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Gravitation field strength help

3bii)

Can someone explain the ratio property thing. This ratio stuff is getting to me lol

http://www.ocr.org.uk/Images/144792-question-paper-unit-g484-01-the-newtonian-world.pdf

Here is my working:

Original post by Adam_1999

Here is my working:

Lots of love x
Question though: How come you can use the mass of jupiter to work out g, that's why i got a bit confused and thought you needed the mass of (M)

Reply 3

Adam_1999

Original post by Super199

Lots of love x
Question though: How come you can use the mass of jupiter to work out g, that's why i got a bit confused and thought you needed the mass of (M)

g = GM/r^2

When using this equation, M is the mass of the object CREATING the gravitational field.

Since, by definition g = F/m, where m is the mass of the object in a field.

Now F = GMm/r^2, meaning g = (GMm/r^2)/m = GM/r^2. The m's cancel.