[v_{T} = \sqrt{\frac{2mg}{C\rho_{air} A}} ] For a penny, we have the following information: m = 2.5 g = 0.0025 kg ρair = 1.29 kg/m3 C = 1.12 Diameter = 2 cm or A = 0.000314 m2 g = 9.81 m/s2 Plugging in all the values, we get. While this appears high, a penny is so light that it cannot do much harm at this speed. For a penny to create a lethal effect, it needs to plummet in an airless environment. In this case, the penny would hit the ground at 210 mph, which is high enough to break the skin.
