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Solar System - Keeping in Shape

Journal Entry - Take out your science journal and answer the following question(s) (use drawings as appropriate):

What keeps our solar system in shape?


  • String - 1 meter long
  • Four large metal washers
  • Stopwatch, timer with seconds, or clock with second hand
  • Student worksheet


  1. Tie two washers on the end of the string.
  2. Swing it overhead, securely holding one end.
  3. Count the number of revolutions it makes in ten seconds. Use the person's nose as a reference point. Record on your worksheet.
  4. Repeat Step 3. Average the two trials.
  5. Fold string in half and repeat Steps 3 and 4.
  6. Add two more washers on the string.
  7. Repeat Steps 3-5.
  8. Complete the remainder of the worksheet.

Student Worksheet

Name ____________________________________________

Prediction: Which combination of washers and string do you think will go the fastest?

Hypothesis: ____________________________________________


Data Table
Experiment First Test Second Test Average
50 cm., 2 washers      
100 cm., 2 washers      
50 cm., 4 washers      
100 cm., 4 washers      
Your experiment:      

Analysis Questions:

  • What did the size of the orbit do to the number of revolutions the washers made?
  • Which of the planets take longer than the others to revolve around the sun?
  • What effect does mass have on a planet’s revolution?
  • What would happen if there was no gravity?
  • What would happen if planets’ forward velocity were changed (e.g. slower, faster)?
  • What did your experiment show?

Conclusion: Remember to restate your hypothesis, and the correctness of your hypothesis, and explain what you learned. Use the back of your worksheet.

utah state board of education This Sci-ber Text was developed by the Utah State Board of Education and Utah educators.