JONATHAN LANSEY

Description: (2005)

Ikemefuna Agbanusi and I built a working Foucault's pendulum in a stairwell at NJIT. It was an official NJIT mathclub event (e-mail mathclub@oak.njit.edu to join the Pi-Landers).

Motivation:

• Measure the Earths rotation!
• Observe that sin(x)=x for small angles.
• Test the period of a pendulum is 2*pi*sqrt(L/g)

Apparatus:

• The bowling ball knocked over the black chess pieces to its left as it made a clockwise precession. In the southern hemisphere it would have knocked over the white pawns to its right.
• 16 pound weight, 17 Meter rope (56 feet), 8 second period (measured for large and small amplitudes!).
  Swing of about a foot after left for 25 minutes. Thanks Claus Holzapfel for use of your way long measuring tape.
  

Ike watches the earth spin before his very eyes.

FAQ:

Why would you purchase a Purple bowling ball?

It was given to me by a stranger in a bowling alley . . . no seriously it was.

Why chess pawns?

There weren't enough bishops.
Note: The humor in knocking over the tiny pins with a bowling ball was not missed.

What did you do to reduce friction?

If your weight is heavy enough, most of the friction comes from the very top.  As shown in the diagram below (not to scale) the weight was supported by the gray bar.  The rope was then held slightly to the side by the tight webbing (black circle per diagram). The rope was able to bend with little friction at such small angles. (The rope always stayed in contact with the webbing).

   
Diagram (not to scale) and The view from the top

That is me at the top

And it all fits in a little bag! (wheels of course)

If we cut the rope instead of burning through- it would jerk the ball into an elliptical path . . .
Not good at all for precise pawn targeting.

Looking up (zoomed in)

 

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