NPCIL Trainee Motion in One Dimension — practice questions

1. The stem asks for the name of the branch of physics that studies motion only, without asking why the motion happens. 2. OpenStax Physics opens this topic by stating: "kinematics—the study of motion without considering its causes." 3. Dynamics, by contrast, studies motion together with the forces that cause it -- the opposite of what the question describes. 4. So the correct term is kinematics. _Source: OpenStax Physics Ch 2 "Motion in One Dimension", p.56 §2.1 Relative Motion, Distance, and Displacement_

1. To describe motion, you must state position relative to something else that is fixed or moving with known speed and direction. 2. The text gives exactly this case: "a rocket launch would be described in terms of the position of the rocket with respect to Earth as a whole." 3. That background object (Earth) against which position is measured is the reference frame. 4. So Earth here is functioning as the reference frame, not merely an origin point or a vector quantity. _Source: OpenStax Physics Ch 2 "Motion in One Dimension", p.56 §2.1 Relative Motion, Distance, and Displacement_

1. Take west as negative and east as positive (or vice versa) along a single axis. 2. Displacement is the vector sum: -3 km (west) + 2 km (east) = -1 km, i.e. 1 km west of the start. 3. The worked example confirms: "The magnitude of the displacement is 1 km." 4. 5 km is a trap -- that is the total distance ridden (3 km + 2 km), not the net displacement. 5. So the magnitude of displacement is 1 km, not the 5 km total distance covered. _Source: OpenStax Physics Ch 2 "Motion in One Dimension", p.62 Worked Example §2.1 Relative Motion, Distance, and Displacement_