# Composition of Forces

Composition of Forces

## Introduction

After reading the lecture it is important to check understanding of basic concepts and definitions of course.

## Objectives

The objectives of teaching of “Theoretical Mechanics” are:

• demonstration prime mechanical terms and concepts to students

• teaching students to describe mechanical model of standard task and to analyze the acquired knowledge

• development of mechanical intuition and generating mechanical culture

## Activity 1: Terms and definitions

## Instruction

Complete the following sentences.

Then read the feedback to check your answers.

The principal vector of a system is called...

the quantity which is the geometric sum of all the forces of a given system

Forces are called concurrent...

whose lines of action intersect at one point

The necessary and sufficient condition for the equilibrium of a three-dimensional system of concurrent forces ...

is that the sums of projections of all these forces on each of three coordinate axes must be zero.

The resultant of a system of concurrent forces is..

equal to the geometrical sum (principal vector) of these forces and that it is applied at the point of their intersection.

If a free rigid body remains in equilibrium under the action of three nonparallel coplanar forces, then the lines of action of these forces..

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