The Technicalities of Technical Terms

EDIT:  NEW WORDS ADDED FOR THIS WEEK MARKED WITH "*".

In this post, I'm going to go over some technical terms that I find are commonly misunderstood or misused.  I decided to write this post because of a teacher in one of my classes.  Now, it's not really because of the teacher that I'm writing this, but more because he made me realize that the media commonly uses words incorrectly and then this carries on to the people who learn the terms that way.

The class I'm talking about is History of Science.  The class is done from a literary and historical perspective and not a technical one.  And, therefore, is taught by someone educated in literature.  And he does a great job in that respect.  However, he sometimes gets his science-y things wrong.  And I know this isn't because he's stupid, it just comes from hearing the terms used incorrectly all the time.

I started to do some research online for some websites that list some incorrectly used terms, but none were really all inclusive.  Here's a list of some of the sites I came across:  A Glossary of Frequently Misused or Misunderstood Physics Terms and Concepts, Misused Technical Terms, and Wikipedia.  I will be pulling the nontechnical definitions from Merriam-Webster.

Some of the following terms have layman's definitions and technical ones.  So, please note that I only mean when they are used in a technical sense, that they are incorrect.  However, I will cover both definitions where applicable.  Without further ado, here is a list of technical terms I have heard used incorrectly.

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*Accuracy vs. Precision:

For the quick and dirty definitions, accuracy is how close to the theoretical value you are and precision is how close together your measured values are.  Let me give some pictorial examples.

*Effect vs. Affect:



I know I am certainly one who has to think about which one I want, so don't get yourself down about this mistake.  Usually, if you mean it as a noun, you want effect; and, if you mean it as a verb you want affect.  However, both have a verb and noun meaning (complicated much?!).

Let's take a look at affect first.  Affect as a noun means "the conscious subjective aspect of an emotion apart from bodily changes;" so, it's about emotions.  Affect as a verb means "to influence or cause."  Affect as a verb can also mean "to put on a pretense of," but this is not easily mistaken as effect.

Now, let's look at effect.  Effect as a noun means various things, such as:  "intent," "appearance," "power to bring about a result," or "distinctive impression."  Scientists use it in the "cause and effect" way.  Such as, "If you take this medicine, then you may feel this effect."  Effect as a verb means "to cause to come into being."  As Merriam-Webster puts effect, "The verb effect goes beyond mere influence; it refers to actual achievement of a final result."

*Heat:

You can never measure the "heat" of a body.  Instead, it is the difference between final and initial values of the body's energy.  Furthermore, energy is exchanged from the more energetic body to the less energetic body.  Temperature is related to the energy of a system; the hotter it is the more energy it has and.visa versa.  So, the energy flows from hot to cold.

I.e. vs. E.g.:

Actually About.com has a great article on this.  But, to sum it up, you can think of i.e. as also known as (AKA) and e.g. as for example.

Imply vs. Infer:

As you guys have probably noticed, I like The Big Bang Theory.  So here is a great clip of Sheldon saying the difference between imply and infer.  Imply means to suggest something, infer means to make an educated conclusion.

Mass vs. Weight:

People typically think of weight and mass to be the same thing.  This is ok if you are on Earth; however, once you leave our fair planet, weight gains a whole new meaning.  Weight is actually how much the force of gravity is pulling something down.  While, mass is how much of something there is.  We think of them as the same because the weight is, basically, constant as we see it.  To relate the two, weight is the mass multiplied by the acceleration from gravity.  This acceleration will change as one moves away from Earth.  For example, the acceleration of the moon is only 17% of Earth's.  So, if someone weights 100 lb on Earth, they will only weight 17 lb on the moon.  That's why the astronauts could jump around like they did.

However, your mass will remain the same no matter where you are.  Magic School Bus also did an episode on how your weight will change called "The Magic School Bus Gains Weight."

Thrust:  Thrust as physicists or engineers use it, means the change in momentum due to a change in mass.  Momentum can be a hard concept to grasp, so, to simplify, you may think of it as the "motion" of an object.  Therefore, thrust is a change in the objects motion caused by a change in mass.  For instance, rockets are a great example of thrust.  They are forced forward by thrust as the fuel decreases.  Here's a quick little picture (with über sweet flames!) to visualize what I mean.

 

Additionally, NASA has a good explanation. There is also a nontechnical definition for thrust.  However, thrust used in this context is a verb, while, in the technical sense it is a noun.  The definition states, "to push or drive with force."

There is a car commercial that was boasting of the car's "thrust" (sorry can't remember which company).  Thus, it uses thrust as a noun.  And, while, yes, a car has thrust, it is, or should be, minimal.  So, if the car has such great "thrust," then it has pretty poor gas mileage.

*Velocity, Speed, & Acceleration:

Speed is often said when people mean velocity.  However, there is a subtle difference that makes what people say incorrect at times.  I wouldn't feel too bad if you've made this mistake.  I've had a physics professor of mine do this very thing, and I probably have too.

Velocity is a vector quantity, which means it is a value that has a certain direction associated with it, or it has "...both direction and magnitude! Oh yeah!".

Speed is the magnitude, or the "length", of the velocity.  First, let me explain the math symbols (I know that can be scary but hold on!).  

Vectors, (1), are typically denoted with an arrow above whatever your vector is, in my example "a".  While, the "a hat," (2), means, roughly, a direction. So vector a will have a value in the a direction.  Consider the following example.

We have a vector that I have called "a".  a is made of an x value and a y value.  So, a is equal to a value, 2, in the x direction plus a value, 1, in the y direction.  If we look in the a direction, a vector equals 1/2 in the a direction.  To get the magnitude of a vector, we, basically, just take the number in front of the direction.  So, the magnitude of x is 2, y is 1, and a is 1/2.  And the magnitude of a is the speed.  Thus, the speed is 1/2.

Acceleration is a change in velocity.  So, both of the following are examples of acceleration:  a change in direction and a change in magnitude.

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Like Carlos did in the first comment, feel free to recommend words you would like me to cover here.

Coming soon!

Combust:
String Theory:
Ether:
Diffuse vs. Difuse:

Edits:
1. 24.02.2011
2. 07.03.2011