Explain how to identify a starting position on a line.

A position vector expresses the position of an object from the origin of a coordinate system.

Explanation:

Position vector is basically a straight line which has one of its ends end fixed to a body and whereas, the other end is attached to a moving point which tells the position of that specific point relative to the body. As the point accelerates, the position vector will vary its length and the direction accordingly.

Pick a reference point on the line to be the zero position. Determine the direction and measure the distance from zero in standard units.

a longitudinal wave moves energy that is to the direction of the wave’s movement. - true