Physics Class 10 medium

Force and Motion

• Newton's First Law (Inertia): An object remains at rest or in uniform motion unless acted upon by a net external force. Inertia is the resistance to change in motion.
• Newton's Second Law: Force equals mass times acceleration (F = ma). Force is measured in Newtons (N), mass in kilograms (kg), and acceleration in meters per second squared (m/s²).
• Newton's Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.
• Example Problem 1: A 2 kg object pushed with 10 N force accelerates at 5 m/s².
• Example Problem 2: A car accelerating from 10 m/s to 20 m/s in 5 seconds has an acceleration of 2 m/s².

Inertia and Momentum

• Inertia: The tendency of an object to resist changes in its motion.
• Momentum: The product of an object's mass and velocity (p = mv).
  • Momentum is conserved in the absence of external forces.

Pressure

• Definition: Force per unit area (P = F/A).
• Units: Pressure is measured in Pascals (Pa).
• Pressure and Gravity: Pressure increases with depth in a fluid.

Heat

• Thermal Energy: The internal energy of a substance due to particle motion.
• Specific Heat Capacity: The heat needed to raise 1 kg of a substance by 1°C.
  • Heat energy (Q) = mass (m) × specific heat capacity (c) × change in temperature (ΔT)
• Thermometer Types: Mercury, alcohol, bimetallic.

Light

• Refraction: Bending of light when passing from one medium to another, governed by Snell's Law.
• Total Internal Reflection: Complete reflection within a medium when the angle of incidence exceeds the critical angle.
• Diffraction: Bending of light waves around obstacles.
• Lenses: Convex (converging) and concave (diverging) lenses, with focal length (f) determining lens power (P = 1/f).
• Human Eye: Focuses light onto the retina; vision defects like myopia and hyperopia exist.

Electricity

• Direct Current (DC): Current flows in one direction.
• Alternating Current (AC): Current reverses direction periodically.
• Magnetic Effects of Current: Current-carrying conductors generate magnetic fields (Right-hand Rule applies).
• Electromagnetic Induction: Changing magnetic fields induce electric current in conductors.
• AC Generator: Converts mechanical energy to electrical energy through rotation in a magnetic field.

The Universe

• Big Bang Theory: The universe originated from a singularity and is expanding.
• Hubble's Law: Galaxies are moving away, and their velocity is proportional to their distance from Earth.
• Future of the Universe: Possible outcomes include closed (collapsing), open (expanding forever), or flat (expanding, but slowing).