Aperson throws a rock at 3 m/s down over the edge of a very tall cliff on earth how far will the rock at fall in 4 seconds if the rock never hit the bottom?

The rock will fall 90.4m downwards

Explanation:

Here, the acceleration is constant and it is equal to acceleration due to gravity. Therefore the question depicts a situation of uniformly accelerated motion in a straight line. So, let us refresh the three equations of uniformly accelerated straight line motion.

v = u + at

where,

u = initial velocity

v = final velocity

s = displacement

a = acceleration

t = time

Since we are dealing with vectors (velocity, acceleration and displacement), we have to take their directions in to account. So we must adopt a coordinate system according to our convenience. Here, we are taking point of throwing as origin, vertically upward direction as positive y axis and vertically downward direction as negative y axis.

Thus,

u = -3m/s (since it is along negative y axis)

a = g = -9.8m/ (since it is along negative y axis)

t = 4s

s = ?

The only equation that connects all these quantities is

Substituting the values in the equation gives,

s = -12 - 78.4

s = -90.4m

Thus the rock will fall 90.4m downwards. The negative sign indicates that the displacement is along negative y axis which is downwards.

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