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Name: Leonie
Status: student
Age: 11
Location: N/A
Country: N/A
Date: 2000-2001


Question:
Why do we weigh less on the moon?


Replies:
Dear Leonie,

Weight is how hard things (floor, ground, etc.) push up on us. Note, I said up and not down. The downward force is the gravitational force. The gravitational force depends on mass (the amount of material you are made of) and the gravitational field intensity. If the gravitational field intensity is lower, as it is on the moon, the gravitational force is lower for the same mass.

Now, what does this have to do with weight? If you are standing still, the upward push by the ground is equal to the downward push due to gravity. If the gravitational force is less, the upward push is less, hence, you weigh less.

So how do you become weightless? Just jump! While you are in the air, you have no supporting force. The gravitational force is still there (the earth eventually catches you after about a second).

Good question!

---Nathan A. Unterman



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