Answer
We can use Newton's third law and Newton's second law to solve this problem.
If the person throws a rock away from the shore, then the person needs to exert a force $F$ on the rock. According to Newton's third law, the rock exerts an equal and opposite force on the person. That is, the rock exerts a force $F$ on the person and this force $F$ points toward the shore.
According to Newton's second law: $F=ma$
Since the rock's force on the person is directed toward the shore, the person will start accelerating toward the shore.
Since there is no friction to stop the person, the person will continue moving toward the shore. If the person continues to throw more rocks away from the shore, the person's speed toward the shore will increase.
Work Step by Step
We can use Newton's third law and Newton's second law to solve this problem.
If the person throws a rock away from the shore, then the person needs to exert a force $F$ on the rock. According to Newton's third law, the rock exerts an equal and opposite force on the person. That is, the rock exerts a force $F$ on the person and this force $F$ points toward the shore.
According to Newton's second law: $F=ma$
Since the rock's force on the person is directed toward the shore, the person will start accelerating toward the shore.
Since there is no friction to stop the person, the person will continue moving toward the shore. If the person continues to throw more rocks away from the shore, the person's speed toward the shore will increase.
