Calculating viscosity of a liquid with a falling object

[Beyar]

Homework Statement

[/B]
A small steel-bearing falls 25.0 cm in glycerol in 23.8 s and the same distance in castor oil in 15.1 s. The densities are for glycerol 1260 kg m−3 , for castor oil 961 kg m−3 , and for steel 7830 kg m−3 . The viscosity for glycerol is 1.490 Pa s. Calculate the viscosity for castor oil. All values are valid for 20 ◦C.

Homework Equations

I guess Viscosity=Density*Velocity where the velocity is equal to Distance/time.

The Attempt at a Solution

Thought I'd put the equation for the distance equal to each other and then rewrite it to get the viscosity of the castor oil, but I get the wrong value. It should be 0,988 Pas. I get the final equation to:
Viscosity of Glycerol= (Density of Castor Oil*Viscosity of Castor*Time the steel bearing fell in the Glycerol)/(Density of Glycerol * time steel bearing fell in Castor oil)

The equation has not regarded the denisty of the steel-bearing though, so that might be the problem but I don't see how I would get around to fit it in.
It is very frustrating.

 

[BvU]

The equation has not regarded the denisty of the steel-bearing though

Well then, could it be that the net driving force for falling is a density difference ?

 

[Borek]

https://en.wikipedia.org/wiki/Stokes'_law

 

[Beyar]

https://en.wikipedia.org/wiki/Stokes'_law

But stokes relation has accounted the radius of the spherical particle, I don't have a radius to utilize.

 

[BvU]

But stokes relation has accounted the radius of the spherical particle, I don't have a radius to utilize.

Call it $R$, cross your fingers and hope it divides out in the answer