Effects of gravity on different elements

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Discussion Overview

The discussion revolves around the effects of gravity on two different materials, lead and copper, specifically in the context of rolling down a ramp at a 35-degree slope. Participants explore whether the material composition affects the speed and force experienced by the balls during the descent.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions if a 100lb ball of lead would roll down a ramp at the same speed as a 100lb ball of copper, considering the effects of gravity.
  • Another participant suggests that, in the absence of interference, both balls would fall at the same speed due to gravity being independent of material.
  • A participant raises the concern that the larger contact area of the copper ball might influence the results, questioning if this could lead to differences in speed.
  • It is noted that previous experiments, including those by Galileo, indicate that the acceleration due to gravity is dependent only on mass, not material composition.
  • One participant elaborates that if all other factors such as size, rolling resistance, and moment of inertia are controlled, both balls would roll down at the same speed.
  • There is a consideration of how differences in density might affect rolling resistance and air drag, potentially influencing the results.
  • Another point raised is the effect of the Earth's magnetic field on the balls, suggesting that while both materials are conductors, the impact would be exceptionally small and hard to detect.

Areas of Agreement / Disagreement

Participants generally agree that, under ideal conditions, both balls would roll down at the same speed due to gravity's independence from material. However, there are competing views regarding the influence of contact area, rolling resistance, and external factors like air drag and magnetic fields, indicating that the discussion remains unresolved.

Contextual Notes

Participants acknowledge the need to control for various factors such as size, rolling resistance, and moment of inertia to draw definitive conclusions about the effects of material composition on rolling speed.

JesseTH
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Hi,

Hopefully this is the right place for this question.

I'm wondering whether a 100lb ball of lead would roll down a ramp (assuming a 35 degree slope) at the same speed as 100lb ball of copper.

Would there be a difference in force while they are rolling down?

Thanks,
 
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Last edited by a moderator:
Thanks CWatters..

I do understand that with no 'interference' the two would fall at the same speed.

But would the larger contact area of the copper ball on the ramp surface be enough to affect results (here on earth)?
 
Last edited:
This kind of experiment has been done many times in many different ways, going back to Galileo. The "effect of gravity" (acceleration due to gravity) depends only on the mass of the object, not the material it is made of.
 
JesseTH said:
Thanks CWatters..

I do understand that with no 'interference' the two would fall at the same speed.

But would the larger contact area of the copper ball on the ramp surface be enough to affect results (here on earth)?

Any difference could potentially change the results but it might be a small. If the balls are different sizes (which they would be as they have different densities) then rolling resistance or air drag might be different and that would change the results.

If you eliminate every possible difference (same mass, size and rolling resistance and EDIT: Moment of inertia) so that they are the same except for the element that are made from then no, they would both roll down at the same speed.

How small a difference counts as different? Both lead and copper are electrical conductors and they have different conductivities. On Earth they would be moving through the Earth's magnetic field and that might affect the results - but it would be an exceptionally small effect that is hard to detect.
 
Last edited:

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