Physics: Energy, Force, and Motion

Energy and Force

Gravity

• Force that attracts two objects with mass towards each other
• Strength of gravity depends on mass of objects and distance between them
• On Earth, gravity pulls objects towards the center with an acceleration of 9.8 m/s^2

Kinetic Energy

• Energy of motion
• Depends on the mass and velocity of an object
• Formula: KE = 0.5 * m * v^2
• Units: Joules (J)
• Examples: rolling ball, moving car, flying airplane

Potential Energy

• Stored energy that can be converted into kinetic energy
• Types:
  • Gravitational potential energy: energy of an object due to its height or position
  • Elastic potential energy: energy stored in stretched or compressed materials
• Formula: PE = m * g * h (for gravitational potential energy)
• Units: Joules (J)
• Examples: ball at the top of a hill, stretched rubber band

Friction

• Force that opposes motion between two surfaces in contact
• Types:
  • Static friction: prevents an object from moving
  • Kinetic friction: slows down an object in motion
• Factors that affect friction:
  • Surface roughness
  • Normal force (force pressing surfaces together)
  • Type of surface (e.g. wood, metal, rubber)
• Formula: F_f = μ * N (where μ is the coefficient of friction and N is the normal force)