EXPERIMENT TO DETERMINE THE VISCOSITY OF GLYCERINE.

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Nneka Ezeigwe. Physics coursework.

EXPERIMENT TO DETERMINE THE VISCOSITY OF GLYCERINE.

Procedure

        A series of different sized ball bearings were dropped into a measuring beaker containing glycerine. The time taken to travel between two marks on the beaker was recorded. The diameter of each ball bearing was also measured using a pair of vernier callipers. Each experiment was repeated three times. The diagram and readings are shown below.  

Readings

Note that the average readings have been taken to reduce or eliminate any error present.

I will now plot a graph to make the relationship between the diameter of the ball bearings and the time taken to travel a distance of 162mm.

        

         


The graph shows that there is an inverse relationship between the time taken and the diameter of the steel ball. The curve has a decreasing negative slope.

        When a steel ball (or any object for that matter) is dropped into a liquid, it experiences certain forces.  They are:

  • The weight of the object acting downwards
  • The upthrust acting upwards and t
  • The Viscous drag F acting upwards.

Every fluid has a property called viscosity. This is an internal property of the fluid that offers resistance to the movement of particles through it. It is also known as fluid friction. It arises because the intermolecular forces existing between the particles of the fluid oppose the movement of a particle through it. The greater the viscosity of the fluid, the stronger its resistance to the flow of particles through it.

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Sir George Gabriel stokes found the formula for the viscous retarding force. It is given by,

                     F=6πηvr

Where η= the viscosity of the fluid.

From this formula, we can see that the viscous drag on the bigger ball is bigger than the viscous drag on the smaller ball. This is because the velocity increases as well as the radius. The weight downward also increases and the graph implies that this does so on a greater scale than the velocity and the radius. Hence, the time taken is less for ...

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