The wind chill tells you how cold it feels as a function of the air temperature and wind speed. Figure 8.35 is a contour diagram of wind chill (◦F).

(a) If the wind speed is 15mph, what temperature feels like −20◦F?

(b) Estimate the wind chill if the temperature is 0◦F and the wind speed is 10 mph.
(c) Humans are at extreme risk when the wind chill is below −50◦F. If the temperature is −20◦F, estimate the wind speed at which extreme risk begins.
(d) If the wind speed is 15 mph and the temperature drops by 20◦F, approximately how much colder do you feel?

wind speed, mph 30 20 10 -80 -60 -40 A -60 -40 -20 0 20 Figure 8.35 020 17 -20 0 40 air temp. F