Why doesn't the Earth collide with the Sun?

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SUMMARY

The Earth maintains its orbit around the Sun due to the balance between gravitational force and centripetal force. According to Newton's laws, the gravitational attraction of the Sun provides the necessary force to keep the Earth in a curved path rather than moving in a straight line. The centripetal force required for Earth's circular motion is equal to mv²/r, where mass and gravitational force are directly proportional. Additionally, the high vacuum of space minimizes resistance, allowing Earth's orbit to remain stable over billions of years.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with centripetal force and its formula (mv²/r)
  • Basic knowledge of gravitational force and its relationship with mass
  • Concept of orbital mechanics and planetary motion
NEXT STEPS
  • Study the principles of gravitational force and its effects on planetary motion
  • Explore the concept of centripetal acceleration in detail
  • Learn about orbital mechanics and the mathematics behind orbits
  • Investigate the impact of vacuum on celestial bodies and their motion
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Students in physics, educators teaching gravitational concepts, and anyone interested in understanding the dynamics of planetary motion and orbits.

porky
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I am in AP Physics and we just got done with Centripetal force and Universal Gravitation. I was wondering since for the planets to stay in motion they need to have the same force as the object they are orbiting around. Since a bigger mass means a bigger force, how does the Earth stay in motion around the Sun.
 
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I'm not sure I understand your point. Consider a planet in circular orbit about the Sun. The force needed to maintain the orbit equals mv2/r (the "centripetal" force), so the more massive the planet the greater the force needed. But gravity is proportional to mass, so it works out just right.
 
also, technically the sun and Earth are both revolving around one another, which may be a helpful way of seeing the situation.
or not.
 
I wouldn't look at it like that, that just leads to confusion in my opinion.

Newtons first law states an object will remain still or continue at a constant velocity in a straight line unless acted on by an unbalanced force.

Think of the Earth as originally moving in a straight line, the gravitational force of the sun acted on it, but not enough to pull it straight into it, it pulled it around in a curve, and the velocity stays great enough that it will keep going round and round.

Think of a hammer throw, the object is getting pulled but not enough to go straight to the center, only enough to move in a circle.
 
porky said:
Why doesn't the Earth collide with the Sun?
Because it is not in the way.
 
A.T. said:
Because it is not in the way.
That's the best answer so far! :smile:
 
No force needed to stay in motion.

The Earth orbits the Sun in high vacuum. So there's very little resistance if any to slow Earth's orbit significantly in its billion years existence.
 
crapworks said:
No force needed to stay in motion.
You might want to rethink that. It's the gravitational attraction of the Sun on the Earth which allows the Earth to remain in orbit. If there were no force, the Earth would take off in a straight line.
 
I have definitely misunderstood the first post!

I was thinking since Porky had just gone through centripetal, etc. what's the point of asking the obvious. I thought he's looking for something else:!)
 
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Also realize that this thread is almost a year old. That ship has sailed and porky is long gone.
 

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