Cylinder on an incline

1. Aug 11, 2007

muppet

The first part to an exam question I had to sit at the end of last year. It defeated me then, and I still can't do it now, which worries me more than a little!
1. The problem statement, all variables and given/known data
A solid cylinder of radius 10 cm and mass 12 kg starts from rest and rolls
without slipping a distance L = 6:0 m down a roof that is inclined at an
angle $$\theta$$ = 30$$\circ$$
Show that the acceleration of the cylinder is given by
a= $$\frac{2gsin\theta}{3}$$

2. Relevant equations
The acceleration of a block down a frictionless incline is just gsin $$\theta$$
The moment of inertia of a solid cylinder of mass m and radius r
is given by I = $$\frac{1}{2}$$mr$$^{2}$$

3. The attempt at a solution
As 2, but I really don't know where the factor of two thirds comes from. The question was worth 6 marks.

2. Aug 11, 2007