Comment by not_a_cumguzzler on 05/03/2025 at 16:41 UTC*

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View submission: Ask Anything Wednesday - Engineering, Mathematics, Computer Science

Regarding the relationship between size and strength in humans vs robots, is it accurate to say that:

- for humans, mass grows cubically relative to length, whereas strength grows approximately quadratically to length (because strength is a function of muscle cross sectional area). So someone who is 6ft tall is approx 2x as tall/wide and 4x as strong as someone who is 3ft tall, but 8x as heavy (hypothetically), so a human's strength to weight ratio goes down as they get taller (specifically, heavier)

- but with electric motors (i.e. the joints of robots), torque grows proportionally to mass (based on what i'm seeing here https://encyclopedia.pub/entry/18480[1][2] and here: https://www.researchgate.net/publication/234118088%5C_Scaling%5C_Laws%5C_in%5C_Robotics[3])

1: https://encyclopedia.pub/entry/18480

2: https://encyclopedia.pub/entry/18480

3: https://www.researchgate.net/publication/234118088%5C_Scaling%5C_Laws%5C_in%5C_Robotics

TLDR: is it accurate to say that in humans, strength grows sub-linearly with mass (1/x). whereas for electric motors, torque grows linearly with mass.

TLDR: robots can scale.

Wait a minute, can someone further this to the effects of the end-manipulator? (i.e. the damage done by the fist at the end of a punch? maybe in terms of energy behind the fist?).

And what about ability lift/carry heavy loads at the end-manipulator (hand).

I wonder how those things change with relation to size.

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