Amazing Aerodynamics

What You Need:

• Flat button with 2 holes
• 5-10 kinds of string (thread, yarn, fishing line, kite string, dental floss, waxed thread, twine, etc.)
• Measuring tape
• Stopwatch
• Paper and pen

What You Do:

1. Ask your child to cut each type of string into 4-foot lengths.
2. Have your child thread the string through one hole of the button and back through the other to make a loop. Then double-knot it.
3. Invite your child to hold one end of the loop in each hand, with the button in middle.
4. Have her swing the button in a circular motion to wind the string.
5. Have her keep winding until she can feel the thread between her fingertips twist.
6. Then, she should gently pull her hands apart (no more than an inch), to start unwinding. In less than a second, she will need to give it a little slack so it can re-wind, then repeat in rhythm with the button's winding/unwinding.
7. Now, hypothesize! She'll predict which strings are more aerodynamic (button spins longer) and which create friction (button spins less).
8. Ask your child to record her hypothesis (prediction), number the strings, and arrange them for testing.
9. Ask your child to decide on number of winds and winding direction, then wind each string the same way.
10. Now it's test time. You'll handle the stopwatch while your child tests each string. She should say "Go!" when the first winding is done and "Stop!" when the button stops. Show her the elapsed time so she can record the data. Invite her to test each string three times to establish an average (divide sum of elapsed times by 3).
11. Review the data together. What do they have in common? Does the data prove her hypothesis? If her prediction was that buttons spin longer on thin threads, do elapsed times show this?