- #1

lucas

- 2

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## Homework Statement

Hi, I am doing a theoretical investigation which will be compared to an experimental I'll do later. I am trying to calculate how much time will it take an object to fall a heigh H. the object is a 5x5x5 cm cube. I have the Reynolds number as this Re=3546*Velocity; and I need both the drag coefficient and the terminal velocity.

Air density ([itex]\rho[/itex]): 1.25 kg/m

^{3}

Air Dynamic Viscosity ([itex]\mu[/itex]): 1.76E-05

Area: 25 cm

^{3}

Cube side length: 0.05 m or 5 cm

Height (H): 30m

## Homework Equations

Re=[itex]\frac{\rho*V*L}{\mu}[/itex]

Cd= F

_{drag}/0.5*ρ*A

_{surface}*V

^{2}*C

_{drag}

## The Attempt at a Solution

Re=3546*V

I used classic mechanics to estimate the avarage of V for a height H of 30m, and got a value of 12.15 m/s so Re=3546*12.15.

I'm stuck from here on.

I need the Drag Coefficient, and the terminal V, and at what time does the object reach the velocity.