Distance traveled by the particle in nth second is defined as the difference between the distance travelled by the particle in n second and the distance travelled by the particle in (n-1) second.
Mathematically,
Distance travelled in nth second= Distance/Time.
Dimensional Formula of Distance= M0L1T0.
Dimensional Formula of Time= M0L0T1.
Putting these values in above equation we get,
Dimensional Formula of Distance traveled in nth second = M0L1T0/M0L0T1 = M0L1T-1
SI unit of Distance traveled in nth second is ms-1.