Physics
Measures physics knowledge and quantitative reasoning: worked mechanics and energy problems, unit conversion, orbital/Kepler estimates, electricity, optics, thermodynamics, Fermi-style order-of-magnitude estimation, and plain-language conceptual explanations of relativity and quantum mechanics. Distinct from Physics Lab, which grades runnable canvas simulations rather than worked answers.
Rounds 10
R46 · Energy conservation on a frictionless incline
A 2 kg block starts from rest at the top of a frictionless incline and slides down to the bottom, dropping a height of 5 m. Using energy conservation …
R47 · Unit conversion: km/h to m/s and mph
A car travels at 108 km/h. Convert this speed to (a) meters per second, and (b) miles per hour (use 1 mile = 1.60934 km). Show the conversion steps an…
R48 · Low-orbit satellite: speed and period (orbital/Kepler estimate)
A satellite orbits Earth in a circular low orbit at 400 km altitude. Using Earth's radius ≈ 6371 km and standard gravitational parameter μ = G*M ≈ 398…
R49 · Ohm's law: resistance and power dissipation
A 12 V battery is connected across a resistor, and the resulting steady current through the circuit is 0.5 A. Using Ohm's law, calculate: (a) the resi…
R50 · Thin lens equation: image distance and magnification
A converging (convex) lens has a focal length of 10 cm. An object is placed 15 cm in front of the lens, on the optical axis. Using the thin lens equat…
R51 · Heat required to warm water (specific heat capacity)
How much heat energy is required to raise the temperature of 2 kg of water from 20°C to 80°C? Use the specific heat capacity of water c = 4186 J/(kg*K…
R52 · Fermi estimate: how many piano tuners in a 10-million-person city?
Using Fermi estimation (order-of-magnitude reasoning, no lookups) estimate how many professional piano tuners work in a city of 10 million people. Wal…
R53 · Why is the sky blue? (conceptual)
In plain, non-technical language, explain why the sky appears blue during the day. Name the physical phenomenon responsible.
R54 · Time dilation: why do moving clocks run slow? (conceptual, special relativity)
In plain, conceptual language (no equations required), explain why a clock moving relative to an observer is measured to run slow (time dilation in sp…
R55 · The double-slit experiment and wave-particle duality (conceptual, quantum mechanics)
In plain, conceptual language, explain the double-slit experiment: what pattern is observed on the screen when particles (e.g. electrons or photons) a…