Physics of Gravity and Orbits

Gravity and Acceleration

• The acceleration due to gravity decreases as distance from the Earth's center increases.
• At a distance of 640 km below the Earth's surface, the acceleration due to gravity is 10% less than at the surface.

Escape Speed

• Escape speed is the minimum speed an object needs to escape the gravitational pull of a planet.
• If the Earth were made of wood, its mass would be 10% of its current mass, but its diameter would remain the same.
• The escape speed from this wooden Earth would be 3.54 km/s.

Orbital Mechanics

• Kinetic energy (KE) is the energy of motion.
• Potential energy (PE) is the energy an object has due to its position in a gravitational field.
• Total energy (TE) is the sum of KE and PE.
• Binding energy (BE) is the amount of energy required to separate an object from its orbit.

Satellite Orbits

• An artificial satellite of mass 2000 kg orbiting at a height of 3600 km above the Earth's surface has the following properties:
  • KE = $40.09 \times 10^7 J$
  • PE = $-80.09 \times 10^7 J$
  • TE = $40.09 \times 10^7 J$
  • BE = $40.09 \times 10^7 J$
• The satellite's KE and BE are equal in magnitude.
• This indicates that the satellite is in a stable orbit.