Direction of Friction Problem .. HELP!!!! 1. The problem statement, all variables and given/known data i am a student studying very basic rotational motion . i recently came across these problem while i was reading my book . 1. in 1 question , when a body was rolling (with external force) on a rough horizontal surface , the force of friction was in the same direction as the applied force . 2. a body was rolling down an inclined plane (with no external force) with angle of inclination [tex]\theta[/tex] the the force of friction was opposite to the direction of motion . Please explain slowly and step by step as this is very important . 2. Relevant equations none 3. The attempt at a solution all i noe is that when a body rotates the friction force is supposed to be opposite and should somehow increase the angular acceleration . but if in a case when it is in the same direction as the motion it should decrease the angular acceleration . please feel free to point out if i m wrong .