I heard that the minimum frame size of an Ethernet packet is determined by how long it takes for a collision to occur. It has to be large enough so that if a collision occurs it will be detected before the transmission is completed.
However, consider this case: What if the transmission of a packet is almost completed. The sender is about to send the last byte when a collision all the way at the other end occurs. Will the collision be detected or not? Making the Ethernet packet long doesn't seem to make any difference.