Body U with mass 5m is stacked on the top body W with mass m, and released. The bodies are in contact along the frictionless interface at 45 to the vertical. The body U is in contact with the...

Body U with mass 5m is stacked on the top body W with
mass m, and released. The bodies are in contact along the
frictionless interface at 45 to the vertical. The body U is
in contact with the frictionless vertical wall. Body W lies
on the floor with coefficient of friction u. Relevant
dimensions are shown in the figure. Express the results in
terms of given quantities: m, g, h and u.

What is the minimal coefficient friction to prevent sliding?

Let the system move. What is the condition that the velocities of U and W must satisfy for the two bodies to remain in contact?