FirstPrinciplesby Physoly

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Lessons and practice for the mistakes that cost points.

Choose AP Physics 1, AP Physics 2, Physics C, F=ma, USAPhO intro, or all of them. Each track has short lessons, practice problems with worked solutions, ladder links and mock tests. Progress is saved in this browser.

Courses
Physics 1 · Physics 2 · Physics C · F=ma · USAPhO
Lessons
19 short lessons
Worked drills
92 problems
Mock tests
37 questions · 113 pts

Pick a lesson below, or go straight to the full problem list.

Open all 92 problems →
  1. 01

    Pick your course.

    Physics 1 gets mechanics foundations. Physics 2 gets thermo, E&M, waves, optics, and modern model choice. Physics C, F=ma, and USAPhO get the heavier constraints and rotation.

  2. 02

    Study one mistake at a time.

    Each lesson explains why the wrong approach seems reasonable, then gives you a method you can use on the test.

  3. 03

    Practise, then take a mock test.

    Warm-up problems build the habit, harder problems check that it carries over, and mock tests show whether it stuck.

Choose your lane

Choose your course.

AP tracks focus on clear conceptual models. F=ma adds timed mechanics problems. USAPhO intro moves to longer written solutions where you justify each step.

All tracks

See the whole AP to F=ma to USAPhO bridge in one sequence.

Use this when you are planning the full platform route or browsing for weak spots.

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19lessons in lane

recommended sequenceAP Physics 1 / AP C entry

AP mechanics foundation

Clean up the force, axis, friction, and circular-motion mistakes that make contest problems feel random.

Best for: You know the formulas but still lose points because the diagram, sign, or force direction is off.

Diagnostic signal: Misses on normal force, static friction, projectile components, or constant-speed circular motion.

You should be able to

Draws free-body diagrams without non-interaction forces.Chooses axes before resolving components.Treats static friction as a response, not a fixed formula.Marks inward acceleration on any curved path.

Lessons

Normal force is not always mgAPStatic friction is not always maximumAPConstant speed does not mean zero accelerationAP/F=maImpulse is a vector, so signs matterAP

Ladder links

R1: Identify the forces on a blockAPR2: Choose axes on an inclineAPR3: Find the normal force on an inclineAPR4: Static friction thresholdAPR7: Circular motion: force directionF=maR11: Apparent weight in an elevatorAPR13: Friction from relative motionF=maR15: Projectile componentsAP

practice Practice problems

Try a problem, then open the hint or the solution.

Warm-up AP concept

What it testsMake the same model choice used in the linked lesson, then carry it into a fresh setup.

First moveUse the component perpendicular to the wrench.

Hint

Use the component perpendicular to the wrench.

Worked solution

τ = rF sin 30° = (0.25)(20)(0.5) = 2.5 N·m.

Common trap: Using τ = rF without the angle factor.

R32 lesson

learn Lessons

Short lessons, one mistake each.

Find my misses
Forces Normal force is not always mg AP · 5 minForces Static friction is not always maximum AP · 5 minCircular motion Constant speed does not mean zero acceleration AP/F=ma · 6 minMomentum Momentum is conserved only after an external-impulse check AP/F=ma · 6 minSystems Energy vs momentum: how to choose F=ma · 7 minConstraints Why constraint equations matter AP C/F=ma · 7 minModeling F=ma problems hide systems F=ma · 6 minRotation Rolling without slipping is a constraint AP C/F=ma · 7 minRotation Tension is uniform only in the ideal string limit F=ma/USAPhO · 6 minMomentum Impulse is a vector, so signs matter AP · 5 minRotation Torque uses the perpendicular lever arm AP · 5 minCircuits Current is not used up AP · 5 minThermodynamics Heat, temperature, and internal energy are different AP Physics 2 · 6 minFluids Pressure, buoyancy, and flow are different fluid models AP Physics 2 · 7 minElectricity Electric field is not electric potential AP Physics 2 · 6 minCircuits Capacitors change role over time AP Physics 2 · 6 minMagnetism Magnetic force is perpendicular to velocity and field AP Physics 2 · 6 minMagnetism Induced current opposes flux change, not flux AP Physics 2 · 6 minWaves and modern Waves, optics, and photons depend on the model you choose AP Physics 2 · 7 min

test Mock checks

Take these once your setups feel reliable.

Completion stays in this browser.

AP → F=ma readiness

Mechanics foundation check

A compact check for the force-direction, normal-force, friction, and circular-motion habits that decide early contest mechanics.

25 min · 6 questions · 15 pts Open mock
F=ma bridge

Forces and constraints mock

A bridge set for pulleys, system boundaries, friction direction, and accelerating frames.

35 min · 6 questions · 19 pts Open mock
AP → F=ma

Energy and momentum mock

A decision-making set for choosing the right conservation law on the right interval.

35 min · 6 questions · 20 pts Open mock
AP C → USAPhO intro

Rotation and rolling mock

A concentrated test of torque arms, rolling constraints, angular momentum, and rotational energy.

40 min · 6 questions · 22 pts Open mock
AP Physics 2

Physics 2 mixed model check

A cross-unit check for the AP Physics 2 habit that matters most: choosing the right model before calculating.

45 min · 9 questions · 27 pts Open mock
AP Physics 1/2

Circuits repair mini-check

A short conceptual check for current, voltage, and series/parallel reasoning.

15 min · 4 questions · 10 pts Open mock

next Not sure what to study?

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