Gravity

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Gravity Noun

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[grav-i-tee]

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Gravity

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The force of attraction between all objects with mass, particularly the pull exerted by a celestial body like Earth.

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Example: This image shows an apple falling from a tree, pulled downwards by the force of gravity, which is represented by the large black arrow.

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Gravitation Noun

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[grav-i-tay-shun]

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Gravitation

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The universal force of attraction that acts between any two bodies in the universe, regardless of their location or mass.

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Example: This image shows that Earth's gravity is a force that pulls everything from all directions towards the planet's center.

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Mass Noun

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[mas]

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Mass

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The measure of the amount of matter within a physical body, which is a primary factor in determining gravitational force.

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Example: This image shows a balance scale comparing a rock and a feather. The rock has more mass (more matter), causing its side to tip down.

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Orbit Noun

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[or-bit]

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Orbit

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The curved path of a celestial object or spacecraft around a star, planet, or moon, caused by gravitational attraction.

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Example: The Moon's forward velocity and the inward pull of Earth's gravity combine to keep the Moon in a stable, curved path, or orbit.

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Orbital velocity Noun

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[or-bi-tal ve-los-i-tee]

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Orbital velocity

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The specific speed required for an object to maintain a stable, circular path around a celestial body under gravity.

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Example: This diagram shows a satellite's orbital velocity (V) as the forward speed that balances the inward pull of Earth's gravitational force (F), keeping it in orbit.

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Escape velocity Noun

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[es-keyp ve-los-i-tee]

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Escape velocity

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The minimum speed an object needs to completely break free from the gravitational pull of a massive body without further propulsion.

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Example: This diagram shows that if an object is launched from Earth, it will fall back or orbit at lower speeds, but will escape Earth's gravity if it reaches escape velocity.

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Trajectory Noun

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[tra-jek-tuh-ree]

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Trajectory

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The path an object follows through space as a function of time, especially when under the influence of gravity.

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Example: When an object is launched, gravity pulls it downward, causing it to follow a curved path called a trajectory.

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Velocity Noun

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[ve-los-i-tee]

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Velocity

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A vector quantity that specifies both the speed of an object and its precise direction of motion in space.

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Example: This image shows the formula triangle for velocity, relating distance (d), velocity (v), and time (t), and lists the three ways to calculate them.