13- Explain Potential energy, and write down the formula? What do the letters stand for? 14- Explain the Law of conservation of energy and give an example.

**13. Potential Energy** Potential energy is the energy stored in an object due to its position, configuration, or state. One common example is gravitational potential energy, which is the energy an object possesses because of its height above a reference level. The formula for gravitational potential energy is given by: \[ U = mgh \] where: - \( m \) is the mass of the object, - \( g \) is the acceleration due to gravity (approximately \( 9.8 \, \text{m/s}^2 \) on Earth), - \( h \) is the height of the object relative to the reference level. --- **14. Law of Conservation of Energy** The Law of Conservation of Energy states that energy cannot be created or destroyed in an isolated system; it can only change forms. This means that the total energy in a system remains constant over time, even though energy may be transformed from one type to another. *Example:* Consider a pendulum. At its highest point, the pendulum has maximum gravitational potential energy \( (U = mgh) \) and minimal kinetic energy. As it swings downward, this potential energy is converted into kinetic energy. At the lowest point of the swing, the kinetic energy is at its maximum while the potential energy is at its minimum. Despite these changes in energy form, the total energy of the pendulum system remains constant (ignoring air resistance and friction).