Page 32 - mechanics

Chapter – 6 Kinematics of a Particle

Regardless the forces acting on a body we discuss the motion
of a particle and this science is called kinematics. If the force is
considered then we will discuss kinetics.
6.1 Position, Velocity, and Speed

The motion of a particle is completely known if the
particle’s position in space is known at all times.
A particle’s position is the location of the particle with respect
to a chosen reference point that we can consider to be the
origin of a coordinate system.

‫إن موضع الجسيم هو موقعُه بالنسُة لنقطُ مجعُع مَاَُاَال الاُم ك ُن أُن َ ُن تعاةُ َج‬
.‫نقط ص َل لنظام إحداثيات‬

Consider a car moving back and forth along the x axis as in
Figure 6.1.a. When we begin collecting position data, the car is
30m to the right of a road sign, which we will use to identify
the reference position x = 0. We will use the particle model by
identifying some point on the car.

We start our clock and once every 10s note the car’s
position relative to the sign at x = 0. The time and the
corresponding car position are recorded in Table 6.1. A
graphical representation of this information is presented in
Figure 6.1.b. Such a plot is called a position-time graph.

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