What do you know about velocity, acceleration and reference frame?

The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of an object's speed and direction of motion (e.g. 60 km/h to the north).

Acceleration, rate at which velocity changes with time, in terms of both speed and direction. A point or an object moving in a straight line is accelerated if it speeds up or slows down. ... Acceleration is defined as the change in the velocity vector in a time interval, divided by the time interval.

In physics and astronomy, a frame of reference consists of an abstract coordinate system whose origin, orientation, and scale are specified by a set of reference points ― geometric points whose position is identified both mathematically and physically.

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.

nah.   i'm just sleepy.