Answer Happy

(2) There was a controversy in pro football a few years ago regarding the intentional deflation of footballs before a game. Since footballs are inflated inside where it is warm, it makes sense that the pressure inside the football will drop when it is brought outside to lower temperature. This issue came up again a year ago before a game in Minnesota where the temperature was projected to be 0°F with strong winds (wind chill of -15°F). When asked how the pressure inside of a football would change when brought outside here is what a physics professor said: "Ignoring the wind chill (meaning the following is a conservative estimate, meaning the wind chill could make the on-field ball pressure even lower), the on-field ball pressure will be about 9 psi (assuming it was pressurized to 12.5 psi at 70F and measured on-field at OF)." The unit psi is pounds per square inch. Please estimate how the pressure inside of the football will change given the conditions. Do you arrive at the same numbers provided in the quote? Wind chill is mentioned as well, but no numbers are provided for its effect