Gravity and Uniformed Circular motion

• am_knightmare
In summary: Some people find diagrams like this more helpful than just a simple picture of gravity. Other people find it confusing.In summary, the force of gravity is a centripetal acceleration, only in special cases will it be a uniform circular motion.
am_knightmare
Is gravity a Uniformed Circular motion? I had this question for a while and i googled searched it but no results, I also did the readings which I do think it is. But in the readings , I never read the statement that says gravity is a form of uniformed circular motion. Can anyone explain why or why not it is or isn't? Thanks.

am_knightmare said:
Is gravity a Uniformed Circular motion?
Gravity is a force, not a motion.

To have uniform circular motion, you need a net centripetal force. In certain cases, gravity can provide that force, such as a satellite in a circular orbit about a planet.

Thanks for the reply. another question would be, gravity is a form of centripetal acceleration ? since they have the same units.

am_knightmare said:
Thanks for the reply. another question would be, gravity is a form of centripetal acceleration ? since they have the same units.
The term 'gravity' is a bit ambiguous. Do you mean the force of gravity? Or the acceleration due to gravity? Those are different, but related, things.

In any case, only in special cases, such as that satellite in circular orbit about a planet, would the acceleration due to gravity happen to be a centripetal acceleration.

Anything executing uniform circular motion is undergoing a centripetal acceleration, so there must be a net centripetal force acting. It may or may not have anything to do with gravity.

Thanks a lot, that was a good explanation.

Satellite orbits: Is this what the OP is basically about?

There is one particular speed for a satellite to travel that will cause its orbit to be exactly circular. This will be when the centripetal force is exactly equal to the gravitational force and it is moving at right angles to a radius. If you take a satellite which satisfies these conditions and give it a change in speed (boost or braking), or direction, it will no longer follow a circular orbit but an elliptical one. The gravitational force varies, depending on their orbital distance (inverse square law) and this is the only 'force law' that will lead to a stable, elliptical orbit afaik.
Most (all) orbits of planets, moons, satellites are, in fact, elliptical and not perfect circles. Sometimes they are far away and move slower and at other times they are closer and moving faster. But they do not 'fall out' of orbit nor do they escape because their total energy (Gravitational Potential plus Kinetic) remains the same.

Also, think of gravity like the picture of a negative charge. All the lines of force point inwards to a central point if the only body in the example is the body causing the gravity. At every distance, the force is the same, but decreases slowly as you move farther and farther away. This picture changes when you introduce another body. It is much like positive and negative charges in the way the force interacts.

Is it really such a good idea to bring in a totally different force (electric) when the forces, lines and fields in gravity can be pictured in just the same way?

Merely trying to explain the idea using a force simpler than gravity.

Simpler?
You're lucky if you find it so.

That diagram is fine on its own but, on that link, it is followed by a whole set of diagrams, which involve numbers of opposite and like charges. Which of those would you relate to gravity and which could you not? If anything, you'd need to choose only the diagrams which involve like charges - but in those, the forces are repulsive.
If someone looks at that link and thinks they can learn about gravity, they may emerge worse off than before. That was my worry.

1. What is gravity?

Gravity is a natural phenomenon by which all objects with mass are brought towards one another. It is one of the four fundamental forces of nature and is responsible for keeping planets in orbit around the sun and objects on Earth from floating away.

2. How does gravity affect uniform circular motion?

In uniform circular motion, an object moves in a circular path at a constant speed. Gravity does not affect the object's speed, but it does affect its direction of motion. The force of gravity acts towards the center of the circular path, causing the object to continuously change direction and maintain a circular motion.

3. What is centripetal force?

Centripetal force is the inward force that keeps an object moving in a circular path. In uniform circular motion, this force is provided by the gravitational force between two objects or by a physical force, such as tension in a string, acting towards the center of the circular path.

4. Can an object in uniform circular motion have a constant speed?

Yes, an object in uniform circular motion can have a constant speed. This is because the speed of an object only refers to its magnitude, while its direction of motion can change. So, even though the object is constantly changing direction, its speed remains the same.

5. What is the difference between uniform and non-uniform circular motion?

Uniform circular motion is when an object moves in a circular path at a constant speed. Non-uniform circular motion is when the object's speed changes as it moves along the circular path. This can be due to changes in the radius of the circular path or the presence of external forces, such as friction, that affect the object's speed.

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