# What if everyone jumped?

Might as well jump. Jump. Go ahead, jump. – Van Halen Suppose everyone in the world got together and jumped. Would the Earth move? Yes. Would it be noticeable? Time for a calculation. Note: I am almost certain that I have done this before, but I can’t find where. Starting assumptions. 7 billion people. Average…

# Basketball shot – real or fake?

I have seen several videos similar to this. Real? Fake? How many tries did this take? Let the analysis begin. Before I do any analysis, let me state that I think this is not fake. I do not know that for sure, just my first guess. How would I tell if it is real or…

# Basics: Electric Potential for a Point Charge

Pre Reqs: electric potential, electric field, work-energy To start, remember that for a constant electric field the change in electric potential energy would be: WARNING: that is only for a constant electric field. I know you will be tempted later to use this for a different electric field, but DON’T DO IT. But if not…

# Basics: Electric Potential

Pre Reqs: Electric Field, Work-Energy, Potential Energy If you are already familiar with the topics listed in the pre-reqs above, this will be uber-simple. Potential energy – short version The work-energy principle basically says: In this most basic form, the energy is just kinetic energy (if you are not going near the speed of light).…

# Physics 2 refresher

So, I hear you are starting your second semester of physics. One of the cool things about physics is that the second semester still uses stuff from the first semester. Maybe you forgot some of that stuff, so here are the bare essentials you will need to get by (this is assuming you are in…

# How hot would the space jumper get?

A new video from the Red Bull Stratos Jump guys came out. Here it is: This reminds me of an unanswered question about the Stratos jump that I didn’t address on my last post on this topic. Commenter Long Drop asked about how much Felix would heat up as he falls from 120,000 feet. This…

# MythBusters and double the speed

In the last episode of MythBusters, Adam and Jamie wanted to test something that Jamie had said earlier: “Two cars crashing head on at 50 mph is the same as one car crashing into a wall at 100 mph” Jamie was wrong, but that is not what I am going to talk about. Instead, I…

# Another example of a dangerous jump

Check this out. So, the guy jumps from 150 feet into some cardboard boxes. Why are the boxes important? You want something that can stop you in the largest distance to make your acceleration the smallest. Here is my Dangerous Jumping Calculator. Basically, you put in how high you will jump from and how much…

# More ESPN Sport Science Goodness

Let me be clear. I am not really an attacker. If someone wrote a report about ski jumping or something and misused the word “momentum”, no big deal. However, if you have a show that claims to be about SCIENCE and you are obviously putting a lot of money into this show AND a whole…

# xkcd and Gravity Wells

Wow. In xkcd 681 comic, there is an impressive illustration of the common term “gravity well”. Here is a small part of that large image: I can’t resist. I must talk about this awesome illustration. My goal for this post is to help someone understand that comic (although the comic itself does a pretty good…