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## Homework Statement

A tile on a roof becomes loose and slides from rest down the roof. The roof is modeled 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 modeled as a particle of mass 'm'kg.

a) Find the acceleration of the particle as it slides down the roof.

## Homework 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

## 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 there's the fact I can't find m. I've tried looking thorugh textbooks 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!