Use the following values: length of forearm = L = 19 cm elbow to bicep distance

Question

Use the following values:
length of forearm = L = 19 cm
elbow to bicep distance = d = 3 cm
mass of forearm = M = 3 kg
mass of baseball = m = 2 kg

a.) Based on torque considerations, you can reason that the force of the bicep must be  ---Select--- less than  greater than the same size as the combined weight of the baseball/forearm. Explain.

b.) How large is the force exerted by the bicep?
N

c.) The force exerted by the upper arm bone (not shown above) on the forearm must be:
N,  ---Select--- upwards downwards to the left to the right

Explanation / Answer

Given that length of forearm = L = 19 cm =0.19m
elbow to bicep distance = d = 3 cm=0.03m
mass of forearm = M = 3kg
mass of baseball = m = 2 kg

a)Since the force due to biceps is near to axis of rotation as compared to the weights of base ball and forearm in order to balence this force must be greater than the combined weights of base ball and arm

b)if F is the force exerted on the bicep then
Fd-Mg(L/2)-mgL=0
F(0.03m)-3(9.8)(0.19/2)-2(9.8)(0.19)=0
  F(0.03m) =5.517
   F= 183.9N
c)if F2 is the force due to bone then applying torque condition about the force due to biceps F2d=Mg(L/2-d)+mg(L-d)        =3(9.8)(0.19/2-0.03)+2(9.8)(0.19-0.03)        =5.047 F2=168.23N

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