DETERMINATION OF LIQUID VISCOSITY COEFFICIENT

Task 1. Determination of time of balls falling down

1.1. Take 5 balls.

1.2. Measure diameter of each ball а_i by means a number of peaches of microscope МПВ-2. Repeat measurements 3 times. Calculate average values a_{i ave} of the ball diameter. Enter the obtained results into table 1.

Table 1

Exp. No	Ball diameter, аi, pitchers	Average value of ball diameter, ai ave, pitchers	Scale factor of microscope, N, mm	Average value of ball radius, ri ave, m	Height, the ball falls from l, m	Time, the ball falling down ti, s	Viscosity,
The first ball
The second ball
The third ball
The forth ball
The fifth ball

1.3. Calculate average value of ball radius r_{i ave} for each ball according to the formula:

where n = 3 is amount of measurements. Enter the results into table 1.

1.4. Measure the distance between the upper and the lower scores l of the cylinder by a ruler. Enter the results into table 1.

1.5. Take the first ball with known radius and fall it down in liquid. Measure the time the ball takes to fall the distance l. Repeat measurement with all other balls. Enter the results into table 1.

1.6. Measure the liquid temperature by a thermometer. Enter the results into table 2.

1.7. Enter values of material density r the balls made of and liquid density r_l into table 2.

1.8. Calculate the internal friction coefficient for each ball according to the formula:

.

Enter the results into table 1.

Table 2

Task 2. Calculation of viscosity measurement error

Calculate average value of the viscosity according to the formula:

where n = 5 is amount of measurements. Enter the results into table 3.

2.2. Calculate deviation from average value Δη_i according to the formula:

Table 3

Exp. No	Viscosity	Average value of vicosity ,	Deviation of mean value ,	Root-mean-square deviation	Absolute error, Dh,	Fractional error,

2.3. Calculate root-mean-square error of the arithmetic mean according to the formula:

2.4. Determine the viscosity measurement absolute error according to the formula: Dh = t_St .

where the Student’s coefficient is t_St = 2,78 (n = 5 and a = 0,95)

2.5. Calculate the viscosity measurement fractional error according to the formula:

2.6. Write down the result in a form: ____________________________,

Conclusions

The data of laboratory work fulfillment

Pass mark Signature

Mark of laboratory work defending Signature

questions to be admitted for doing laboratory work and its defending

1. Name the transport phenomena. What quantity is transferred during each of them?

2. Explain the cause of internal friction.

3. Explain the cause of heat conductivity.

4. Explain the cause of diffusion.

5. Write and explain Newton’s law for a steady laminar stream.

6. How does the coefficient of internal friction depend on temperature?

7. What is physical sense of velocity gradient?

8. Describe the Stock’s method for the coefficient of internal friction determination.

9. What forces make the ball move in liquid?

10. Deduce the formula for calculation of the coefficient in our experiment.

LABORATORY WORK

Date: 2015-01-12; view: 1227