Posted by **Morgan** on Wednesday, February 24, 2010 at 8:04pm.

Here is a question on my science worksheet, "if a projectile's fall matches Earth's 'BLANK', the projectile will not hit earth." i need help figuring out what would go in the blank!

- Science -
**bobpursley**, Wednesday, February 24, 2010 at 8:18pm
It is a very bad question.

I suspect the question is trying to make you understand that if something that is falling due to gravity, but it stays the same height from Earth, then it will never hit Earth, but remain in orbit.

The question is really bad if that is what it is aimed to elicit.

Sir Issac Newton described this problem; see his diagram

http://en.wikipedia.org/wiki/File:Newton_Cannon.svg

If it is fired too slowly, Earth's gravity pulls it and it hits Earth.

If it is fired too fast, Earth's gravity pulls on it, but it continues away, either ending in an elliptical orbit, or escaping from Earth entirely.

If it fired just right, it falls toward Earth, but never gets closer: it is in circular orbit.

- Science -
**bj**, Friday, February 26, 2010 at 12:54am
what are two types of technologies that help people study the surface and composition of earth

- Science -
**lim**, Saturday, February 27, 2010 at 9:12am
noooooooooooo

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