1D Motion & Kinematics - Physics 101 / AP Physics 1 Review with Dianna Cowern

Hello
   Iam Ram from INDIA. Why should we take delta before the values
such as delta v, delta t , delta x 12:18
    why u changed delta y over delta x as delta x over delta t in the first place 06:00
does delta x means position
 pls sis say