A spherical hailstone that has a radius ro is formed in a high-altitude cloud at -20 °C. Consider ro a parameter that takes values from 2.5 mm to 12.5 mm with increments of 2.5 mm. If the stone begins to fall through warmer air at 5 °C, determine for each value of ro:
1. How long will it take before the outer surface begins to melt.
2. What is the temperature of the stone’s center at this point in time.
3. How much energy (J) has been transferred to the stone in this time interval.
A convection heat transfer coefficient of 250 W/m²K may be assumed, and the properties of the hailstone may be taken to be those of ice.