Which of the following are true statements about friction? check all that apply. a. the amount of friction depends on the type of surface and the force of contact. b. friction is a force that acts between two surfaces that are in contact. c. frictional forces cannot cause acceleration of an object. d. the direction of the frictional force varies such that it always opposes motion.

The space within which a test north pole experiences a force magnetic poles 2. a powerful stream of electrons flowing high above the earth in the ionosphere electrojet 3. a concept to explain the directional nature of a magnetic field field lines 4. coil of wire designed to produce a magnetic field by a current passing through its windings ionosphere 5. that region above the earth's atmosphere where particles exist in an ionized state magnetic field 6. the extremities of a magnet where the field lines tend to converge or concentrate aurora borealis 7. a phenomenon that occurs in the northern latitudes; the northern lights solenoid