Levi and clara are trying to move a very heavy box. levi is pushing the box with a force of 30 n, and clara is pulling the box with a force of 50 n. the box exerts a frictional force of 65 n. which best explains the forces? there is a net force of 15 n against them and they cannot move the box. there is a net force of 15 n allowing levi and clara to move the box. there is a net force of 65 n against them and they cannot move the box. there is a net force of 80 n allowing levi and clara to move the box.

A = force by which levi push the box = 30 N

B = force by which clara pulls the box = 50 N

f = frictional force acting on the box = 65 N

the pushing and pulling forces acts in same direction and the frictional force acts in opposite direction. hence the net force is given as

Net force = Sum of pushing and pulling force - frictional force

Net force = 30 + 50 - 65

Net force = 15 N

hence the correct choice is

There is a net force of 15 N allowing Levi and Clara to move the box.

i believe the answer would be:

d. violin, clarinet, french horn, and tuba

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