Physics
Physics is the largest category on the site by tool count, anchored by Kinematics (projectile motion, momentum, velocity) and Astrophysics (black holes, redshift, the Drake equation), with Everyday Physics covering more hands-on questions like why the sky changes color at sunset. Sixteen subcategories map out the field, from mechanics through relativity.
Categories in Physics
Kinematics
If a physics problem involves position, velocity, or acceleration changing over time, it's almost certainly covered somewhere in this list, the largest physics subcategory on the site, spanning projectile motion, momentum, and vehicle-specific problems like quarter-mile time.
Astrophysics
Black hole properties, cosmic distance measures like redshift and parallax, the Drake equation for estimating extraterrestrial civilizations, and the physics behind Olbers' paradox make up this large-scale physics subcategory.
Everyday Physics
Why the sky looks a certain color at a given sun angle, how buoyancy works in a bathtub experiment, or whether a smartphone projector setup will actually focus: physics questions you'd run into day to day, less formal than the rest of the physics subcategories.