Physics Fundamentals

The SI unit of force is Newton (N). It is named after Sir Isaac Newton. One Newton is the force required to accelerate 1 kilogram of mass at 1 meter per second squared.

A moving car possesses kinetic energy, which is the energy of motion. Any object that is moving has kinetic energy, which depends on its mass and velocity.

When the pitch of sound increases, its frequency increases. Pitch and frequency are directly related - higher pitch means higher frequency and vice versa.

Refraction explains why a pencil appears bent in water. When light passes from water to air (or vice versa), it bends due to the change in speed, causing the optical illusion.

Motion is the change in position of an object with respect to time and its surroundings. Three examples of different types of motion: 1. Linear motion: A car moving on a straight road 2. Circular motion: Earth revolving around the Sun 3. Oscillatory motion: A pendulum swinging back and forth Other types include rotational motion (spinning top) and random motion (gas molecules).

Speed and velocity are related but different concepts: Speed: - Scalar quantity (has only magnitude) - Rate of change of distance - Always positive - Formula: Speed = Distance/Time Velocity: - Vector quantity (has both magnitude and direction) - Rate of change of displacement - Can be positive or negative - Formula: Velocity = Displacement/Time Example: A car moving at 60 km/h eastward has speed = 60 km/h and velocity = 60 km/h east.

The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. The total energy of an isolated system remains constant. Example: When a ball is dropped from a height: - At the top: Maximum potential energy, zero kinetic energy - During fall: Potential energy converts to kinetic energy - At the bottom: Maximum kinetic energy, minimum potential energy - Total energy remains constant throughout the process This principle applies to all energy transformations in nature.

The process of hearing involves several steps: 1. Sound Collection: The outer ear (pinna) collects sound waves and funnels them into the ear canal. 2. Vibration: Sound waves hit the eardrum, causing it to vibrate. 3. Amplification: The middle ear bones (hammer, anvil, stirrup) amplify these vibrations. 4. Conversion: The inner ear (cochlea) converts vibrations into electrical signals. 5. Transmission: The auditory nerve carries these signals to the brain. 6. Interpretation: The brain interprets these signals as sound. Each part plays a crucial role in the complex process of hearing.

Newton's Three Laws of Motion: **First Law (Law of Inertia):** Statement: An object at rest stays at rest, and an object in motion stays in motion at constant velocity, unless acted upon by an external force. Mathematical Expression: ΣF = 0 (when acceleration = 0) Example: A book on a table remains at rest until someone pushes it. A moving car continues moving until brakes are applied. **Second Law (Law of Acceleration):** Statement: The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Mathematical Expression: F = ma Where F = force, m = mass, a = acceleration Example: Pushing a shopping cart - more force produces more acceleration, and a heavier cart needs more force for the same acceleration. **Third Law (Action-Reaction Law):** Statement: For every action, there is an equal and opposite reaction. Mathematical Expression: F₁₂ = -F₂₁ Example: When you walk, you push backward on the ground, and the ground pushes forward on you. When a rocket burns fuel downward, it is pushed upward. These laws form the foundation of classical mechanics and explain most motion we observe in daily life.

**Properties of Light:** 1. **Rectilinear Propagation**: Light travels in straight lines 2. **Speed**: Light travels at 3 × 10⁸ m/s in vacuum 3. **Electromagnetic Nature**: Light is an electromagnetic wave 4. **Dual Nature**: Light exhibits both wave and particle properties **How We See Objects:** We see objects through the following process: 1. Light sources emit light rays 2. These rays fall on objects 3. Objects reflect light in various directions 4. Some reflected rays enter our eyes 5. The eye focuses these rays on the retina 6. The retina converts light into electrical signals 7. The brain interprets these signals as images **Reflection:** - Definition: Bouncing back of light when it hits a surface - Laws of Reflection: 1. Incident ray, reflected ray, and normal lie in the same plane 2. Angle of incidence = Angle of reflection - Types: Regular reflection (smooth surfaces) and Irregular reflection (rough surfaces) - Applications: Mirrors, periscopes, kaleidoscopes **Refraction:** - Definition: Bending of light when it passes from one medium to another - Cause: Change in speed of light in different media - Examples: Pencil appearing bent in water, rainbow formation, lenses - Applications: Spectacles, cameras, telescopes, microscopes Both phenomena are crucial for vision and many optical instruments we use daily.