Unit 3 Reflection

This unit came fairly easy to me.  We started off with a lab that related Newton's 2nd law, Fnet=a/m, to Newton's 3rd law, which states that for every action, there is a reaction that is equal and opposite to the original action.  The lab asked the question, "If a mac truck collides with a small car, which will experience the greater force?  The answer is that they will experience the same force, which is actually what I hypothesized.  We then discussed briefly, systems of actions.  The most common example we used is:

A horse says that there is no point in pulling the buggey because it will just pull back and they will not move.  However, if the horse proceeds to walk forward, it pushes the ground, and the ground pushes back as per Newton's 3rd law, which states that for every action there is an equal and opposite reaction.  This, in turn, moves the entire system (horse and buggey).

Near the end of this lesson, I became very comfortable with this example.  It helped to explain the entire subject.  A similar example used tug of war to show that the team who wore cleats would beat the team who wore just socks because the cleat team would exert more force on the ground.

We then proceeded to discuss free body diagrams, which are complicated.  A completed diagram looks like this:



It is very important to make sure the Fweight and Fsupport vectors are of equal length.  I generally did poorly on these, but I asked for help from a student in AP Physics, and I also took more time on them, and I became  more proficient with the diagrams.

Finally, we discussed the Universal Law of Gravity.  We learned an equation to find the net force between two objects when the masses and distance is known:

F = Gm1m2 / d^2

I found it difficult to plug in massive numbers into the equation.  But later on, Mrs. Lawrence taught us how to solve the equation quite easily without a calculator, and though I am not completely proficient, they are easier to solve now.  Lastly, we discussed the cycles of the moon, and the different types of tides, Neap and Spring.

This all relates to the real world in some way.  I realized that the law of universal gravitation could have an affect on College Wrestling, for example.  Let's say an athlete wrestles for Iowa State University, which is fairly close to sea level.  He will have to take into account his weight change when he wrestles at United States Air Force Academy, for example, which is high up in the Rocky Mountains, above sea level.  Because he is high up, his weight will decrease, because F and d are inversely proportional.

The cycles of the moon and tides can come into play when going fishing.  For some fish, it is better to go when the tide is low.  Knowing what the moon will be like can help you know how high the tide will be.