Key Concepts in Physics

Key Concepts in Physics

Fundamental Forces

1. Gravitational Force:

   • Attraction between masses.
   • Weakest force but infinite range.

2. Electromagnetic Force:

   • Interaction between charged particles.
   • Responsible for electricity, magnetism, and light.

3. Weak Nuclear Force:

   • Involved in radioactive decay.
   • Short range and affects subatomic particles.

4. Strong Nuclear Force:

   • Holds protons and neutrons together in nuclei.
   • Strongest force but has a very short range.

Motion and Kinematics

• Newton’s Laws of Motion:

  1. An object in motion stays in motion unless acted upon by a force.
  2. F=ma (Force equals mass times acceleration).
  3. For every action, there is an equal and opposite reaction.

• Kinematic Equations (for constant acceleration):

  1. ( v = u + at )
  2. ( s = ut + \frac{1}{2}at^2 )
  3. ( v^2 = u^2 + 2as )

Energy

• Kinetic Energy (KE):

  • ( KE = \frac{1}{2}mv^2 )

• Potential Energy (PE):

  • Gravitational: ( PE = mgh )
  • Elastic: ( PE = \frac{1}{2}kx^2 )

• Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Waves and Sound

• Wave Properties:

  • Wavelength, frequency, amplitude, speed.

• Types of Waves:

  • Transverse: Particles move perpendicular to wave direction (e.g., light).
  • Longitudinal: Particles move parallel to wave direction (e.g., sound).

Thermodynamics

• Laws of Thermodynamics:

  1. Energy cannot be created/destroyed.
  2. The entropy of an isolated system always increases.
  3. Absolute zero cannot be reached.

• Heat Transfer:

  • Conduction: Transfer through direct contact.
  • Convection: Transfer through fluid movement.
  • Radiation: Transfer via electromagnetic waves.

Electricity and Magnetism

• Ohm’s Law:

  • ( V = IR ) (Voltage = Current × Resistance).

• Circuit Elements:

  • Resistors, capacitors, inductors.

• Magnetic Fields:

  • Produced by moving charges; affects other charged particles.

Modern Physics

• Quantum Mechanics:

  • Describes behavior of particles at atomic scales.

• Theory of Relativity:

  • Einstein’s theories of Special and General relativity.
  • Time dilation and mass-energy equivalence ( E=mc^2 ).

Important Measurements

• SI Units:

  • Length (meter), mass (kilogram), time (second), electric current (ampere), temperature (kelvin), amount of substance (mole), luminous intensity (candela).

• Common Abbreviations:

  • Joule (J) for energy, Newton (N) for force, Watt (W) for power.