Задача id13288

A person is supported in the air at a constant altitude by a small jet engine behind his back. The engine emits a stream of gases vertically downward at a speed relative to a person u = 1000 m/s. Fuel consumption is automatically maintained so that at any moment while the engine is running, the reaction force balances the weight of the person and the load. How long can a person stay at a constant altitude if his mass m1 = 70 kg, the mass of the engine without fuel m2 = 10 kg, initial

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