. VISCOSITY OF A LIQUID BY STOKE’S METHOD AIM To determine the co-efficient of viscosity of the given liquid by stoke’s method APPARATUS REQUIRED A long cylindrical glass jar, highly viscous liquid, metre scale, spherical ball, stop clock, thread. FORMULA η δ σ r g ( ) N s m - where η - Coefficient of viscosity of liquid ( N s m – ) r → radius of spherical ball ( m ) δ → density of the steel sphere ( kg m – ) σ → density of the liquid ( kg m – ) g → acceleration due to gravity ( . m s – ) V → mean terminal velocity ( m s – ) DIAGRAM Spherical Ball Point B Point A Given Experimental Viscous Liquid EXPERIMENTAL SET UP OF MEASURING VISCOSITY BY STOKE’S METHOD UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical PROCEDURE ¾ A long cylindrical glass jar with markings is taken.
¾ Fill the glass jar with the given experimental liquid. ¾ Two points A and B are marked on the jar. The mark A is made well below the surface of the liquid so that when the ball reaches A it would have acquired terminal velocity V. ¾ The radius of the metal spherical ball is determined using screw gauge.
¾ The spherical ball is dropped gently into the liquid. ¾ Start the stop clock when the ball crosses the point A. Stop the clock when the ball reaches B and note down the time ‘t’. ¾ Note the distance between A and B and use it to calculate terminal velocity.
¾ Now repeat the experiment for different distances between A and B. Make sure that the point A is suitable for the ball to acquire terminal velocity. OBSERVATIONS To find Terminal Velocity: S.No. Distance covered by the spherical ball (d) (m) Time taken (t) (s) Terminal Velocity (V) d t (m s – ) MEAN CALCULATION Density of the spherical ball δ = kg m − Density of the given liquid σ = kg m − Coefficient of viscosity of the liquid η δ σ r g ( ) = N s m – RESULT The coefficient of viscosity of the given liquid by stoke’s method is found to be η = N s m – UNIT- (XI- - ) PRACTICAL FIRST UNIT- (XI- - ) PRACTICAL FIRST - - - - Practical