Suppose, a ball of mass M is thrown upwards from a point A and it reaches up to the highest point B and returns back to point A, which one among the following is correct ?

According to the principle of conservation of mechanical energy, the total energy of a closed system remains constant [1]. When a ball of mass M is thrown upwards from point A, it possesses maximum kinetic energy (KE) and minimum potential energy (PE) at the launch point. As the ball rises toward point B, its speed decreases, causing its kinetic energy to convert into gravitational potential energy [1]. At the highest point B, the ball stops momentarily, meaning its kinetic energy becomes zero and all its initial energy is now stored as potential energy. Therefore, the kinetic energy at the starting point A is equal to the potential energy at the maximum height B, assuming no energy is lost to air resistance. This exchange illustrates that while individual energy types change, the sum of KE and PE remains constant throughout the trajectory [1].

Sources

1. [1] https://satheeneet.iitk.ac.in/article/physics/physics-conservation-of-mechanical-energy/