Angle of rotation problems can come up in several NCEES FE Exams: Civil, Mechanical, and Other Disciplines. In mathematics, the angle of rotation is a measurement of the amount, of namely angle, that a figure is rotated about a fixed point, often the center of a circle.
A clockwise rotation is considered a negative rotation, so that, for instance, a rotation of 310 degrees (counter clockwise) can also be called a rotation of negative 50° (since 310 degrees + 50 degrees = 360 degrees, a full rotation ( or turn)).
A counter clockwise rotation of more than one complete turn is normally measured modjulo 360 degrees, meaning that 360 degrees is subtracted off as many times as possible to leave a non-negative measurement less than 360 degrees.
Before I move ahead, let me remind you that the FE EXAM or fundamentals of engineering – is the first step to getting your professional engineering license, and through the videos on this channel, including this one, you will learn not only how to properly prepare for the exam, but how to ensure you PASS THE FE EXAM!
Subscribe to our YouTube channel here, as our weekly videos will help you Pass the FE Exam. Leave your FE questions in the comments below and we will answer them in future videos.
This sample problem has been provided to us by PrepFE.
PrepFE is one of the most effective FE exam self-study prep services out there and happens to be one of the most affordable too. PrepFE is an app that gives you access to countless sample FE problems to bolster your self study efforts. You can visit www.prepfe.com/redeem and use the discount code in the description of this video to receive 10% off and get some great FE practice problems.
So Here’s the Problem:
Find the Explanation Given Below:
Refer to the Mohr’s Circle section in the Mechanics of Materials chapter of the FE Reference Handbook.
Ultimately, we must determine the angle rotation needed to get the stress element to a principal stress state.
Steps To Determine the Angle of Rotation Needed:
- Draw a quick Mohr’s circle based on what’s shown in the stress element.
- Draw a right triangle from the center of the Mohr’s circle to a known point along the circle. Determine the Mohr’s circle’s angle between the known point and the sigma axis (x-axis), which is where the principal stress occurs. That will be the Mohr’s circle rotation angle needed to get to a principal stress state.
- Convert the Mohr’s circle’s rotation angle needed to get to a principal stress state to the stress element’s angle needed to get to a principal stress state.
The correct answer is D.
I hope you found this week’s video helpful. In upcoming videos, I will share some more studying strategies and also cover some more problems including engineering economics practice problems.
We publish videos weekly on our Pass the FE Exam YouTube Channel. Be sure to visit our page here and click the subscribe button as you’ll get expert tips and tricks each week – to ensure your best success – that you can’t get anywhere else. Believe me, you won’t want to miss a single video.
Lastly, I encourage you to ask questions in the comments of the videos or here on this page and I’ll read and respond to them in future videos. So, if there’s a specific topic you want me to cover or answer, we have you covered.
I’ll see you next week.
Anthony Fasano, P.E.
Engineering Management Institute
Author of Engineer Your Own Success