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Document Title
Fundamentals of Stress and Vibration 2. Engineering Mechanics Chapter
[A Practical guide for aspiring Designers / Analysts]

Let us also verify the fact discussed, for [F = ma]. Writing the units for [F = ma], we get:

mm tonne mm kg × 10 3 kg
3
N = volume ∗ density ∗ = mm ∗ ∗ = mm = m
s 2 mm 3 s 2 s 2 s 2
Therefore, for all inertial forces, where density is involved, its unit must be in tonne mm . This
3

fact only holds for engineering simulation or FEM analysis.

2.5 Equations of Motion

2.5.1 Straight Line Motion

The analysis of straight line motion is useful, not just for vehicles, but also for mechanisms and
mathematical schemes, used for transient analyses. These equations are derived based on
conservation of energy and work done. The set of equations that are going to be derived for linear
motion are also going to be used for angular motion.

For curvilinear motion, we need new acceleration terms, to define the motion, which would be
taken up subsequently.

2.5.2 Energy and Work done

[Fig 2.1: mass(m) travelling on a frictionless platform]

QP No. SSC/Q4401, Version 1.0, NSQF Level 7, Compliant with Aero and Auto Industries, Page 9 age 9
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