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,
your first task is to look it up.
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
ahead of your educational curve) per volume, you can calculate the
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...@xxxxxxx 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


.

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