A 2.0-kilogram laboratory cart moving with a velocity of 0.250 meter per second due east collides with and sticks to a similar cart initially at rest. After the collision, the two carts move off together with a velocity of 0.125 meter per second due east. The total momentum of this frictionless system is (1) zero before the collision (2) zero after the collision (3) the same before and after the collision (4) greater before the collision than after the collision

   (3) the same before and after the collision

Explanation:

The sum of products of mass and velocity before the collision is ...

  (2 kg)(0.250 m/s) + (2 kg)(0 m/s) = 0.50 kg·m/s

The sum of products of mass and velocity after the collision is ...

  (2 kg +2 kg)(0.125 m/s) = 0.50 kg·m/s

The total momentum is unchanged.

f=ma newton

f=100x2.5=250n

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