Describe the conservation of energy in a projectile.

The conservation of energy in a projectile refers to the constant total energy of the projectile throughout its motion.

In the context of physics, the conservation of energy is a fundamental concept that states that the total energy of an isolated system remains constant, regardless of the changes that may occur within the system. This principle applies to the motion of a projectile, which is an object thrown into the air or space, subject only to the forces of gravity and air resistance.

When a projectile is launched, it possesses kinetic energy due to its motion and potential energy due to its height from the ground. The kinetic energy is highest at the point of launch when the speed is greatest, and it decreases as the projectile rises and slows down under the force of gravity. Conversely, the potential energy is zero at the launch point and increases as the projectile gains height. At the highest point of the trajectory, the projectile momentarily comes to rest, so the kinetic energy is zero, and the potential energy is at its maximum.

As the projectile descends, the process is reversed. The potential energy decreases as the height decreases, and the kinetic energy increases as the speed increases. The sum of the kinetic and potential energy at any point during the flight is equal to the total energy of the projectile. This total energy remains constant throughout the motion, demonstrating the conservation of energy.

However, this idealised model assumes no air resistance or any other forces except gravity. In reality, air resistance can do work on the projectile, converting some of its mechanical energy into thermal energy, which is then dissipated into the surrounding air. This can cause the total mechanical energy of the projectile to decrease over time. But if we consider the thermal energy as part of the system, the total energy, including mechanical and thermal energy, is still conserved.

In conclusion, the conservation of energy in a projectile's motion is a demonstration of the broader principle of energy conservation, which states that the total energy of a system remains constant if no net work is done by external forces.