Final answer:
The statement concerning 'let go' current before sustained contraction is false. Muscle contraction involves the release of calcium ions and power strokes are initiated by the dissociation of ADP and phosphate from the myosin head.
Step-by-step explanation:
The statement "'Let go' current occurs before sustained contraction" is false. When discussing muscle contraction, particularly in the context of motor neurons and muscle fibers, there is no 'let go' current. The process involves an action potential that triggers the release of calcium ions (Ca²+) in the muscle, leading to cross-bridge formation by the myosin heads on the thick filaments, and subsequent muscle contraction. The power stroke actually occurs when ADP and phosphate dissociate from the myosin head, after myosin has bound to actin, not during the hydrolysis of ATP.
To address some other misconceptions: a pebble dropped in water creates ripples or waves, not a pulse wave, which is a single disturbance moving through a medium, hence that statement is false. A photoconductive cell does indeed generate a current when a photon strike expels an electron, so that statement is true. The position vs. time graph for an accelerating object is not a straight line but rather a curve, making that statement false. Finally, dropping a bar magnet through a copper tube does induce an electric current due to electromagnetic induction; thus, the statement is true.