Statics of a human arm

Let's talk about the statics of a human arm holding a weight. Let's try to calculate how many Newtons of Force is the biceps tendon carrying, and what is the moment in the shoulder joint?

We assume that a person of 100 kg is holding a dumbbell weighing 10 kg. 

Thus, weight of the upper arm = approx 4% of body weight = 4 kg, 
and weight of the fore arm = approx 3% of body weight = 3 kg. 

We take the length of the fore arm = 30 cm. Also, for keeping calculations simple, we take g = 10m/s2.

Cutting the system free

Fw1 = 40 N, Fw2 = 30 N, Fwd = 100 N

α = 10°

d1 = 5 cm, d2 = 15 cm, d3 = 30 cm

We can calculate 

Force on the Bicep, FB = 172.62 N
Shoulder Moment, MA = 34.5 Nm


This is fun!Credit: Udemy Course 'Biomechanics: The Physics Of Human Movement' by Emil Cordes'

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