Tamil Nadu Board Class 9 Science — Flashcards for Quick Revision

A: Fundamental quantities cannot be expressed in terms of any other physical quantities. Example: Length, mass, time, temperature. Derived quantities can be expressed in terms of fundamental quantities.

A: 1. Length - metre (m) 2. Mass - kilogram (kg) 3. Time - second (s) 4. Temperature - kelvin (K) 5. Electric current - ampere (A) 6. Luminous intensity - candela (cd) 7. Amount of substance - mole (mol)

A: A unit prefix is a symbol placed before a unit to specify the order of magnitude of a quantity. It helps express very large and very small quantities. Examples: - kilo (k) = 10³ - milli (m) = 10⁻³ -

A: Motion is the change in position of an object with respect to its surroundings. Example: A car moving on the road, a fan rotating, a person walking, or a train traveling are all in motion. Motion is r

A: Motion is relative. From the car's reference frame (moving observer), the tree appears to move backward because the observer's position is changing. From a person standing on the road, the tree is at

A: (a) Distance = 500 m + 300 m = 800 m (total path length) (b) Displacement = 500 m - 300 m = 200 m east (straight line from start to final position) Key difference: Distance is scalar (800 m), displace

A: Step 1: Calculate thrust (weight) = mg = 90 × 10 = 900 N Step 2: Apply pressure formula: P = F/A = 900/0.036 Step 3: P = 25,000 Pa or 25 kPa Key insight: Pressure depends on both force AND the area o

A: A sharp pin has a very small area of contact, so the same force is concentrated over a tiny area, creating extremely high pressure. A blunt needle distributes the same force over a larger contact area

A: Using formula: P = hρg P = 0.85 × 1000 × 10 P = 8,500 Pa or 8.5 kPa Key point: Pressure in liquids depends on THREE factors: 1. Depth (h) - deeper means more pressure 2. Density (ρ) - denser liquid m