Two identical balls from rest fall vertically down onto the sports ground. Name the frame of reference

Two identical balls from rest fall vertically down onto the sports ground. Name the frame of reference relative to which one of the balls is at rest.

One ball relative to the other.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.