Sphere of Death (मृत्यु गोल)

The 'sphere of death' is a well-known circus act in which one or more two-wheeler riders perform circles inside a large hollow sphere. The performance typically begins with small, nearly HORIZONTAL circles near the sphere's equator -- governed by exactly the same dynamics as the conical pendulum of section 1.3.4, since here too the linear speed is larger for the bigger (equatorial) circles while the angular speed (frequency) is larger for the smaller circles traced nearer the top or bottom of the sphere -- and only gradually builds up to full VERTICAL circles. Once the rider is performing genuine vertical circles, the dynamics become identical, position for position, to the string-and-bob analysis of section 1.4.1 (uppermost minimum speed $\sqrt{rg}$, lowermost minimum speed $\sqrt{5rg}$, extreme force difference $6mg$, and so on), with exactly ONE substitution: since there is no string here, the role played by the string's tension T is played instead by the sphere wall's NORMAL REACTION force N, which …