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Photo of Albert Einstein

What is a 4 Vector?

Special relativity is super simple when it’s all time dilations and length contractions. But if you study relativity a little more deeply, you’ll notice a lot of talk about 4 vectors? What the heck is a 4 vector and why do you need them? A simple analogy I’m assuming you know what […]

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Students taking the AMC 8 at Olympiads School

Olympiads School: Your Ticket to the IPhO

If you live in Toronto and you want to go to the IPhO, then you should definitely visit Olympiads School. They have courses for all levels of physics, ranging from absolute beginner to olympiad level. In fact, Olympiads School has courses specifically for physics olympiad preparation. And the courses work! Every year, […]

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Two springs in series

How to Solve Springs in Series

Most physics students have studied springs before, but not many have studied springs in series. Did you know that having  identical springs end to end actually makes a new spring that’s half as strong? Cool right? How do you figure this out? Take a look at the diagram above and see […]

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If your car is travelling at the speed of light, how fast are your headlights moving?

This is a classic problem in relativity. Let’s rephrase it a little bit for clarity. Let’s say is moving past at the speed of light and is moving past at the speed of light. and are all moving in the same direction. How fast is moving relative to ? I’ll give […]

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Not Your Typical Block on a Ramp

This is the shortest, most beautiful solution I’ve ever seen in a physics problem. It was found on Morin’s problem of the week site here. For more questions like these, buy his textbook Classical Mechanics on Amazon. Give it a shot. Imagine you have an infinitely long and wide plane inclined at an […]

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Cruise ship staying afloat because of buoyancy

Explaining Buoyancy Once and for All

Buoyancy is everywhere in our everyday lives. Boats can sail above the water, hot air balloons rise up into the sky, and (most) humans are able to swim. In this lesson, I’ll try to explain what exactly buoyancy is, and how you can calculate it. If you’re an absolute beginner, read the first part. If you’re […]

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Acceleration in Special Relativity?

A lot of people think that you need to learn general relativity to deal with acceleration, but that’s not true at all! You only need general relativity when there’s gravity. To strike this point home, I’ll give you not 1, not 2, but 3 different ways to analyze accelerating objects! To understand the first solution, all you need […]

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The area is the same!

This is one of the coolest relativity problems I’ve ever seen. It’s taken from Problem Book in Relativity and Gravitation by Lightman, Press, Price, and Teukolsky. It’s a great compilation of problems and solutions. You should definitely check it out. Here’s the problem. Imagine you have a parallel beam of light (think of a […]

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Tennis ball on top of basketball

How does it bounce that high?

Want to see something amazing? Check out this video (skip to 20s). Here’s the problem statement: You stack a super bouncy tennis ball on top of a super bouncy basketball as shown in the image below. The bottom of the basketball is at a height above the ground. The balls […]

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How long till it crashes?

Hey guys, Check out this cool problem! Here’s the problem statement: Two point masses   and   are initially stationary and separated by a distance . Assume that so that the mass never moves. Under only the influence of gravity, how long does it take for the two masses to collide? This is a fantastic […]

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