Energy

Energy  is something that is found all over the physical and life sciences. Thermal Energy is what you experience when you burn your hand on the stove (again). Chemical Energy is what causes that (safely contained) explosion in chemistry class. In this section, we will focus solely on mechanical energy , or energy due to the movement (or potential movement) of an object. 
 Types of Mechanical Energy 
 Kinetic 
 Kinetic energy is the amount of energy an object has due to its movement ( velocity ).  
 Example 
 Mr. Box, who has a mass of 10 kilograms (kg) , is sliding on a patch of ice at 2 meters per second (m/s) of velocity.  How much kinetic energy would he have? 
 
 Mr. Box would have 20 Joules of Kinetic Energy . 
 Potential 
 Potential energy is the energy of an object or system due to its position relative to other objects. 
 Gravitational 
 Gravitational potential energy is calculated using an object's position within a gravitational field. Typically, this is considered to be the height ( h ) above the surface of the earth, which provides a constant gravitational acceleration ( g ) of around 9.8 meters per second squared. 
 Example 
 Mr. Box, who has a mass of 10 kg , is lifted 5 meters into the air above the surface of the Earth, which provides a gravitational acceleration of 9.8 meters per second squared . How much gravitational potential energy would Mr. Box have? 
 
 Mr. Box would have 490 Joules of gravitational potential energy . 
 Elastic Potential 
 Although similar to gravitational potential energy, elastic potential energy instead deals with the energy provided by a spring (or elastic) rather than gravity. A spring's constant ( k ), also known as "stiffness", is determined by its shape and material . 
 
 Example 
 Mr. Box ( mass of 10 kg ) is pressed against a spring with a spring constant of 1 N/m for 10 centimeters (or 0.1 meters ). How much elastic potential energy does Mr. Box now have? 
 
 Mr. Box would have an elastic potential energy of 0.005 Joules . 
 Conservation of Energy 
 The conservation of energy is a fundamental principle of physics, which states: 
 
 The total energy of an isolated system is constant despite internal changes. 
 
 What this means within the context of our work in mechanical engineering is that the type of energy a system experiences may change, but the total amount of energy in that system will not. 
 For example: 
 In a previous question, we lifted Mr. Box (mass of 10 kg ) to a height of 5 meters, which gave him a gravitational potential energy of 490 Joules . Dropping him from that height would begin to convert the potential energy into kinetic energy . When Mr. Box gets back to the ground (height of  0 meters ) his potential energy will have been entirely converted to kinetic energy. 
 
 How much velocity is he moving with when he hits the ground ( GPE = 0 J, KE = 490 J )?