Does the velocity of a skateboard affect the impact of a flat-landing drop?

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Discussion Overview

The discussion revolves around the impact of velocity on the landing force experienced when a skateboarder drops from a height of 4-10 feet onto a horizontal surface. Participants explore the relationship between horizontal velocity and the resulting impact upon landing, considering factors such as gravity, rotation, and air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asserts that the velocity of the skateboard does not affect the impact force upon landing, as gravity acts uniformly on the object regardless of horizontal motion.
  • Another participant counters that while the vertical velocity remains unchanged, the time spent in a half-suspended state affects the rotation of the skateboard, which could influence landing stability.
  • Concerns are raised about whether the increased speed leads to a greater impact force, with one participant emphasizing the need for a perfect landing to assess impact accurately.
  • Air resistance is mentioned as negligible at lower speeds, but one participant notes that it could become significant at much higher speeds, although such speeds are impractical for skateboarding.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between velocity and impact force, with no consensus reached on whether the speed of the skateboard affects the impact experienced upon landing.

Contextual Notes

Participants acknowledge various factors that could influence the outcome, such as the position of the center of mass and the conditions of the landing, but these factors remain unresolved in terms of their overall impact on force experienced.

Neeson
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I've been having a bit of a discussion with a friend lately, about an object dropping off a horizontal surface, falling a certain amount, and then landing on another horizontal surface.

The question is whether the impact of landing on the horizontal surface, will be affected by the velocity of the object.

It started about flat-landing drops on a skateboard. Do you land as hard going fast as you do going slow? The size of drop would be between in the range of 4-10 feet.

From my understanding, the velocity will make no difference, as an object is always affected by gravity in the same way, ie accelerating downward vertically at 9.8m/s. The horizontal velocity would not factor in, as when you land you would continue moving at the same velocity as take-off due to Newtons law, thus there is no force dissipated here. Sorry, my ability to explain physics is quite limited!

Could there be anything that I am not taking into account? I am assuming air resistance, would be negligible at these speeds. Is this correct?


Any clarification and explanation of this matter would be highly welcomed.
 
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Everything is right, but there is one factor to which the speed makes a difference.

When you leave the edge, the rear wheels are supported for a while after the front ones went over. If you aren't careful about placing your CM neatly over the rear wheels, you'll pick up a bit of a rotation going over. When you are moving faster, you spend less time in this half-suspended state, and so pick up less rotation, giving you better odds of safe landing.

The vertical velocity with which you hit the ground, however, does not change. It is completely independent from horizontal motion.

Air resistance would play a role if you were going fast enough, but that'd be something in the neighborhood of 100mph to make any sort of a noticeable difference. I'm pretty sure you'd have other problems if you tried to go that fast on the skateboard.
 
K^2 said:
When you leave the edge, the rear wheels are supported for a while after the front ones went over. If you aren't careful about placing your CM neatly over the rear wheels, you'll pick up a bit of a rotation going over. When you are moving faster, you spend less time in this half-suspended state, and so pick up less rotation, giving you better odds of safe landing.

Will this increase the amount of force that you land with though? It's not the odds of landing that I'm looking for (I'm assuming a perfect landing), just the amount of impact.
 
If you land on the wheels in both cases, no difference. If you land on your face, it's going to depend on many things.
 

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