Why is Statics so hard? – November 9, 2018
Statics is the first real challenging class that most engineering students encounter in their academic career. This class is usually taken during the first semester sophomore year along with many other challenging courses such as Physics II, Multivariable calculus, and linear algebra. Many students find the material in Statics very challenging. This is because statics is the first REAL engineering course you take. It requires advanced critical thinking and visualization skills. Don’t be upset if you don’t get it the first time! In this class, you are tasked to solving mechanics problems by properly selecting and analyzing the correct free-body diagrams in the most efficient way. It’s much harder than it sounds! Here are some quick tips to keep you thinking in the right direction when tackling engineering mechanics problems:
- First, ask yourself: what is going on here?
- Looking at the diagram, how would this thing move? What is the purpose of the forces and moments acting on the system? What would happen if I change the system a little bit?
- This part requires no knowledge of the numbers. Usually, a good diagram will suffice.
- Then ask yourself: What am I looking for?
- Identify the component of the system that you are interested in. Circle it!
- Think of the general ideas that are required to get you there. At this point, you should have an idea of how to get what you need if you did step 1 correctly.
- Begin executing the problem with the appropriate steps and ask:
- What is the next step?
- Why is this the correct step?
- Repeat
- Lastly, check your answer by asking: does my answer make sense?
- Do I expect my answer to be positive or negative?
- Do I expect my answer to be relatively large or relatively small?
- Be awesome
Statics Tip: Shear and Moment Diagrams
Shear moment diagrams is one of my favorite topics in the course not because it’s easy, but it’s very applicable to the future engineer. In future classes such as Deforms and Mechanical Design, professors are going to expect you to know how to draw shear and moment diagrams quickly and effectively. I have 4 rules (with explanations) that will help you draw them and understand the beam loading.
- The V (shear) and M (moment) at the ends of the beam are ALWAYS 0
- You start your pencil at 0 and then use rules 2 and 3 to decide which way to go from there.
- Point forces cause jump in shear
- Your reaction force and basically any force you draw with a single arrow will cause a jump in the shear. Upward forces (such as reaction forces) cause a positive jump in the shear graph while downward forces (such as point loadings) cause negative jump in the shear graph.
- Point moments cause jump in moment
- Similar to point forces, point moments cause jumps. However, the signage is different. Clockwise moments cause positive jumps and counterclockwise moments cause negative jumps on the moment graph. If the beam is “smiling” then the moment value at that section should be positive. If the beam is frowning, the moment value will be negative at that point.
- The shear equation is the negative anti-derivative of the weight equation for distributed loads. The moment equation is the anti-derivative of the shear equation.
- Don’t forget +C! Your C values for your leftmost equations (i.e. usually the first equations you find) are going to usually be the value of the reaction. Note that pins and rollers have no moment reaction forces so usually the +C for the moment equation is 0 at the start of the beam.
Statics Practice Final Exam: Sample.Final.Exam.Statics
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