20. The Earth's core is made from iron and nickel and is divided into parts.
21. The Earth's inner core is made of
and outer core is made of.
22. The magnetic north pole in reality is the Earth'smagnetic pole.
23. The magnetic south pole in reality is the Earth'smagnetic pole.​

Which subatomic particle has a negative charge

Assume that a person skiing high in the mountains at an altitude of h = 15100 ft takes in the same volume of air with each breath as she does while walking at sea level. determine the ratio of the mass of oxygen inhaled for each breath at this high altitude compared to that at sea level. assume that the air composition (i.e. % of air that is oxygen) is the same at sea level as it is at 15100 ft.

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?