Apparatus:
Measuring cylinder, Glycerine, Stopwatch, small steel ball-bearings of varying diameter, Micrometer screw gauge, and metre ruler. Hydrometer, thermometer 0-100°C
Observations:
Zero error of micrometer screw gauge=………………..mm
Distance between ‘X’ and ‘Y’ (1) =…………………….x 10-3 m
Diameter of the largest ball bearings=………………………m
Radius of the largest ball bearings (r1) =………………….m
Diameter of the medium ball bearing =………………..m
Radius of the medium ball bearings (r2) =………………m
Diameter of the small ball bearings =………………….m
Radius of the small ball bearings (r3) ………………….m
Density of glycerin a = ……………….kg-3
| No.of Obs | Micrometer Readings mm | Average Diameter mm | Time of fall for xy ‘t’ sec | Terminal Velocity ‘v’ m/s | (Radius)2 ‘r2’ mm2 |
| 1 2 3 |
Density of steel p = ………………kg-1
Temperature of glycerine =……………..C
Calculation of Viscosity
Terminal velocity ‘v’ is such that the apparent weight (4/3)ar (-) g is equal to the viscous drag baην
Vt (2r2/9 ) (Ps-PG) g
η (2/9m) (Ps – PG) g where m is the slope of Vt Vsr2 graph
Procedure:
Note the zero error of the micrometer screw gauge and then measure the diameters of zeel ball bearings of different sizes in two perpendicular directions with micrometer screw muge. Find the radius of respective ball bearings.
Fill the measuring cylinder ‘A’ with glycerin. Fix a mark ‘X’ on the cylinder well below me top of the liquid, so that the ball bearings reaches a steady velocity by the time it reaches ‘X’ is a second mark ‘Y’ near the bottom of the cylinder. Measure the distance between ‘X’ and ‘Y’ Drop the largest ball bearings. As the ball bearings reaches the mark ‘X’, start the stop atch. Stop the stopwatch when the ball bearing reaches the mark ‘Y’. Note the time of aveling between X and Y as ‘t’. Find the velocity of the ball bearing using the formula. S=Vt
V=S/t
Or V=( /t
Repeat this experiment with different ball bearings of different sizes. Record the observations in the table. Plot a graph between velocity V and the r³ (square of the radius) anc draw the best line passing through the origin Calculate its gradient E/F
VIVA VOCE
Q.1. What is meant by viscosity?
Ans. The internal resistance between two layers of a liquid is known as viscosity.
Q.2. What is the unit of viscosity?
Ans. The unit of viscosity in Sl units is NS m² or poise.
Q.3. What is terminal velocity?
Ans. The velocity attained by a body when two forces become equal to zero.
Q.4. What is freefall body?
Ans. A body which falls under the action of gravity.
