Consider a body moving in the x-y plane with a constant acceleration a
. It is located at point P at time t = 0, which has a position coordinate r0
and velocity v0
. It reaches point P’ at time t, has a position coordinate r
and velocity v
. Constant acceleration a
is equal to change in velocity by time. Average velocity = displacement/time.
These equations imply that a body can have two independent simultaneous motions in x and y directions with constant acceleration. Similar equations can be written for three-dimensional motion also.
: Consider two bodies A and B moving in the x-y plane with velocities VA
, respectively, with respect to the co-ordinate system. The velocity of A with respect to B is written as VAB
When subtracting two vectors, to obtain the relative velocity vector, reverse the second vector and add the two vectors.