posted by Brittany .
An object whose mass is unknown is held by two rigid rods. The whole system is at rest. The angle between the vertical direction and the left rod from point A to B is 60 degrees. The angle between the vertical direction and the right rod from point C to D is 30 degrees. The forces in the rods are along the direction of the rods. It is known that the force in rod AB is 20 N. Another box, whose mass is 1.20kg is sitting ont he top of the unknown object through another rigid rod. What is the mass of the unknown object? Carefully draw the free body diagrams and show your calculations.