A book starts on a shelf 1 m off of the ground. You then move the book to a higher shelf that is 3 m off of the ground. If the system gained 20 J of gravitational potential energy, what is the mass of the book?

The field lines around one end of a bar magnet are shown below based on the diagram, what can you conclude about the pole of the magnet? a. is a south pole because the field hnes spread out from this end b. a north pole because the field lines spread out from this end c. a nouth pole because the field lines enter the magnet at this end d. is a north pole because the field lines enter the magnet at this end