2. Consider the forces exerted on your forearm to keep it in equilibrium in the

Question

2. Consider the forces exerted on your forearm to keep it in equilibrium in the horizontal position. Most of this force is provided by the tension in your bicep muscle (see figure below).

2. Consider the forces exerted on your forearm to keep it in equilibrium in the horizontal position. Most of this force is provided by the tension in your bicep muscle (see figure below). Choose your elbow joint to be the location of the axis of rotation. Indicate this choice by drawing a big dot at the appropriate location on the figure below. The figure below shows the 3 forces that you need to consider. Which force is the most effective at producing a torque about your chosen axis? Which force is the least effective ? Explain. Suppose you are holding a 5-pound dumbbell in your hand (1pound= 0.45kg) For your forearm to be in equilibrium, there must be sufficient tension in your bicep muscles. You may assume that L=12.5cm and the mass of your forearm is 1.25 kg. The distance a??da?? in the figure is 3.5cm. Calculate the tension in your muscle and compare to the weight of the dumbell. What do you conclude from this comparison? Please try to write carefully and clearly.

Explanation / Answer

2) ball is the most since it has the longest moment arm

3) sum torque about elbow

F*3.5E-2 - 1.25*9.81*12.5E-2 - 5*0.45*9.81*2*12.5E-2=0

F=201.5 N

W dumbell = 5*0.45*9.81 = 22.08 N

4) The force of your bicep is much greater than the weight of the dumbell. It is quite difficult to hold the dumbell this way

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