Gravity, Mass and Weight for Kids: Why You Weigh Less on the Moon (Grade 6 to 8 Science)

Hi, I'm Luna from DoodleBeez. Why do things fall down instead of up? And why could you bounce so easily on the Moon? Today we will explore gravity, and the difference between mass and weight.

Gravity is a force of attraction between any two objects that have mass. Everything pulls on everything else! The pull is usually tiny, but a huge object like Earth pulls strongly enough to hold us down.

Two things control the strength of gravity. More mass means a stronger pull. More distance means a weaker pull. That is why the Sun, with its enormous mass, keeps all the planets in their orbits.

Mass is the amount of matter in an object. It is measured in kilograms, and it stays the same wherever you go. Your mass is the same on Earth, on the Moon, or floating in space.

Weight is the force of gravity pulling on your mass, measured in newtons. The Moon has much less mass than Earth, so its gravity is only about one sixth as strong. You would weigh far less there.

Here is a surprise. Without air resistance, a heavy hammer and a light feather fall at the same rate. Astronauts tested this on the Moon, where there is no air, and both landed at the same moment.

Now it's your turn. An astronaut has a mass of sixty kilograms on Earth. What is her mass on the Moon? Pause and try. Still sixty kilograms! Her mass stays the same. Only her weight changes.

Great job! Remember, gravity pulls masses together, and it gets stronger with more mass and weaker with distance. Mass stays the same everywhere, but weight changes. Practice gravity, mass and weight in the Science Lab at doodlebeez.com. See you next time!