AP Physics 1 & 2 What is Physics?

Hi everyone, and welcome to educator.com. Here we are starting our first lesson in algebra based AP physics. I'm Dan Fullerton and I'd like to welcome you to the course.0000

To begin with, let's talk about what physics is.0011

We are going to talk about how we recognize the questions of physics, we are going to list several disciplines within the study of physics, and finally we are at least going to start to define matter, mass, work and energy.0014

These are some of the key concepts that are going to play out throughout this entire course.0026

So, what is physics? I like to think of physics as the answer to all of the questions a two year old might ask.0031

What does a two year old say constantly? "Why? why? why?"0039

The dictionary says physics relates to matter and energy and their interactions.0044

Some questions that might come up are: "What is matter?", "What is energy?", "How do they interact?", and most importantly, "Why do we care?"0048

The "why" questions are really what start to get more interesting when you take it beyond just a dictionary definition.0057

Why is the sky blue? Why does the wind blow? Why does my teacher smell funny? Why do objects fall down instead of up? Why do airplanes fly and why can't I? Why do the stars shine? Or why do I have to eat my vegetables?0065

To do this, we have to start talking about what the world, the universe is made up of.0082

We are going to start with matter. Matter is anything that has mass and takes up space, where mass is the amount of "stuff" making up an object.0088

We can get into a little bit more detailed definition than that, but for now, we think of it basically as anything you can touch. Stars, electrons, Neal Diamond. They are all mass, they are all matter.0096

There are actually two types of mass. We could talk about inertial mass, and inertial mass is really how hard it is to accelerate an object.0108

Likewise, we could talk about an objects gravitational mass, which refers to how large a gravitational force an object experiences.0130

So, inertial mass and gravitational mass. Two types of mass. But what is really slick in physics, anytime we have ever measured anything, the inertial mass and the gravitational mass have always been the same.0154

There is no theoretical reason we really understand, yet that says why, but it always works out and, man, is that slick for us as we start our study of mechanics coming up here shortly.0166

So let's do a problem. On the surface of the earth, a spacecraft has a mass of 2 × 10⁴ kilograms.0177

What is the mass of the spacecraft to the distance of one earth radius above earth's surface?0185

We know the mass is 2 × 10⁴ kilograms on the surface of the earth. We want to know what its mass is up in space.0190

Mass, the amount of "stuff" an object is made up of, doesn't change. It does not matter where you are, you still have the same mass in the same object. Therefore, our answer must be number two. The same mass.0201

We talked about matter, let's talk about energy. Energy is the ability or capacity to do work.But work in physics has a specific definition. Work is the process of moving an object.0216

We are simplifying these a little bit, we will get into more depth later. But if we wanted to put those together, we could say that energy, really, is the ability or capacity to move an object.0227

A baseball coming at your nose has kinetic energy; it has energy of motion. When it hits your nose, it has the ability to move your nose. That's how you know it has energy.0251

On the same token, if we had a bowling ball suspended up above my head, it would have gravitational potential energy. Why? Because it has the ability or capacity to move an object.0260

If it were released, it would start to speed up and that potential energy, would become kinetic energy and move faster and faster until it collided with me, in which case, it would move parts of me, in what would probably be a very unpleasant experience.0271

In both cases, energy is the ability or capacity to move an object.0284

In the early twentieth century, a famous physicist with wild hair, Albert Einstein, formalized a relationship between mass and energy and it's become one of the most famous formulas in physics.0291

His relationship says E=mc², where what he is saying is that the mass of an object, a key characteristic of matter, is really a measure of its energy.0301

Energy equals mass times the square of the speed of light. That is just a constant, that is just a number, a fudge factor to make the units work out.0312

What we know is that the source of all energy here on earth is the conversion of mass into energy. They are really two different sides of the same coin. Or you could think of it as, mass is a measure of an object's energy and energy is a measure of mass. There is a very, very close relationship there that is going to play out through the world of physics as well.0320

To come back to "what is physics?", physics is the study of matter and energy and how they interact, which turns out to be everything.0341

Try and think of something that is not related to matter and/or energy.0350

Baseball? It's all about physics. Matter, energy, even the roar of the crowd, even the crackerjacks to eat in the stands. You eat matter, you swallow it, you digest it, as you do that, chemical reactions occur. Those chemical reactions are transfers of energy, then that energy allows you to do work later on. Everything is physics.0354

That is an awfully big bullet list of things to do for an introductory course in physics, so we have to limit ourselves.0379

What we are going to focus on are some of the fundamentals.0387

We are going to start with mechanics; talking about how objects move, what makes them move, how they move in circles, how things like gravity work, and work, energy and power, momentum, collisions, explosions.0390

Then we will talk about fluids, fluid dynamics, getting to thermo physics, thermodynamics, heat.0403

We will talk about electricity and magnetism, circuits. We will talk about waves, sound, optics, light.0411

And finally, we will even touch a little bit on a topic known as modern physics. Things like nuclear physics and a couple other small topics that are much more modern. Modern, meaning in the last one hundred years or so.0418

That should get us going in algebra based AP physics.0430

What I would like you to do before we move on is take just a minute or two and write down three things you would like to learn about in physics. Then, if you can, try and think of ways in which matter and energy relate to those topics. Just a couple of minutes to start to see how all of these things play into our study of physics and the universe.0446

Thanks for watching educator.com. Make it a great day.0465