If for every action force an equal and opposite reaction force exists, how can anything ever be accelerated? a.)the action and reaction forces act on different objects, therefore the net force is not always zero. b.)the action force, when accelerating, is greater than the reaction force. c.)the reaction force is not always in the same vector direction as the action force. d.)none of the above

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

Find the magnetic field a distance r from the center of a long wire that has radius a and carries a uniform current per unit area j in the positive z direction.

What are the north and south poles of a solenoid change with?