Weight of the box = 50 Newtons
In the diagram attached,
The gravitational force is broken into two components.
The component of the gravitational force that acts along the inclined plane is 50 SinФ.
Ф = 30°
Sin 30° = 0.5
Gravitational force down the inclined plane = 50 Sin 30°
= 50 × 0.5
Gravitational force down the inclined plane = 25 Newtons or 25 N
Hence, the option A is correct.
