1. The problem statement, all variables and given/known data I'm trying to develop an expression for the maximum accerlation of a person pushing an object up a slope. I've figured out an expression for acceleration using F = MA based on the forces acting on the person and the object. Now I need to find the max accerlation. We were given a very similiar example and solution (same situation, expect the person and the object are on a flat surface). This is an assignment, so I dont want to ask for help on the actual question (pretty sure the uni calls that cheating :P), just the similar example, and hopefully someone will be able to explain what is going on. 2. Relevant equations A = F1 - U2kMG / (M1 + M2) subscripts are in lower case letters. F1 is the frictional force of the person walking Uxk is mu the coffiecent of kientic friction for object x. MG is the mass * Gravity M1 and M2 is the mass of the person and the object. The solution is then goes: The acceleration will be a maximum when f1 has reached it maximum at limiting friction as specified above, when a = ( U1M -U2M / (M1 + M2) )g 3. The attempt at a solution I'm only asking for an explaination for a example question and answer.