Gravity: Key Concepts

Gravity

  • Gravity is the force that governs motion in the solar system.
  • Newton's law of universal gravitation states every object in the universe attracts every other object.
  • The force of gravity is measured in units called newtons.

Factors Influencing Gravity

  • Mass: Objects with more mass have more gravity.
  • Weight: Weight is the force of gravity pulling on an object.
  • Weight changes based on location, while mass remains constant.
    • Weight=mass∗gravityWeight = mass * gravity
  • Distance: As distance increases, gravitational force decreases

Inertia

  • Inertia is the tendency of an object to resist a change in motion.
  • Newton's first law of motion (law of inertia): An object at rest stays at rest, and an object in motion stays in motion with constant speed and direction unless acted upon by a force.

Orbital Motion

  • Gravity and inertia keep the moon in orbit around the Earth.
  • Without Earth's gravity, the moon would move in a straight line.
  • The sun's gravity keeps Earth in orbit, and Earth's inertia prevents it from crashing into the sun.