The torque on the shoulder joint is 23.54 N·m
How to solve
We can calculate the torque on the shoulder joint by using the following formula:
torque = force x distance
force = mass x gravity
In this case, the force is the weight of the steel ball and the arm acting downwards. The distance is the length of the arm from the shoulder to the center of gravity of the ball and arm system.
force = (2.0 kg + 4.0 kg) × 9.81 m/s² = 58.86 N
distance = 70 cm - 30 cm = 40 cm = 0.4 m
torque = 58.86 N × 0.4 m = 23.54 N·m
Therefore, the torque on the shoulder joint is 23.54 N·m
The Complete Question
An athlete at the gym holds a 2.0 kg steel ball in his hand. His arm is 70 cm long and has a mass of 4.0 kg with the center of gravity 30 cm from the shoulder. What is the torque on the shoulder joint?