What is the force between two small charged spheres that have charges 2x10(power -7)c and 3x10(power -7)c and are placed 30 cm apart in air?

An object has a weight of 500 on earth what is the mass of this object

What properties of a moving object are used in determining the object's energy of motion

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.