You throw a stone vertically upward with a speed of 26.0 m/s. (a) How fast is it moving when it reaches a height of 15.0 m? (b) How much time is required to reach this height when it's falling down? a. 19.5 m/s , b. 4.51 s a. 17.9 m/s , b. 0.620 s a. 19.5 m/s , b. 0.800 s a. 17.9 m/s , b. 4.28 s a. 380 m/s , b. 8 s

v = 19.5 m/s

t = 4.51 s

Explanation:

a)

given:

height is 15m from the ground

initial velocity Vi = 26 m/s

acceleration a or g = 9.81 m/s²

formula: Vf² = Vi² + 2aΔy

26² = Vi² + 2 (9.81) 15

Vi = 19.5 m/s

now you can calculate the time by using the equations below:

Δy = 1/2 (Vi + Vf) t

Vf = Vi + a t

Δy = Vi t + 1/2 a t

time must be 4.51 s

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