Like any other profession, engineering gets divvied up between several factions of sub-engineering classes. I don’t pretend to know what they all do or even all of their names, but I do know a little about some of the prominent ones.
I actually started my education career as a mechanical engineering major. A few years into it I met with a counselor and she said that if I wanted to secure a position within the general radius of my family, I needed to switch to civil engineering; so I did.
There were more factors involved, but the short and long of it is that I switched to civil and never looked back. One of the side-effects was a rare inside look at how the two disciplines look at each other.
A conversation about the difference between civil and mechanical engineering wouldn’t be complete without the all-too-common ‘the difference is that mechanicals build weapons, civils build targets’. Funny, huh.
The real difference is actually more fundamental. In a classic oversimplification, you could almost say that mechanical engineers deal with moving bodies, while civil engineers deal with non-moving (static) bodies (while this is obviously not always the case).
One of the first exposures to engineering for both disciplines is a course called ‘Statics’. In this class you learn that, for non-moving bodies, the sum of the moments about any axis need to equal zero and the net sum of the forces on the entire body about any axis also need to be zero. In lay speak, this means that for every force applied on something, there needs to be an equal and opposite force that ‘cancels’ it out.
In non-mathematical lingo, the equation would look like:
Sum of the forces about (axis) = 0
Sum of the moments about (axis) = 0
(In case you don’t know, a moment = force x distance. It is a twisting force and is also known as torque which is given in foot-pounds or Newton-meters.)
This is perhaps the underlying principle of civil engineering (especially structural). To fully understand this principle, you also need to understand that non-moving objects can exert a force. If you weighed 200 pounds and are standing on the floor, the floor is ‘pushing’ back up with 200 lbs.
We know this because if it were less, you would fall through the floor, but if it were more, it would be an elevator. For many this will seem elementary, but when some students first hear it, it is a difficult concept to grasp.
After Statics, you take a course called Dynamics. For many, this class is rather intimidating, but in reality, it is very similar to Statics. In fact, most of the equations are derived from almost the same equations, except for one small change:
Sum of forces about (axis) ≠ 0
Sum of moments about (axis) ≠ 0
Did you catch that? Instead of the object being at rest, the forces are not equal and therefore either move or twist the object, setting it in motion. For example, if a box is pushed with a force of 5 pounds and is resisted by a friction force of 2 pounds, the net 3 pounds will put it in forward motion. If the 5 pushing pounds were resisted by 5 friction pounds, sum of the forces would equal 0 and it would not move.
Both mechanical and civil engineering broaden their respective scopes as courses become more complicated, but these equations are truly the fundamental differences between mechanical and civil engineering.
More general differences include (remember that these are not absolutes):
- Civil engineers deal more with infrastructure, mechanicals deal more with machinery
- There is more of a public demand for civil engineering and less so for mechanical
- Mechanical engineers often need to work closely with electrical engineers
- Some of the major branches of mechanical engineering:
- HVAC (Heating Ventilation and Air Conditioning)
- Industrial Manufacturing
- Mechatronics and Robotics
- Some of the major branches of civil engineering:
- Structural
- Geotechnical
- Transportation
Samuel L. Lytle - Samuel is aspiring to be an engineer and writer and the culmination of these interests manifests itself in the Semi-Pro Engineering ...
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