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**1. The problem statement**

what role does torque play in body stability and ergonomics ?

- Thread starter pennywise1234
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what role does torque play in body stability and ergonomics ?

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If you want a mathematical definition:

$$ \tau_{Total} = \sum_{i} \tau_{i} = \sum_{i} \vec{r_{i}} \times \vec{F_{i}} $$

Where ##\tau_{Total}## is the total torque on the body, and is the sum of a number of torques, ##\tau_{i} = \vec{r_{i}} \times \vec{F_{i}}## where, ##\vec{r_{i}}## is the position vector, and ##\vec{F_{i}}## is the force.

The angular momentum of a body is related to the torque applied:

$$ \vec{L} = \vec{r} \times \vec{p} $$

$$ \frac{d\vec{L}}{dt} = \frac{d\vec{r}}{dt} \times \vec{p} + \vec{r} \times \frac{d\vec{p}}{dt} $$

So

$$ \frac{d\vec{L}}{dt} = \vec{r} \times \vec{F} $$

i.e -if we don't have any torque, then the angular momentum must be constant in time. The body cannot be spinning up or spinning down - in cannot be changing its motion in any rotational sense. So in this way, we see that a

Does that help at all?

- #3

CWatters

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Penny... have a think about the joints in the human body. I think all (?) Involve rotation.

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