Why does a spinning coin settle down?
Show answer & explanation
Answer: Friction dissipates energy
Gravity pulls it down — Wrong. Gravity provides downward force, but coin spins down because friction (air resistance + table contact) dissipates rotational energy.
Magnetism from table — Wrong. No magnetism involved (unless magnetic table). Coin settles because friction converts kinetic energy to heat, slowing rotation.
Friction dissipates energy ✓ — Correct! Spinning coin has rotational kinetic energy. Two friction sources dissipate it: (1) Air resistance—coin pushes air molecules as it spins. (2) Contact friction—edge touching table. Energy converts to heat and sound (vibration). As energy decreases, spin slows. Eventually insufficient angular momentum to maintain balance—falls flat. Faster initial spin = longer duration. Smooth table/coin = less friction, longer spin!
More Physics in Daily Life questions
- In a warm office that already reads 26 C, which change can make people feel cooler without lowering the thermostat?
- Why might 26 C feel acceptable in a breezy naturally ventilated summer building but too warm in a sealed winter office?
- On a warm humid day, why can the same 27 C room feel much worse once you start sweating?
- Why can moving air make a 27 C room feel cooler without changing the thermometer?
- Which hidden factor can make a desk beside a cold window feel chilly even when the thermostat across the room still reads 22 C?
- In the same 22 C room, why might someone who just climbed stairs feel warm while someone sitting in a T-shirt feels chilly?