# Mechanics: Statics and Dynamics

**Topics:**Force, Classical mechanics, Newton's laws of motion

**Pages:**6 (1607 words)

**Published:**October 8, 1999

TABLE OF CONTENTS

INTRODUCTION.........................................................1

Chapter

I. General Principles........................................2 I. Systems of Force.........................................4 II. Stress..................................................6 III. Properties of Material.................................7 IV. Bolted and Welded Joints................................10 V. Beams -- A Practical Application.........................13 VI. Beam Design.............................................17 VII. Torsional Loading: Shafts, Couplings, and Keys........19 VIII. Conclusion............................................20

BIBLIOGRAPHY.........................................................21

INTRODUCTION

Mechanics is the physical science concerned with the dynamic behavior of bodies that are acted on by mechanical disturbances. Since such behavior is involved in virtually all the situations that confront an engineer, mechanics lie at the core of much engineering analysis. In fact, no physical science plays a greater role in engineering than does mechanics, and it is the oldest of all physical sciences. The writings of Archimedes covering buoyancy and the

lever were recorded before 200 B.C. Our modern knowledge of gravity and motion was established by Isaac Newton (1642-1727).

Mechanics can be divided into two parts: (1) Statics, which relate to bodies at rest, and (2) dynamics, which deal with bodies in motion. In this paper we will explore the static dimension of mechanics and discuss the various types of force on an object and the different strength of materials.

The term strength of materials refers to the ability of the individual parts of a machine or structure to resist loads. It also permits the selection of materials and the determination of dimensions to ensure the sufficient strength of the various parts.

General Principles

Before we can venture to explain statics, one must have a firm grasp on classical mechanics. This is the study of Newton's laws and their extensions. Newton's three laws were originally stated as follows:

1. Every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it.

2. The change of motion is proportional to the motive force impressed and is made in the direction in which that force is impressed.

3. To every action there is always opposed an equal reaction; or the mutual actions of two bodies on each other are equal and direct to contrary parts.

Newton's law of gravitational attraction pertains to celestrial bodies or any object onto which gravity is a force and states: "Two particles will be attracted toward each other along their connecting line with a force whose magnitude is directly proportional to the product of the masses and inversely proportional to the distance squared between the particles.

When one of the two objects is the earth and the other object is near the surface of the earth (where r is about 6400 km) / is essentially constant, then the attraction law becomes f = mg.

Another essential law to consider is the Parallelogram Law. Stevinius (1548-1620) was the first to demonstrate that forces could be combined by representing them by arrows to some suitable scale, and then forming a parallelogram in which the diagonal represents the sum of the two forces. All vectors must combine in this manner.

When solving static problems as represented as a triangle of force, three common theorems are as follows:

1. Pythagorean theorem. In any right triangle, the square of the hypotenuse is equal to the sum of the squares of...

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