Its kinetic energy is maximum.
Explanation
The scenario is governed by the Law of Conservation of Mechanical Energy. For a freely falling body (neglecting air resistance), the total mechanical energy remains constant throughout the motion. This energy exists as a sum of Gravitational Potential Energy (PE) and Kinetic Energy (KE). As the body falls, potential energy is continuously transformed into kinetic energy.
Option-wise Analysis:
- Its potential energy is maximum. is Incorrect: Gravitational Potential Energy is defined by \( PE = mgh \), where \( h \) is the height relative to the ground. Just before impact, the height \( h \) is effectively zero. Therefore, the potential energy is at its minimum (zero), not maximum.
- Its kinetic energy is maximum. is Correct: Kinetic Energy is defined by \( KE = \frac{1}{2}mv^2 \). As the object falls, gravity accelerates it, causing its velocity to increase. Just before impact, the object has fallen the maximum distance, meaning all initial potential energy has been converted into kinetic energy. Thus, velocity and kinetic energy are at their maximum.
- Its mechanical energy is zero. is Incorrect: Mechanical Energy is the sum of PE and KE. According to the conservation law, this total value remains constant and non-zero (equal to the initial PE) throughout the fall.
- Its velocity is zero. is Incorrect: The velocity is zero only at the starting point (when \( t=0 \)). During the fall, velocity increases due to gravitational acceleration (\( g \)). Just before impact, the velocity is at its peak.
Key Takeaway:
During free fall, Potential Energy is maximum at the release point and minimum at the ground, whereas Kinetic Energy is minimum at the release point and maximum just before impact.