A ball is dropped from rest from the top of a building of height h. At the same instant, a second ball is projected vertically upward from ground level, such that it has zero speed when it reaches the top of the building. a. When do the two balls pass each other?
b. Which ball has greater speed when they are passing?
c. What is the height of the two balls when they are passing?

Find the answer in the explanation

Explanation:

Given that a ball is dropped from rest from the top of a building of height h. At the same instant, a second ball is projected vertically upward from ground level, such that it has zero speed when it reaches the top of the building.

a. When do the two balls pass each other?

The the balls will pass each other before the second ball reach half of the height of the building. Because the velocity of the second ball decreases as it goes upwards while the velocity of the first ball increases as it moves downwards

b. Which ball has greater speed when they are passing?

The first ball of course because the velocity of the second ball decreases as it goes upwards while the velocity of the first ball increases as it moves downwards

c. What is the height of the two balls when they are passing?

Taking the height from the bottom of the building upward

Since the two balls meet at a certain point, they will both have the same height.

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