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AP Course

AP Physics 1

Updated for the AP Physics 1 framework effective fall 2024, including mechanics, rotation, oscillations, and fluids.

Study every current unit through original concept lessons, formula derivations, experiments, quizzes, and practice sets.

Lessons
Scalars and Vectors in One DimensionDisplacement, Velocity, and AccelerationRepresenting MotionReference Frames and Relative MotionVectors and Motion in Two DimensionsSystems and Center of MassForces and Free-Body DiagramsNewton's Third LawNewton's First LawNewton's Second LawGravitational ForceKinetic and Static FrictionSpring ForcesCircular MotionTranslational Kinetic EnergyWorkPotential EnergyConservation of EnergyPowerLinear MomentumChange in Momentum and ImpulseConservation of Linear MomentumElastic and Inelastic CollisionsRotational KinematicsConnecting Linear and Rotational MotionTorqueRotational InertiaRotational Equilibrium and Newton’s First Law in Rotational FormNewton’s Second Law in Rotational FormRotational Kinetic EnergyTorque and WorkAngular Momentum and Angular ImpulseConservation of Angular MomentumRollingMotion of Orbiting SatellitesDefining Simple Harmonic Motion (SHM)Frequency and Period of SHMRepresenting and Analyzing SHMEnergy of Simple Harmonic OscillatorsInternal Structure and DensityPressureFluids and Newton’s LawsFluids and Conservation Laws
Quizzes
Practice Problems Formula notes, diagrams, and practice sets will be added here.

AP Physics 1 · Unit 3 · Reviewed representative lesson

Conservation of Energy

Energy conservation is an accounting principle: the total energy of an isolated system remains constant, while energy can move between kinetic, potential, thermal, and other forms. The chosen system boundary determines whether a transfer is internal or external.

Definition and Model

For a model using kinetic and potential energy, nonconservative work can be included as energy transferred into or out of the modeled system.

\[K_i+U_i+W_{\mathrm{nc}}=K_f+U_f\]

\(K\) is kinetic energy, \(U\) is potential energy defined for interactions inside the system, and \(W_{\mathrm{nc}}\) represents other modeled transfers.

Why the System Boundary Matters

If Earth and an object are both inside the system, gravitational interaction energy can be represented as gravitational potential energy. If Earth is outside, gravity transfers energy across the boundary by work. Both descriptions can be consistent, but they must not be mixed in one ledger.

Worked Example

Question: A \(2.0\,\mathrm{kg}\) object is released from rest \(5.0\,\mathrm m\) above the ground. Ignore air resistance and use \(g=9.8\,\mathrm{m\,s^{-2}}\). Find its speed just before impact.

\[mgh=\frac12mv^2\quad\Rightarrow\quad v=\sqrt{2gh}=9.9\,\mathrm{m\,s^{-1}}\]

Answer: The speed is approximately \(9.9\,\mathrm{m\,s^{-1}}\). Mass cancels because both energy terms are proportional to mass.

Common Mistakes

  • Using energy conservation without defining the initial and final states.
  • Counting frictional work and the same thermal-energy increase twice.
  • Assigning potential energy to an object alone instead of an interaction within a system.
  • Keeping a negative speed after solving for (v^2); speed is nonnegative.

Key Takeaways

  • Define the system and states before writing the ledger.
  • Track transfers once and keep units in joules.
  • Use conservation to relate states even when the detailed motion between them is complicated.
Practice connection

Use the quiz and practice tabs to include springs, friction, power, and energy graphs.

Official curriculum reference: College Board AP Physics 1 course page. The explanation and worked example are independently written for this study site.