Happy Day

Happy 40th year anniversary of the moon landing!!!

Gravity!

Edit: I mistook which way things went as far as latitude vs. gravity goes, so I had to fix it.

This is absolutely exciting and amazing: we changed gravity yesterday!

Yes!!!!
Hurrah!!!

You probably all know that gravity changes with height, right? The farther you are away from the earth, the less you way?

Well that is not the only thing that affects gravity, or I should say the gravity constant of your perceived weight.

You all know that you weigh less the farther you go from the earth now(I just told you above, so you should know). But you don't actually lose anything from your body, right? No. That is because all the stuff of your body is actually the mass of your body, and that doesn't change.

Weight is the mass of your body times a gravity constant. And the gravity constant gets smaller the farther out from the earth you go. That's why you "weigh less".

But there is another thing that changes the gravity constant. And that is the rotation of the earth.

If you take a string and attach some object to it (which has a mass) and then swing the the string around and around, you can feel the object "pulling" on the string (there are physical laws explaining why it does so). We have sort of created a "weight" of the object.

You see, the earth is split up into a number of latitudes (the horizontal lines that go across a globe). And at each latitude, the ground beneath you is rotating at a different speed (too long to explain now, so sorry if you didn't know that before).
And we are attached to this earth through the friction that comes up through our feet.

So here we are spinning on this earth but the speed at which we are spinning changes depending on where on earth we are. And like that object on the string, our "created weight" changes with that rotation.

So the gravity constant isn't constant all over the earth even if there were absolutely no mountains or anything tall (the height piece of gravity).
Generalizing, we could say it is only at the standard at the North Pole and the decreases down to the equator.

If the earth spun faster we would eventually all fly off and that would solve our over-weightness problem in the United States, but probably not our over-massiveness problem.

And fly off into space!!!!!

The Quote of Wednesday

This quote comes from a problem from Fundamentals of Physics, seventh edition, part 1 by David Halliday, Robert Resnick, and Jearl Walker.

Chapter 8, Prob. 53
A large fake cookie sliding on a horizontal surface is attached to one end of a horizontal spring with spring constant k = 400 N/m; the other end of the spring is fixed in place. The cookie has a kinetic energy of 20.0 J as it passes through the spring's equilibrium position.

Now what I am particularly wondering is why they are using a large fake cookie. It doesn't really make a lot of sense. Why didn't they use a real cookie? Or even all those balls and weights common to beginner's physic's problems? No, they had to use a cookie. And to make it worse, it was a fake cookie. I mean, they couldn't even eat it when the experiment was done.
Problem writers are really strange or have a weird sense of humor.

Still Job Hunting

It is almost fun hunting for jobs. Everyone finds one they think you will be interested in, but of course you aren't, or they tell you they wish they could help but they know of no openings. Then you yourself look out for signs on stores and in stores and in newspapers. And it is amazing how many places are looking for people to hire. But actually finding a good job is a little more difficult.

However, I am set for Fridays. I am working for a professor on Fridays. There are three other students in his lab on Fridays. One is tall and quiet. I do not know what he is working on. I think he would prefer to work alone but that is impossible in such a tiny crowded lab. Another is pioneering in some study of nanoparticles. He has been working on his project for at least two summers now. He likes to talk and patronizes the two newcomers, myself and a short round guy. The short round guy is working on a similar project as myself, so we share many of the same materials and give each other advice. We work with some nasty chemicals which ought to be used under a fume hood except there isn't enough room for us there.
My mum got slightly worried after I described this situation, so I think she is glad I go there only once a week.

Perhaps you are wondering what a fume hood is? It is a tall box thing in a lab that has counter on which you put things and a great big hood over the top of it like a cabinet that is hollow and opens underneath. There are ventilation holes all around it and I believe it pulls the fumes up and out. There is a picture of a fume hood on Wikipedia.

Nanoparticles

Do you know what nanoparticles are? They are tiny pieces of some kind of metal like gold or silver. They are a little larger than molecules.
I hope to do some research with nanoparticles this summer. They are very interesting.

e/m ratios for electrons

What do you know about electrons? Well, probably you know that they are little particles that fly around the nucleus of atoms. At least, you would know that if you ever studied atoms in school, which most people are supposed to do. So we have these little particles called electrons and here's something else: they have a charge. An electrical charge. So you can use electrical things to talk about electrons like voltage and current and stuff like that. Also, have you ever played with magnets? And you know how if you put the two south poles close together, they push each other away, but that the north and south poles like each other? Well, the magnets have something called a magnetic field. It's kind of related to electricity, so we can use magnetic fields and electric stuff to talk about electrons.

That's what I did in physics today. Actually, we were finding the ratio between the electron's charge and its mass, e/m.

We used a neat little equation and some very interesting equipment. We had a glass vacuum globe filled with a gas. Then we shot a stream of electrons into the globe and had a magnetic field nearby. The magnetic field caused the electrons to all move in a large circle. The electons had energy which they gave to the gas in the globe causing the gas to glow green. That was how we could see that the electrons were moving in a circle. There was a large green circle in the globe. By playing with some knobs, we adjusted the current which made the electron circle grow bigger or smaller. When we had gotten the circle to the right size, we looked to see how much current we were using. Then we could use this nice little equation:

e/m = 2V/r²B²

The V means the voltage we used, the r is the radius of the circle of electrons, and the B is the magnetic field. In our experiment, B was 7.80*10 to the -4th power times I. I is the current we found.

It was a great deal of fun.