Clarifying the Relationship Between Centripetal Force and Gravity

In summary: Welcome to PF, where we try to answer questions as best as we can! In summary, centripetal force is what keeps the bucket and water up in the air when they are swinging, and gravity always pulls objects towards the center of the Earth.
  • #1
gamabunta
3
0
Hi,

I'm currently taking 1st semester Physics and am trying to understand centripetal force relative to the Earth's rotation.

From what I understand (using a bucket of water tied to a string as an example), swinging a bucket in a circular motion, when the bucket is completely above your head, gravity will pull the water towards the bottom of the bucket (in this case up, away from the string) while centripetal force (pointing inward towards the string) is what keeps the bucket from flying off in the direction of velocity.

If this is so does this mean that what we interpret as gravity (9.8 m/s^2) "pulling" us down towards the Earth in actuality is centripetal force while the "true" gravitational force points 180 degrees in the opposing direction (in this case up towards the sky?)

I spent a good hour looking online for answers and have reread my textbook 3 times and still need clarification. Any help is appreciated. Thanks in advance!
 
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  • #2
gamabunta said:
From what I understand (using a bucket of water tied to a string as an example), swinging a bucket in a circular motion, when the bucket is completely above your head, gravity will pull the water towards the bottom of the bucket (in this case up, away from the string) while centripetal force (pointing inward towards the string) is what keeps the bucket from flying off in the direction of velocity.
No. Gravity always acts towards the center of the earth--downwards. Since the bucket is being spun in a circle--and thus centripetally accelerating--there will be a net force acting on it towards the center (the centripetal force). When the bucket is overhead, the centripetal force is downward; the centripetal force is the sum of the weight and the string tension.
If this is so does this mean that what we interpret as gravity (9.8 m/s^2) "pulling" us down towards the Earth in actuality is centripetal force while the "true" gravitational force points 180 degrees in the opposing direction (in this case up towards the sky?)
No.
 
  • #3
Crap, I just realized I was only thinking in terms of the Earth.

The centripetal force for the Earth is provided by its revolving around the Sun correct?
 
  • #4
gamabunta said:
The centripetal force for the Earth is provided by its revolving around the Sun correct?
Whenever there is circular motion there is a centripetal force. When considering the Earth orbiting the Sun, the centripetal force is provided by gravity.
 
  • #5
Doc Al said:
Whenever there is circular motion there is a centripetal force. When considering the Earth orbiting the Sun, the centripetal force is provided by gravity.

Thank you!
 
  • #6
Sorry to bring this question back from the dead, but if tension and gravity are both causing centripetal acceleration and therefore a centripetal force toward the center than what keeps the bucket and water up? What is this force and is there a way to explain it.
 
  • #7
ha9981 said:
Sorry to bring this question back from the dead, but if tension and gravity are both causing centripetal acceleration and therefore a centripetal force toward the center than what keeps the bucket and water up? What is this force and is there a way to explain it.
What keeps the bucket and water "up" is their inertia. They are being swung in a circle. At the top of the swing the forces all act downward while the bucket and water move horizontally. Thus the change in the velocity is downward and the bucket turns in a circle as it moves.
 
  • #8
Welcome to PF!

Hi gamabunta! Welcome to PF! :smile:
gamabunta said:
gravity will pull the water towards the bottom of the bucket (in this case up, away from the string) while centripetal force (pointing inward towards the string) is what keeps the bucket from flying off in the direction of velocity.

No, the string pulls the bucket down, and the bucket pulls the water down.

Nothing pulls the water up. :rolleyes:

You could do away with the bucket if only someone would make string that could pull water. :wink:
 

What is the difference between centripetal force and gravity?

Centripetal force is the force that keeps an object moving in a circular motion, while gravity is the force that attracts objects towards the center of the Earth or other massive objects.

How are centripetal force and gravity related?

Centripetal force is a type of force that can be caused by gravity. In circular motion, the centripetal force is directed towards the center of the circle, which can be the Earth or another massive object due to the force of gravity.

Which one is stronger: centripetal force or gravity?

This depends on the specific situation. In most cases, gravity is a much stronger force than centripetal force, as it is responsible for keeping planets in orbit around the sun and moons around planets. However, in certain situations, such as the centrifugal force experienced in a spinning amusement park ride, centripetal force can be stronger.

Can an object experience centripetal force without gravity?

Yes, an object can experience centripetal force without gravity. This can occur in situations such as a car turning a corner or a ball being swung on a string. In these cases, the centripetal force is caused by the object's inertia and the force applied by an external source, rather than the force of gravity.

How is the centripetal force of an object calculated?

The centripetal force of an object can be calculated using the formula Fc = (mv^2)/r, where Fc is the centripetal force, m is the mass of the object, v is the velocity, and r is the radius of the circular motion. This formula shows that the centripetal force is directly proportional to the mass and velocity of the object, and inversely proportional to the radius of the circular motion.

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