Answer:
1. Action-reaction force. 2. It is not a rigid body
Step-by-step explanation:
1. The force involved during the impact is an action-reaction force pair. The plasticine ball exerts a force on the metal block, while the metal block exerts an equal but opposite force on the plasticine ball.
2. The plasticine ball changes its shape after the impact because, it is not a rigid body. A rigid body is a body that does not change its shape when external forces are applied to it.