Experimental part

1. Select 5 balls of approximately equal radius.

2. Fix the upper ring at the point of 0.1 m under liquid level. Place the lower ring CD at the distance 0.35 m from the upper one.

3. Measure radius of a ball by the vernier caliper. Drop the ball into the cylinder. Switch on the stopwatch at the moment the ball passes by the upper ring, and switch off it when the ball moves near the lower ring. Put down time of crossing the distance between rings into the table 8.1.

Table 8.1

№	, mm	, m	, s	, m/s	, Pa · s
		0.35
		0.40
		0.45
		0.50
		0.55
	=

5. Draw the graph versus . Make conclusions about character of ball’s motion. Determine the speed of motion as a slope of the line to the - axis.

6. Substituting speed and average radius into (8.6), calculate the coefficient of viscous friction .

7. Find out what is the main error in determination of . Estimate .

8. Examine condition (8.3).