Learning physics is a lot like building a house, you need to have a good foundation in order to build a strong house.  In this lesson, we will be learning about the fundamentals of physics in order to have a good foundation to build our knowledge on.  Each chapter in College Prep Physics builds on previous knowledge.  You won't forget anything that we have previously learned! (Hopefully!)

Precision and Accuracy:

Look at the three pictures above.  If you were at a target range and lined your shot up with the scope and all three of your shots were very close to each other, but not near the target, you would assume there was something wrong with your scope and try to adjust it.  You were close with all of your shots, but not near where you wanted to be.  This is what scientists call precision.  Your lab data might have a good curve when graphed, but your individual data points are off.  In physics, this happens a lot.  It is hard to be accurate because there are a lot of external factors that can affect our data, temperature, humidity, wind, etc.  This is why we graph a lot of data in physics.  We are more concerned about the trend and the overall picture than with the individual pieces of data.

Going back to the target range, if your shots were all close to the target, then you would be very accurate.  We celebrate when that happens in physics (it is not often!), but in Chemistry, that is required.  In chemistry, you will compute your percent error a lot to see how far off from the target you are.

Of course, we always strive to have both precision AND accuracy, but sometimes, there are factors that are out of our control when completing various laboratory investigations.

Where you are looking from is important!

You have always been taught to read laboratory equipment from eye level.  This is important because readings look different if you look at them from the side, top, or bottom.  A parallax is the apparent shift of a position when viewed from different angles.  It is important to read any measuring devise from eye level to get an accurate reading.

Describing Motion:

Before we start talking about motion, we have to be able to describe it in the same way so everyone in the class is on the same page.

Frame of Reference:  It is a coordinate system used to define motion.  We can define motion in many ways.  In math, we use the x and y axis as our frame of reference.

Reference Point:  A reference point is the zero location in a coordinate system or frame of reference.  A reference point can be anything!  With my math example above, the reference point would be the origin (0, 0.)  When demonstrating this in class, I usually pick on a student to be my reference point.  Lets pretend Issac is a student in our class and he is now my reference point.

Position:  Position is the separation between the object and the reference point.  If Issac is our reference point, it would be the distance from Issac to the window, or Issac to the door, or Issac to the smart board... we could go on forever.  If Issac moves to sharpen his pencil, then all of my positions would change, because the separation between Issac (my reference point) and those objects changed.

To calculate change in position, ∆d (displacement,) you can use the equation, ∆d=df-di . The triangle is a math symbol for an english word.  It means change in.  It is the greek letter delta.  Whenever you see delta, ∆, you always subtract the final quantity from the initial quantity.  The little f in the equation, ∆d=df-di means final.  The little i means initial.  Subscripts are letters that we use to help us define the abbreviation a bit more.  We will use subscripts a lot this year.  In this case, df means final position and di means initial position.

What is Relative Motion?

Motion is relative.  It depends on where you are looking from.  What if I asked you if you were moving right now?  What would you say?

Yes?  No?

What if you said NO:  You might be thinking... I'm just sitting in a chair/laying on the couch, I'm not moving anywhere.

What if you said YES:  You might be thinking... I'm breathing, my lungs are moving or I am traveling at approximately 335 m/s here on the surface of the Earth in Michigan, the Earth rotates once a day - I'm really moving FAST!

Who is correct?

Everyone.  If you said no, your frame of reference was the room you were sitting in.  With respect to the room, you are not moving.  If you said yes, your frame of reference was your body if you throught of any bodily movement and your frame of reference was the Earth if you thought of traveling at 335 m/s.  Both individuals were correct because I did not define our motion.  In physics we need to be specific about how we are looking at things and referencing them so there is one correct answer.