Escape velocity and orbital velocity are two fundamental speeds related to how objects move in a planet’s gravitational field. They determine whether an object stays in orbit or completely leaves a planet’s gravity.
Orbital Velocity
Orbital velocity is the minimum speed required for an object to stay in a stable circular orbit around a planet without falling back to the surface.
At this speed, gravity pulls the object inward, but its forward motion keeps it continuously falling around the planet instead of crashing into it.
Where:
- G = gravitational constant
- M = mass of the planet
- R = distance from the planet’s center
Example: Satellites and the International Space Station use orbital velocity to stay in orbit.
Escape Velocity
Escape velocity is the minimum speed required for an object to completely escape a planet’s gravitational field without further propulsion.
Once an object reaches this speed, it will not return back to the planet (ignoring air resistance).
Escape velocity is always higher than orbital velocity because the object must overcome the full gravitational pull of the planet.
Key Difference
- Orbital velocity → keeps an object in orbit
- Escape velocity → allows an object to leave the planet permanently
Escape velocity is related to orbital velocity:
Escape velocity = √2 × Orbital velocity
- Orbital velocity = continuously falling around the planet
- Escape velocity = breaking free from the planet’s gravity
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