1. **Problem Statement:** We have an elbow joint with a 120° angle, a forearm weight of -80 N located 14 cm from the axis of rotation, and a biceps brachii force of 433 N parallel to the humerus. We want to analyze torque and moment arm. 2. **Torque Formula:** Torque is calculated as $$T = F \times r$$ where $F$ is force and $r$ is the moment arm (distance from axis of rotation). 3. **Part b) Torque Calculation:** Given $F = -80$ N and $r = 0.14$ m, $$T = (-80)(0.14) = -11.2 \text{ N} \cdot \text{m}$$ The negative sign indicates clockwise torque. 4. **Part c) Moment Arm Calculation:** Using the sine relation for the vertical component of the biceps force: $$\sin 120^\circ = \frac{F_y}{433}$$ $$F_y = 433 \times \sin 120^\circ = 433 \times 0.866 = 374.98 \text{ N}$$ Torque $T$ is also: $$T = F_y \times r$$ Rearranged to find $r$: $$r = \frac{T}{F_y} = \frac{11.2}{374.98} = 0.0298 \text{ m}$$ Convert to cm: $$r = 0.0298 \times 100 = 2.98 \approx 3.0 \text{ cm}$$ 5. **Indicating Unknown in Part a):** For part a), if you are solving for an unknown (e.g., force, torque, or moment arm), place a question mark next to the variable you want to find, for example: - $T = ?$ if torque is unknown - $r = ?$ if moment arm is unknown - $F = ?$ if force is unknown This clearly shows what you are solving for. **Summary:** - The calculations for parts b) and c) are correct. - For part a), indicate the unknown variable with a question mark to clarify the goal.