1011 past contests
Topic 25 · The electron as a fundamental particle among electron/antiproton/neutron
Topic 12 · Riddle: the kilogram as the only si base unit still defined by an artifact and having a prefix
Topic 31 · Thermal expansion of a plate with an eccentric hole: hole also expands (true/false)
Topic 31 · Thermal expansion of a plate with a central hole: hole also expands, does not shrink (true/false)
Topic 31 · Thermal expansion of a plate with a central hole: both plate and hole expand (true/false)
Topic 55 · Ohmic vs non-ohmic devices: incandescent lamps, pn junctions and metallic conductors (true/false)
Topic 39 · Problem of the day: resistivity unit conversion, wire length, and transformer primary current for a heating element
Topic 30 · Why metal feels cooler than wood at the same temperature (thermal conductivity)
Topic 31 · Why a mercury thermometer's column briefly falls before rising in warmer water
Topic 30 · Why ceiling air is warmer than floor air without ventilation (convection/stratification)
Topic 14 · Linearizing hooke's law for graphing
Topic 2 · Linearizing the inverse-square gravitational force law for graphing
Topic 5 · Linearizing the inverse-square electrostatic force law for graphing
Topic 30 · Temperature difference across a slab from heat-transfer rate, conductivity, area and thickness
Topic 30 · Heat transfer rate across window glass from thermal conductivity, area, thickness and temperature difference
Topic 30 · Heat transfer rate across a slab from thermal conductivity, area, thickness and temperature difference
Topic 61 · Acceleration of an shm oscillator at a given displacement
Topic 61 · Maximum velocity of an shm oscillator from amplitude and frequency
Topic 61 · Time for an shm oscillator to first reach a given displacement
Topic 31 · Riddle: the thermometer and thermal equilibrium