posted by Katie .
A lunch tray is being held in one hand, as the figure below illustrates.
The mass of the tray itself is 0.182 kg, and its center of gravity is located at its geometrical center. On the tray is a 1.08 kg plate of food and a 0.279 kg cup of coffee. Assume L1 = 0.0590 m, L2 = 0.138 m, L3 = 0.258 m, L4 = 0.381 m and L5 = 0.401 m. Obtain the force T exerted by the thumb. This force acts perpendicular to the tray, which is being held parallel to the ground.