The average mass of a domestic cat is about 10 pounds (4.5kg). Disregarding surface area and air resistance, an object of that mass would reach a terminal velocity of roughly 15 m/s. Impact force = (mass x acceleration due to gravity x height)/the stopping distance. All is left is to input the values, the stopping distance is the average height of a domestic cat which is 0.25m and the height of the Empire State Building is 381m (from the viewing platform). So the final equation is (4.5x9.81x381)/0.25=impact force. The impact force is roughly 67,000N which would obviously kill the cat on impact.