The height of a helicopter above the ground is given by h = 2.80t3, where h is in meters and t is in seconds. At t = 2.45 s, the helicopter releases a small mailbag. How long after its release does the mailbag reach the ground?

Which of the following is part of the explanation or description of electromagnetic waves? (select all that apply) a. electrically charged molecules in a medium transfer their energy to nearby electrically charged molecules. b. a changing electric field causes a changing magnetic field. c. magnetic molecules in a medium transfer their energy to nearby magnetic molecules. d. a changing magnetic field causes a changing electric field.