Ball Bearing Ø/mm 1.59 2.38 3.175 Golden Syrup 200- 175 mm - N/A - 135.92 89.36 175-100 mm - N/A - 432.68 Time to fall marked distance (/s) Washing up liquid 268.25 100- 25 mm 15.19 3.18 3.79 Table 1 25-0 mm 4.21 1.91 1.09 100 - 25 mm 2 0.47 Olive oil 0.21 25-0 mm 1.31 0.21 0.14 Exercise B - Measurement of Viscosity Objective To determine the viscosity of various liquids at atmosphere pressure and temperature. Background theory Viscosity is a measure of a fluid's resistance to flow. It describes the internal friction of a moving fluid or can be described as the friction that a fluid will exert on an external object as travels in that fluid medium. The theory behind this experiment is as follows: From the Figure 2; when the ball is moving with a uniform velocity u, then forces acting on the sphere are: a. the gravitational force on the ball mg. b. the buoyant force or upthrust FB c. the viscous force resisting motion Fy Since the velocity of fall is uniform, then algebraic sum of these forces must be zero. mg - FB-Fv=0 The gravitational force on the ball can be calculated as: 4 mg = Ps9 3 where Ps= density of ball, r = radius of sphere. The buoyant force can be calculated as: 4 FB = P193 P193 πr.² πr² where P1 = density of liquid. Fv=6yX₂ The viscous force from Stokes Law can be calculated as: Where μ = coefficient of viscosity, u = mean velocity of ball. 4 μ = - Ps9²₁². Results 4πr³g 3x6πμru u= == 쓰 V = Calculate the velocity of the ball passing through the marked distances (between 100 to 25 and 25 to 0) using Equation 4 and find the average. Distance through which ball falls Time 4 Liquid Water πρ3 – 6πμru = 0 Calculate the average Dynamic viscosity for three different diameter balls passing through each liquid. Complete Table 3 for Dynamic Viscosity. Calculate Kinematic Viscosity by considering density of the liquids found in the first experiment A (Table 2) using the following equation: (Ps - P₁) = ²/r² g (Ps-P₁) u Barometric pressure 774.0635 mm Hg. Temperature 16°C. Specific gravity of steel: 7.8 Olive oil washing up liquid Golden Syrup Equation 3 Table 3. Results for Dynamic and Kinematic Viscosity Dynamic Viscosity, μ (kg/ms) Using equation 3 Equation 4 Equation 5 Kinematic Viscosity, v (m²/s) Using equation 5