18th August 2020

JSS 2 : PHYSICS : WEEK 3

NEW APPROACH

WEEK/TERM: THIRD TERM/WEEK 3

DATE: 05.05.2020

CLASS: J.S.S 2

SUBJECT: PHYSICS

TOPIC: VISCOSITY AND CAPILLARITY

REFERENCE: ESSENTIAL PHYSICS FOR SENIOR SECONDARY SCHOOL

BRIEF EXPLANATION: To demonstrate viscosity, (liquid friction) we can allow a coin or ball bearing to fall through a liquid. The liquid in which the motion of the ball bearing or coin slows down is said to be more Viscous than that in which the motion is fast. Also a less viscous liquid travels faster than a more viscous liquid in a pipe.

Notes for students (Lesson one)

Viscosity is the force that acts in order to oppose motion in fluids (liquid or gas). It can be called liquid friction. It is the property of liquids, which opposes the relative motion between different layers.

NSM-2 (S. 1 unit) and it is a vector quantity.

Thus n =

Examples of liquids that are more viscous

1. Engine oil
2. Castor oil
3. Palm oil
4. Honey
5. Coal tar

These are thick liquids

Examples of liquids that are less viscous

1. Kerosene
2. Water
3. Alcohol (ethanol)
4. Spirit
5. Salt solution etc

Effects of temperature on viscosity

1. Temperature reduces viscosity.
2. There are certain liquids whose viscosity does not change appreciably with changes in temperature such liquids are called VISCOSTATIC liquids.

Effects of viscosity

1. Viscosity affects the motion of objects in fluid
2. Viscosity in air causes turbulence in aerodynamics.

Application of viscosity

1. Viscous liquids are used as lubricants. Examples of such liquids are oil and grease
2. Viscosity idea is applied in the design of ships and air craft.

Lesson two

Capillarity means the ability of a liquid to rise and fall in a narrow tube.

Application (examples) of capillarity.

1. The movement of ink in pen.
2. The rising up of water in the stem of a plant.
3. The circulation of blood across the body through the capillaries.
4. The rising of kerosene up the wick of a lamp.

Exercises /Assignment

1. What is viscosity?
2. What is the effect of temperature in viscosity?
3. Write two applications of viscosity.
4. What is capillarity?