- Planets, cars, people and atoms all have kinetic energy due to their motion.
- When a force is applied to an object, its kinetic energy can change.
- Kinetic energy is the energy of motion, while potential energy is the energy of position or state.
- Most interactions between objects involve forces and can transfer energy.
Energy
- Energy is the capacity to do work. It can exist in different forms such as kinetic, potential, thermal, and electromagnetic.
- Energy cannot be created or destroyed; it can only be converted from one form to another.
- Objects at absolute zero do not have any thermal energy to transfer, but they can still interact and exchange other forms of energy.
Force
- Force is a term used to describe the interaction between objects that causes a change in motion or shape.
- Galaxies, human beings and electrons can all apply forces to the things around them.
- Work is defined as the product of the force applied on an object and the distance it moves in the direction of the force.
At an atomic scale
- Electrical energy passes through a circuit as electrons flow, transferring their kinetic energy to other electrons in the circuit.
- Heat is produced as photons strike an object, transferring their energy to electrons within the atoms or molecules of its surface.
At a human scale
- The human senses of sight, hearing, and touch are tuned to respond to different forms of energy when a force interacts with our bodies.
- When a person hears a sound or sees something, that is evidence of energy having been transferred to their senses.
- So when a person sees something, it is evidence of energy having been transferred to their senses through forces like light waves.
- The fact that light waves exist and travel through space is evidence of the electromagnetic force without which electromagnetic waves wouldn’t be possible.
- The amount of energy carried by the light wave is directly related to the perceived brightness of an object.
- This means that the intensity (or amount of energy) carried by these light waves determines how bright the object appears to us.
- The stronger the electromagnetic force acting on the source of the light (like a star or a light bulb), the more energy the light waves carry and the brighter the object appears.
Here is another example
- A person pushes a heavy boulder up a hill.
- Each time they push they apply force to make the boulder move.
- They feel exhausted by the time they reach the top because of the work involved in overcoming the force of gravity and friction.
- But the energy is not lost, instead, it is transferred to the boulder as kinetic energy.
- As soon as the boulder is released and starts to roll back down the hills, the kinetic energy it has gained is transferred to other boulders it crashes into.
- If the boulder is too heavy to move, no work is done on the boulder. However, the person’s muscles still expend energy, which is released into the environment as heat.