Too Late for Turkey-Day

You can’t wow the family for Thanksgiving, but maybe the gang is still around, or you can store these away for a future family gathering.

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From 10 quirky science stunts

One step better would be an explanation for the inevitable “How does that work?” (or similar) question that arises, so here’s a quick explanation of the physics-y ones. The ping-pong ball tends to stay in the column of air owing to Bernoulli’s principle — pressure decreases the faster the air moves, so there is lateral pressure gradient which gives you a restoring force. The coin and card trick works because the force on the card is probably larger than the force on the coin, and even if they are comparable, card is less massive so it undergoes a much larger acceleration. Consequently, it moves away much faster than the coin, so the coin doesn’t get displaced very far.

Jabbing a sharp pencil through a bag tends to form a hole that conforms to the pencil, and water seals small gaps at low pressure owing to the surface tension. Straws are stronger along their length and covering then end with your thumb means air can’t escape; the increased pressure from the potato being forced into it makes it even stronger against collapsing. Matches burning heat up air and make it expand, so the density is lower than outside. When the matches go out the air cools, lowering the pressure. The egg provides a good seal, and the outside pressure forces the egg inside.

The others have elements of chemistry biology/physiology. So I will pass on those explanations.