Chapter 2
Motion in One Dimension
In the study of Kinematics, familiarity with the following symbols is essential.
· x : distance, expressed in meters (m)
· t : time, expressed in seconds (s)
· v : velocity, expressed in meters per second (m/s)
· a : acceleration, expressed in meters per second squared (m/s2 )
2.1 Displacement, Velocity and Speed
2.1.1 Displacement (units in m)Linear Motion
Linear motion describes the motion of a particle along a straight line. Position is where the object is relative to the "origin." Along the number line, the particle is said to be positive if it is to the right of the origin, negative if it is to the left, positive if it is up, and negative if it is down.
Displacement is defined as the change in position:
(displacement,
m) (2.1)
This involves objects that move from one position to another position. This movement is usually shown by using coordinates to identify their locations, e.g., initial position xi to final position xf., as shown in Fig. 2.1.
Displacement has both magnitude (the number) and direction and requires a reference point and must carry a sign (i.e., +/-).
Note:
- The position of an object is simply the displacement of it from the reference point e.g., origin in coordinates systems.
- While the magnitude of an object is its size.
- Distance - no sign (always positive) “Distance is not necessarily the same as displacement”.
