Ellipse
The oval path followed by a satellite
escape speed
The speed that a projectile, space probe, or similar object must reach to escape the gravitational influence of Earth or of another celestial body to which it is attracted.
Inverse-square law
The intensity of an effect from a localized source spreads uniformly throughout the surrounding space and weakens with the inverse square of the distance.
law of universal gravitation
everybody in the universe attracts every other body with a force the strengths of which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their center.
Parabola
the curved path followed by a projectile under the influence of constant gravity only.
projectile
Any object that moves through the air or through space under the influence of gravity.
satellite
A projectile or small celestial body that orbits a larger celestial body.
Weight
the force that an object exerts on a supporting surface, which is often. not always, due to the force of gravity.
weightless
Being without a support force, as in free fall.