QED Insight (Santo D’Agostino)

Recent Posts
 How does the value of an inverse cosine function change when the unit of its argument changes?
 Why do Airplanes Fly?
 New Online Tutoring Site: QED Infinity
 “Religious Right’s Rejection of Science is Baffling,” by David Suzuki
 The Day Niagara Falls Ran Dry
 “A Lesson in Teaching to the Test, From E.B. White,” by Anne Stone and Jeff Nichols
 “Student Learning Can Only Be Described, Not Measured,” by Rog Lucido
 A Neat Trick For Determining The Integrals Of exp(x) cos x And exp(x) sin x
 “No Student Left Untested,” by Diane Ravitch
 Confusing Use Of Numbers: BestBefore Dates
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Category Archives: Thinking puzzles
A Number Riddle, Updated With Solution, And Some Comments On Iterative Playgrounds
Two weeks ago I posted a puzzle sent to me by my nephew Matthew: 1 is 3, 3 is 5, 5 is 4, and 4 is cosmic. Why is 4 cosmic? What happens to the other numbers? As I mentioned … Continue reading
A Number Riddle
My nephew Matthew sent me a number riddle (thanks, Matt!), which I pass on here: 1 is 3, 3 is 5, 5 is 4, and 4 is cosmic. Why is 4 cosmic? What happens to the other numbers? As is … Continue reading
Posted in Math puzzles, Thinking puzzles
Tagged 4 is cosmic, math puzzle, riddle, thinking puzzle
1 Comment
A Question From The USSR Olympiad Problem Book; Updated With Solution
A few days ago I posted on a problem (Problem 4(a) on Page 7) from the very nice The USSR Olympiad Problem Book, by D.O. Shklarsky, N.N. Chentzov, and I.M. Yaglom: We are given 80 coins of the same denomination; … Continue reading
A Question From The USSR Olympiad Problem Book
I just picked up a copy of The USSR Olympiad Problem Book, by D.O. Shklarsky, N.N. Chentzov, and I.M. Yaglom, and it looks delightful. The book’s foreword states that it is intended for highschool students, although outstanding middleschool students might … Continue reading
Round Trip On A Treadmill; Updated With Solution
Well, it’s been a while, but here at last is the promised solution to the treadmill puzzle posted here. I saw a version of the puzzle here (in the midst of a great discussion of extreme examples and counterexamples) at … Continue reading
Mathematics Puzzle: Roundtrip On A Treadmill
Alice and Basil are bored while waiting in an airport. They decide to play a game with one of the nearby “moving sidewalks” (treadmills). They decide that Alice will walk on the treadmill at constant speed v (with respect to … Continue reading
Puzzle: A Cube Of Resistors, Updated With Links To Solutions
I posted this puzzle a few days ago: Consider 12 identical resistors connected to form a cube. That is, each resistor lies on the edge of a cube, and there is an electrical connection joining three resistors at each of … Continue reading
Posted in Physics problems, Physics puzzles
Tagged cube of resistors, Kirchhoff's laws, resistors, resistors in a cube
1 Comment
Puzzle: A Cube Of Resistors
Here’s a puzzle I just read in Clifford Stoll‘s book High Tech Heretic (paraphrased by me): Consider 12 identical resistors connected to form a cube. That is, each resistor lies on the edge of a cube, and there is an … Continue reading
“The Coconut Problem”; Updated With Solution
This is a famous old problem. I shall just state the problem here for you, and will follow up in a day or two with a solution and some of its amusing history. Update: Scroll down for a straightforward solution … Continue reading
Why Does A Propane Torch Get Cold When Used? Updated, With Refrigerators
I was fixing a leaky water pipe in my garage yesterday, and so I had occasion to use a propane torch to heat up the pipe and melt the solder into the joint. It’s not something I do often, but … Continue reading
Posted in Physics, Physics puzzles, Thinking puzzles
Tagged air conditioner, boiling, Carnot cycle, evaporation, heat capacity, heat pump, kinetic energy, laws of thermodynamics, phase transition, potential energy, propane tank, refrigerator, second law of thermodynamics, specific heat capacity, thermodynamics
9 Comments