B..

Question 4. 121 pts] You try to design a workout system for yourself for one arm preacher curl to

strengthen your biceps. The system you create has three wires as shown in the figure below. Three

wires are fixed to the floor. If you fix your elbow (G) to acts a pin, determine the force your biceps

muscle is producing when you lift up the forearm to create a defromation of 1 cm in wire 3. Assume

all the wires defrom vertically, have a diameter of 4 mm, and a Young's modulus of E-200 GPa.

Assume the forearm acts as a rigid beam.

Чтт

meter of 4mm.

200 GPa 200x109 Pa

A

NAB NO

Wire length:

30 cm

Wire 1

-0.004 m

Forearm: 40 cm

B

E

8 cm 8 cm

D

A NEF

Wire 2 Wire 3

1

H 30°

Nicep

90°

2 cm

fo

Gy

Gy

A. [5 pts] Draw a figure showing the forearm after deformation occurs. Then create an equation

which relates the defromation in wire 3 (1 cm) to wires 1 and 2.

B. [6 pts] Determine normal forces acting on wires 1, 2, and 3.

C. [10 pts] Determine the bicep force and forces acting on the elbow joint. Hint: Draw a FBD of

the when the forearm when its is horizontal.