A 64-kg woman stands on frictionless level ice with a 0.10-kg stone at her feet.She kicks the stone with her foot so that she acquires a velocity of 0.0017 m/s in the forward direction.The velocity acquired by the stone is:
A)1.1 m/s forward
B)1.1 m/s backward
C)0.0017 m/s forward
D)0.0017 m/s backward
E)none of these

Question

Quizplus · Accepted Answer

The law of conservation of momentum states that the total momentum of a closed system is constant if no external forces are acting on it. When the woman kicks the stone, she exerts a force on it, and the stone exerts an equal and opposite force on her, according to Newton's third law. Since the system (woman + stone) is initially at rest, its total momentum is zero. After the kick, the total momentum must still be zero. If the woman moves forward with a small velocity, the stone must move backward with a velocity that keeps the total momentum of the system at zero. The correct answer is the stone moving backward, but the specific velocity isn't provided in the choices based on the information given, so the correct choice is B, indicating the direction of the stone's velocity.

A 64-Kg Woman Stands on Frictionless Level Ice with a 0.10-Kg