Two masses are connected by a string which passes over a frictionless, massless pulley. One mass hangs vertically and one slides on a horizontal surface. The horizontal surface has a coefficient of kinetic friction 0.2. The vertically hanging mass is 4.0 kg and the mass on the horizontal surface is 6.0 kg. Find the acceleration of the mass.
The Attempt at a Solution
I've basically done this problem without factoring friction, and this my problem, I don't know how to factor friction.
a = (mBg)/(mA + mB) is what I used.