Work procedure technique and data processing. 1. Measure the radius of the ball by means of a microscope

1. Measure the radius of the ball by means of a microscope. Place the microscope on a white sheet against a sun light. Get a clear picture of a scale’s net by turning a limb of the microscope top lens back and forth. Get a clear picture of the ball by turning a limb of the microscope bottom lens back and forth. Count the number of pitches N on the scale net corresponding to the diameter of the small-shot ball. Scale factor c is written on the microscope body so it is possible to calculate the radius of the ball by the formula:

Repeat measurements 3 times turning the ball concerning to the scale. Calculate arithmetic mean r of three radii.

2. Set the observer’s eye against the upper score behind the cylinder. Drop the ball into the liquid stop; turn on a stopwatch just when the ball is passing the upper score. Remount the eye against the lower score and turn off the stopwatch just when the ball is passing the lower score. Write down the time of ball falling. Repeat measurements with 5-8 other small-shot balls.

3. Measure the distance between the upper and the lower scores L by a ruler.

4. Find the values of the ball and the liquid densities in the density table. The teacher gives material of the ball and the liquid.

5. Put the results down into table 6.2.

6. Calculate the internal friction coefficient for each ball by the formula (6.14).

7. Calculate these coefficient errors as direct measurement errors.

Table 6.2.

Exp. №	r, m	t, s	η,		Δ η i	Sn	Δ η