Finding the Minimum Angle for Motion on an Inclined Plane

[physics_freak]

Homework Statement

A box with mass of 45 kg is placed on a flat board. It starts moving when the board is inclined at 27 degrees. If the mass is doubled, what is the minimum angle needed so that it starts moving?

Homework Equations

Frictional force = mgsin$$\theta$$

The Attempt at a Solution

 

[PhanthomJay]

Homework Statement

A box with mass of 45 kg is placed on a flat board. It starts moving when the board is inclined at 27 degrees. If the mass is doubled, what is the minimum angle needed so that it starts moving?

Homework Equations

Frictional force = mgsin$$\theta$$

The Attempt at a Solution

Your (or is it the book's?) solution is correct.