- #1
Flor
- 10
- 0
Why does the Earth attract the apple and the apple at the same time does not attract the Earth (the Earth does not move to the apple)?
Why Does an Apple Fall to Earth, But Earth Doesn't Fall to the Apple?
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Discussion Overview
The discussion revolves around the question of gravitational attraction between an apple and the Earth, specifically why the Earth does not appear to move towards the apple while the apple falls to the ground. Participants explore concepts of gravitational force, inertia, and the relative masses of the objects involved.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant questions why the Earth does not move towards the apple, suggesting that the apple's fall is observable.
- Another participant asserts that while the forces of attraction are equal and opposite, the Earth's large inertia makes its movement negligible compared to that of the apple.
- A different viewpoint emphasizes the role of inertia by comparing the ease of pushing an apple versus a car, questioning how one can be sure the Earth is not moving towards the apple.
- One participant proposes an experiment involving climbing an apple tree to illustrate that the apple does not move relative to someone falling with it, implying that the Earth is moving towards both the apple and the observer.
- There is a suggestion that the intensity of the gravitational field of the Earth is much greater than that of the apple, leading to the question of what would happen if the Earth's radius expanded significantly.
- Another participant clarifies that gravitational force depends on mass rather than radius, emphasizing that both the apple and Earth experience the same force but with different accelerations due to their mass differences.
- One participant reiterates the gravitational force equation, highlighting that the force is equal for both objects but results in different accelerations due to their respective masses.
- There is a repeated inquiry about the observability of the Earth's movement towards the apple, indicating a desire for a clearer explanation of the phenomenon.
Areas of Agreement / Disagreement
Participants express differing views on the observable effects of gravity and inertia, with no consensus reached on the best explanation for the phenomenon. Multiple competing perspectives remain regarding the implications of mass and gravitational force.
Contextual Notes
Some participants reference concepts such as gravitational fields and inertia without fully resolving the implications of these ideas. The discussion includes hypothetical scenarios that remain untested and speculative.
- #2
Rear Naked
- 48
- 0
It does :-)An apple is so much less massive than Earth, so its effects are negligible go unnoticed.
The forces of attraction will be equal and opposite. However, you must take inertia into account. The inertia of the Earth is very great, but the ineria of the apple is small. The force is strong enough to move the apple, but not strong enough to noticeably move the Earth.
The forces of attraction will be equal and opposite. However, you must take inertia into account. The inertia of the Earth is very great, but the ineria of the apple is small. The force is strong enough to move the apple, but not strong enough to noticeably move the Earth.
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- #3
Flor
- 10
- 0
I know, but is it observable? Or what is the best way to explain what we observe? I see an apple falling down :)
- #4
Rear Naked
- 48
- 0
It is inertia.
Push an apple across a desk. Now try to push a car using that same force.
How do you know the Earth is not moving up towards the apple?
Push an apple across a desk. Now try to push a car using that same force.
How do you know the Earth is not moving up towards the apple?
- #5
HallsofIvy
Science Advisor
Homework Helper
- 42,895
- 983
That's because you are standing on the Earth and are moving along with it. The Earth does not move relative to you.
Try this experiment instead- climb up into an apple tree and, as the apple falls, let go of the tree and fall with it. You will see that the apple does not move (relative to you) while the Earth is moving very rapidly toward both you and the apple!
- #6
Flor
- 10
- 0
Is it because the intensity of gravitational field (g) of Earth is much bigger than the intensity of gravitational field of an apple? I can give you another question - what happens if the Earth radius will expand for example 1 x 10^30 times? Then the Earth will fall on apple! Is it true? :)
- #7
Rear Naked
- 48
- 0
Gravitational force doesn't depend on the radius, only mass.
- #8
Rear Naked
- 48
- 0
m2 = mass of apple
r = distance between them
G = gravitational constantThe magnitude of force F will be the same for both objects, only in opposite directions.Everything is the same...except mass (ie. inertia)
If the mass of the apple is increased an incredible amount, we then might observe the effects.
- #9
chrisbaird
- 610
- 5
Flor said:
No, the force is the product of both masses, and they both feel the same force (action and reaction forces equals). Think of F = m a for the apple the for the earth, where F is the same for both. For the earth, m is huge, so the acceleration a must be tiny to keep F constant and equal to the F that the apple feels.
- #10
- 32,812
- 4,723
Flor said:
You may want to start by reading this FAQ
https://www.physicsforums.com/showthread.php?t=511172
Zz.
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