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Oil Drop Timer

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From Amazon: BUY NOW Drop Timer 

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Oil Drop Timer: immiscible liquids (typically, colored oils in kerosine) in two connected containers with interesting semi-translucent white and opaque black oils in this variation on the bubble timer theme. The oil in each container falls through a small drop forming hole in between clear walls of acrylic- note how surface tension forms the drops into nearly perfect circles and regulates the size of the drop formation. In addition the drops fall at terminal velocity with smaller drops falling faster than larger ones. One of my favorite inexpensive physics toys. 

Flippe Puzzle Ball

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From Etsy: BUY NOW: Flippe Puzzle Ball

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Flippe Ball Puzzle: this ball is a puzzle that explodes and flies apart when spun. The puzzle is made of three identical pieces and a ball bearing which mysteriously locks the pieces together only to release them after a period of spinning. The main challenge is to fully explain why this spontaneous disassembly occurs. A slow motion “instant replay” of it coming apart reveals how conservation of momentum has each of the three equal mass pieces fly away on equally spaced trajectories (120°) with the ball bearing remaining stationary at the center and falling straight down. A product of puzzle master George Bell.