1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Urgent: Help with Estimating Total Area

  1. Jan 24, 2010 #1
    This is not a HW but someone said in a previous thread that it sounds like it so I will post it here because it fits the format I guess.

    1. The problem statement, all variables and given/known data

    I have a flat plat that is x by y. It has an unknown number of holes in it but I do know the diameter of the holes is D.

    I also know that s/D = 4 where s is the spacing between holes of diameter D. Using this how can I estimate the total area absent in the flat plat, i.e. the amount missing.

    2. Relevant equations

    s/D = 4

    area rectangle = x*y

    area circle = pi*r^2

    D = 0.05"

    x = 4

    y = 3

    3. The attempt at a solution

    I've been over thinking this but I can maybe estimate the amount of circles of diameter D can possible fit in there and leave it at that but is there a mathematical way to do this as oppose to me just drawing it out and guessing the amount of holes.
     
  2. jcsd
  3. Jan 24, 2010 #2
    find s find the total area of x and y d=.05" d/2 = radius of the wholes and find the area of one and divide the area of x and y by the area of the holes and find the equation this is basic math with a twist to it why did u need help?
     
  4. Jan 24, 2010 #3
    I don't see where you used s.

    Also, I do not know how many holes there are so I can't just find the equation. If I knew the amount of holes and therefore cannot calculate the area of holes.

    The area of holes is what I am trying to estimate. I'm thinking I have to use the expression s/D = 4.

    It might be something simple but I miss simple things. Sorry if it offends you.
     
  5. Jan 24, 2010 #4
    Hi higha level

    Yes, you have to use the expression s/D = 4 to find s. Actually, you can determine the number of holes that contained in the plat.

    Let's consider the x-side. Basically, you have x, D, and s. Just think a simple one. If D = 1, then s = 4, so if x = 3, you can only have 1 circle on x-side. Now do it regarding the data from the question. :smile:
     
  6. Jan 25, 2010 #5
    That's what I was saying I did.

    D = 0.05" so I got a s= 0.2".

    x = 4 inch so therefore there probably can only be about 15 circles along x. And subsequently 11 in the y=3. This gives an estimate of 165 circles and I can calculate the missing area, etc. I previously did this already and moved forward. The question wasn't a hw problem but someone said it sounded like it.

    My question was is there a simple way to calculated it with an equation using s/D to find that missing area without finding the amount of holes there are? Still coming up with a relatively close answer?

    Sorry if I didn't ask correctly before.
     
  7. Jan 25, 2010 #6
    I don't think there's a way to find the missing area without finding the number of circles...
     
  8. Jan 25, 2010 #7

    Mentallic

    User Avatar
    Homework Helper

    Just for clarification, is s the distance between the outsides of the circles or the centres of the circles?
    Also, I am assuming here that the circles are formed in a pattern such that the first and second rows are in a straight line parallel to each other, except the circles in the second row are not vertically beneath the circles in the first row. As such:

    http://img687.imageshack.us/img687/3927/circleareaapprox.png [Broken]

    I was surprised to find that the diameter of each circle isn't needed to find the answer, all you need is x and y.

    I'll give the answer now, and if you're interested in the maths behind it, just ask. And I haven't tested the result myself so be weary. Use at own risk :wink:

    The area, A, of all the circles combined by using the layout I showed above is given by [tex]A\approx \frac{\pi}{25\sqrt{3}}xy[/tex]
    The constant would be more appropriately approximated: therefore [tex]A\approx 0.073 xy[/tex]

    If you can post a picture of what the layout of the design is, we could give a better approximation.
     
    Last edited by a moderator: May 4, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Urgent: Help with Estimating Total Area
  1. Urgent Help Please (Replies: 5)

  2. Urgent Help needed (Replies: 7)

  3. Need Urgent Math Help (Replies: 13)

Loading...