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A ball bearing made of carbon steel (1%C), with a radius of 0.75cm, will cool from...

A ball bearing made of carbon steel (1%C), with a radius of 0.75cm, will cool from 500°C to 100°C under air flowing with a convection coefficient of 110 W/m2 K at 25°C. How long will it take for the ball to cool to 25°C?

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