Final answer:
The initial kinetic energy of a projectile is equal to the gravitational potential energy at its maximum height.
Step-by-step explanation:
According to the conservation of energy principle, the initial kinetic energy of a projectile is equal to the gravitational potential energy at its maximum height. This means that the energy used for the projectile's motion is converted into potential energy at the highest point of its trajectory. Hence, Conservation of energy is used to find the maximum height reached by a projectile. It states that the initial kinetic energy is equal to gravitational potentialenergy at the maximum height.