A target lies flat on the ground 4 m from the side of a building that is 10 m tall, as shown below. The acceleration of gravity is 10 m/s^2.
Air resistance is negligible.
A student rolls a 4 kg ball off the horizontal
the roof of the building in the direction of the
target.
The horizontal speed v with which the ball
must leave the roof if it is to strike the target
is most nearly

1. v =√3 /4 m/s.
2. v =4√3 /3 m/s.
3. v = 4 m/s.
4. v = 2√2 m/s.
5. v =√2 / 4 m/s.
6. v =√5 / 4 m/s.
7. v = 4√3 m/s.
8. v = 4√5 m/s.
9. v = 6 m/s.
10. v = 4√2 m/s.

v = 2√2 m/s

Explanation:

The following data were obtained from the question:

Height (h) = 10 m

Acceleration due to gravity (g) = 10 m/s²

Horizontal distance (s) = 4 m

Horizontal velocity (v) =.?

Next, we shall determine the time taken for the ball to get to the target.

This can be obtained as shown below:

Height (h) = 10 m

Acceleration due to gravity (g) = 10 m/s²

Time (t) =?

h = ½gt²

10 = ½ × 10 × t²

10 = 5 × t²

Divide both side by 5

t² = 10/5

t² = 2

Take the square root of both side.

t = √2 s

Finally, we shall determine the horizontal velocity as shown below:

Horizontal distance (s) = 4 m

Time (t) = √2 s

Horizontal velocity (v) =.?

s = vt

4 = v × √2

Divide both side by √2

v = 4 /√2

Rationalise the denominator

v = (4 /√2) × √2/√2

v = 4 × √2 / √2 × √2

v = 4 × √2 / 2

v = 2√2 m/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