Unit 4 Reflection

This unit was not incredibly difficult.  We started off learning about momentum.  We were prompted with the question, "Can a skateboard, which has very little mass, have more momentum than a big 18-wheeler?"  To answer this question we were taught the equation for momentum.  It is very simple: P=mv.  Using this equation, it can be inferred that if the skateboard picks up more velocity than the truck, it will actually have more momentum.  
It is mind boggling, but I found something else with a low mass and a very high momentum:

This car is very small, but it can reach dangerous speeds-so dangerous that the makers actually warn that the car is "only for experts".  During class, we actually defined momentum as "inertia in motion".  Here is an example problem:

If a bowling ball has a mass of 12 kg, and rolls at a speed of 5 m/s, what is its momentum?
Answer: P=mv, so P=12(5), P=60 kgm/s.

We then transitioned to impulse.  Impulse is the term used to describe a change in momentum.  The equation for impulse is J=f(delta)t.

Throughout the unit we used a set of very similar questions to apply this knowledge.  They were worded as follows: Why do we need airbags?  Why do padded floors help protect gymnasts?  Why is it better to roll with the punches?  These questions are all answered the exact same way.  The most important thing to remember is to include all equations and back up each assertion with an equation.  To answer these questions, you need to first state that p=mv, and the object the object will change velocity, therefore the momentum will change.  You then state that J=F(change in time).  Since J is constant, if the time increases the force will decrease.  These questions were difficult for me at first, but then I started to get used to the pattern.  These questions relate the most to the real world.  For instance, if you ever decide to be a boxer, you will know how to make sure you receive minimal pain when being punched.

Finally, we discussed conservation of momentum.  The equation for conservation of momentum is: mvbefore=mvafter.  The law of conservation of momentum states that momentum will stay constant before and after a collision.  For instance, if a moving car hits a stationary car and the two stick together, the momentum of the system will equal the momentum of the moving car before the collision (we disregard the other car because it had no velocity, and no momentum).

This is a great video on conservation of momentum:

One thing I found to be very difficult about this unit was knowing which formulas to use for each question.  Thus, my problem solving skills declined.  However, Ms. Cianculli helped our class one day, and she explained a few problems very clearly, and I was able to grasp these ideas a little better.  

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.

                                                                         

Unit 2 Reflection

Physics for me got exponentially harder during this unit.  It seemed like the more we studied the more complicated the material became, mostly in terms of mathematics, but also conceptually.  The concepts seemed blatantly obvious at first, but there turned out to be deep complicated explanations behind everything.  The first concept we studied was Newton's Second Law of Motion, which states that an object's acceleration is directly proportional to its Net Force, and inversely proportional to its mass.  In equation form, a=Fnet/m.  This concept actually got easier for me over the course of this unit.  I began to relate everything back to this easy to remember formula.  We then studied the physics of throwing objects straight up, dropping them, and also free fall.  We had to call upon the old formula, d=1/2gt^2 quite often while studying these concepts.  We learned that while an object is in free fall, its acceleration equals 10 m/s^2 (9.8 m/s^2 for lab purposes).  This was a fairly easy concept to understand.  We often had to use the formula v=at to find the instantaneous velocity.  Throwing an object straight up became alot easier to understand when Mrs. Lawrence showed us how to draw and label a picture to go with the question.  Now, I am efficient with solving those problems accurately.  Projectiles were very tricky to me.  I found it difficult to relate them to throwing objects straight up.  When we carried out the "Hit the Bull's Eye" lab, my partner and I ran into many speed bumps.  In the end we realized that with alot of work, it is possible to render an estimate of where the projectile will land that is very close to the target.  My partner and I won the contest, and it did help me understand the concept.  Finally, our class looked at air resistance.  I found this interesting because our studies of Unit 2 would finally be relating to the real world.  I found this concept to be easier than projectiles, but not as easy as Newton's Second Law.  The podcast about cats really helped me to understand this topic too.  I realized that when an object has reached terminal velocity, the impact with the ground will not be as violent as one accelerating to the point of contact, which is why cats that fell from the 5th floor were more harmed than those that fell from the 10th floor.

My Initial Physics Hypotheses and Questions

After being educated in the fields of biology and chemistry at the Asheville School, I have arrived at physics, what I believe to be the study of how things around us move and work.  That however, is only my initial thought.  As with other sciences, I hope to be able to further define what "physics" really implies.  I am looking forward to examining every day things, such as a basketball, or a car, and seeing how they work, as well as things that aren't just everyday items, such as a hovercraft.  I believe that the study of motion and laws is just as important as the study of living things, because if it were not for the laws of physics, our world would be much different.  Physics has also furthered the development of chemistry and the study of atoms.  I do wonder how much of physics is directly related to the environment and the anatomy of living things however.  Just as I have expectations of the class, I have expectations of myself.  I hope to improve my math skills dramatically by using them in physics, in addition to my primary math class.  I also hope to improve my lab writing skills as well as my ability to work in a group.  In the past, I have been distracted by others in my group, but this year I hope to be able to focus on the task at hand and get the job done in a timely and neat fashion.  Finally, I want to improve my test taking skills.  This does not apply solely to physics, but it is a goal of mine for every class.  I believe that my drive to accomplish my goals while studying the world of physics will lead to a great year for me, and I am excited to start.

Unit 1 Reflection

During the first unit of physics this year, I learned the concepts of inertia and motion.  While learning about that, we studied Newton's first law of motion, and applied our knowledge during the hovercraft lab which gave us a visual representation of the law.  We then moved into different forces that act on objects in the real world, such as gravity, friction, and outside forces.  I learned about the concept of net forces.  Finally, we studied velocity and acceleration, and the differences between the two, and how the relate to Galileo's study of motion with ramps and free fall.  I found it rather difficult to synthesize all the different formulas in my mind.  On a quiz, I often become confused as to which formula I need to use on a particular problem.I also found it difficult to calculate net forces on different objects.  At the start of this section, I did not find many chances to use problem solving skills, as most problems were simply common sense or conceptual.  The questions in the later area of the unit were more numerical and complicated.  The trip question was by far the most complicated problem, and I had to apply my problem solving skills thoroughly to solve it. 
I feel like this unit relates greatly to the real world, especially when talking about speed and acceleration.  There were many questions on quizzes concerning cars and driving.  Also, learning more about rates and time was beneficial to students studying algebra, as rates become a point of focus during the year.  Finally, we learned how to make graphs in excel very quickly, and this is a skill that is important in many classes.