Answer:
Newton's Third Law
Step-by-step explanation:
Newton's Third Law is: If object A exerts a force on object B, then object B must exert a force of equal magnitude and opposite direction back on object A.
In this case, Object A is the Phone, and Object B is the ground. When the phone(Object A) hits the ground(Object B), the ground pushes up on the phone making the time increase and makes the reaction force less. Hope this helps!