Luc, who is 1.80 m tall and weighs 950 n, is standing at the

center of a playground merry-go-round with his arms extended,

holding a 4.0 kg dumbbell in each hand. the merry-go-round can

be modeled as a 4.0-m-diameter disk with a weight of 1500 n.

luc’s body can be modeled as a uniform 40-cm-diameter

cylinder with massless arms extending to hands that are 85 cm

from his center. the merry-go-round is coasting at a steady

35 rpm when luc brings his hands in to his chest. afterward,

what is the angular velocity, in rpm, of the merry-go-round?

the device is called “ rocket engine”

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

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