Key Concepts in Physics

Key Concepts in Physics

Fundamental Forces

1. Gravity:

   • Attracts two masses.
   • Weakest of the four forces.

2. Electromagnetism:

   • Acts between charged particles.
   • Responsible for electricity and magnetism.

3. Weak Nuclear Force:

   • Responsible for radioactive decay.
   • Plays a key role in nuclear reactions.

4. Strong Nuclear Force:

   • Holds protons and neutrons together in the nucleus.
   • Strongest force but operates at very short ranges.

Laws of Motion (Newton's Laws)

1. First Law (Inertia):

   • An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.

2. Second Law (F=ma):

   • The force acting on an object is equal to the mass of the object multiplied by its acceleration.

3. Third Law (Action-Reaction):

   • For every action, there is an equal and opposite reaction.

Energy

• Kinetic Energy:

  • Energy of motion, calculated as ( KE = \frac{1}{2}mv^2 ).

• Potential Energy:

  • Stored energy based on position, commonly gravitational ( PE = mgh ).

• Conservation of Energy:

  • Energy cannot be created or destroyed, only transformed.

Waves and Oscillations

• Wave Properties:

  • Wavelength, frequency, amplitude, and speed.

• Types of Waves:

  • Mechanical (requires medium) vs. Electromagnetic (can travel through vacuum).

Thermodynamics

1. First Law:

   • Energy cannot be created or destroyed (conservation of energy).

2. Second Law:

   • Entropy of an isolated system always increases.

3. Third Law:

   • As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Electromagnetism

• Coulomb’s Law:

  • Describes electric force between charges; proportional to product of charges and inversely proportional to the square of the distance.

• Faraday’s Law of Induction:

  • A change in magnetic field can induce an electric current in a conductor.

Relativity

• Special Relativity:

  • Time dilation and length contraction occur at high speeds; speed of light is constant in a vacuum.

• General Relativity:

  • Gravity is the curvature of spacetime caused by mass.

Quantum Mechanics

• Wave-Particle Duality:

  • Particles exhibit both wave-like and particle-like properties.

• Uncertainty Principle:

  • It is impossible to know both the position and momentum of a particle precisely at the same time.

Essential Formulas

• Kinematics: ( d = vt + \frac{1}{2}at^2 )
• Momentum: ( p = mv )
• Work: ( W = Fd \cos(\theta) )
• Power: ( P = \frac{W}{t} )
• Ohm’s Law: ( V = IR )

Important Units

• Length: Meter (m)
• Mass: Kilogram (kg)
• Time: Second (s)
• Force: Newton (N)
• Energy: Joule (J)
• Power: Watt (W)

Applications of Physics

• Engineering
• Medicine (radiology, MRI)
• Astronomy
• Environmental Science (renewable energy sources)

Fundamental Forces

• Gravity: Attracts two masses. Weakest of the four forces.
• Electromagnetism: Acts between charged particles. Responsible for electricity and magnetism.
• Weak Nuclear Force: Responsible for radioactive decay. Plays a key role in nuclear reactions.
• Strong Nuclear Force: Holds protons and neutrons together in the nucleus. Strongest force but operates at very short ranges.

Laws of Motion (Newton's Laws)

• First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.
• Second Law (F=ma): The force acting on an object is equal to the mass of the object multiplied by its acceleration.
• Third Law (Action-Reaction): For every action, there is an equal and opposite reaction.

Energy

• Kinetic Energy: Energy of motion, calculated as ( KE = \frac{1}{2}mv^2 ).
• Potential Energy: Stored energy based on position, commonly gravitational ( PE = mgh ).
• Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Waves and Oscillations

• Wave Properties: Wavelength, frequency, amplitude, and speed.
• Types of Waves: Mechanical (requires medium) vs. Electromagnetic (can travel through vacuum).

Thermodynamics

• First Law: Energy cannot be created or destroyed (conservation of energy).
• Second Law: Entropy of an isolated system always increases.
• Third Law: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero.

Electromagnetism

• Coulomb’s Law: Describes electric force between charges; proportional to the product of charges and inversely proportional to the square of the distance.
• Faraday’s Law of Induction: A change in magnetic field can induce an electric current in a conductor.

Relativity

• Special Relativity: Time dilation and length contraction occur at high speeds; speed of light is constant in a vacuum.
• General Relativity: Gravity is the curvature of spacetime caused by mass.

Quantum Mechanics

• Wave-Particle Duality: Particles exhibit both wave-like and particle-like properties.
• Uncertainty Principle: It is impossible to know both the position and momentum of a particle precisely at the same time.

Essential Formulas

• Kinematics: ( d = vt + \frac{1}{2}at^2 )
• Momentum: ( p = mv )
• Work: ( W = Fd \cos(\theta) )
• Power: ( P = \frac{W}{t} )
• Ohm’s Law: ( V = IR )

Important Units

• Length: Meter (m)
• Mass: Kilogram (kg)
• Time: Second (s)
• Force: Newton (N)
• Energy: Joule (J)
• Power: Watt (W)

Applications of Physics

• Engineering
• Medicine (radiology, MRI)
• Astronomy
• Environmental Science (renewable energy sources)