vocab ch.4


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.


the curved path followed by a projectile under the influence of constant gravity only.


Any object that moves through the air or through space under the influence of gravity.


A projectile or small celestial body that orbits a larger celestial body.


the force that an object exerts on a supporting surface, which is often. not always, due to the force of gravity.


Being without a support force, as in free fall.