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What is Mass? - Windows to the Universe

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What is mass?

Would it be more difficult to pull an elephant or a mouse?
If you pulled each animal with the same amount of force, the elephant would respond less to pulling, even if he didnít pull back at all. Thatís because an elephant has more mass than a mouse.

Mass is the amount of material in an object and is usually measured in units called kilograms (kg).

Sometimes people confuse weight and mass. Weight is a measure of force and depends on both the amount of mass and the amount of gravity. This means that with Earthís gravity, the elephant weighs more than the mouse because it has more mass than the mouse.

Because mass is the amount of material in an object, it stays the same no matter what force is acting on the object. This means that even though our elephant weighs less on the moon, its mass stays the same.


Last modified September 10, 2002 by Lisa Gardiner.

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