🎯 Physics I: How Things Move

What you’ll learn

1. Describing MotionSet up motion using frames of reference, position, and displacement.Motion is always described relative to a chosen reference frame, and position is a number along an axis. Displacement is the straight-line change in position with direction, distinct from total distance traveled.
2. Speed and VelocityDistinguish speed from velocity and average from instantaneous.Speed is distance over time with no direction, while velocity adds direction. Average velocity spans a whole trip, whereas instantaneous velocity is the value at a single moment.
3. AccelerationDefine acceleration as any change in velocity, including turning.Acceleration is the rate of change of velocity in size or direction, controlled by forces. Speeding up, braking, and even steady turning are all accelerations.
4. Free Fall and GravityExplain that gravity accelerates all objects equally, absent air.Near Earth, gravity gives every object the same acceleration of about 9.8 m/s² regardless of mass, as Galileo argued against Aristotle. Air resistance normally masks this by producing a terminal velocity.
5. Projectile MotionAnalyze projectiles by splitting motion into horizontal and vertical parts.A projectile follows a parabola under gravity, with independent steady horizontal motion and accelerating vertical motion. Launch angle sets range, with about 45 degrees giving the maximum on level ground.
6. Newton’s First LawState the law of inertia and recognize it in everyday life.A body stays at rest or in uniform motion unless a net force acts, its resistance to change being inertia. Newton set out the three laws in the 1687 Principia, unifying earthly and celestial motion.
7. Newton’s Second LawApply F = ma relating force, mass, and acceleration.Net force equals mass times acceleration, so a bigger force gives more acceleration and more mass gives less. Mass is an object’s resistance to being accelerated.
8. Newton’s Third LawExplain action–reaction force pairs and thrust.Forces come in equal, opposite pairs acting on different objects, so pushing water back drives a boat forward. Recoil, rowing, and rocket thrust all follow, and rockets work even in vacuum.
9. Free-Body DiagramsBuild and use free-body diagrams to find net force.A free-body diagram isolates one object and draws every force as an arrow, which add head-to-tail into a net force. A fixed method—isolate, draw forces, choose axes, apply F = ma—solves most mechanics problems.
10. FrictionDescribe static versus kinetic friction and how to reduce it.Friction opposes sliding between surfaces, with static friction exceeding kinetic so objects lurch into motion. Bearings and lubrication replace sliding with rolling or shearing to cut friction and waste heat.
11. Circular MotionExplain centripetal force and orbits.Circular motion requires a centripetal force directed toward the center, supplied by tension, banking, or gravity. A satellite orbits because gravity pulls it inward while its sideways speed keeps it falling around Earth.
12. Work and PowerDefine work and power and how machines redistribute effort.Work is force times distance moved along the force, and power is the rate of doing work in watts. Levers and pulleys trade force for distance but cannot create energy.
13. Energy and Its ConservationTrack kinetic and potential energy under conservation.Kinetic energy grows with the square of speed, while lifting stores gravitational potential energy. Energy is conserved, only changing form, as a pendulum trades height for speed and back.
14. Momentum and CollisionsUse momentum conservation to analyze collisions.Momentum is mass times velocity, and total momentum is conserved in collisions without outside forces. Elastic collisions preserve kinetic energy while inelastic ones convert some to heat and sound.
15. Rotation, Torque, and EquilibriumExplain torque, rotational balance, and stability.Torque is force times distance from a pivot, so a longer lever turns more effectively. An object balances when opposing torques cancel and stays upright while its center of mass sits over its base.

Questions this course answers

Grounded in trusted sources

• Isaac Newton, 'Philosophiae Naturalis Principia Mathematica' (1687)
• OpenStax, 'University Physics, Volume 1' (openstax.org)
• Halliday, Resnick & Walker, 'Fundamentals of Physics'
• NASA — Glenn Research Center, 'Beginner's Guide to Aeronautics' (grc.nasa.gov)

Every Wunder lesson is built from real, reputable sources — never invented.

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