explan simply

15. An object starts from rest and slides with negligible friction down an air track tipped at an angle 6 from the horizontal. A student records values of the object's position along the track at various times. The value of 8 can best be determined from which of the following? (A) The y-intercept of a graph of position as a function of time (B) The y-intercept of a graph of position as a function of the square of time (C) The slope ofa graph of position as a function of time The slope of a graph of position as a function of the square of ime