In the ftgure, a 21 kg block is held in place via a pulley system. The person\'s

Question

In the ftgure, a 21 kg block is held in place via a pulley system. The person's upper arm is vertical; the forearm makes angle e - 35 with hand together have a mass of 1.7 kg, with a center of mass at distance di - 16 cm from the contact point of the forearm bone puls vertically upward on the forearm at distance d2 - 2.0 cm behind that contact point. Distance dy is 31 cm. Take the upward direction to be positive What are the forces on the forearm from (a) the triceps muscle and (b) the humerus? Triceps ? Block (a) N Open Show Work Click if you would like to Show Work for this question:

Explanation / Answer

In equilibrium net torque about the point of contact = 0

T*d3*costheta - mhand*g*d1*costheta - Ftriceps*d2*costheta = 0

m*g*d3 - mhand*g*d1 - Ftriceps*d2 = 0

21*9.8*0.31 - 1.7*9.8*0.16 - Ftriceps*0.02 = 0

F = 3057 N

(b)

In equilibrium net force = 0

Ftriceps + T - mg + Fhumerus = 0

3057 + (21*9.8) - (1.7*9.8) + Fhumerus = 0

Fhumerus = -3246 N

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