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btpolk

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## Homework Statement

A penny is dropped from a skyscraper.

a) Determine the terminal speed

b) How long will it take to reach terminal speed.

c) Will it exert enough force at terminal speed to break skin (460 psi is needed).

## Homework Equations

a) F(air drag)=(1/2)(air density)v^2(surface area)(drag coefficient)

F= mg

c) conservation of energy?--P=F/A→Fd=(1/2)mv^2→P=(mv^2)/(2Ad)

## The Attempt at a Solution

a) V(terminal)= √((2mg)/(air density*surface area*drag coefficient))=11.067 m/s

m= 0.0025kg air density=1.204 kg/(m^3) surface area= 0.000284m^2 drag coe=1.17

b) I completed an iterative process on excel and came up with t ≈11s d ≈122m

c) When I used the energy approach I get a pressure lower than that of when the penny is just laying on your skin. I'm not sure what went wrong. Oh and I'm assuming the penny is falling flat the whole way.

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