1. The problem statement, all variables and given/known data A tile on a roof becomes loose and slides from rest down the roof. The roof is modelled as a plane inclined at 30 degrees to the horizontal. The co-efficent of friction between the tile and the roof is 0.4. The tile is modelled as a particle of mass 'm'kg. a) Find the acceleration of the particle as it slides down the roof. 2. Relevant equations Fr(Friction Force)=uR Reaction force from the plane = mgcos(angle) Fr= 0.4mgcos(angle) The force of the particle sliding down the plane x = mgsin(angle) Total force going down the plane is x - Fr=ma 3. The attempt at a solution R = mgcos(30) F = uR Fr= 0.4mgcos(30). Total force down the plane as it is sldiing down is: mgsin(30) - 0.4mgcos(30) = ma I can't solve this, as there are TWO unknowns, then theres the fact I can't find m. I've tried looking thorugh text books but no avail. This is my first post here =) I am attempting to complete as many practice examination questions throughout March and started early instead. I believe once I answer a), the rest will be easy as well (a needs to be answered for b and c). Thanks to all!