O/T: Biomechanics Question

mpm · 11-02-2006, 11:25 AM

Hey all,

I have a slightly off topic question. I have a biomechanics problem for an assignment, and I was hoping someone could help me out a little.

I am trying to figure out the reaction force at the ocipital condyles if torque is neglected. This is of a head that receives a blow to the chin 63 degrees from horizontal.

I know linear acceleration, mass, moment of inertia.

I have used the parallel axis theorem to find my actual inertia.

I'm thinking I need to sum the moments to find a reaction force, but I am not sure how to do that or if thats right.

Can anyone maybe shed some light?

If any more info is needed let me know.

flying scotsman · 11-02-2006, 02:27 PM

I'm sorry, I appear to have stumbled into a mathematics forum instead of my favourite fitness forum.

I'll get my coat.

Oh, and I'm sorry I couldn't have been of help 'mpm'.

Newlife · 11-02-2006, 02:36 PM

If you come to Vermont, we can test it!

JoshDunn · 11-02-2006, 06:39 PM

I could be way off here, actually probably am. Been awhile.

Do you know the movement of the head? Wouldn't you need to add the sum of the forces hitting the head, then subtract the resistance force that of the head and that'll get you total force.

If you need to work out resistance forces you would need to work out the movement of the head otherwise you can only just say what the total forces hitting the head could be.

2 thoughts there.

mpm · 11-02-2006, 06:46 PM

Yeah I ended up totally neglecting the moment of inertia because it told me to neglect torque. I couldn't find any other reason to need moment of inertia. So that would just mean there is linear movement and not angular. I did the sum of forces and came up with about 9500 N. I'm not sure if this number is reasonable. I guess it could be.

Thanks for your suggestions.

JoshDunn · 11-02-2006, 07:07 PM

from that number i imagine it would be right. forces applied to the body are huge. Standing on one leg doing a calf raise puts 12x your bodyweight on your calf. Intense hey.

mpm · 11-02-2006, 07:12 PM

I have one last question i just thought about. I have that force, but it is a distance, d, away from the place that I'm supposed to find the reaction force.

Couldn't I just multiply that force by that distance, d, and thats my reaction?