Page 172 - Physics

Physics for Secondary Schools

Chapter Eight

Linear Motion

Introduction

In your life, you have experienced different situations in which bodies are in motion.
Examples of such situations include falling leaves from trees, fl owing water in rivers,
and moving vehicles. If there is a change of position of a body with respect to time,
then motion has occurred. In this chapter, you will learn the distinction between
distance and displacement, speed and velocity and the interpretation of distance,
displacement, and velocity-time graphs. You will also learn about acceleration
and equations of uniformly accelerated motion. Moreover, you will learn about
motion under gravity and how to determine the acceleration due to gravity. The
competencies developed from this chapter will enable you to apply motion in daily
life situations including riding bicycles, motorcycles, and driving cars.

Think
if there would be no motion on earth

Concept of motion in a straight line is referred to as linear
An object is said to be in motion when its motion.
position is continuously changing relative
to a reference point such as an observer
or a fi xed object. For example, when you
walk or run, your position is continuously
changing with respect to the ground. When
you see a car (Figure 8.1) passing by the Figure 8.1: Car in motion past an observer
road, it is moving with respect to you. When scientists study a physical
Suppose you are in a car that is moving phenomenon like motion, the fi rst step
at the same speed as another car, the other is to observe the event. The second step
car will not be moving with respect to you. is to develop the necessary concepts to
Both cars are now moving with respect to describe those observations. What are
the ground. Therefore, motion is relative to the concepts that are useful in describing
the observer or some fi xed object. Motion motion?

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