How can you make an observation?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

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.

Dao makes a table to identify the variables used in the equations for centripetal acceleration. what quantities belong in cells x and y?