# Formula needed for displacement

Page 1 of 3
• posted on August 4, 2005, 8:55 pm

How do you calculate the displacement of a cylinder 22 inches long with a circumference of 12.5 inches.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:09 pm

Well, the circumference is 2 * pi * radius, and the volume is pi * radius * radius * height you do the math.
BTW - how do you remember the value of pi? Wow, I need a drink, alcoholic of course! (count the number of letters in each word)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 11:25 pm
Dan Major wrote:

How I wish I could determine pi Eureka! cried the great inventor Christmas pudding, Christmas pie is the problem's very centre.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 11:42 pm
JoeTaxpayer wrote:

Pi are squared? No, pi are round, cornbread are square!
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 5, 2005, 12:42 am
If you have a 4 function calculator - Take the 1st 3 odd digits and double them up thusly - 113355 Then divide thusly: ____ 113|355 The ascii art is probably not going to show correctly but should show 113 divided into 355.
The result is correct to 0.00000027, or about 0.1PPM.
Art

<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 15, 2005, 12:57 pm
Convert values to ft, go to http://www.dep.state.pa.us/dep/deputate/waterops/Redesign/calculators/volcalchtm.htm
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:10 pm
on 8/4/2005 3:55 PM Andrew Walsh nomail said the following:

The volume of a cylinder equals the (area of the base)*height = π r2 h
I'm not going to do all the math for you but determine the radius the easy way (measure or it) or extrapolate it from the circumference and go. I'd just use 3.14 for pi and let it go at that.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:16 pm

Pi r squared H is the formula for a cylinder. 3.1416*3.9788*3.9788*22 1094?
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:26 pm

oops. 12.5 / 3.14 = 3.9788 which should be divided by two to give radius. 273.5
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:20 pm

First find the radius of the base with:
diameter = circumference/?
Then divide the diameter by 2 to get the radius, then plug in below
Then use the area of the base (? r2 ) times the height of the cylinder to get the volume:
V = (? r2) (h)
--
www.e-woodshop.net
Last update: 7/31/05
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:23 pm

a
Sorry ... my characters screwed up: ? is "pi" ... (use 3.14 for pi and you'll be close enough).
--
www.e-woodshop.net
Last update: 7/31/05
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:29 pm
On Thu, 04 Aug 2005 13:55:21 -0700, Andrew Walsh

Volume of a cylinder is pi R squared x height. R= C/pi/2
12,5 circumference is a circle with a radius of 1.99 squared is 3.96 times 3,14 is 12.43
Hey is this a trick question ;-)
times 22 is around 273 cu/in
I suppose if you solved it algibraically you would skip a few steps.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 9:36 pm
On Thu, 04 Aug 2005 13:55:21 -0700, Andrew Walsh

Well, the area of the circle describing the cylinder is pi*r^2, so to find r we must first determine the diameter by dividing the circumference by pi :
12.5"/pi = 3.97899" (diameter)
The radius then is 3.97899/2 = 1.989"
Then we find the area of the circle described by the cylinder as pi * r^2
1.989^2 = 3.958 3.958 * pi = 12.434 in^2
Every linear inch of the length of that cylinder then is 12.434 in^3, so the cylinder volume is 273.555 in^3
However, displacement perhaps isn't the right word. Most often when discussing a cylinder, displacement means how much volume is displaced when a piston is moved in it, which is a function of the stroke of the piston, not the length of the cylinder.
Or, displacement could also mean how much water is displaced when a cylinder of the size described is placed in it, but that's a function of the weight of the cylinder in addition to the volume and can't be easily determined with the information given.
Which all means I might have missed the point of the question entirely.
--
LRod

Master Woodbutcher and seasoned termite
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 10:08 pm
Andrew Walsh nomail wrote:

V = pi*r^2*h
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 10:21 pm
wrote:

That's easy. Now if I just knew what V was, and r, and h I would have this solved.:)
Thank God some of the other answers were a bit less cryptic.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 10:25 pm
Andrew Walsh nomail wrote:

Well, if you can't even figure out that the volume is a functionof the radius and height, I think there's no hope... :(
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 5, 2005, 3:53 pm
Duane Bozarth wrote:

Although I grant I made the (perhaps rash) assumption that you could somehow muddle through to find the radius of a circle knowing the circumference...
If that's the root of the problem, then since c = pi*d = 2*pi*r ==> r c/(2*pi)
From which it follows that
V = pi*[c/(2*pi)]^2*h = c^2*h/(4*pi)
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 5, 2005, 1:32 am

Nothing cryptic about if for 7th or 8th grade math students. Ok, a hint, V = volume. Just think about what the others may be and you can solve it.
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 4, 2005, 11:28 pm
On Thu, 04 Aug 2005 13:55:21 -0700, Andrew Walsh

C = 2Pi*R so R = C/(2Pi)
A = Pi*R^2 = PI * (C/2*Pi)^2 = (C^2) / (4Pi)
V = Ah = (C^2)*h/(4Pi)
Stick in the numbers and calculate.
Method 2: Find a graduated cylinder large enough [or make one] and drop it into some water and measure the increase in volume.