Re-Cap of Physics I

Hey everyone!

First things first:  I forgot to tell you what constants you need to know for Test Day.  Here are the big seven:

acceleration due to gravity:  g = 9.8 m/s² although you can always use 10

speed of light in a vacuum:  c = 3.0 x 10⁸ m/s

density of water:  rho = 1.0 g/cm³

specific heat of water:  c = 1.0 cal/g K

Avogadro's number:  N = 6.02 x 10²³ mol^-1

Faraday's constant:  F = 96,485 C/mol e- although you can always use 100,000

atmospheric pressure:  Patm = 101,325 Pa although you can always use 100,000 = 760 mmHg = 1 atm

And a couple quick reminders:

-If you haven't yet sent me your Student Questionnaire, please do so!  If you haven't taken your Diagnostic, likewise!

-The blog is mchv10702.blogspot.com; username is mchv10702 and password is letsgo45T.  I eagerly await your questions!

After every classroom session you will receive a comprehensive email that will include the following:

• A reminder of the preview assignments (i.e. our fancy word for homework) required for the upcoming session.
• A discussion of some key points of the previous session.
• A discussion of the review assignments associated with the session we just completed.
• Helpful hints.
• Links to stuff that may or may not be related to the MCAT/medicine that I happened to find interesting for some bizarre reason.

Now, I’m aware the depth with which we covered the material during Physics I may have been overwhelming, but do not become disheartened.  It’s going to take a few revolutions for everything to come together.  The key is that you engage in these reps NOW.  Some students adopt the “well, I don’t have time for this so I’ll just come to the classes and take notes and then figure it all out later.”  This is not an efficient way to learn, because three months from now you will not remember what we talked about this past week.  The time to review our previous lesson is right now!  Even if the Physics I made complete sense to you, open up your Lesson Book and go over it all once again.  Strive to reach the point where you can look at a blank Lesson Book page without any of your notes and be able to recall and verbalize all of the key physics concepts.  Yes, it takes time.  However, once you truly understand the core science concepts you will not forget it, because you will understand how it all works.  And once you have reached that point, you are ready to play.  You will be ready to see the connections between physics and biology.  That’s when it becomes fun, and that’s when you’ll start to realize that getting ready for the MCAT will help you succeed in medical school and thus help you become a better physician. 

So, to “come ready to play” for General Chemistry I, here’s the required homework:

• General Chemistry Review Notes Chapters 1-3 and 7
• These chapters review Atomic and Electronic Structure, Bonding, and Gases.  Similar to the reading for Physics I, a thorough understanding and familiarity with these concepts is required to facilitate an understanding of higher-yield topics that we will discuss in Unit II.  The most challenging aspect will probably relate to understanding the behaviors of gases under non-ideal conditions, but we will engage in a review of that topic in class.

For those of you who haven’t seen general chemistry in a while, I recommend the following:

• General Chemistry Foundation Review Unit 1
• Online Workshop & Quiz (OWQ): Quantum Numbers and Electronic Configuration
• This OWQ does a very nice job of presenting all of the information you need to know about quantum numbers and electronic configuration.  We will open our discussion of general chemistry with a brief review of these concepts.

To reinforce what we have covered in Physics 1 try the following:

• Physics Subject Tests 1, 2, & 3
• Translational Motion Topical Test 1
• Force, Motion, Gravitation and Equilibrium Topical Test 1
• Work, Energy, & Momentum Topical Test 1

All of these items are available on your KapTest syllabus.

Helpful Hints:

• For Translational Motion Test 1, Passage I, Question 5, use critical thinking rather than math to solve the ratio.
• For Trans. Motion Test 1, Passage II, use critical thinking to minimize the amount of math; especially for Question 12 – check out units!
• The Force, Motion, Gravitation and Equilibrium Test 1, Passage I, is a very difficult passage and question set.  It may require multiple go-throughs in order to gain complete understanding.

Also, before progressing to the associated topical tests for Physics I, ensure that you know and understand these Physics I concepts:

• Kinematic formulas
• The big ones are in the middle of page 21 of the Review Notes.
• Be comfortable applying these concepts to projectile motion (ex: Question 7 from the Lesson Book on page 44).
• Newtonian Mechanics
• Understand how to draw a free-body diagram and use Newton’s 2^nd law to solve physics problems.  In class we used this approach to solve:
• why an object in free-fall will reach an acceleration of zero (force of air resistance opposes force of gravity)
• why a scale will register a person’s weight to be greater if the person and scale are in an elevator accelerating upwards (F_net = N – F_g)
• Be able to distinguish between forces arising from Newton’s 3^rd Law and the normal force (recall the “book on the desk”).
• Kinetic vs. static friction
• Be able to interpret the graph on page 39; recall that F_{static friction} = F_applied as long as F_applied < F_{s max}
• Inclined Plane
• Be able to resolve the force due to gravity into its component vectors.
• Be able to explain what will occur to F_applied, F_s, F_{s max} as the angle of inclination changes.
• Be able to derive algebraic expressions for the net force (or acceleration) of the block.
• Centripetal Motion = Uniform Circular Motion
• Know the basic definition: object moves at constant speed, net force points to center of circle, F_c = mv²/r = F_net
• Net force may be result of one force (gravity, magnetism), or it may be the result of two or more forces (see “roller coaster” passage in Force, Motion, Gravitation, and Equilibrium Test 1).
• Be able to derive new expressions for velocity of object by equating F_c expression to F_net (ex: mv²/r = GMm/r² à v² = GM/r)
• We will revisit this concept in the context of angular frequency when we discuss simple harmonic motion in our Physics II session.
• Rotational Motion
• Know the torque formula, the +/- convention, its units, and recall that it is a vector quantity.
• Work & Energy
• When we discuss thermodynamics in Physics II, we will distinguish between work done on a system versus work done by a system.  The formula W = Fdcosθ is referring to the work done ON a system by an external force applied to the system over some displacement d. 
• The Work-Energy Theorem states that the net work performed on an object is equal to the change in its energy. 
• Mechanical Energy = K + U (any Jayhawks fans?)
• Conservation of Mechanical Energy: ME_i = ME_f
• Many equations can be derived from this relationship, thus it is important to know when mechanical energy is conserved.
• Conservative forces = gravity, electrostatic, elastic.
• Non-conservative forces = dissipative (air resistance, kinetic friction, etc.).
• We also took the time to review the concepts above in equation form:
• W_net = ΔE
• W_conservative = ΔKE = - ΔPE (i.e. no change in mechanical energy)
• In other words, if there is conservation of energy any change in KE is reflected in an opposite change in PE.  For example, an object in free-fall gains KE as it loses PE.
• W_{nonconservative} = ΔKE + ΔPE (i.e. change in mechanical energy)
• The derivation is below, but the key point to understand is that the work performed on a system by a non-conservative force can result in a change in the object’s mechanical energy.
• Derivation of expression for the work done by a non-conservative force.
• Power
• Know the definition and formula, as well as its units
• Momentum
• Beyond the basic formula mv, understand the differences between the three different types of collisions.  The critical thinking exercise question on page 48 nicely contrasts the key differences, so if you have a good understanding of that question you should be good to go for momentum questions. 
• The impulse formula can come in handy on some questions; it usually comes into play for objects that experience a significant change in momentum in a very short time period.  The example we reviewed in class is a head-on collision, but the clown blasted out of a cannon is another example where we can use that formula (see topical test discussion below).

Once you have a firm grasp of these fundamental concepts it is time to take it to the next level and challenge yourself with the Physics 1 topical tests: 

• Translational Motion Test 1
• Passage II is a challenging experimental passage that features a clown shot out of a cannon.  The sixth question is particularly challenging; when you don’t know how to get started use the answer choices as a clue to deduce the concept behind the question.
• Force, Motion, Gravitation and Equilibrium Test 1
• Passage I is the infamous roller coaster passage.  The key is to derive an expression for the normal force.
• Work, Energy and Momentum Test 1
• The best question from this set is the discrete question that illustrates a block sliding down a frictionless surface and subsequently colliding with a stationary block in a totally inelastic collision.  The reason this question is good is that it requires an application of the conservation of momentum and the conservation of energy.  The MCAT is unlikely to contain many questions as involved as this one, but the purpose of the Topical Tests is to help deepen your understanding of the concepts so don’t be put off by this challenging problem.  Embrace it!

Please remember that these science topical tests exist to serve as learning tools, NOT testing tools!  Do not get upset or fed up when you miss a question – read through the explanations of all the questions to ensure you have learned the material!