The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing the temperature-time history of a sphere fabricated from pure copper. The sphere, which is \(20 \mathrm{~mm}\) in diameter, is at \(75^{\circ} \mathrm{C}\) before it is inserted into the gas stream having a temperature of \(27^{\circ} \mathrm{C}\). A thermocouple on the outer surface of the sphere indicates \(55^{\circ} \mathrm{C} 97 \mathrm{~s}\) after the sphere is inserted into the hydrogen. Assume and then justify that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient.