|Aim||The aim of this experiment is to determine the coefficient of viscosity of a given viscous liquid by measuring the terminal velocity of a given spherical body.|
|Apparatus Required||A viscometer or a tall glass jar|
A stopwatch or timer
A spherical body (e.g., ball bearing)
A ruler or meter scale
A container of the given viscous liquid
|Theory||When a spherical body is dropped into a viscous liquid, it experiences a resistive force due to the viscosity of the liquid. As a result, the body’s velocity decreases over time until it reaches a constant terminal velocity. The magnitude of the resistive force depends on the velocity of the body, the size and shape of the body, and the viscosity of the liquid.|
The terminal velocity of the body can be expressed as:
Vt = (2/9) * (g * R^2) * (p – q) / η
where Vt is the terminal velocity, g is the acceleration due to gravity, R is the radius of the spherical body, p and q are the densities of the body and the liquid respectively, and η is the coefficient of viscosity of the liquid.
In this experiment, we will measure the terminal velocity of the spherical body in the given viscous liquid and use the above formula to calculate the coefficient of viscosity.
|Procedure||Measure the diameter of the spherical body using the ruler or meter scale, and calculate its radius.|
Weigh the spherical body using the balance and record its mass.
Fill the viscometer or tall glass jar with the given viscous liquid up to a certain height.
Measure the temperature of the liquid using the thermometer.
Drop the spherical body into the liquid and start the timer as soon as the body enters the liquid.
Measure the time taken for the body to reach the bottom of the viscometer or jar.
Repeat steps 5-6 for multiple trials and record the time taken for each trial.
Calculate the average time taken for the body to reach the bottom of the viscometer or jar.
Using the average time and the distance travelled by the body, calculate the terminal velocity of the body.
Use the formula mentioned above to calculate the coefficient of viscosity of the liquid.
Repeat steps 3-10 for different heights of the liquid in the viscometer or jar to obtain more data points.
Plot a graph between the coefficient of viscosity and the height of the liquid.
Draw the best-fit line through the data points and calculate the slope of the line. The slope represents the coefficient of viscosity of the liquid.
|Observation and Result||Result: The result of the experiment is a coefficient of viscosity of the given viscous liquid. This is obtained by calculating the terminal velocity of the spherical body in the liquid and using the formula mentioned above to calculate the coefficient of viscosity.|
Observation: During the experiment, we observe that the spherical body experiences a resistive force due to the viscosity of the liquid, which causes its velocity to decrease over time. The time taken for the body to reach the bottom of the viscometer or jar increases with the height of the liquid. This indicates that the resistive force increases with the height of the liquid, which is a characteristic of viscous liquids.
We also observe that the coefficient of viscosity calculated from the data points obtained by varying the height of the liquid in the viscometer or jar follows a linear relationship. The slope of the best-fit line through the data points represents the coefficient of viscosity of the liquid. This experiment helps us understand the concept of viscosity and how it affects the motion of objects in fluids.