .305 cubic feet. this is all
> the information I have. How can I find the diameter of the ball. I
> would like to program the formula on my hp50. thank in advance

Since you managed to find this site, hopefully my assumption that you
Googled "Volume of a Sphere" was done or you already knew the formula.

The question is how to best do this with the calculator. I would enter
NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
diameter or just get the radius and multiply by 2). Simply enter the
value you have into the appropriate field, move cursor to the other
value and solve for that value.

The nice thing is you can save your equation. When you get out of the
screen, the equation you used is saved under the name EQ. Using the
filer, rename it to something you'll remember. Next time you use
NUM.SLV, select CHOOSE and select your renamed equation.

7. ## Re: need help finding a formula for my calc

On 24 Mar 2007 09:39:44 -0700, "bern" wrote:

>On Mar 24, 9:03 am, gotu...@aol.com wrote:
>> Let's say you have a ball (shpere) that weighs 10 pounds the
>> material is brass which have a density of .305 cubic feet. this is all
>> the information I have. How can I find the diameter of the ball. I
>> would like to program the formula on my hp50. thank in advance

>
>Since you managed to find this site, hopefully my assumption that you
>Googled "Volume of a Sphere" was done or you already knew the formula.
>
>The question is how to best do this with the calculator. I would enter
>NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
>diameter or just get the radius and multiply by 2). Simply enter the
>value you have into the appropriate field, move cursor to the other
>value and solve for that value.
>
>The nice thing is you can save your equation. When you get out of the
>screen, the equation you used is saved under the name EQ. Using the
>filer, rename it to something you'll remember. Next time you use
>NUM.SLV, select CHOOSE and select your renamed equation.

Sounds like it might be a problem that could be solved using LaGrange
Multipliesrs.
See Mary Boas's Book "Mathematical Methods for the Physical
Sciences". The 3rd edition is the latest edition out
Harold A Climer
University of Tennessee at Chattanooga
Dept of Physics,Geology,& Astronomy
Room 309 Grote Hall
615 McCallie Ave
Chattanooga TN 37403
Harold-Climer@utc.edu

8. ## Re: need help finding a formula for my calc

On Mar 24, 6:26 pm, Harold A Climer wrote:
> On 24 Mar 2007 09:39:44 -0700, "bern" wrote:
>
>
>
> >On Mar 24, 9:03 am, gotu...@aol.com wrote:
> >> Let's say you have a ball (shpere) that weighs 10 pounds the
> >> material is brass which have a density of .305 cubic feet. this is all
> >> the information I have. How can I find the diameter of the ball. I
> >> would like to program the formula on my hp50. thank in advance

>
> >Since you managed to find this site, hopefully my assumption that you
> >Googled "Volume of a Sphere" was done or you already knew the formula.

>
> >The question is how to best do this with the calculator. I would enter
> >NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
> >equation you have (adjusting for and replacing the radius with the
> >diameter or just get the radius and multiply by 2). Simply enter the
> >value you have into the appropriate field, move cursor to the other
> >value and solve for that value.

>
> >The nice thing is you can save your equation. When you get out of the
> >screen, the equation you used is saved under the name EQ. Using the
> >filer, rename it to something you'll remember. Next time you use
> >NUM.SLV, select CHOOSE and select your renamed equation.

>
> Sounds like it might be a problem that could be solved using LaGrange
> Multipliesrs.
> See Mary Boas's Book "Mathematical Methods for the Physical
> Sciences". The 3rd edition is the latest edition out
> Harold A Climer
> University of Tennessee at Chattanooga
> Dept of Physics,Geology,& Astronomy
> Room 309 Grote Hall
> 615 McCallie Ave
> Chattanooga TN 37403
> Harold-Cli...@utc.edu

Which reminds that the density of brass varies but a good number is
8400kg/m^3. The units (right shift 6) menu is nice for converting kg
to pounds and m^3 to ft^3. This calculator really is a masterpiece.
Just need to get used to it.

9. ## Re: need help finding a formula for my calc

On Mar 24, 6:26 pm, Harold A Climer wrote:
> On 24 Mar 2007 09:39:44 -0700, "bern" wrote:
>
>
>
> >On Mar 24, 9:03 am, gotu...@aol.com wrote:
> >> Let's say you have a ball (shpere) that weighs 10 pounds the
> >> material is brass which have a density of .305 cubic feet. this is all
> >> the information I have. How can I find the diameter of the ball. I
> >> would like to program the formula on my hp50. thank in advance

>
> >Since you managed to find this site, hopefully my assumption that you
> >Googled "Volume of a Sphere" was done or you already knew the formula.

>
> >The question is how to best do this with the calculator. I would enter
> >NUM.SLV (right shift 7), and take option 1 (Solve Equation), enter the
> >equation you have (adjusting for and replacing the radius with the
> >diameter or just get the radius and multiply by 2). Simply enter the
> >value you have into the appropriate field, move cursor to the other
> >value and solve for that value.

>
> >The nice thing is you can save your equation. When you get out of the
> >screen, the equation you used is saved under the name EQ. Using the
> >filer, rename it to something you'll remember. Next time you use
> >NUM.SLV, select CHOOSE and select your renamed equation.

>
> Sounds like it might be a problem that could be solved using LaGrange
> Multipliesrs.
> See Mary Boas's Book "Mathematical Methods for the Physical
> Sciences". The 3rd edition is the latest edition out
> Harold A Climer
> University of Tennessee at Chattanooga
> Dept of Physics,Geology,& Astronomy
> Room 309 Grote Hall
> 615 McCallie Ave
> Chattanooga TN 37403
> Harold-Cli...@utc.edu

Which reminds that the density of brass varies but a good number is
8400kg/m^3. The units (right shift 6) menu is nice for converting kg
to pounds and m^3 to ft^3. This calculator really is a masterpiece.
Just need to get used to it.

10. ## Re: need help finding a formula for my calc

>> How can I find the diameter of the ball.

> Sounds like it might be a problem that could be solved using LaGrange
> Multipliesrs.

> How can I find the diameter of the ball.

I think we're making this way too complex. All he needs is the volume
formula.

Unfortunately, he does not mention how many dimensions are involved.
The volume of an n-dimensional sphere is given to be:

V_n = (2*pi^(n/2)*R^n)/(n*Gamma(n/2))

This provides opportunity to use your calculator's GAMMA function: LS-
MATH, SPECIAL FUNCTIONS, GAMMA.

Don't forget to double the radius to find the diameter.

-wes

11. ## Re: need help finding a formula for my calc

On Mar 25, 3:58 am, "Wes" wrote:
> >> How can I find the diameter of the ball.

> > Sounds like it might be a problem that could be solved using LaGrange
> > Multipliesrs.
> > How can I find the diameter of the ball.

>
> I think we're making this way too complex. All he needs is the volume
> formula.
>
> Unfortunately, he does not mention how many dimensions are involved.
> The volume of an n-dimensional sphere is given to be:
>
> V_n = (2*pi^(n/2)*R^n)/(n*Gamma(n/2))
>
> This provides opportunity to use your calculator's GAMMA function: LS-
> MATH, SPECIAL FUNCTIONS, GAMMA.
>
> Don't forget to double the radius to find the diameter.
>
> -wes

Boy, we are sure having fun today!

Are we in Euclidean space? As the saying goes, "Hyperbolic balls are
better than no balls at all!".

12. ## Re: need help finding a formula for my calc

The other fellows on this list seem to have been having a lot of fun,
but allow me to gently remind them: you were not always as
knowledgeable as you are now. Here's a response a little more in line
with the questioner's apparent level of experience.
1. You know the formula for the volume of a sphere, I hope. If not,
So you will have a formula that looks something like
V = 17 R^4
where the "17" is a constant you will have discovered (it involves pi,
which is available on the calculator as a constant -- see the SPC key)
and the "^4" means "use the y^x key to raise the radius R to the power
4". By the way, the actual power is not 4. That's one of the things
you're supposed to look up.
You'll also need to be aware that the formula you find will almost
certainly be in terms of the radius, not the diameter D. But you know
the relation between the diameter and the radius. So re-write the
formula by substituting for R its definition in terms of the diameter
D. Let's just pretend that you found D = 3 R below.
2. Likewise, you probably know that given the "density" of a material,
i.e. the weight (really, the mass, but this distinction may be yet
weight via the formula
W = K V
for weight as a function of densityK and volume.
You will need to find the density of brass. Again, it's on the Web. I
strongly
3. Solve the above two formulas. Remember algebra rules: anything you
do to one side you do to the other. And also remember that you can
raise things to fractional powers. For the example I gave, you would
have
W = D * 17 * (D/3)^4 (it's "3" because of what we are pretending
from point 1 above, but you should use the correct number there)
You isolate the R^4 on one side and then raise both sides to the power
1/4. Remembering that raising a^b to the power c you get a^(b*c), you
now have an equation with R all by itself on one side and other stuff
on the other.
4. write a program to implement the left side, given the weight, and
out will pop the right side. The only problem is that you have to make
sure you have consistent units. Briefly, to convert from one unit to
another, e.g., pounds (mass) to kilograms, if you have a formula in
terms of kg you may want to multiply by 1. But you write the 1 in a
useful way:
1 kg = 2.205 lb
divide by the right hand side, you get
1 kg/(2.205 lb) = 1
You can multiply any formula by this 1 and not create an error. For
example, suppose you know you weigh 220 lbs. You have
MyWeight = 220.5 lb
multiply by 1:
MyWeight*1 = (220.5 lb)*(1 kg/2.205 lb) = 100 lb*kg/lb; cancel the lb
and you get
MyWeight = 100 kg.
Easy, no? You just have to choose the right form of "1". For example,
given MyWeight in lb, you would use 1 = (2.205 lb)/1 kg instead.
Hope this helps. Good luck.
P.S. Please sign your notes in the future. We don't like anonymous
posts, much. Not your whole name and address, just a useful handle.
Irl
On Mar 24, 9:03 am, gotu...@aol.com wrote:
> Let's say you have a ball (shpere) that weighs 10 pounds the
> material is brass which have a density of .305 cubic feet. this is all
> the information I have. How can I find the diameter of the ball. I
> would like to program the formula on my hp50. thank in advance

13. ## Re: need help finding a formula for my calc

opticsmith wrote:
[snip]
> 1 kg = 2.205 lb
> divide by the right hand side, you get
> 1 kg/(2.205 lb) = 1
> You can multiply any formula by this 1 and not create an error. For
> example, suppose you know you weigh 220 lbs. You have
> MyWeight = 220.5 lb
> multiply by 1:
> MyWeight*1 = (220.5 lb)*(1 kg/2.205 lb) = 100 lb*kg/lb; cancel the lb
> and you get
> MyWeight = 100 kg.
> Easy, no? You just have to choose the right form of "1". For example,
> given MyWeight in lb, you would use 1 = (2.205 lb)/1 kg instead.
> Hope this helps. Good luck.
> P.S. Please sign your notes in the future. We don't like anonymous
> posts, much. Not your whole name and address, just a useful handle.
> Irl
> On Mar 24, 9:03 am, gotu...@aol.com wrote:
>> Let's say you have a ball (shpere) that weighs 10 pounds the
>> material is brass which have a density of .305 cubic feet. this is all
>> the information I have. How can I find the diameter of the ball. I
>> would like to program the formula on my hp50. thank in advance

[Assuming that enough time has gone by now that any assignment is late,
if indeed it is an assignment.]

You don't need all the unit conversion stuff if you simply want answers
in the same units as the original input values.

So:

1) From Google or a textbook, find that the formula for the volume of a
sphere is
v = 4/3*pi*r^3

2) Enter this into the 50G as an algebraic expression:
'v=4/3*pi*r^3'
where pi is the symbol for Pi (left-shift space), and leave it on the stack.

3) We also know that the density of the brass material of the sphere is
1lb = 0.305 cubic feet

and leaving it on the stack:
'v/0.305=10'

5) Now we've got two equations so we use the multiple equation solver.
This expects to find the equations stored as a list in the special
variable EQ. So first put them into a list by entering
{ }
onto the stack. And then press + twice

6) You should now have
{ 'V=4/3*pi*r^2' '.305*v=10' }
on the stack. Store in EQ by executing the STEQ command.

7) The multiple equation solver needs flag -117 (Soft MENU) set, so do
that in the MODES FLAGS menu.

8) Now press APPS, choose Equation Library and then press the MES menu
key. This displays the Multiple Equation Solver menu.

9) Press MINIT to initialise.

10) Press MSOLV to start the equation solver.

11) You should see R & V displayed black on white as the first two menu
keys.

12) Press left-shift R and you'll see the display flash up "Solving for
V", then "Solving for R" and then you'll see:
R:.853307602597

This is the radius (in feet) of a brass sphere that weighs 10lbs.

13) If you press right-shift V then you will see 3.05000000001 which is
the volume (in cubic feet) of 10lbs of brass.

HTH

Of course this is all "magic" in that the calculator does everything for
you. You might want to do the substitution for yourself on paper so that
you can see what is happening.

Regards,

--
Bruce Horrocks
Surrey
England
(bruce at scorecrow dot com)

14. ## Re: need help finding a formula for my calc

What about temerature?? Is it cold?? How cold?? Is it cold enough to
freeze the balls off of a steel monkey??

Or could it be??

15. ## Re: need help finding a formula for my calc

Bruce Horrocks wrote:

> 13) If you press right-shift V then you will see 3.05000000001 which is
> the volume (in cubic feet) of 10lbs of brass.

Which it isn't, of course, even with the supplied density value. My
brain was addled at that point.

Which means that R must be wrong as well. :-(

Omigod the multiple equation solver is buggy - cue thread on rubbish
calcs. ;-)

--
Bruce Horrocks
Surrey
England
(bruce at scorecrow dot com)

16. ## Re: need help finding a formula for my calc

Spence wrote:
> What about temerature?? Is it cold?? How cold?? Is it cold enough to
> freeze the balls off of a steel monkey??
>
> Or could it be??
>

Actually, it's nicely warm outside at the moment. Will this make a
difference?

--
Bruce Horrocks
Surrey
England
(bruce at scorecrow dot com)