Mass stays, weight changes
Show on a big screenA bag of sugar goes to the Moon. Is there less sugar in it?
- The same 1 kg block is on the Earth and on the Moon.
- On the Earth it weighs about 10 N.
- On the Moon it weighs about 1.6 N.
- Same mass. Different weight.
No. The bag holds the same amount of sugar on the Moon. Only its weight changes.
New word
- Mass — the amount of matter in an object. We measure it in kg or g.
Matter is what things are made of. The unit kg means kilogram, and g means gram.
The rule
is the amount of matter. It is the same everywhere. Weight is the pull on an object. It changes from place to place.
The Moon pulls less than the Earth. On the Moon, weight is about one-sixth of its Earth weight. Each kg weighs about 10 N on the Earth. Each kg weighs about 1.6 N on the Moon. Take 5 kg. On the Earth, 5 × 10 N = 50 N. On the Moon, 5 × 1.6 N = 8 N.
| Mass | Weight on the Earth | Weight on the Moon |
|---|---|---|
| 5 kg | 50 N | 8 N |
| 10 kg | 100 N | 16 N |
Watch out!
A shopkeeper says, "This sugar weighs 2 kg." In science, 2 kg is its . Its weight is about 20 N.
Pick a . Switch the place.
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