1. The problem statement, all variables and given/known data A wooden block of mass M resting on a rough horizontal floor is pulled with a force F at an angle θ with the horizontal. If μ is the coeeficient of kinetic friction between the block and the surface, then acceleration of the block is? 2. Relevant equations 3. The attempt at a solution The horizontal component of the force - the friction force = ma. And the formula for kinetic friction is f=μkN. The normal reaction will be Mg. But I suppose the vertical component of force must also fit in somehow. Should I add it or subtract it to Mg? my initial hunch was to add it but the answer says it's been subtracted. Can someone explain why?