Questions tagged [dynamics]

Questions about the dynamics of a system. Currently there is a very large scope ranging from from dynamics in mechanics, vehicle and flight dynamics, to system dynamics and fluid dynamics.

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Angular acceleration of the CD bar

Determine the angular acceleration of the $CD$ bar for the situation illustrated in the figure. The solution is $474 rad/s^2$ $counterclockwise$ I've done: $v_B = v_A + w *r_{AB} <=> v_B= -3j$ ...
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Why are percent errors between theoretical and simulated values so large with my linear models compared to my nonlinear models?

I have 4 mathematical dynamic models (2 linear and 2 nonlinear) where I am solving for 4 state variables or 6 state variables simultaneously. I have run simulations of the models and gotten steady ...
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Fault Recovery of a UAV using MATLAB

I'm currently investigating fault recovery in a UAV using MATLAB. I've been given several variables: phi = the roll angle psi = the yaw/heading angle beta = the side slip p = roll rate r = yaw/...
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41 views

Proof of angular velocity identity

I've been going thru the book by Hodges and Roithmayr regarding dynamics theory and I can't seem to prove that: I have tried using multiple substitutions, including the fact that every component of ...
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Speed of the 50 kg cylinder after it has descended a distance of 2 m

This was the solution: However I tried $ΣM = ΣM eff$ $P(D) * 0.1 = I(B)α(B) + I(A)α(A) + m(D) * a(D) * 0.1$ with $ I(B)=27/40, I(A)=5/32$ and $α(A)=(-4/3)α(B)$ and got $α(B)=50.74 rad/s^2$ so i know ...
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why do we need state feedback in H-infinity concept instead of output feedback

I have faced control of a flexible manipulator which have a zero dynamic related to flexible parts dynamic. the zero dynamic states (generalized states) are not observable in input-output dynamic and ...
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Linearisation of the Equations of Motion of an Inverted Double Pendulum

I am working to develop a deep reinforcement learning model for balancing an inverted double pendulum. To do so, I needed to derive the equations of motion, via the Euler-Lagrange (EL) method and now ...
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39 views

Pulley with mass dynamics question

A pulley system has mass moment of inertia of 1.4kgm^2. If 8kg block is released from rest from S=1, by using energy approach what is angular velocity at S=2? Radius of pulley is 250mm. Note S is from ...
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Angular Acceleration

Need confirmation for this question please: A pulley with Radius of 90mm and a mass moment of inertia 0.28$kgm^2$ about its central axis is subjected to a torque of 50Nm about this axis. What is ...
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Condition for equilibrium of a rigid body on a horizontal surface

The following question is from a past paper from Further Mechanics and it has been bothering me immensely I have spent hours cracking at a way to make sense of it, the question is in two parts Part ...
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Mechanics Dynamics Question

Alright so this is my question lasses and lads: a disc with a mass moment of inertia 0.125kgm^2 about its central axis is rotating at 180rad/s about the axis. What is the angular momentum of the disc ...
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Sprocket Angular Velocity [duplicate]

I have a question please that I need help on. Consider the chain that is draped over the sprocket with mass moment of inertia of 0.005kgm^2 about central axis. If 4kg block is released from rest from ...
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Are there examples of spring-mass-damper system that exhibit increasing growth in an unstable way

Simply, are there examples of spring-mass-damper systems that exhibit unbounded behavior or at least increasing behavior for a period of time. I am trying to do some vibrations research, but I am ...
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Force and the reactions on the supports

Consider the movement in the vertical plane of an $AB$ bar with a mass of $20 kg$, $0.8 m$ long and supported by two cursors: one at the end A and the other at point G coinciding with the center of ...
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Is controlling humidity more precise when calculating with relative or absolute humidity?

I have a tubing system where I need to precisely control relative humidity. All my sensors are giving me temperature [°C] and ...
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How to find the speed of a boat needed to become airborne on a wave

I am doing a small dynamic project that needs to predict the boat's (boat with propeller) movements in a wavy sea condition as shown below: as the boat is at the peak of the wave, how to determine ...
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37 views

Determine Stiffness (k) and Mass (m) of a system from impulse response

I have a test sample (Piezo Diaphragm) which I am actuating with a voltage supplied to the sample to assess the impulse response. When this voltage is supplied to the sample a deformation per unit ...
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Shell Breathing Modes and Base Excitation

I have been reviewing "Vibration of Continuous System" by S. Rao as part of self-studying to help with work. I started reviewing the chapter regarding shells and noticed that shells have ...
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How are circular dependencies dealt with inside MBSE?

How are circular dependencies (best) managed inside of MBSE environments? Let's say I have two properties that are linked to each other / they are linked to properties that affect each other. How is ...
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What is the order of execution in system models?

I'm learning SysML/MBSE right now. In what order is a model "executed", that is: in what order are dependencies between properties reconciled? For instance, if I have one component/subsystem ...
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51 views

If aboard a train being driven along a track by centripetal force, would it feel like you were on a regular straight track?

Question: If aboard a train being driven along a track by centripetal force, would it feel the same as if you were on a regular straight track? I hope this isn't subjective, I think there is a right ...
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97 views

Determine the angular velocity and angular acceleration of the AB bar at the instant shown

Consider a sliding cursor C that is fixed to the disk which has a constant angular velocity counterclockwise at 4 rad/s. Determine the angular velocity and angular acceleration of the AB bar at the ...
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How to determine the angular velocity of the platform as a function of motor rotations per second?

Hello all of you engineering geniuses. Awhile ago a very talented individual on here helped me work out the conceptual mechanics of this design. As you can see from the model, there is a lead screw ...
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Damp vibration on phone attached to car seat

I'd like to create a 3d printed system to damp the vibrations on the phone when we are on the road. The idea is to be able to hold the phone for my little kid when we travel First I tried a spring ...
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37 views

Why is longitidunal force of tyre calculated negative in SIMULINK?

With the help of the Vehicle Dynamics Blockset of SIMULINK, it is easy to obtain longitidunal force (tractive force) of tyre by some of inputs. You can see one of examples below. In this simulation, ...
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Degrees of Freedom for Complex Pulley Systems

I'm trying to understand DOF clearly, but this pulley system has me doubting myself. When I try to determine the degrees of freedom, I sum the DOF of each object, and subtract the constraints. for ...
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Moment placed off-centre on a rotating body

Imagine a body which is allowed to rotated around its centre of gravity. I place a rotating moment, $M_d$ on a point which is a distance d from the body's centre. $M_d$ is only required to put the ...
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how do i keep static deflection in a spring at a minimum upon applying gravity in a mass spring system without altering the response?

i modelled a simple mass spring damper system (with a vertical orientation) with base excitation in solidworks. After applying all necessary parameters, i plotted responses with and without gravity ...
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Gear/Mechanics problem: How to design to allow for 2 types of rotation

I am designing a new mowing system that can effectively mow around poles. The machine consists of an arm that is attached to the back of a tractor and runs off its PTO. At the end of the arm is a ...
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36 views

Is the relative acceleration with respect to a translating frame equal to that with respect to a fixed one?

My book, written by Beer, states that the rate of change of a vector is the same with respect to a fixed frame and with respect to a frame in translation. But while it says the derivative ˙rB/A ...
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correcting mode shape for modal damping

I have mode shapes and eigen frequencies from FE simulation. I have modal matrix and eigen frequencies corresponding to each mode. The mode shape is mass normalized. I am required to correct each ...
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Modal analysis in Abaqus AMS solver

I have a huge model for which I am performing modal analysis. Abaqus fails to solve with Lanczos solver and hence I use AMS solver, which successfully computes the solution. But since AMS solver ...
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33 views

How do I determine the angular acceleration?

In this question I understand what we have to do to solve it and is equate the sum of moments with the moment of inertia. However I am not sure on how the LHS became negative as I see that the angular ...
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1answer
38 views

Quantifying the reaction force on fixed tubing connected to a peristaltic pump

I am not sure how I should consider the forces due to hydrostatic pressure when calculating the reaction force due to a fluid being pumped through fixed tubing with a peristaltic pump that I am using ...
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40 views

Find frictional losses as box exits ramp

I have a box traveling on a ramp just before the ramp levels out. At this point all values are known: I want to calculate the frictional losses from this point to when the box is completely off the ...
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Changing the quality of the transient process in a nonlinear system (Part II)

My question is a continuation of the topic. https://math.stackexchange.com/questions/3910814/changing-the-quality-of-the-transient-process-in-a-nonlinear-system-in-mathemat Unfortunately, last time I ...
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Why does the frequency of a bottle filling up changes?

Today as I was filling up a bottle of water, and I could hear the distinctive change in pitch that signals that the bottle is near filling up, I started wondering what equation determines the ...
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79 views

Determining Friction and Contact forces

I am looking at a rod that has an acting force along one end that's pinned into a frictionless track. The other end is pinned into a track that has friction. I am trying to determine the contact ...
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How to determine the linear and angular velocity of one end of a rod that is pinned on a track on each side?

I am working on trying to determine the velocity of one end of a rod that is pinned on both ends into two different tracks. One track is linear and the pinned end has known values. The other side is ...
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Changing the quality of the transient process in a nonlinear system (in Mathematica)

I urgently need advice and help. I have a system of differential equations like this: $\begin{cases} \frac{dx}{dt} = y[t] \cdot \alpha \cdot sin(\omega t) + \frac{d}{dt}(\alpha \cdot sin(\omega t)) ...
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Coulomb damping time calculation

I'm designing a movable cover on rails under a spring and with added friction to dampen the movement. The model that describes it's movement the best is Coulomb damping model. The cover is moved from ...
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70 views

How to calculate the torque for motors for a Core XY movment?

I am trying to design a simple setup that follows the core XY movement shown: I have been researching the statics behind this movement in order to calculate the minimum torque for the motor so I ...
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1answer
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What is the maximum force needed to move the roller block from point A to point B and where does that maximum force occur?

Hello everyone. This project is for a very specific application and I am trying to determine the force necessary to get the block from point A to B. Specifically the maximum force necessary and at ...
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Estimation of Beam Displacement from Acceleration

Hi Engineering Exchange, I have a beam with pinned-pinned boundary conditions (free to rotate but not free to translate). A legacy computer analysis provided me with the maximum mid-span acceleration ...
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Research of transients in nonlinear systems with linear dynamic links

I am having difficulties of this nature. There is a nonlinear system of the following type: I need to analyze analytically the transient process in such a system. The analytical study of the ...
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162 views

Disc Brakes - Swept Area , why is larger better?

I am trying to understand why a bigger swept area on disc brakes provides higher braking force for the same force being exerted on the brake lever/pedal by the rider. If we use the same exact brake ...
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1answer
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At what volume would air bubbles become static in a fluid with viscosity of 7000cps

I would appreciate any help with this as its been a few years since my fluid dynamics courses at University! Basically I am trying to determine the cause of voids that we are seeing in a set resin. ...
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Triggering of eigenmodes

When conducting an eigenmode analysis, we get a sequence of different modes with their respective eigenfrequencies. My question is: Are all of those really relevant in every application? Take for a ...
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Force on suspension when hitting a step

I'm trying to calculate the magnitude and direction of the force exerted on a wheel when encountering a step. The wheel and the steps are non-deformable. I found two different approaches: energy ...
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3answers
92 views

Difference between Linear Force and Force about an Axis

I am confused between How forces work when applied in singular linear direction vs Force Applied to a continuous mass about an axis(example to rotate it). Example 1: Consider an object of mass $m$ ...

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