1) A 2.5 kg ball strikes a wall with a velocity of 8.5 m/s to the left. The ball bounces off with a velocity of 7.5 m/s to the right. If the ball is in contact with the wall for 0.25 s, what is the
constant force exerted on the ball by the wall?

Force = -10 Newton.

Explanation:

Given the following data;

Initial velocity = 8.5m/s

Final velocity = 7.5m/s

Time = 0.25 seconds

Mass = 2.5kg

To find the force exerted;

First of all, we would determine the acceleration of the ball;

Acceleration = (v - u)/t

Acceleration =(7.5 - 8.5)/0.25

Acceleration = -1/0.25

Acceleration = -4 m/s²

Now, to find the force exerted;

Force = mass * acceleration

Force = 2.5 * -4

Force = -10 Newton

Note: The force is negative because it is an opposite reaction.

true tan speed = ang vel x radius

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