Question : basic physics - ball bearing falling through oil

Hi

If you had a ball bearing falling through a cyclinder of oil until it reached terminal what is the name of the force opposing the motion of the ball bearing? Is it friction? Presumably whatever this force is increases with the speed of the ball bearing in the same way that the amount of air resistance increases with the speed of a falling object?

If you had a ball bearing dropping through a tall cyclinder of oil how would you show it had reached terminal velocity? Is that just showing when it starts travelling at a constant speed?

thanks

Answer : basic physics - ball bearing falling through oil

Viscosity, which is proportional to velocity to the 4th power.