Cause's He's Batman (and has a new game out)

Crtl+Alt+DelTo answer his question: No. Throwing a razor sharp boomerang knife is not a good way to incapacitate someone. However, from my boomerang throwing experience I think that a normal, non-knife-like boomerang could do the job. Batman would then need a separate shuriken weapon for quick cutting but nonlethal pain.
Building Batman will be training with shuriken next month. ' Can't wait.

Penny Arcade
Penny Arcade
P.S. Disney bought Marvel this morning (assuming the investors ok the 4 billion dollar deal).

Fermi Question: What is the mass of the Atmosphere

What's the total mass of all the oxygen in the atmosphere?

Useful unit conversion: 1atm = 10^5  N/m^2.


Would the Real Superman Please Standup

Superman Fermi QuestionThe mass of the train should be the same (recap: car of a train is heavier than a truck [we've heard the term oneton-truck so let's say a truck weighs 1 ton]. It's probably more than 10 trucks but less than 100 so we say 30 tons. And there are 6 cars so about 2 * 10^5kg.

In the Spider-man question we said the train was going about 30km/hr. But this is Metropolis, the city of tomorrow! So let's say the city has levitating Shinkansen which can travel upto 600km/hr. Since it probably didn't have time to reach it's fastest speed in the city we'll say the train has a velocity of 100km/hr = 100km/hr *  1000m/km * 1hr/3600s = 100/3.6 m/s = 30m/s when it comes flying of the tracks.

Just like before we can find it's original kinetic energy (KE = 0.5 * m * v^2 = 0.5 * 2 * 10^5kg * (30m/s)^2 =10^8J). That's an order of magnitude larger than the train Spidey stopped.

But here's the second kicker: whereas Spider-man took 10 blocks to stop the train Supes has only half a block if this train isn't going to crash into a crowded skyscraper. So remember there's 10 blocks in every kilometer - so half a block is about 50m.

So the force is F=W/d = 10^8J  / 50m = 5 * 10^6N.

That implies Superman is about 500 times stronger than Spider-man. If that's not a 'super' Fermi problem, I don't know what is.

All this talk about Superman is a good excuse for me to put up this link to a Comedy.com post

Metropolis' Marvel - Stronger than a Locomotive

Stronger than a locomotive
This superhero Fermi problem is just like the last Spider-man one so we'll use it as warm up.

In Matt Wagner's Trinity, Superman catches an out-of-control train (with say 6 cars again) that comes off it's tracks as it rounds a corner. He brings it to a stop before it can hit any buildings.

How much force did the Man of Steel use to do this?


How to Replace Batman's Bottom Bracket

I mentioned that I have running, swimming and biking each about twice a week throughout the

It turns out that all of that biking isn't just hard on me – It's hard on my bike too. My bike developed a grinding sound if I accelerated at all. Repairs needed to be done. But I figured that this could be a worthwhile exercise too. The Batman doesn't depend on anyone. Readers from the very beginning may remember that I suggested I don't really buy into the whole “Batman's the goddamn Batman. He built his bat-mobile from scratch, he personally programmed the bat-computer. All while staying out every night fighting crime and singlehandedly running a multinational corporation.” I tend to prefer the incarnations where Barbara handles all things computers, The Outsiders act as crack-squad, Harold (and later Hiro) takes care of equipment, Alfred manages Bruce Waynes' personally life and Mr. Lucius Fox runs the family business – rather than versions where Batman does everything himself. Not only is it more realistic it's also far more interesting.

BatfamilyBUT that being said, I have no doubts that Bruce is handy with mechanics and all things technical so I decided to fix my bike myself rather than bring it in to a shop.

I didn't know what I was getting into. First off, it would have been far cheaper to bring it into a shop since I had to buy a bunch of specialized tools and second I ended up doing way more repairs than I had expected to.

The funny sound came from my bottom bracket. Mine is a Cartridge bearing which just means that the bearings and the axle are housed in a sealed tube. The bracket is fitted to the frame of the bicycle by a square taper. This thing sucks. I had to buy an adaptor and the adaptor is a real pain.

So to change your bottom bracket you need to take it out before you buy a replacement (unless of course you work on your bike a lot and if that's the case why are you reading an introduction to replacing your bottom bracket?) To take it out you first remove your crankset (if your unlucky like me that requires a specialized tool called a crank extractor). This isn't difficult but just be careful when you screw the extractor into the crank – they are pretty fine threads. It's a clockwise turn to get the crankarms off.

Before doing anything else you have to measure the length of axle you are replacing and the width of the frame where it sits in. This is important. You then ask the boys at your local bike shop for a bottom bracket of those dimensions (the guy didn't believe me so I had to hull my bike all the way to the shop – I guess it's an uncommon size).

To remove the old bottom bracket you start on the non-drive side (i.e. the left hand side when you look down while sitting on you bike – the side without the chain). Using the stupid adaptor turn COUNTER-CLOCKWISE. Other side next (drive side). This time turn CLOCKWISE. Did I ever have a hell of a time getting these out. They were really seized in (I guess with rust). I had to buy a larger wrench to get more torque.

Inserting the bottom bracket is pretty simple since it's just two pieces and you just took it out. The only thing to remember is to grease the tapers! This is so that the bracket doesn't seize to the frame like it did for me.

Transformer Batmobile
While I was doing all of this I realized how warped my chainring was. Those are the big gears at the front. Since the bike was all apart I got a new one. In fact, the bike shop sold me my bottom bracket and the crankset as a single package. I guess that's pretty common.

I also decided to replace the hub gear. You have to know that my bike is a single speed and so doesn't have all those cassettes. It's just a single cogged freewheel like on a BMX. To remove this I needed another specialized adaptor. The trick to getting this off is to not use a wrench. PLEASE do yourself a favor and put the adaptor in a vice, set the wheel on top of it and then just turn the wheel (or maybe this is better but whatever). You get so much more torque and it is perfectly balanced.

Since I had this off I took out all the bearings, cleaned them and put them back in a ton of disgusting heavy grease. I also did this for my pedals.

This took a long time but it's finally done. In the spirit of Batman, I did it myself and I'm ready to be back on the road training.

Unfortunately, it's been pouring for hours.

The Dark Knight Returns

I registered and payed for my beginner-level Jiu-Jitsu yesterday. It feels like I've been wait forever to start. The first class is on Sept. 2nd. Classes occur once a week and go for 10 weeks. I'll post what I learn each week.
Batman's a SamuriaP.S. I'll post all the other Fermi problems this weekend and then we'll be done with them.