Terminal Velocity of a Penny
A penny is a flat object and does not weigh a lot (~2.5 g). Because of its low density, a penny does not experience much drag force. When thrown out of a building, it reaches its terminal velocity within 50 feet of drop. Let us now calculate its terminal velocity using the given equation.
\[v_{T} = \sqrt{\frac{2mg}{C\rho_{air} A}} \]
For a penny, we have the following information:
m = 2.5 g = 0.0025 kg
ρ_{air} = 1.29 kg/m^{3}
C = 1.12
Diameter = 2 cm or A = 0.000314 m^{2}
g = 9.81 m/s^{2}
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.

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Article was last reviewed on Wednesday, June 22, 2022