notes/uni/mmme/2046_dynamics_and_control/dynamics.md

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---
author: Akbar Rahman
date: \today
title: MMME2046 // Dynamics
tags: [ mmme2046, uon, uni, dynamics ]
uuid: 98a5449a-02d3-492c-9d0e-3d3eb74baab5
---
# Machine Dynamics
- Rigid Body - Distances between any two particles on a body remain constant---in real life we are
looking for negligible deformation
# Lecture 2 (W04/41)
## Relative Motion
![](./images/vimscrot-2022-10-17T09:09:23,080550083+01:00.png)
where $_{BA}$ is read as "$B$ as seen by $A$".
These equations must be treated as vectors.
# Lecture 3 (W05/42)
## Instantaneous Centre of Rotation
This is a point with zero velocity at any particular moment.
![](./images/vimscrot-2022-10-17T09:13:09,972195575+01:00.png)
$$v_A = 0$$
$$v_B = v_{BA}$$
To find the centre of rotation you can draw to perpendicular lines to velocities from two non
stationary points.
The centre of rotation will be where the lines intersect.
![](./images/vimscrot-2022-10-17T09:14:37,194818034+01:00.png)
## Point Velocity Projections on Joining Axis
Take two points $A$ and $B$ and their velocities at one instant
\begin{align}
v_B &= v_A = v_{BA} \\
\text{then } \pmb{v_B} || AB &= \pmb{v_A} || AB + \pmb{v_{BA} || AB \\
\text{but } \pmb{v_BA} || AB &\equiv 0 \text{(since $\pmb{v_BA} \perp AB$)} \\
\text{or } \pmb{v_B| || AB &= \pmb{v_A} || AB \\
v_B\cos\beta = v_A\cos\alpha \\
\end{align}
# zack.jpg
![zack.jpg](./images/zack.jpg)