Why does a spinning coin settle down?
Show answer & explanation
Answer: Contact losses and air resistance dissipate mechanical energy
Contact losses and air resistance dissipate mechanical energy ✓ — Contact with the table and resistance from the air dissipate the coin’s mechanical energy. Energy passes into heat, vibration and sound rather than disappearing. The coin eventually lies flat, though its final wobble can speed up while its total mechanical energy continues to fall.
The table’s magnetism drains energy from every kind of coin — A coin can stop on a nonmagnetic table, so magnetism is not required. The ordinary losses come from its interaction with the table and surrounding air.
Gravity steadily removes the coin’s mechanical energy — Gravity alone does not dissipate a spinning coin’s mechanical energy. It can exchange gravitational potential energy with motion, but contact losses and air resistance are needed to explain the lasting loss of motion.
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