- Today, we are gonna
talk about MCAT Physics.
Many students struggle
with Physics in college
and assume that they will
struggle with Physics on the MCAT.
In addition, many students
who have taken practice exams
find themselves forgetting equations
or getting tripped up by
seemingly complex math.
If that sounds like
you, you are not alone.
(air whooshing)
(keyboard clacking)
(air whooshing)
I'm Vikram Shaw, MCAT
expert and 528 MCAT scorer.
In this video, we will
go over study strategies
you can use to wade through
the sea of equations,
formulas, graphs, and math.
My goal for this video
is for you to walk away
understanding what topics are on the exam,
how to approach seemingly
impossible practice problems,
and how to study your mistakes
so that you don't make
them again on test day.
Let's get started.
How much Physics is actually on the MCAT?
First, a little MCAT Physics overview.
When you take the MCAT,
the exam is broken down
into four sections.
The first section tests you on
chemistry and Physics with 59 questions.
44 of these questions are passage-based
while are 15 stand-alone questions.
Physics falls into this
Chemistry and Physics,
or Chem Phys section.
According to the AAMC,
Physics will be about 25%
of your chemistry, Physics
section, give or take 5%.
So that means between 20% to 30%
of your MCAT Chem, Phys
section will focus on Physics.
In other words, your
exam will likely contain
between 12 and 18 questions
discussing Physics.
Since chemistry Physics is
only one of four sections,
however, Physics plays a smaller
role in your overall score.
In fact, Physics will actually
be only about 5% to 7%
of your entire exam
or 12 to 18 questions out
of 230 total questions.
Now, let's get into a general overview
of the topics that AAMC will test you on
in the Chemistry and Physics section
and study strategies you can use to answer
difficult questions.
Students often wonder what
Physics subjects will show up,
so we've broken it down for you here.
We will discuss strategies in the context
of the first few topics,
but they will apply
to the remaining topics mentioned as well.
So, let's get started.
Topic one covers what
generally corresponds
to the first semester of
Physics at your university.
Translational motion.
Forces.
Energy.
Work and equilibrium.
The difference, however,
is that you are applying these concepts
to biological systems.
A topic one question is not likely to ask,
if Sarah throws a rock off of a cliff,
how far in the ocean does it land?
Instead, a Physics-like
question on the MCAT might ask,
how much work is done,
when a protein is extended
by five nanometers using
50 piconewtons of force?
Like many students, terms
such as work or force
ring a bell in your head,
but you may not have the formulas
on the tip of your tongue.
However, just as it is
essential on the MCAT
to know your amino acids
backwards and forwards,
big formulas like the
work or force formulas
are no exception.
What do we mean by big formulas?
We define a big formula for the MCAT
as any formula you see on
an AAMC practice question
whether it comes from the question packs
or one of the AAMC full-length exams.
If a formula shows up on
AAMC practice questions,
it is fair game for your actual exam.
So we will now introduce MCAT
Physics strategy number one.
Know the big formulas and their units.
How does this strategy help us?
Let's go back to our example.
How much work is done
when a protein is extended
by five nanometers using
50 piconewtons of force?
If we know that the formula for work
is work equals force times distance,
we can solve this question by simply
multiplying five nanometers
by 50 piconewtons.
A lot of students tend to panic
when asked Physics questions
in a biologic context.
We are much more used to
seeing the following question,
How much work is done,
when a student moves
a block five meters using
50 newtons of force?
Remember, the formulas you are using here
are the exact same.
The multiplication from
our original problem,
five nanometers by 50 picoNewtons
brings us to another
point, that students often
struggle with.
How do we multiply five times
10 to the negative ninth
by 50 times 10 to the negative 12th?
MCAT math is tricky, but it's manageable.
You are not allowed to use
a calculator on the exam
and the AAMC knows this.
Use it to your advantage
with strategy number two.
Let the answer choices guide
your approach to math problems.
Let's say the four answer
choices for our problem are,
A, 1.50 times 10 to the
negative 18th Joules.
B, 2.50 times 10 to the
negative 19th Joules.
C, 2.55 times 10 to the
negative 20th Joules.
And D, 5.50 times 10 to
the negative 21 Joules.
At first glance, those
answer choices look tricky
because they are very similar.
But let's take an even closer look.
Let's say we simplified our math
by removing the scientific notation.
So we go from five times
10 to the negative ninth
times 50 times 10 to the
negative 12th to five times 50.
That's easier, right?
We know the answer is 250.
Now, let's simply the answer choices
by removing the scientific
notation in our problem.
The four answer choices
for our problem are now,
1.50 Joules, 2.50 Joules,
2.55 Joules and 5.50 Joules.
Which answer choice is
most similar to 250?
If you said answer choice
B, you would be correct.
It does not matter where
we place the decimal.
Anytime we multiply five by 50,
we'll get a number that
looks similar to 250,
but not 150 choice A, 255
choice C, or 550 choice D.
Without even looking at
the scientific notation,
we were able to determine
the correct answer.
Let's say however, the answer
choices for our problem
looks something like this.
A, 250 times 10 to the
negative 18th Joules.
B, 250 times 10 to the
negative 19th Joules.
C, 250 times 10 to the
negative 20th Joules.
And D, 250 times 10 to
the negative 21 Joules.
Now, we do care about
the scientific notation.
How do we multiply five times
10 to the negative ninth
by 50 times 10 to the negative 12th?
Use this tip, think of solving the problem
as a two-part process.
First, multiply the numbers
before the scientific notation.
When we multiply five by 50, we get 250.
Second, add the exponent
values, which are negative nine
and negative 12 in this case.
There's no need to fear
this math equation either.
If we add two negative numbers together,
we get an even bigger negative number.
Negative nine plus negative
12 is the same thing
as negative nine minus 12, or minus 21.
When we piece together
step one, which was 250
and step two, which was negative 21,
we arrive at answer choice D, 250 times 10
to the negative 21.
Now that we've covered
scientific notation,
let's look at another
slightly different problem.
The MCAT Physics section
will contain graphs,
and you should make
these graphs your friend
in order to answer these
Physics questions correctly.
Let's say the passage gave you this graph.
Figure one, dependence of
force on tweezer speed.
And then let's say the question reads,
What is the power exerted on a protein
when the tweezer speed
is 10 meters per second?
A, a 100 Watts.
B, 50 Watts.
C, 25 Watts.
Or D, 15 Watts.
Here, let's look at two more strategies.
MCAT physic strategies number three.
Pay attention to images and
graphs, especially axis labels
and the title, as they
made hide key information
needed to answer your question.
And MCAT Physics strategy four,
use the units to your advantage.
So, let's apply those
strategies to our problem.
You look at the title,
which talks about a force
and a speed.
The x-axis defines a tweezer
speed in nanometers per second
and the y-axis defines a force in Newtons.
The question stem is asking about power,
and using MCAT Physics
strategy number one,
we know that the equation
for power is work over time
or W over T.
You look at the graph, however,
and there is no work over
time, but don't panic.
Here, MCAT Physics strategy four,
or using the units to
your advantage, kicks in
and you can break down the
units that you do have.
Power is equal to work over time
and the units are Joules per second.
We know that the equation for
work is force times distance
and force is represented by Newtons
while distance is represented by meters.
So, let's replace Joules
with newtons times meters.
So our first equation is power
which is equal to work over time.
The units for power
are Joules per seconds.
The next equation is work, which is equal
to force times distance
and the units for work
are newtons times meters.
Now, let's combine this two equations.
Power can now, be equal
to force times distance
divide by time and the units
will be Newtons times meters
divided by seconds.
Now, you look back to
the graph and see that
our final unit solution for
power includes all of the units
on both axis.
The y-axis has newtons, and we see newtons
in our new power equation.
The x-axis has meters and seconds,
and we also see meters and
seconds in our equation.
If you multiply the units on
the x-axis meters per second,
by the units on the y-axis newtons,
you get the same units
as the power equation
that we derived.
So, all that is left to do is find where
the tweezer speed is 10 meters per second,
find that point on the line
and see what the corresponding
value is for force.
The value is 10 newtons,
so we multiply 10 by 10
and get our answer, a 100 Watts.
Remember, Watts are the units for power.
Before we move onto the next topic
let's summarize what
we've discussed so far
with five takeaway points.
Mastering the MCAT Physics
section is within your grasp.
Here is takeaway number one.
From now on, for every
Physics question you take
using AAMC test materials,
write the formula down
along with the relevant
units and variables
on a sheet of paper or
flashcards until you've compiled
a comprehensive list
of all of the formulas
and units you need to know.
For example, for force you
would write, force is equal
to mass times acceleration.
In addition to writing this
formula down you would also want
to include the variable
letter and the units.
Takeaway number two.
Do not get overwhelmed
by Physics math problems.
Let the answer choices guide your approach
and don't spend too much time on hard math
if there is a shorter path to the answer.
Takeaway number three.
Always, always, always
read the title of a graph
and the axis as they can help you solve
seemingly complex problems.
Takeaway number four.
Remember your units and how
they relate to one another.
And here's a final piece of advice
before we move on to the
remaining MCAT Physics topics.
Takeaway number five.
If you find yourself spending
more than one to one and a half minutes
on any given Physics problem,
choose your best guess,
flag it, move on, and come back to it
at the end of your
section if you have time.
Now, we will cover the
remaining MCAT Physics topics
that you'll see on you exam.
Again, we will not cover
every topic in depth here
so that we can show you
the high-yield strategies,
but we'll provide the full
list at the end of the video.
MCAT Physics topic number two
covers fluids in the body,
including blood circulation, gas movement,
and gas exchange.
Here is example problem.
At which of the following
locations in the body
is hydrostatic pressure the greatest
if a student is standing up?
A, feet.
B, knees.
C, hands.
Or D, head.
Using MCAT Physics strategy number one,
we should recall the formula
for hydrostatic pressure.
Even though no numbers
are used in this problem
we can use the formula to our advantage.
MCAT Physics strategy
number five, says that
formulas show us relationships that help
answer non-math questions.
Now, how do you solve this problem?
Do you remember the formula
for hydrostatic pressure?
Remember MCAT Physics takeaway number one.
If this was an AAMC
problem, when you come back
and review the question, you would add
the hydrostatic pressure formula
to your list of formulas.
Hydrostatic pressure is the
pressure in a given liquid
at a certain depth.
The formula is pressure is
equal to density times gravity
times height or depth.
In variable terms, this
formula is p is equal rho
times g times h.
D or density is often notated
by rho, or a tilted p.
Now does this equation
relate back to our situation?
Let's think of the student
as a container of blood
with the student's head being
the top of this container
and the student's feet being
the bottom of this container.
Now, back to our formula
pressure is equal to density
times gravity times height.
Since the fluid density and
gravity will be the same
in this student's case, the
only variable we can alter
is depth.
If we define the top of the
container as height zero,
where is the deepest
part of the container?
Is the container deepest
where it corresponds
to the student's head,
hands, knees, or feet?
If you said feet, then you are correct.
Pressure and depth are
directly proportional
according to our formula.
So, when depth is the greatest,
pressure will also be the greatest
and you will choose feet as your answer.
The two main variable relationships
you should be familiar with
are directly proportional
and inversely proportional.
A direct relationship means
that one variable will increase
with the other and looks
like this x is equal y.
When y increases, so must x.
An inverse relationship means
that if one variable increases
the other must decreases.
You might draw it like this,
x is equal to one over y.
When y increases, x decreases.
So here's MCAT Physics
takeaway number six.
Be able to apply direct
and inverse proportionality
to equations in order to
solve non-math problems.
We will now mention the remaining topics
in the Chem Phys section, and
you can apply the strategies
and takeaways we have
talked about to topics
three through 10.
Topic three covers electrochemistry
and electrical circuits.
Topic four covers optics and sound.
Topic five covers atoms, nuclear decay,
electrical structure, and
atomic chemical behavior.
Topic six covers water and its solutions.
Topic seven covers molecules
and their interactions.
Topic eight covers
separations and purifications.
Topic nine covers the structure, function
and reactivity of macromolecules.
And finally topic 10 covers
thermodynamics and kinetics.
Note, some of these topics
are more Physics-oriented,
such as topic one, so
you will likely see more
Physics-related questions on
that topic during your exam.
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Thanks again for watching
and we'll see you next time.
(upbeat music)
