The biomechanics of elbow extension

Thread starter thegoose
Start date Nov 25, 2023
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Biomechanics Physics Sin

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SUMMARY

The discussion centers on the biomechanics of elbow extension, specifically analyzing the forces involved in the movement. The formula presented, 𝐹𝑃𝑥 = 93.6650N sin (85 − 90) + 28.11N sin(180 − 85 − 79), results in a calculated force of 𝐹𝑃𝑥 = -0.4154 N. Participants emphasize the importance of considering torques in addition to forces and suggest a more detailed analysis of the shoulder joint's role in elbow extension mechanics.

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Understanding of basic biomechanics principles
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Knowledge of muscle force dynamics
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Nov 25, 2023

thegoose

Homework Statement: I noticed that when I do a calculation of the form 85-90 it gives a result of -5, which affects my overall answer by giving a negative number. I think I didn't correctly determine the angle of my muscle strength. Would it be possible for this angle to be 0°? So, by doing the 85-0 calculation, we would get a positive number.

Relevant Equations: Σ𝐹⃗ = 0

X=

Σ𝐹𝑥 = 0

−𝐹𝑃𝑥 + 𝐹𝑀 sin (𝛽 − 90°) + 𝐹𝑒𝑙 sin (180 − 𝛽 − 𝜃) = 0

𝐹𝑃𝑥 = 𝐹𝑀 sin ( 𝛽 − 90°) +𝐹𝑒𝑙 sin(180 − 𝛽 − 𝜃)

𝐹𝑃𝑥 = 93.6650N sin (85 − 90) + 28.11N sin(180 − 85 − 79)

Fpx= -8.16344N +7.74816N

𝐹𝑃𝑥 = -0.4154 N←

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Nov 25, 2023

haruspex

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Please define all your variables.
I assume FM means the force exerted by a muscle, but it seems to be exerted directly down at the shoulder pivot, which is not going to achieve anything. You need to analyse torques, not just forces, and consider the shoulder joint in more detail.

Last edited: Nov 25, 2023

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