Turning on snowboard or surfboard

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    Turning
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Discussion Overview

The discussion revolves around the physics of turning on a snowboard or surfboard, specifically focusing on the g-forces experienced by the rider during a turn. Participants explore the relationship between bank angles, speed, and turn radius, as well as the calculations involved in determining the forces at play.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant suggests that the g-force experienced by a rider leaning at 45 degrees is independent of speed and turn radius, questioning if simple trigonometric calculations apply.
  • Another participant argues that the force due to gravity is constant and does not depend on angles, emphasizing that the rider maintains weight over the board while angling it to trace a curved path.
  • A different viewpoint states that the g-force can be calculated based on the bank angle, asserting that the resultant gravitational acceleration vector must pass through the board to maintain balance, leading to a specific calculation for a 45-degree bank angle resulting in 1.4g.
  • Another participant mentions that the g-forces experienced depend on the rider's velocity and the radius of curvature, referencing the equation for normal acceleration in circular motion.
  • A later reply expresses preference for one participant's explanation, indicating a subjective agreement without resolving the underlying technical disagreements.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between bank angle, speed, and g-forces, with no consensus reached on the correct approach to calculating these forces.

Contextual Notes

Some calculations and assumptions regarding the forces and angles involved remain unresolved, and the discussion reflects varying interpretations of the physics principles at play.

evnmorfun
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In a turn, a rider might be leaning over at around 45 degrees at times. What is the g-force at that point going down into his feet ? I'm thinking that it is essentially independent of the speed and turn radius. Also, I'm thinking the rider is close enough to standing straight - no bent knees or hips, arms near to by his or her sides. What about getting really low - say 30 degrees ? Is it a simple sin cos or tan calculation ?
 
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the force due to gravity is his mass times the local gravitational field strength- neither depend on any angles. In snowboarding the rider himself doesn't lean, you still keep your weight more or less over the board (maybe a little in a fast tight turn), mostly you angle the board so that the "bloated" ends bend upwards slightly, and then you trace a curved path.
 
That's not correct. You can calculate the g-force (acceleration) required for a balanced turn for a snow board, surf board - even an airplane, knowing only the bank angle.

For a snowboard and surfboard, in order to not fall over, the resultant effective gravitational acceleration vector of your center of gravity must pass through your board. Ie, if you lean to far to the right, you fall over to the right. So to balance the forces, you draw a diagram showing the resultant vector pointing from your CoG to the board, the gravitational force vector straight down, and a third vector horizontal into the turn. You have all three angles and the magnitude of one side, so you can solve for the magnitude of the other sides.

For a 45 degree bank angle, you have a 45/45/90 right triangle, so the horizontal and vertical components are both 1g and the resultant force (the one you "feel") is 1.4g.
 
I think about this when I'm riding my boards all the time!

How many g's you are pulling is dependent on your velocity and radius of curvature.

Take the constant velocity circular motion equation for normal accelleration:

a=(velocity)^2/(radius of your turn)

to find how many g's you pull divide 'a' by 'g', gravity constant.
 
Thanks , Russ , I definitely like yours the most.
 

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