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# AP Physics C: Mechanics - A Rundown

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### AP Physics 1ย ๐ก

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AP Physics C: Mechanics is one of the hardest AP classes with its rigorous content, with the 2019 test reported as the hardest in 15 years amongst students.ย  Yet, most students who take the test pass every year.ย  Trevor Packer, the head of the AP programme, tweeted the distribution of "The 2019 AP Physics C: Mechanics scores: 5: 35.9%; 4: 27.2%; 3: 18%; 2: 10.4%; 1: 8.4%."
According to these stats, this means that over half of all students pass the exam!ย  At Fiveable, our main goal is to help you pass!ย  To pass, you'll need to know what will be on the test and how it will be tested.ย  Most of the content in this article is from the AP Physics C: Mechanics Course and Exam Description officially released by College Board.

## Prerequisites

College Board recommends that AP Physics C: Mechanics be a second-year physics course.ย  Even so, many succeed in taking this course as their first physics course.
The main prerequisite for this course is calculus.ย  This means that you need to build confidence with both calculus and algebra skills.ย  If you are taking calculus at the same time as physics, you won't need to worry about studying ahead.ย  From my experience, the two most advanced calculus topics on the exam are separable differential equations and calculations involving density.ย  These include deriving the moments of inertia and centers of mass of rigid objects.ย  Besides calculus and algebra, you also need to be able to with vectors easily.ย  Vector algebra and analysis is typically covered in pre-calculus courses.

## Course Units

AP Physics C: Mechanics has 7 units, each of which willย be discussedย in detail below.ย ย Each unit contains different topics and learning objectives, and I willย brieflyย outline each topic.

### Unit 1: Kinematics (14-20% of the exam)

This shows a calculus-based representation of displacement, velocity, and acceleration.ย Image courtesy of Wikimedia Foundation.

Kinematics is the study of motion and how it can be described using the quantities of time, position, velocity, and acceleration.ย
In Topic 1.1, one-dimensional motion is covered.ย  This includes relations between the kinematic quantities and the fundamental equations of kinematics.ย
Topic 1.2 deals with kinematics in two dimensions, where vector components have to be considered and projectile motion is covered.ย

### Unit 2: Newton's Laws of Motion (17-23% of the exam)

This is a free body diagram of a block on an inclined plane, which is a simple version for many AP questions about blocks on ramps.ย Image courtesy of diagram.alimb.us.

Newton's Laws of Motion form the cornerstone of mechanics that explains the motion of objects.ย
Topic 2.1 covers Newton's first two laws.ย  The first law of motion states that "An object at rest stays at rest, and an object in motion stays in motion until acted on by an external force."ย  The second law of motion gives the relationship between force, mass, and acceleration through the equation F_net = ma.ย  This is arguably the most important equation in mechanics and will be used throughout the rest of the course.ย
Next, in Topic 2.2, circular motion is covered (not to be confused with rotational motion), and centripetal force is introduced.Introduced in Topic 2.3, Newton's Third Law says that every action force must have an equal and opposite reaction force.

### Unit 3: Work, Energy, and Power (14-17% of the exam)

This shows the difference in energies at different positions.ย Image courtesy of Luverne Band.

This unit introduces the concept of energy and connects it to Newton's Laws.ย
Topic 3.1 introduces work and its relation to both the net force and kinetic energy.
Going along with the first topic, Topic 3.2 introduces the concept of potential energy and its relationship to work.ย
The next topic, Topic 3.3, teaches conservation of energy.ย  This is the concept that the initial energy of an object is the same as the final energy of the object if no external forces act on the system.ย  This is definitely a powerful tool that will be used to simplify kinematics and dynamics problems.ย
Finally, to talk about the efficiency of work, we use power.ย  Power is introduced in Topic 3.4 as the work done divided by the change in time.ย

### Unit 4: Systems of Particles and Linear Momentum (14-17% of the exam)

Momentum is conserved in Newton's cradle when the balls collide into each other.ย Image courtesy of Pragmatic Capitalism.

Unit 4 introduces the concept of momentum and collisions, extending the ideas of dynamics to larger systems.ย
Topic 4.1 starts with a discussion of an object's center of mass and its derivation.ย
Next, Topic 4.2 covers the definition of momentum and impulse, which is defined as the change in an object's momentum.ย
Finally, Topic 4.3 introduces the idea that momentum is conserved in collisions.ย  The topic also covers the calculation of kinetic energy conservation in certain collisions.

### Unit 5: Rotation (14-20% of the exam)

This shows the relationship between angular and linear displacement.ย Image courtesy of Santa Rosa Junior College.

Rotation is the motion of spinning around an axis.ย  This motion looks very different from translational motion.ย  Yet, many of the equations used for rotation are similar to those used in translational motion.
Topic 5.1 introduces torque, the force that causes angular acceleration and rotation.ย
The remaining three topics in this unit rehash the concepts in kinematics, dynamics, energy, and momentum with rotational variables instead of the translational variables.ย

### Unit 6: Oscillations (6-14% of the exam)

This shows the motion of a pendulum.ย Image courtesy of Yousense.info.

Unit 6 consists of a single topic about simple harmonic motion.ย  Simple harmonic motion describes the behavior of waves, spring systems, and pendulums.ย

### Unit 7: Gravitation (6-14% of the exam)

This is a representation of the force of gravity between two bodies.ย Image courtesy of ELTE.

The last unit deals with large distances in space instead of distances near a planet's surface.
Topic 7.1 talks about Newton's Law of gravitation between two celestial bodies, while Topic 7.2 deals with planetary orbits and Kepler's laws.

## The Big Ideas

AP Physics C: Mechanics contains four Big Ideas: Change, Force Interactions, Fields, and Conservation.ย  These topics are combined among different units.
Change deals with changes in motion with kinematics and momentum in collisions.Lastly, Conservation introduces the idea that net energy and momentum cannot be created or destroyed.ย
Force Interactions is concerned with dynamics, which includes the interaction of forces.
Fields deals with forces that act through a distance which, in this course, is only gravity.ย  But, this Big Idea is a great introduction for electricity and magnetism, which are both field forces as well.

## The Science Practices

In addition to Big Ideas, the AP Physics C: Mechanics course has 7 Science Practices.ย  These practices emphasize skills that you should develop in the course and will be used on the exam.

### Science Practice 1: Visual Representations

College Board wants you to know how to understand visualsโespecially models and charts.ย  Visuals are powerful representations that can teach us about how the world works by simulating behaviors.ย  You should learn how to read models and try to understand what the model is representing.ย

### Science Practice 2: Question and Method

The heart of science is the scientific method, where experiments are done toย propose new theories.ย  You will be expected to know the different parts of an experiment and how changing certain variables can affect it.

### Science Practice 3: Representing Data and Phenomena

College Board expects you to know how to make a scatterplot of bivariate data with proper scaling and labeling.ย  Scatterplots represent a set of data and can be used to show relationships between two or more variables.

### Science Practice 4: Data Analysis

Practice 4 is a continuation of Practice 3 with the emphasis on analyzing graphs.ย  Practice 4 also wants you to be able to identify trends and linearize data.

### Science Practice 5: Theoretical Relationships

Practice 5 wants you to be able to solve mathematical problems and understand the theories behind them.ย  In addition, the practice deals with understanding equations algebraically and how the variables relate to each other.ย

### Science Practice 6: Mathematical Routines

Practice 6 also wants you to develop strong mathematical skills, and it deals with plugging numbers into formulas.ย  This is where your algebra and calculus skills kick in.

### Science Practice 7: Argumentation

Argumentation is the last science practice, and it may be the hardest one to master.ย  For this skill, you will have to explain why phenomena occur the way they do.ย  Moreover, you will also explain why errors and variable changes affect different situations.ย

## The Exam

The AP Physics C: Mechanics exam consists of two parts like most other AP exams: a multiple choice section and a free response question.ย
However, unlike other AP tests, there are no breaks between the two sectionsโeach lasts 45 minutes.
In the first multiple choice section, there are 35 questions with 5 options each.ย  The section tests concepts from all 7ย units and applies all the Science Practices except Practice 3.
On the other hand, the free response portion consists of 3 open answer questions, each worth 15 points.ย  One of the three questions requires a scatterplot and linearization, usually worth 5 points.ย  All three questions combine concepts from multiple units.

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Browse Study Guides By Unit
๐Unit 1 โ Kinematics
๐Unit 2 โ Dynamics
๐Unit 3 โ Circular Motion & Gravitation
โก๏ธUnit 4 โ Energy
โณ๏ธUnit 5 โ Momentum
๐ธUnit 6 โ Simple Harmonic Motion
๐กUnit 7 โ Torque & Rotational Motion
๐กUnit 8 โ Electric Charges & Electric Force
๐Unit 9 โ DC Circuits
๐Unit 10 โ Mechanical Waves & Sound
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