GE DPXH46EA2CC dryer getting power but won't turn/start

I have a GE Spacemaker DPXH46EA2CC dryer that won't start. The dryer is getting power because when I move the start knob to the start position it sounds as though electricity is flowing to the appliance but the drum doesn't turn. The drum does rotate manually although it takes a good bit of force to make it turn. The belt appears to be in good shape.