Collision between two rigidbody 2d that causes movement not requested

Hi everybody, I've got a question for you. I'm making a simple 2D endless runner game with a player that has to avoid oblacles that causes player's death if there is a collision between player and an obstacle. The death works perfectly but when the player hits a flying obstacle this obstacle flys away or rotate on itself, depending on the direction of the player at the moment of the collision (for example if the player hits the obstacle from the bottom it start to rotate or if the player hits it from the left the obstacle goes to its right). Both the player and the obstacles are rigidbody 2d. DO you know why I've got this problem and what can I do to fix it? Thanks in advance