Block B rests on Block A. Block B is restrained with a string, while Block A slides down the incline. During the time Block A is between Block B and the inclined plane, Block A slides with constant velocity. If the weight of Blocks A and B are both w, and the coefficient of friction is the same between Block A and B and between Block A and the plane, find the value of the coefficient of friction u. [The angle of the incline is 45].
The professor's solution has a free body diagram for Block A, with two frictional forces and a normal force. This I understand, but he draws weight straight down with magnitude w+w. I thought this was incorrect, as Block A only experiences a Normal force from Block B.
The Attempt at a Solution
The rest of the problem is inconsequential, but my proposed diagram for Block A has 2 frictional forces up the slope, Normal A normal to the slope, Normal B perpendicular to the surface between Blocks A and B, and weight of w.