A block (mass m1) lying on a frictionless inclined plane is connected to a mass m2 by a massless cord passing over a pulley.
a) Determine a formula for the acceleration of the system of the two blocks in terms of m_1, m_2 , \theta and g. Assume that positive axis is directed down the plane.
b) What conditions apply to masses m1 and m2 for the acceleration to be in one direction (say, m_{\rm 1} down the plane), or in the opposite direction?