Question about the role of mass in inclined planes

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Discussion Overview

The discussion revolves around the role of mass in the dynamics of inclined planes, particularly in relation to sledding on snow. Participants explore how mass affects acceleration and the implications of friction, air resistance, and rolling resistance in different contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that, according to their understanding, mass does not affect the acceleration of a block on an inclined plane, regardless of friction.
  • Another participant suggests that the nature of snow as a surface may alter the frictional dynamics, as it can compact and melt against the sled, potentially lowering the coefficient of friction.
  • A later reply agrees that the compaction and melting of snow can significantly reduce friction, drawing a parallel to ice-skating on hardwood floors.
  • Another participant raises a related question about the differences between wind resistance, rolling resistance, and friction on inclined planes, noting that increased weight can lead to faster acceleration in air.
  • One participant explains that in sledding, having more mass can lead to greater gravitational force with relatively unchanged air resistance, particularly when multiple people sit behind one another on a sled.
  • The discussion includes a reference to bobsled competitions, where teams may add ballast to maximize weight, suggesting that heavier sleds tend to go faster.

Areas of Agreement / Disagreement

Participants express differing views on the impact of mass on acceleration in inclined planes, with some asserting that mass does not influence acceleration while others provide examples where increased mass appears to enhance performance. The discussion remains unresolved regarding the general applicability of these insights.

Contextual Notes

Participants rely on specific conditions such as the type of surface (snow vs. hard surfaces) and the context of sledding versus theoretical models of inclined planes. The discussion does not resolve the implications of these factors on the broader understanding of mass and acceleration.

tovisonnenberg
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Hi! I have a question about inclined planes. In the diagram I attached, you can see that, with or without friction, mass does not affect the acceleration of the block. However, in my experience, the more people I put on my sled, the faster it goes. Why is this?
IMG_0005.jpeg
 
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Sled, as in snow? Snow doesn't work like a hard, dry surface for friction. It compacts and maybe even melts a little against the sled.
 
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russ_watters said:
Sled, as in snow? Snow doesn't work like a hard, dry surface for friction. It compacts and maybe even melts a little against the sled.
Ah, so a combination of greater compaction and a little melting decreases the coefficient of friction?
 
tovisonnenberg said:
Ah, so a combination of greater compaction and a little melting decreases the coefficient of friction?
Considerably. Every try ice-skating on a hardwood floor? Same principle
 
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So a related question is why wind resistance and rolling resistance are different from friction on an inclined plane. Clearly extra weight makes masses fall faster in air, and makes bike riders accelerate faster down hills...
 
tovisonnenberg said:
Hi! I have a question about inclined planes. In the diagram I attached, you can see that, with or without friction, mass does not affect the acceleration of the block. However, in my experience, the more people I put on my sled, the faster it goes. Why is this?
In general, air resistance depends on the surface area in the direction of travel. If one person is sitting behind another on the sled, then you have twice the mass and twice the gravitational force against almost the same air resistance.

For example, in the bob-sled competitions there is a maximum weight allowance.

https://adventure.howstuffworks.com/outdoor-activities/snow-sports/bobsled2.htm

"Heavier sleds go faster, so teams that do not reach the maximum occupied weight may add ballasts to make their bob heavier. Officials weigh the sleds at the end of the run to make sure they meet the weight requirement."

I guess it makes sense that all sleds are weighed up to the maximum - otherwise the heaviest team would probably win. I had no idea that teams could add ballast - but that does explain why generally there are only a few hundredths of a second between teams. The difference between first and last in a bob-sled competition is essentially experimental error!
 

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