The entrance to a private car park is protected by a boom, which closes the entrance as shown in the figure below. The boom can be made to balance by fixing a counterweight W a short distance (0.5 m) from the pivot on the main support.
a) If the weight of the boom alone, F, is 400 N, and acts 3.0 m from the pivot as shown, calculate the counterweight required for the boom to be balanced.
b) If the actual counterweight fitted to this boom was 2350 N:
i) what additional downward force must be applied by the car park attendant to lift the boom
ii) what will be the normal reaction, N, at the end support when the boom is resting on it?
c) Calculate the reaction force at the pivot when the counterweight is 2350 N and the other end of the boom is supported.
d) If the boom is replaced with a strong one of weight 470 N and the 2350 N counterweight is to be used again, where should the counterweight be fixed to exactly balance the boom.

mass and volume are the answers you are looking for

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

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2