A Quick Note On Energy

I will often use the term energy when writing. This is not a mystical concept, but rather a bastardization of the term as it relates to physics. I will attempt an explanation, however you might find the Wikipedia articles on kinetic energywork, and momentum to be of more use.

TL;DR – The term energy will be used to refer to either kinetic energy or momentum as the context dictates. I will attempt to use the word force per its definition.

We begin with a mass, say in kilograms (kg). My mass is about 90 kg.

Next consider two positions in space. The distance between them is measured in meters (m).

This distance can be traversed over some amount of time, which for purposes here will be measured in seconds (s).

The distance that an object moves per unit time is its speed. This is measured in units of meters per second (m/s).

Next consider the speed of an object in a particular direction. This is called velocity, which is a vector quantity that also has units of meters per second (m/s). Note that a quantity being a vector simply means that it has a direction associated with it.

Now, in addition to moving, an object might speed up and slow down over time. That is, it has has acceleration or deceleration. This is also a vector and is expressed in units of meters per second squared (m/s²).

But movement requires that something be moved.

When we throw a punch our hand and arm accelerate away from our body while our body accelerates away from the ground below us. Accelerating a mass requires a force (kg m/s^2). Force is also a vector.

The force is applied over a distance, again in meters. The amount of force required to accelerate  a mass a particular distance is called work. It is measured in units of Joules, or in basic units, kilogram meter squared per second squared (kg m²/s²). This quantity is a scalar. It has no direction associated with it.

Now, kinetic energy is merely a measure of the work required to accelerate a mass over a given distance. It is also a scalar.

A related concept is momentum. This is a vector quantity with units of mass times velocity (kg m/s). Once a force has been applied and work has been done, a mass will be traveling at some velocity. This is momentum.

You throw a punch by accelerating your mass and you now have momentum. Next, you transfer that momentum with your fist into the object with which it makes contact. This creates a deceleration of your mass and perhaps an acceleration of theirs. Work is done. Energy is imparted.

When I write about energy, losing energy, having energy, focusing energy, imparting energy, etc. I am almost always referring to either momentum or kinetic energy, though more often it will be momentum. This lack of precision is not really that important as the precise technical concept should be clear from context.

I will attempt to use the term force correctly.


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