Question

(The experiment is to find the viscosity of the fluid by dropping the steel ball into the fluid. The steel ball will reach the terminal velocity and the total time taken to travel in the fluid was recorded. )

Consider a method of changing the falling velocity of a steel ball for the same fluid and the same diameter and density from the viewpoint of drag force.

Answer 1

The drag force F can be given by the following equation

Here eta represents the viscosity of the fluid, r is the object's radius and v is the object's velocity.

At terminal velocity F will be given by weight

Here, m is the mass anf g is the acceleration due to gravity. Since the density (rho) of the fluid , the diameter (hence area of crosssection A) and the time t is known so the mass m can be obtained by as

Putting in (2) , F becomes

Substituting (4) in (1) we get

By using the above formula we can calculate the viscosity of the fluid.

Here, r=(diameter/2)