# work

### How Much Work Is Small-Scale Farming?

Meg emails to ask me "How much work is small-scale farming, anyway?" I want to farm and I'm planning on trying it out over the summer as an intern, but what I'm worried about is not being able to keep up with everyone else. I'm healthy and reasonably energetic, but everyone makes it sound so hard! Should I even try?" Well first of all, I think Meg is doing exactly the right thing in trying it out. The best way to understand whether you are suited to small-scale agriculture is to get some experience, idealy on several different small farms that do the kinds of things you want to do.…

### 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 fake? This is tricky. I can't really get a good trajectory of the ball to make some measurements on it because of the camera angle (next time people, make sure you set the camera up perpendicular to the plane of motion and far enough away to avoid perspective problems - thanks!) Really, the best I can do is to look at the…

### Turn or go straight? Quick!

This is a classic problem. You are in a car heading straight towards a wall. Should you try to stop or should you try to turn to avoid the wall? Bonus question: what if the wall is not really wide so you don't have to turn 90 degrees? Assumption: Let me assume that I can use the normal model of friction - that the maximum static friction force is proportional to the normal force. Also, I will assume that the frictional coefficient for stopping is the same as for turning. Stopping I am going to start with the case of trying to stop. Suppose the car is moving towards the wall at a speed…

### More Dangerous Kids

My car had a flat tire. When you get a flat tire, you might as well make something useful of it - right? As I was jacking the car up, I had a great idea. Use this for one of my "Spoof Science" videos. The only problem is that this takes a ton of work to put together a short video. So, I am just going to talk about what I could have done. Here is a quick clip of my 4 year old lifting the car. So, he lifted the car - it maybe be difficult to tell, but he did. HE LIFTED THE CAR! Ok, I know, he only lifted part of the car. If I were to use this in a real Spoof Science video, I would have…

### 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 that, then how do find the change in electric potential for a point charge? Let me start with a conceptual question. Suppose there were two point charges, both positive but one is held in place. If I hold the other point charge a distance r away from the other charge and…

### 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 distance you will take to land and it tells you your acceleration. You will probably need this G-force tolerance info from wikipedia. One problem - this calculator doesn't really work for this case. It doesn't take into account air resistance. Does air resistance even matter in this…

### My Wisconsin Death Trip on Twitter

Some time back, I was researching a feature for Wired when I stumbled across the US Department of Labor's Occupational Safety and Health Administration. One of the responsibilities of this office is to monitor workplace fatalities. Each week, a roundup of deaths in the workplace are posted online. They make for compelling reading. As Secretary of Labor Hilda Solis states on the site: "With every one of these fatalities, the lives of a worker's family members were shattered and forever changed. We can't forget that fact". Yet the lists only hold the briefest of details. The company…

### What could you do with 54,000 watts?

I already looked at ESPN's Sport Science episode where they calculate that Marshawn Lynch produces 54,000 watts when pulling some tires. Yes, that is way too high. However, what would happen if some was actually that powerful? What could that person do? How fast could they run 100 meters? That is what I am going to calculate. First, I am going to assume that Marshawn has a mass of about 100 kg. Also, let me say that he can produce 54,000 watts no matter what his speed. Take a short time interval. During this time, Marshawn will increase his speed from say v1 to v2 this would be a…

### 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 bunch of people will see and think this is science - then you need to be a little careful. I think shows like ESPN's Sport Science are a good idea - you know, introduce some cool science ideas by using cool sports. This show just needs some help. Yes, I know I make mistakes. I try to correct them when I become…

### The Physics of an Inclined Treadmill

A bad day for your ego is a great day for your soul. -Jillian Michaels One of the most popular exercises at the gym is the treadmill. And why wouldn't it be? Whether you're running or walking, it's a great way to get your heart rate up, get your body moving, and for many people, a great way to burn calories. But however you use a treadmill, there's one extremely simple thing you can do to dramatically intensify your workout: incline it! If you're an outdoor walker/runner, this is the equivalent of going uphill instead of over level ground. There are many physiological differences in walking…

### Sport Science: Pulling and Power

I would like to continue my attack on the show Sport Science - ESPN. In this short episode, they are comparing the power of NFL player Marshawn Lynch with that of a truck. You can watch it here if you would like. There are two things that are not quite right with this episode, first, the power thing. I will save the friction problem for another post. So, if you didn't watch that clip, the basic idea is that Marshawn pulls some heavy tires. Sport Science then calculates the power needed to do this and then repeats a similar thing for a truck. Quick review. What is power? In short,…

### Semi-Dorky Poll: Super Meeting!

I have to go to the Happy Fun Meeting this afternoon, which will be both Happy! and Fun! To keep things lively while I'm there, here's a question that is dorky, but not in the usual way for this blog: What superpower would you most like to have to help you deal with annoying meetings? The most useful meeting-related superpower to have would be:(survey software) Bonus essay question: How does the Justice League/ Legion of Doom function when all the attendees at their regular meetings have superpowers? Wouldn't that get out of hand in a hurry?

### MythBusters, Falling, Stopping, and Integration

In a MythBusters episode some time ago, Adam and Jamie jumped off a building. There was some cool stuff in this, but I want to focus on the acceleration data they collected. Before jumping into a pit of foam, they first wanted to test the set up by dropping a dummy into it and measuring the accelerations. Lucky for me, they showed a quick screen shot of their data. Note: I previously posted the calculations for jumping and stopping off of a building. For me, I see this and think - numerical integration. Before that, let me look at the physics. Here is a diagram of someone jumping off a…

### 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 job). Energy Energy is the key here. Here, I will talk about two types of energy - kinetic energy and field energy. In this case, kinetic energy is basically just the energy associated with something moving. Field energy is the energy stored in the gravitational field. You could…

### RP 3: Turn off daytime running lights, or reduce speed? Which saves more?

Which wastes more fuel? (and thus produces more carbon dioxide). This is a difficult to question to answer for a variety of reasons. The main reason is that a speed change from 71 mph to 70 mph is different than a reduction from 56 to 55 mph. First, let me be clear that the question of how much fuel is wasted using daytime running lights (or DRL as they are called) has already been addressed. The first source I found was howstuffworks.com Assumptions The daytime running lights on a car run at about 100 watts (for the pair) The energy density of gasoline is 1.21 x 108 Joules/gallon. A car is…

### Energy in an exploding water heater

The more I think about the last MythBusters' exploding water heater, the more cool things I see. How about I look at the energy of the explosion. There are three things I can look at: How much energy went into the water heater from the electric source? How much kinetic energy did the water heater have right after the explosion? How much thermal energy did the water and water heater have? How much gravitational potential energy did the heater have at it's highest point? Hopefully, I can show that the energy in from the electric source is greater or equal to kinetic plus thermal. Also, the…

### Punkin Chunkin - they will never make a mile range

In my previous post on launching a pumpkin (punkin chunkin) I essentially just looked at what happens to the pumpkin after it is launched. How fast would you have to shoot it to go 1 mile? The answer seems to be around 1000 mph and they are currently shooting them around 600 mph. The question for this post, how fast can you launch a pumpkin so that it does not smash into smithereens? First, why would it smash at all? Here is a diagram of a pumpkin being launched while still in the tube. The pumpkin launcher works by releasing compressed air inside the tube. This means that the force…

### More Measurements of the Projectile Velocity

The last time I looked at this projectile motion lab, I was confused. My different methods for measuring the launch speed of the ball were not even close to being consistent. So, I am bringing out the big guns - video. I made a video of the ball shot both horizontally off the table and vertically. No point posting the whole video (unless you really need it), but here is a screen shot of what the setup looked like. These videos were made with my flip video camera, it doesn't have adjustable shutter speed so that there is some blur. Also, notice the carbon paper on the floor. This is so…

### Snow Board Jump Help

I really shouldn't do this. I might be helping someone to set up something dangerous. But, I am going to anyway. Here is a question posted on some forum. (actually, it is from math help forum) "I'm anticipating a good winter this year, one with lots of snow. My yard is sloped quite a bit and it would be the ideal place for a huge snowboard jump, only problem is I need to calculate how fast I will be traveling when I hit the jump, how high and what angle the jump should be, and the distance and angle of the landing ramp to optimize my range." So, what am I going to do? I am going to give…

### How much would "free" energy cost you?

This was on my 'to do' list, but Tom at Swans on Tea beat me to it. Basically, this grocery store has these plates that when depressed produce electrical energy. Tom does a good job pointing out that this is not free energy (the original article says this also). Clearly, the energy comes from the cars. How much would this cost the cars? As always, let me start with some assumptions. The original article says that the bumps will generate 30 kW of energy every hour. That is an odd thing to say. I am going to interpret that as 30 kW of power for all hours (every hour). They couldn't have…