Consider holding a carton of milk in your hand, as shown in the image.
The force of the bicep muscle acts at an angle of 15
o
to the vertical, while
the weight of the arm and the milk both act downwards. The distance
from the elbow to where the bicep muscle is attached via the the distal
bicep tendons to the radius and ulna bones is 5 cm. The distance from the
elbow to the center of mass of the forearm is 16.5 cm and the distance
from the elbow to the hand, holding the milk, is 35 cm. The forearm has
a mass of 4 kg and the milk carton a mass of 2 kg.
a) Assuming the forearm is kept perfectly horizontal, find the tension in the bicep muscle.
b) As a function of the angle of the forearm with respect to the horizontal direction (as the forearm is
lowered) calculate the tension in the bicep muscle.
c) Include a plot of tension in the bicep as a function of the angle of the forearm relative to the
horizontal (don't forget to label axis)