You are conducting an experiment inside a train car that may move along level rail tracks. a load is hung from the ceiling on a string. the load is not swinging, and the string is observed to make a constant angle of 45 degrees with the horizontal. no forces other than tension and gravity are acting on the load. which of the following statements are correct? choose all that apply. a) the train is an inertial frame of reference b) the train is not an inertial frame of reference c) the train may be instantaneously at rest d) the train may be moving at a constant speed in a straight line e) the train may be moving at a constant speed in a circle f) the train must be speeding up g) the train must be slowing down h) the train must be accelerating