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Foil, Balloons, and Black Holes
Student Worksheet

Materials needed per group: three 30-35 cm sheets of aluminum foil, 1 balloon, 1 tape measure, 1 scale (that weighs to a tenth of a gram), 1 graphics calculator

Trial Circumference Radius Volume Mass Density


  1. Blow up the balloon until the diameter is about 15 cm. Tie off the end. Cover the inflated balloon with the sheets of aluminum foil. This will be your "Model Star".
  2. Measure the circumference of the aluminum foil star. Repeat this 3 times, using 3 different paths around the star. Calculate the mean of these 3 measurements. In your data table, record this average value as Trial 1 Circumference.
  3. Place the Model Star on the scale. Record the mass (grams) under Trial 1 Mass.
  4. Now Supernova! Break your balloon by squeezing it. Gently shape the aluminum foil back into a "sphere". Measure the circumference of the now collapsed Model Star three times. Average these 3 measurements. Record the value as the Trial 2 Circumference.
  5. Obtain the mass of the collapsed Model Star and record the value as Trial 2 Mass.
  6. Squeeze the collapsed star a little me. Repeat the procedure for determining the new average circumference and record your data as Trial 3.
  7. Repeat the mass measurement and record your value appropriately.
  8. Squeeze the collapsed star so that you make it as small as you possibly can. Repeat the circumference and mass measurements and record that data. For each circumference, calculate the radius of the sphere. Remember, this is done by dividing the circumference by 2p. Record the results appropriately in your data table.
  9. Now calculate the volume [(4/3)pr3] of the sphere for each radius.

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Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

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Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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