1. The problem statement, all variables and given/known data A right-triangular wooden block of mass M is at rest on a table, as shown in figure. Two smaller wooden cubes, both with mass m, initially rest on the two sides of the larger block. As all contact surfaces are frictionless, the smaller cubes start sliding down the larger block while the block remains at rest. What is the normal force from the system to the table? (A) 2mg (B) 2mg + Mg (C) mg + Mg (D) Mg + mg(sin α + sin β) (E) Mg + mg(cos α + cos β) A picture can be found here : http://www.aapt.org/physicsteam/2014/upload/exam1-2013-1-6-unlocked.pdf Page 4 Problem 11 2. Relevant equations F_gravity =mg 3. The attempt at a solution I did a FBD getting a force of mg down on the cubic blocks and Mg on the triangle block and a normal force of mgcos(alpha) and mgcos(beta) up respectively on the cubic blocks and Mg up on the triangle block. I added up all the forces to get (E) but the right answer is (C). Where did I go wrong?