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!

Surface Area of Hollowed Hemisphere - Basic Geometry

  1. Mar 22, 2012 #1
    I need to find the total surface area of the hollowed out hemisphere (picture attached), with an inner diameter of 1.86 cm and what looks like an outer radius (also what I am assuming as height) of 1.25 cm.

    Surface area of a sphere is 4∏r2, so half the sphere is 2∏r2.
    Since the outer hemisphere has a radius of 1.25 cm, its SA is 2∏(1.25cm)2. The inner hemisphere has a diameter of 1.86cm, therefore a radius of .93 cm. Inner hemisphere then as a SA of 2∏(.93cm)2. Adding the two SA, I get:

    2∏(1.252+.932) = apprx. 15.25 cm2.

    However, the back of the book says the correct answer is apprx 17.44 cm2. So what am I doing wrong???
     

    Attached Files:

  2. jcsd
  3. Mar 22, 2012 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi anniecvc! :smile:

    erm :redface:

    what about the ring on the top? :wink:
     
  4. Mar 22, 2012 #3
    thank you tiny tim! i included it before it and the numbers didn't work out, but now it does, so i must've made a simple calculation error. thanks again.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Surface Area of Hollowed Hemisphere - Basic Geometry
  1. Geometry/Area Problem (Replies: 4)

  2. Surface Area help (Replies: 3)

Loading...