A disc of mass `m=50g` slides with the zero initial velocity down an inclined plane set at an angle `alpha=30^@` to the horizontal, having traversed the distance `l=50cm` along the horizontal plane, the disc stops. Find the work performed by the friction forces over the whole distance, assuming the friction coefficient `k=0.15` for both inclined and horizontal planes.

Explanation

To solve the problem step by step, we will calculate the work done by friction as the disc slides down the inclined plane and then along the horizontal plane until it stops.

### Step 1: Convert mass to kilograms
The mass of the disc is given as \( m = 50 \, \text{g} \). We need to convert this to kilograms:
\[ m = 50 \, \text{g} = 50 \times 10^{-3} \, \text{kg} = 0.05 \, \text{kg} \]

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