Further Mechanics: Energy

Concepts of Energy

Energy is a fundamental concept in physics that can neither be created nor destroyed - only transferred or transformed. This is the principle of conservation of energy.
Physical systems can possess several types of energy such as kinetic energy, potential energy, thermal energy, etc.
The unit of energy in International System of Units (SI) is joules (J).

Kinetic Energy

Kinetic energy is the energy possesed by a body due to its motion.
The kinetic energy (KE) of an object of mass m moving with velocity v can be calculated using the formula: KE = 1/2 mv^2.
Changes in kinetic energy can be calculated by considering forces acting on the body and resulting work done by or against these forces.

Potential Energy

Potential energy is the energy possessed by a body due to its position or configuration.
The most commonly encountered types of potential energy include gravitational potential energy and elastic potential energy.
The gravitational potential energy (PE) of an object located at a height h from the ground, in the earth’s gravitational field of strength g, is given by PE = mgh.

Work and Energy Principle

Work done on an object is equal to the change in its energy. This principle provides the basis for work-energy theorem.
The definition of work in physics is quite specific - it’s the force applied on an object multiplied by the displacement of the object in the direction of the force: Work = Force x displacement.
Note that work is done when a force applied on an object causes a displacement. No work is done if there is no displacement, regardless of the force applied.

Principle of Conservation of Energy

The total energy (kinetic + potential) of an isolated system remains constant if the only forces doing work are conservative. This is the conservation of mechanical energy.
Energy can be transferred from one form to another (like kinetic energy to potential energy and vice versa), but the total amount of energy in the system does not change.
Energy transformations and transport play a crucial role in our understanding of how the universe works, from the microscopic interactions of atoms to the large-scale, astronomical phenomena.

Practical Applications of Energy Principles

The principles of energy are applied in many real-world systems such as vehicles, bridges, machines, and more.
Calculations involving kinetic energy, potential energy, and work are common in physics problems and often involve using the principles of energy conservation.
The concept of potential energy, in particular, can be used to calculate the energy stored in an object at height, in a spring, or in many other situations.