Find the minimum force required to keep a block of mass `m` in equilibrium on a rough inclined plane with inclination `alpha` and coefficient of friction `mu( lt tan alpha)`.

Explanation

To find the minimum force required to keep a block of mass \( m \) in equilibrium on a rough inclined plane with inclination \( \alpha \) and coefficient of friction \( \mu \) (where \( \mu < \tan \alpha \)), we can follow these steps:

### Step 1: Identify the forces acting on the block
The forces acting on the block are:
- The gravitational force \( mg \) acting vertically downward.
- The normal force \( N \) acting perpendicular to the inclined plane.
- The frictional force \( f \) acting parallel to the inclined plane, opposing the motion.

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