Gravitational Forces
Elementary School
Definition
The attractive force that pulls objects with mass toward one another. On Earth, gravity pulls everything toward the ground, giving objects weight, and on a larger scale it keeps moons and planets in their orbits.
Worked examples
\(F = G \frac{m_1 m_2}{r^2}\)
Newton's law of universal gravitation: force depends on both masses and the square of the distance between them.
A 50 kg student has a weight of \(F = mg = 50 \times 9.8 = 490\) N on Earth.
Weight is the gravitational force Earth exerts on the student; it equals mass times gravitational acceleration.
The Moon orbits Earth because Earth's gravity provides the centripetal force keeping it in a curved path.
Gravity acts as the inward force that prevents the Moon from flying off in a straight line.
Common mistakes
- Mass and weight are the same thing. → Mass is the amount of matter; weight is the gravitational force on that mass. Mass stays constant everywhere, but weight changes with gravitational strength (less on the Moon, more on Jupiter).
- There is no gravity in space, which is why astronauts float. → Gravity exists in space; astronauts float because they are in free fall, orbiting Earth. The space station and astronauts fall toward Earth together, creating the sensation of weightlessness.
- Only planets and stars have gravitational forces. → Every object with mass exerts gravitational force on every other mass. Even small objects attract each other, but the forces are too tiny to notice without massive objects like planets.
Where you'll use it next
You'll use gravitational forces when studying orbital mechanics, tides, planetary motion, and Einstein's general relativity in advanced physics, as well as analyzing satellite launches and space travel.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026