Math Is Fun Forum

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Newton's Third Law

One last question on Newton's Third Law! I have to label a free body diagram of the earth, that is orbiting the sun. The only force I can think to put is the gravitational pull from the sun. Is that all that goes on there? If so why doesn't the earth move into the sun?

Sorry to jump in this late, but I'm not sure Ganesh's answer fully covers this.
The force from the sun is far greater than the forces from anything else, so they can all be approximated to be 0. However, the Earth still doesn't move into the sun because it has velocity that is more or less perpendicular to the sun's force. This means that instead of approaching the sun, the Earth moves in a circle around it. You'll learn more about it in M3 (and possibly also physics lessons).

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Why did the vector cross the road?
It wanted to be normal.

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: Newton's Third Law

Ohh ok . thanks.