Motion Along a Straight Line

Study Notes

Motion along a straight line is the simplest type of motion.
The object starts its journey from a reference point O and moves along a straight path.
The position of the object at different instants is represented by A, B, and C.
Displacement and distance are used to describe the overall motion of an object and to locate its final position with reference to its initial position at a given time.

Distance is the total path length covered by an object.
Distance is measured by specifying only its numerical value and not the direction of motion.
The magnitude of displacement is the shortest distance measured from the initial to the final position of an object.
Displacement is a directed quantity and has both magnitude and direction.

Consider the motion of an object moving from O to A, then back to B, and finally to C.
The distance covered by the object is OA + AC = 60 km + 35 km = 95 km.
The magnitude of displacement from O to C is the shortest distance, which is 35 km.
The magnitude of displacement is not equal to the distance travelled by an object.
Activity 8.3: Measure the distance covered by walking along the sides of a basket-ball court and compare it with the magnitude of displacement.

An odometer is a device that shows the distance travelled by an automobile.
The difference between the final and initial readings of the odometer gives the magnitude of the displacement between two points.

The magnitude of displacement can be zero, but the corresponding distance covered is not zero.
The distance covered in a journey may not be equal to the magnitude of displacement.