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Physics · Mechanics

Forces & Motion

Predict where the ball lands, then let a real physics engine prove you right or wrong — ramps, collisions, pendulums and springs.

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The course

12 worlds · 59 lessons

World 1 · Kinematics

FREEMotion, free fall & projectiles
  1. 01Free FallHow gravity speeds a falling ball · 5 min
  2. 02How Far It FallsDistance grows with time squared · 6 min
  3. 03Horizontal LaunchSideways motion + gravity · 6 min
  4. 04Projectile RangeThe classic 45° cannon shot · 7 min
  5. 05Peak HeightHow high a shot climbs · 6 min
  6. 06Mass Doesn’t MatterGalileo’s falling-bodies result · 5 min
  7. 07Velocity Over TimeReading v = g·t · 5 min
  8. 08Throwing UpRise, stop, and fall back · 6 min
  9. 09Float, sink, or stay suspended?Compare the block and the liquid · 6 min

World 2 · Newton & Friction

PROForces, ramps & the laws of motion
  1. 01InertiaNewton’s 1st law: no force, no change · 5 minPRO
  2. 02Force on a RampNewton’s 2nd law: F = m·a · 6 minPRO
  3. 03Steeper Is FasterMore slope, more acceleration · 5 minPRO
  4. 04Gentle SlopesSmall angle, slow gain · 5 minPRO
  5. 05Mass on a RampAcceleration ignores mass · 6 minPRO
  6. 06Force Over TimeThe longer it pushes, the faster · 5 minPRO
  7. 07Friction GripsSliding becomes rolling · 6 minPRO
  8. 08Friction & MassDoes a heavier ball roll differently? · 5 minPRO
  9. 09Friction Shortens the TripDistance lost to friction · 6 minPRO

World 3 · Energy & Momentum

PROCollisions, pendulums & conservation
  1. 01Falling EnergyHeight turns into motion · 6 minPRO
  2. 02Impact SpeedHow fast it hits · 5 minPRO
  3. 03Elastic CollisionEqual masses swap velocity · 7 minPRO
  4. 04Heavy Hits LightUnequal elastic collisions · 7 minPRO
  5. 05Sticking TogetherPerfectly inelastic collisions · 6 minPRO
  6. 06Momentum Is ConservedThe bookkeeping never changes · 6 minPRO
  7. 07The BounceRestitution and lost height · 6 minPRO
  8. 08Pendulum SpeedFastest at the bottom · 6 minPRO
  9. 09Mass on a PendulumBottom speed ignores mass · 5 minPRO

World 4 · SHM & Springs

PROOscillations, springs & pendulums
  1. 01Spring OscillationA mass bouncing on a spring · 6 minPRO
  2. 02Stiffer SpringsBigger k, quicker bounce · 5 minPRO
  3. 03Heavier MassMore mass, slower bounce · 5 minPRO
  4. 04Hooke’s LawHow far a spring stretches · 6 minPRO
  5. 05Pendulum PeriodTimekeeping by length · 6 minPRO
  6. 06Longer PendulumsMore length, slower swing · 5 minPRO
  7. 07Pendulum & MassWhy the bob’s weight is irrelevant · 5 minPRO

World 5 · Buoyancy & floating

PROMeasure the liquid that supports a block
  1. 01The water you push asideArchimedes’ principle under a clamp · 6 minPRO
  2. 02A block that neither rises nor sinksBalance two equal forces · 5 minPRO
  3. 03Why salt water lifts you higherSame block, denser liquid · 6 minPRO

World 6 · Release, shape and hollow hulls

PRO
  1. 01A release takes timePRO
  2. 02Same volume, different journeyPRO
  3. 03How the same metal can floatPRO

World 7 · One launch, different gravity

PROFollow the ball all the way to its first landing
  1. 01A launch on Earth and on the MoonPRO

World 8 · Block on a ramp: friction and net force

PROStatic grip, sliding friction and the push that wins
  1. 01When does a block start to slip?Static friction and the slip angle · 8 minPRO
  2. 02Sliding: net force and accelerationKinetic friction and F = m·a · 8 minPRO
  3. 03Push up the ramp: which way does friction point?Static friction can point downhill · 8 minPRO

World 9 · Circular motion: curves, wheels and orbits

PROCentripetal force, banked curves, the Ferris wheel and satellites
  1. 01Moving in a circle at a steady speedv = 2πr/T and a = v²/r toward the centre · 9 minPRO
  2. 02A car on a flat curveFriction is the centripetal force: v ≤ √(μ·g·r) · 9 minPRO
  3. 03The banked curveIdeal speed √(r·g·tanθ), and the friction window around it · 9 minPRO
  4. 04Ferris wheel and satellites: feeling lighterApparent weight N = m(g ∓ v²/r), and v = √(GM/r) in orbit · 9 minPRO

World 10 · Momentum and collisions

PROAir-track gliders, bumpers, photogates and billiard balls
  1. 01Momentum is conserved in every collisionp = m·v, before = after, but kinetic energy only when elastic · 10 minPRO
  2. 02Stop dead: equal masses and impulseElastic, equal masses, one at rest: the velocities swap. J = Δp = F·Δt · 10 minPRO
  3. 03How bouncy? Finding e with photogatese = speed of separation ÷ speed of approach · 10 minPRO
  4. 04Billiards: momentum is a vectorEqual masses, elastic, glancing: the balls leave at 90° · 10 minPRO

World 11 · Springs and pendulums: period, energy and resonance

PROMeasure periods, big swings, a driven spring and two coupled pendulums
  1. 01Spring or pendulum: what sets the period?T = 2π√(m/k) and T = 2π√(L/g) · 9 minPRO
  2. 02Energy back and forth, and big swingsKE ↔ PE, and why a big swing takes longer · 9 minPRO
  3. 03Resonance: driving a springDamping, steady amplitude and the resonance peak · 9 minPRO
  4. 04Coupled pendulums: handing the energy overBeats and the two normal modes · 9 minPRO

World 12 · Rigid bodies: rolling, spinning and flipping

PROMoment of inertia, gyroscopes and the tennis-racket flip
  1. 01Rolling race: why shape beats massMoment of inertia and rolling down a ramp · 10 minPRO
  2. 02Why doesn’t the spinning wheel fall?Torque, angular momentum and precession · 10 minPRO
  3. 03The tennis-racket flipPrincipal axes and the unstable middle axis · 10 minPRO
Read first

Guides for Forces & Motion

All guides →
Exam prep
Forces & MotionAP Physics 1 Forces and Motion: A Free Study GuideMap the forces and motion topics of an introductory physics course to free interactive lessons, with a four-week study plan and tips for the practice exams.4 min read
Explainer
Forces & MotionHow Free Fall and Projectile Motion Work: KinematicsWhy falling speed grows steadily, why distance grows with time squared, and how splitting a throw into two parts predicts range and height. With a live physics lab.5 min read
Explainer
Simple MachinesHow Levers Work: Fulcrum, Torque and Mechanical AdvantageUnderstand the three classes of lever, why a longer arm gives more lifting force, and the balance rule that ties it together. With a live simple-machines lab.4 min read