Motion in 1 dimension In 1-D, we usually write position as X Since it's in 1-D. all we need to indicate direction is or Displacement in a time△t=t+-tis△X=x-X; X some particle's trajectory △X in 1-D △t Physics 121: Lecture 4, Pg 11Physics 121: Lecture 4, Pg 11 Motion in 1 dimension In 1-D, we usually write position as x . Since it’s in 1-D, all we need to indicate direction is + or −. Displacement in a time t = tf - t i is x = xf - xi t x t i t f  x  t xi xf some particle’s trajectory in 1-D