Answer Happy

A person balances a 20-N object on the back of their hand while their entire arm is outstretched as shown in the Figure. The main muscle responsible for holding the arm is the deltoid muscle shown in the Figure (note the angle that it makes with the horizontal humerus); assume that the deltoid muscle attaches to the humerus 5.0 cm from the shoulder joint. Use the entire arm as the system and do the following: a. Estimate the weight of the system. (You are not allowed to use the internet.) b. Estimate the distance from the shoulder joint that center of mass of the system is located and the distance from the shoulder joint that the object is located. (You are not allowed to use the internet.) c. Apply the laws of equilibrium to determine the force that the deltoid muscle exerts on the arm, and the magnitude of the force that the contact in the shoulder joint exerts on the arm.