Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. in one test, this gun accelerates a 5.0-kg projectile from rest to a speed of 4.0 × 103 m/s. the net force accelerating the projectile is 4.9 × 105 n. how much time is required for the projectile to come up to speed?

The time taken by the projectile to reach the required speed is 41 ms.

Calculate the acceleration  a of the projectile of mass m, using Newton's second law.

Substitute 5 kg for m and 4.9×10⁵N for F, the force needed for acceleration.

Use the equation of motion to determine the time taken by the projectile to reach a speed v from rest under the acceleration calculated.

Substitute 4.0×10³m/s for v, 0 for u and 9.8×10⁴m/s² for a.

The time taken to reach the required speed is 41 ms.

so easy. just google the electromagnetic waves and it’ll pop up.

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