Terminal Velocity Steel Ball Bearing in Oil

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SUMMARY

The terminal velocity of a 1.5-mm-diameter steel ball bearing in SAE 30 oil can be calculated using the principles of fluid dynamics. The density of the steel ball bearing is 7830 kg/m³, while the oil has a density of 917 kg/m³ and a viscosity of 0.26 kg/(m·s). The drag force equation, which includes the coefficient of drag and Reynolds number, is essential for determining terminal velocity. The user is struggling to isolate velocity due to the cancellation of variables in their calculations.

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  • Understanding of fluid dynamics principles
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  • Knowledge of Reynolds number calculations
  • Basic proficiency in algebraic manipulation of equations
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A 1.5-mm-diameter steel ball bearing (7830 kg/m^3) is dropped into a tank of SAE 30 oil. What is its terminal velocity?

The density of oil is 917kg/m^3, and the viscosity of oil is 0.26kg/(m*s).

Help is much appreciated!
 
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What have you tried so far?

Where are you stuck?
 
Force of drag = 1/2 * (density of fluid) * (area of sphere) * v^2 * (coefficient of drag)
Force of drag = 3 * pi * (coefficient of fluid) * (diameter of obj) * v

Coefficient of drag = 24 / (Reynolds number)

Reynolds number = (density of fluid * velocity of fluid * chracteristic length)/(viscosity of fluid)

When I combine the equations, v cancels out so I cannot solve for it. Is there another equation I should be using?
 

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