Class IX Science

Govt. of Tamilnadu Department of School Education Bridge Course Class IX-Science

I.MEASUREMENTS – VERNIER CALIPER PLAY THE VIDEO no. 1.

measurement of length length  measuring tape accuracy = 1 mm / 0.1 cm / m  metre/half-metre rule

measurement of length the jaws are closed until the points just touch the object to be measured remove the calipers and measure the distance between the jaws with a ruler.

Vernier calipers measure small lengths accurately up to 0.01 cm. vernier calipers measurement of length accuracy = 0.1 mm / 0.01 cm inside jaws outside jaws main scalevernier scale tail

reading on main scale (between A and B) = 2.4 cm reading on vernier scale (C) = 0.08 cm actual reading of object = = 2.48 cm vernier calipers measurement of length main scale (fixed) vernier scale (movable) object being measured AB C 9 mm

vernier calipers measurement of length When the two jaws of the vernier calipers touch each other, both zero marks on the main scale and on the vernier scale should coincide. If not, there is a zero error in the vernier calipers.

supposing observed reading is 3.24 cm, then corrected reading = observed reading – zero error = 3.24 – (+0.01) = 3.23 cm measurement of length zero error = cm main scale (fixed) vernier scale (movable) 01 vernier calipers If the two jaws touch each other, but the zero marks of the main scale and vernier scale do not coincide as shown below, the zero error is positive.

supposing observed reading is 4.03 cm, then corrected reading = observed reading – zero error = 4.03 – (-0.02) = 4.05 cm measurement of length 010 zero error = cm main scale (fixed) vernier scale (movable) 01 If the two jaws touch each other, but the zero marks of the main scale and vernier scale do not coincide as shown below, the zero error is negative. 5 vernier calipers

measurement of time Time can be measured by using the following:  analogue stopwatch  digital stopwatch  clocks All timing devices make use of some regular process. time

measurement of time Time can also be measured by using the following simple pendulum.  oscillations are regularly repeating motions  the period is time in which 1 oscillation occurs  oscillations are regularly repeating motions  the period is time in which 1 oscillation occurs the period of a simple pendulum pendulum bob tied to one end of a thread BA O

watch measurement of time wrist watch

II.Newton’s Laws of Motion I. Law of Inertia II. F=ma III. Action-Reaction

1 st Law of Motion (Law of Inertia) An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity, unless acted upon by an unbalanced force.

1 st Law Inertia is the tendency of an object to resist changes in its velocity: whether in motion or motionless. These pumpkins will not move unless acted on by an unbalanced force.

1 st Law Once airborne, unless acted on by an unbalanced force (gravity and air – fluid friction), it would never stop!

1 st Law Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

Why then, do we observe every day objects in motion slowing down and becoming motionless seemingly without an outside force? It’s a force we sometimes cannot see – friction.

Objects on earth, unlike the frictionless space the moon travels through, are under the influence of friction.

Slide a book across a table and watch it slide to a rest position. The book comes to a rest because of the presence of a force - that force being the force of friction - which brings the book to a rest position.

In the absence of a force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)

Newtons’s 1 st Law and You Don’t let this be you. Wear seat belts. Because of inertia, objects (including you) resist changes in their motion. When the car going 80 km/hour is stopped by the brick wall, your body keeps moving at 80 m/hour.

III.Temperature is a measure of… The total amount of energy in an object The total amount of thermal energy in an object How much heat something gives off How fast the molecules in an object are moving

Heat is… Energy given off or absorbed by an object A measure of the motion of the molecules in an object The total amount of molecular energy in an object

How do we measure temperature? Think about using a thermometer

How does the thermometer know how hot the substance is?

Temperature is a measure of… The total amount of energy in an object The total amount of thermal energy in an object How much heat something gives off How fast the molecules in an object are moving

Heat is… Energy given off or absorbed by an object A measure of the motion of the molecules in an object The total amount of molecular energy in an object

Put this bottle with the coin on top in the freezer for a half hour. What happens when you take it out and put it on a table at room temperature?

Gases do not necessarily expand when you heat them Gases do not necessarily contract when you cool them

The heat balance of the Earth

IV. Sound

The Facts Sound … 1. Is a form of energy produced & transmitted by vibrating matter 2. Travels in waves 3. Travels more quickly through solids than liquids or gases

The Ear Sound is carried to our ears through vibrating air molecules. Our ears take in sound waves & turn them into signals that go to our brains. Sound waves move through 3 parts of the ear; outer ear, middle ear, & inner ear. Middle Ear

Vibration -Back and forth movement of molecules of matter -For example,

Compression -Where molecules are being pressed together as the sound waves move through matter -For example, -a wave travels through the springs just like sound waves travel through the air -the places where the springs are close together are like compressions in the air.

Wavelength & Frequency -Wavelength is the distance between one part of a wave and the same part of the next wave -Frequency is the number of waves moving past a point in one second

Pitch A measure of how high or low a sound is Pitch depends on the frequency of a sound wave For example, - Low pitch - Low frequency - Longer wavelength - High pitch - High frequency - Shorter wavelength

Sonar -An instrument that uses reflected sound waves to find underwater objects -For example, Animals use sonar or echo location to find their prey; these sounds have such a high pitch or frequency that the human ear cannot hear Humans use sonar to locate or map objects

Sound and Instruments -Instruments can be played at different pitches by changing lengths of different parts. -For example, -Another way to make different pitches is to change the thickness of the material that vibrates. -For example, A trombone’s mute absorbs some of the sound waves produced, thus producing a softer note when played.

V.Optics Mirrors and Lenses

Reflection – angle in (incidence) equals angle out (reflection) – angles measured from surface “normal” (perpendicular) – Reflection off a flat surface follows a simple rule: surface normal same angle incident ray exit ray reflected ray

Reflection Vocabulary Real Image – – Image is made from “real” light rays that converge at a real focal point so the image is REAL – Can be projected onto a screen because light actually passes through the point where the image appears – Always inverted

Reflection Vocabulary Virtual Image– – “Not Real” because it cannot be projected – Image only seems to be there!

Virtual Images in Plane Mirrors If light energy doesn't flow from the image, the image is "virtual". Rays seem to come from behind the mirror, but, of course, they don't. It is virtually as if the rays were coming from behind the mirror. "Virtually": the same as if As far as the eye-brain system is concerned, the effect is the same as would occur if the mirror were absent and the chess piece were actually located at the spot labeled "virtual image".

LEFT- RIGHT REVERSAL

Curved mirrors What if the mirror isn’t flat? – light still follows the same rules, with local surface normal Parabolic mirrors have exact focus – used in telescopes, backyard satellite dishes, etc. – also forms virtual image

Convex Mirrors Curves outward Reduces images Virtual images – Use: Rear view mirrors, store security… CAUTION! Objects are closer than they appear!

Refraction Light also goes through some things – glass, water, eyeball, air

n 2 = 1.5 n 1 = 1.0 A B Refraction at a plane surface Light bends at interface between refractive indices – bends more the larger the difference in refractive index

VI. CHEMICAL BONDS PLAY THE VIDEOS NO. 5 & 6

VII. PATHOLOGY

CITRUS CANKER - lesion/patches found on the fruit are the affected part-bacterial disease

WHITE RUST- Raddish - white pustules on the leaves are due to bacterial infection.

TUBERCULOSIS -affected by Mycobacterium tuberculosis

ANTHROX

LEPTOSPIROSIS

HIV -viral disease

VIII. CELL DIVISION-MITOSIS

REAL TIME (videos: click from video file 1, 2) CELL DIVISION OCCURS IN VERY FEW SECONDS AS YOU SEE IN THE VISUAL. DON’T MISS THE DIFFERENT STAGES OF MITOSIS THAT OCCURS IN ROOT TIP OF ONION, VERY FASTLY.