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    A Inertial Frames

    This question concerns inertial frames. I am aware that an inertial frame is one that is not accelerating. I am aware of an alternative definition: it is one on which no forces are applied. (Yes, they are the same thing.) I am also aware of the d'Alembert "forces" that appear when a frame is...
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    Force in Center of Mass frame equaling zero

    1. Homework Statement Suppose I have particles with masses m1 and m2 , both are in freefall: Then , looking at the center of mass coordinates , I know that the sum of momentums of masses m1 and m2 in the center of mass coordinates is equal to zero : P1c + P2c = 0 so now I know that the...
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    Frenet Frame

    1. Homework Statement The Frenet frame of a curve in R 3 . For a regular plane curve (and more generally for a regular curve on a 2-dimensional surface - e.g. the 2-sphere above) we could construct a unique adapted frame F. This is not the case for curves in higher dimensional spaces. Besides...
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    B Different frames of reference

    Ok I have a really basic question. Say you and I are floating in space and there is a single electron in front of us stationary to our frame of reference. Now I start hopping up and down. I see the electron accelerate up and down from my hopping frame of reference. I see a EM wave be...
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    Relativity of Simultaneity and lightening

    1. Homework Statement You are standing at x = 9.0 km and your assistant is standing at x = 3.0 km. Lightning bolt 1 strikes at x = 0 and lighting Bolt #2 strikes at x = 12.0 km. You see the flash from Bolt #2 at t = 10 μs and the flash from Bolt #1 at t = 50 μs. According to your assistant...
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    Coordinate transformation - NED and ECEF frames

    Hi, I have a reference device that outputs euler angles, which are angles that relate the sensor body frame to the north east down frame. These angles are called pitch roll and yaw. The sensor is an accelerometer. I know how to get the rotation matrix that will put accelerations from the...
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    (APDL) use two sections in an static analysis (beam/column)

    Hi, i'm just start using APDL but i have been stuck trying to make an analysis with two diferent sections, i'd like to make a frame with two column and a beam but i don't know how, thank you.
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    Structural frame analysis

    1. Homework Statement Hello. I've created a small program to find shear and bending diagrams of the members of a frame. I was able to get the reactions at the support but don't know how to continue from now. This is an example of a frame all columns are 3m in height and the beams 8m. All the...
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    Kinetic energy of a rotating and translating body?

    1. Homework Statement Not a homework or coursework question, but given the simplicity of the problem I feel that this is an appropriate subforum. Consider a person spinning a rock on a string above their head at a constant angular velocity, walking away from the observer at a constant linear...