*errata: at 6:05 I state that force of friction on 8.0 kg block combined with force of gravity on the 5.0 kg block will be the only forces determining acceleration along the inclined plane. This is an error. I forgot to mention that the x-component of the force of gravity acting on the 8.0 kg block will also be very important. The question is solved correctly, just this statement is incorrect.
*also acceleration = 4.9x10^-1 (0.4927)