Courses · PHY 101

PHY 101: Physics and Astronomy

14 lessons and an exam, in order, from a falling ball to the edge of the observable universe. Each lesson opens with one big question and answers it with measurements, pictures, and a little math. Lessons 1 and 2 are open; the rest are coming.

Texts: OpenStax College Physics 2e; OpenStax Astronomy 2e

Quiz: practice questions from the open lessons

1. Lesson 1Motion, speed, and acceleration

   Big questionDrop a bowling ball and a baseball together. Which lands first, and how would you find out?

   Key ideasPosition and displacement; speed vs velocity; vectors; acceleration; free fall at 9.8 m/s²; Galileo's ramp.

   You will seeA strobe picture of a falling ball, a drop simulator, and velocity arrows.

2. Lesson 2Forces and Newton's laws

   Big questionWhy does a hockey puck keep sliding, and what finally stops it?

   Key ideasForce; inertia; F = ma; action and reaction; friction; weight vs mass.

   You will seeFree-body diagrams and a tablecloth-pull animation.

3. Lesson 3 · Coming soonEnergy, work, and momentum

   Big questionWhere does a roller coaster's speed come from, and where does it go?

   Key ideasWork; kinetic and potential energy; conservation of energy; power; momentum and collisions.

   You will seeA roller-coaster energy-bar slider and colliding carts.

4. Lesson 4 · Coming soonGravity and orbits

   Big questionWhy doesn't the Moon fall down? Or does it?

   Key ideasKepler's laws; Newton's universal gravitation; the inverse-square law; orbits as falling around; weightlessness; tides.

   You will seeNewton's cannonball interactive and an ellipse that sweeps equal areas.

5. Lesson 5 · Coming soonWaves and sound

   Big questionHow does a voice cross a room when no air actually travels across it?

   Key ideasFrequency, wavelength, amplitude, and wave speed; interference; resonance; the Doppler effect.

   You will seeA slinky wave animation and a passing siren's Doppler rings.

6. Lesson 6 · Coming soonLight and the electromagnetic spectrum

   Big questionWhat is light, and what colors exist that our eyes cannot see?

   Key ideasElectromagnetic waves; radio to gamma rays; the speed of light; reflection and refraction; telescopes; photons.

   You will seeA spectrum strip with the telescope that sees each band, and a prism.

7. Lesson 7 · Coming soonHeat, temperature, and entropy

   Big questionWhy does hot coffee always cool down and never warm itself up?

   Key ideasTemperature vs heat; moving molecules; conduction, convection, radiation; the laws of thermodynamics; entropy; glowing hot objects.

   You will seeA molecule-speed animation and a color-versus-temperature glow chart.

8. Lesson 8 · Coming soonSpace, time, and relativity

   Big questionIf you could ride alongside a light beam, what would you see?

   Key ideasThe constant speed of light; time dilation; length contraction; E = mc²; GPS clock corrections; gravity as curved spacetime.

   You will seeA light-clock animation and a curved-spacetime diagram.

9. Lesson 9 · Coming soonAtoms and the quantum world

   Big questionHow can we know what a star is made of without going there?

   Key ideasAtomic structure; energy levels; photons; emission and absorption spectra; wave-particle duality; the uncertainty principle.

   You will seeAn electron energy-jump animation and the spectral barcodes of hydrogen, sodium, and the Sun.

10. Lesson 10 · Coming soonThe nucleus: radioactivity, fission, and fusion

    Big questionWhat keeps the Sun shining for billions of years?

    Key ideasProtons and neutrons; the strong force; isotopes; half-life; fission; fusion; mass turned into energy.

    You will seeA half-life decay chart and the Sun's proton-proton chain.

11. Lesson 11 · Coming soonThe solar system

    Big questionHow did people measure the size of Earth and the distance to the Sun?

    Key ideasEratosthenes; the scale of the solar system; the Sun's layers; rocky and giant planets; moons and comets; how planets formed; planets around other stars.

    You will seeA to-scale solar system walk and Eratosthenes' shadow diagram.

12. Lesson 12 · Coming soonStars: birth, life, and death

    Big questionWhy do some stars end as white dwarfs and others as black holes?

    Key ideasBrightness vs luminosity; parallax; the H-R diagram; nebula to main sequence to giant; white dwarfs, neutron stars, black holes; elements made in stars.

    You will seeAn interactive H-R diagram and a star life-cycle flowchart.

13. Lesson 13 · Coming soonGalaxies and the Milky Way

    Big questionHow big is our galaxy, and how do we know where we sit in it?

    Key ideasThe Milky Way's shape; the cosmic distance ladder; Cepheid stars; Hubble and other galaxies; galaxy types; dark matter from rotation curves.

    You will seeA distance-ladder chart and a galaxy rotation-curve plot.

14. Lesson 14 · Coming soonThe expanding universe

    Big questionDid the universe have a beginning, and what is the evidence?

    Key ideasRedshift and the Hubble-Lemaître law; the Big Bang model; the cosmic microwave background; light-element amounts; an age of about 13.8 billion years; dark energy; open questions.

    You will seeA raisin-bread expansion animation, the microwave-background map, and a timeline of the universe.

15. Exam · Coming soonPHY 101 Exam