Physics Puzzle: Know Thy Center of Mass!
Ok - this week you get two puzzles wrapped up in one. Here we go:
You are given an arbitrary rigid object (say, a statue of the head of Elvis ) and asked to determine/estimate the position of its center of mass without doing any calculations. You can perform any simple experiment you’d like. Can […]
Physics Puzzle: the Inverting Mirror
Here’s a nice puzzle that left me scratching my head for a while:
If you stand in front of the mirror with a shirt that has something written on it, you will see it “inverted” (left-to-right becomes right-to-left). Informally, we can say that a mirror inverts left and right. However, note that up & down are […]
Physics Puzzle: Infinite Resistor Network
Another weekend has come, and another puzzle with it! This time, we’ll be making good use of Ohm’s law.
Quite a few physics puzzles ask you to find the equivalent resistor of a given network - a particularly famous one is finding the equivalent resistor between two opposite corners of a cube having a resistor R […]
My Top 5 Mechanics Textbooks
Or: “What, No Goldstein?”
Of all of physics, mechanics is my favorite subject (followed by electromagnetism). It’s the easiest to grasp, because it deals with daily phenomena, but the problems can be very challenging. As a service to the aspiring physics undergraduate and graduate student, here is a list of my top 5 mechanics textbooks.
An Introduction […]
Physics Puzzle: Crooke’s Radiometer
Here’s a riddle about a well known object known as Crooke’s radiometer. This is a glass “bulb”-like object with four plates fitted on a metal rod, free to rotate (much like a horizontal windmill). Each plate has a black side and a silver side, as is evident from the photo:
The inside of the bulb is […]
Physics Puzzle: Gas Pressure
After our last week’s excursion into computer science, we’re back to physics and an interesting puzzle, which I’ll split into two parts - one will be given in a few days.
An ideal gas of temperature T1 is stored in a container with walls at a fixed temperature T2. Will the pressure exerted by the gas on the […]
Physics Puzzle: Balls on a Stick
There’s an interesting physics puzzle hiding behind that painful title.
Consider an infinitely long stick, with masses m initially placed along it (at rest) at distances d:
A constant force F is applied to the first, leftmost mass. Assume completely inelastic collisions. Can you compute, after a long enough time, the velocity of the initial mass? Can you compute the velocity […]
Physics Puzzle: the Bulbs and the Students
Here’s a nice puzzle to challenge your understanding of simple electricity.
Two students live in adjacent houses in the dorms (ignore the dodgy art, I can only draw as well as Microsoft Word lets me … and yes, the weird beings are the students, courtesy of the Office Clipart). The lightbulbs in their rooms are connected in […]
Physics Puzzle: Changing an Oscillator’s Spring
Here’s a nice physics puzzle I was asked a while ago.
Suppose you had a harmonic oscillator - a very simple one, with no friction or driving force. Suppose your oscillator’s oscillating with an amplitude A and that the spring constant is k. Now suppose you slowly change k from its initial value to some final […]
Physics Puzzle: Newton’s Cradle
We’ve all seen this executive toy somewhere:
As the ball comes down and a collision occurs, it comes to rest while another ball at the other end rises up. This repeats ad infinitum - at least in theory - and illustrates perfectly the principle of conservation of momentum - the momentum of the colliding ball on […]
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