Friction on Inclines

1. Define the term "coefficient of friction" and explain its role in determining the force of friction between two surfaces.

2. Explain why the normal force on an object on an inclined plane is not equal to the object's weight (mg), but rather to mg cos θ.

3. A box with a mass of 10 kg is resting on an inclined plane that makes an angle of 30° with the horizontal. If the coefficient of static friction between the box and the plane is 0.4, calculate the force of static friction acting on the box.