(a) Explain the following terms:
(i) viscosity;
(ii) terminal velocity.
(b)(i) Describe an experiment to determine the terminal velocity of a steel ball falling through a jar of glycerine..
(ii) State two precautions that should be taken to ensure accurate result.
(c) State two
(i) effects of viscosity
(ii) applications of viscosity.
Explanation
(a)(i) Viscosity is the property of a fluid which tends to prevent or oppose motion of one layer or part over another. It varies with the temperature and nature of the fluid. (ii) A body falling through a fluid eventually attains a steady velocity called terminal velocity. At this point the weight of the body equals the upthrust and viscous force. (b)(i)
Description: A tall glass jar is filled with glycerine anJ supported vertically. Bands (acting as markers) are attached to points A.B.C.D.E and F at equal intervals. The ball is allowed to fall from the top of the jar while the time is noted as the ball passed each marker in turn. It will be observed that the time intervals between A and B, B and C are different while the time intervals for C and D, D and E, E and F are equal. Showing that a steady terminal velocity is reached from C. This ;Weans that
(frac{CD}{t} = frac{DE}{t} = frac{EF}{t}) is the terminal velocity.
(ii) Precautions:
(1) Drop the ball gently.
(2) Ball must fall centrally down the glycerine
(c)(i) (1) Viscosity is responsible for the different rates of flow of fluid
(2) Viscosity affects motion of bodies in fluids.
(ii) (1) Viscous liquids are used as lubricants
(2) The knowledge of viscous drag is applied in the design of ships and aircraft.