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Unformatted text preview: Muddy Card Responses Lecture M3 Can you describe what the physical meaning of a moment is, and how do you choose r in rxF. A moment (or more correctly a moment of a force) is the effect of a force acting about an axis to cause an angular acceleration (or rotation). r is to some extent arbitrary. It is the position vector of some point on the line of application of the force F. Why is it that a moment at the corner of the box is the same as that moment at the origin. This is a key concept in this lecture. Namely that a pure moment (such as caused by a couple - a pair of forces) is a vector quantity that does not vary with its point of application. A moment due to a force acting at a distance, has to be represented by a force and a moment, and in general these will vary with the point of application. Difference between a torque and bending force. A torque (or twisting moment) has a vector aligned with the structural axis (the wing in the example in class) the bending moment is the component of the moment vector that is orientated perpendicular to the structural axis....
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- Fall '05