Friday, August 22, 2014

225: Penny circle

Here's a screen grab of one of @ddmeyer's videos: Penny Circle.



What sizes of circle would be best for packing in 0.75" pennies with as little wasted space as possible?

Wednesday, August 20, 2014

223: Combination (?) Locks 1

Which one is most secure?

Three numbers ...

This one with three extra wheels you can swap in ...

Or this one, with three letters?


Tuesday, August 19, 2014

222: Which would you rather push?

Would you rather ...



Which one is "easier"?

Monday, August 18, 2014

Sunday, August 17, 2014

220: Three Scales

There are three scales.
The one on the right (navy shirt) indicates a 10 N force to the right ... +10 N.
The one on the left (green shirt) indicates a 10 N force to the left ... -10 N.
What will the scale in the middle read?


Thanks to for posting this.

Saturday, August 16, 2014

219: How far out can you go?

A series of identical blocks.


A series of identical rectangular blocks is stacked out at their balancing points from the top down. You can show with a simple center of mass calculation the total "stick-out" distance; that is, the horizontal distance from the back of the bottom block to the back of the top block is
d = ½(1 + ½ + ⅓ + ¼ + ...)

Thanks to for finding these.