A wood block is placed on a rough surface. The surface starts horizontal, and one end is then raised so that the angle the surface makes with the horizontal gradually increases until, at an angle θ , the block begins to move down the surface, as shown in the figure. From this observation, which of the following can be concluded for angles greater than θ ? A) there is no frictional force on the block.

B) The gravitational force is equal to the frictional force.

C)The component of the gravitational force along the surface is greater than the frictional force.

D)The normal force is equal to the gravitational force.

E )The component of the normal force along the surface is greater than the gravitational force.

The correct option is;

C) The component of the gravitational force along the surface is greater than the friction force.

Explanation:

The force of static friction acts along the plane in opposite direction to the component of the force of the weight acting down (along) the plane.

The magnitude of the frictional force, is given by the following formula;

= μ·N = (m·g·cos(θ))·μ

The magnitude of the weight acting along the incline plane = m·g·sin(θ)

As θ increases, sin(θ) increases, and cos(θ) decreases, such that magnitude of the weight acting downwards, along the inclined plane becomes larger than the frictional force acting upwards along the incline plane.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia